Use of silica fume as water-reducing agent and corresponding alkali-activated cementitious materials and preparation methods

Abstract

Disclosed in the present invention is a use of silica fume as a water-reducing agent, the water-reducing agent is used for a fly ash-based low-calcium system alkali-activated cementitious material and / or a slag-based high-calcium system alkali-activated cementitious material. Further disclosed are a fly ash-based low-calcium system alkali-activated cementitious material, a slag-based high-calcium system alkali-activated cementitious material, and corresponding preparation methods. The incorporation of silica fume as a water-reducing agent significantly improves the spread and compressive strength of the slag-based high-calcium system alkali-activated cementitious material, with a spread reaching 236 mm, an increase of 30%, and a 28-day compressive strength reaching 104.6 MPa, an increase of 2%. Similarly, it significantly improves the spread and compressive strength of the fly ash-based low-calcium system alkali-activated cementitious material, with a spread reaching 222.5 mm, an increase of 40.8%, and a compressive strength reaching 58 MPa, an increase of 11.7%.

Description

Use of silica fume as a water reducing agent and corresponding alkali-activated cementitious materials and methods of preparation TECHNICAL FIELD

[0001] The present invention relates to the field of new environmentally friendly low-carbon building materials, and relates to a new use of silica fume as a water reducing agent, as well as a fly ash-based low-calcium system alkali-activated cementitious material and a slag-based high-calcium system alkali-activated cementitious material prepared according to the use, and a method of preparing the corresponding alkali-activated cementitious material. BACKGROUND

[0002] Alkali-activated cementitious materials (AAM) are inorganic polymers composed of Si-O-Al-O bonds produced by the polymerization of Si-Al-rich precursor materials under the activation of an alkaline solution. They have excellent mechanical properties, low shrinkage, and good durability in corrosive environments. Compared to ordinary Portland cement (OPC), which produces a large amount of CO2 emissions due to the calcination of raw materials (limestone, clay) during production, the production of AAM can reduce CO2 emissions by about 76%. Moreover, the production of an average ton of OPC clinker requires 1700-1800 Joules of energy. If AAM is used to replace OPC, energy consumption can be reduced by 60%. Therefore, AAM is considered a sustainable and green cementitious material that can replace OPC in the future to reduce high carbon emissions and high energy consumption caused by the cement industry. According to the different Ca content of the precursor material, AAM can be divided into high-calcium systems represented by alkali-activated slag (AAS) and low-calcium systems represented by alkali-activated fly ash (AAF). The high-calcium system can generate C-A-S-H gel and have a tobermorite-like structure due to the high calcium content of the raw materials. The low-calcium system often forms N-A-S-H gel and has a highly cross-linked, disordered pseudo-zeolite structure. Regardless of which system, the preparation of AAM can reduce the impact on the environment caused by the production of OPC while achieving the goal of recycling industrial waste.

[0003] Similar to OPC, the liquid-solid ratio can significantly affect the performance of AAM. According to research, using a lower liquid-solid ratio can significantly improve the mechanical properties of AAM. However, too low a liquid-solid ratio can result in poor flowability of the cementitious material, making it difficult to cast and form, which affects its engineering application. Therefore, in order to ensure excellent mechanical properties and workability at the same time, the development and use of water reducing agents are particularly important in the preparation process of concrete. Generally, water reducing agents can reduce the water-cement ratio while increasing the flowability of the cementitious material, making it possible to prepare modern high-performance concrete. Currently, the development and research of water reducing agents are mainly focused on OPC and its concrete.

[0004] The conventional water-reducing agents for OPC systems have no obvious effect on the fluidity improvement of AAM, and often result in the decrease of mechanical strength. This is mainly due to the fact that most water-reducing agents are unstable in high alkaline environment (PH>13), thus reducing their plasticizing function and possibly changing their chemical composition when in contact with alkali activators, and different precursor materials also have an impact on the effect of water-reducing agents. Taking the most widely used polycarboxylate (PC) and naphthalene (N) in the OPC concrete industry as an example, for low calcium AAM (AAF), polycarboxylate shows better effect than naphthalene in improving workability. However, in terms of mechanical properties, the incorporation of both can lead to a decrease in the compressive strength of AAF. For high calcium AAM (AAS), the incorporation of naphthalene can also significantly reduce the mechanical properties of AAS. The application of polycarboxylate in AAS prepared by activating slag with water glass also has no obvious effect on improving workability. In general, the conventional water-reducing agents used in OPC systems cannot produce good results in different AAM systems.

[0005] In recent years, borax and sodium hexametaphosphate have been found to have the potential to be used as new water-reducing agents. Borax (B) is an inorganic compound with the molecular formula Na2B4O7·10H2O, usually white powder containing colorless crystals, easily soluble in water. In recent years, some scholars have noticed that it can significantly improve the workability of AAF with high calcium fly ash as precursor material, and is expected to become a new type of water-reducing agent for AAM. Oderji used borax in the preparation of AAM with 85% F-class fly ash and 15% slag as precursor materials, and compared it with sodium tripolyphosphate (STP), polycarboxylate, sodium gluconate (SG), calcium lignosulfonate (CL), and sodium lignosulfonate (SL). The results showed that borax had better effect than other water-reducing agents in improving the performance of AAM, and also significantly improved the compressive strength while improving the fluidity. In addition to borax, sodium hexametaphosphate (SH) can also reduce the liquid-solid ratio of hydrated magnesium silicate cement, and finally reduce the liquid-solid ratio to 0.4 with an addition of 1%, and the compressive strength of the sample after 90 days is increased to more than 70MPa. However, so far, there have been few studies on the application of borax and sodium hexametaphosphate as water-reducing agents in different AAM systems, especially sodium hexametaphosphate has almost no research on its application in AAM.

[0006] Silica fume (SF) is an industrial waste material, which is a by-product of the production of silicon metal and ferrosilicon. It is a fine, spherical particle containing a large amount of glassy silica component. According to statistics, the annual production of silica fume in the world is as high as 1 million tons. In order to promote the recycling of this kind of industrial waste, silica fume is mainly used as an auxiliary cementitious material in the current building material industry to prepare concrete by mixing with cement. Generally speaking, the incorporation of silica fume into concrete often leads to more water demand. However, in the previous research of the research group, it was accidentally found that it might have the efficacy of a water reducer in AAM.

[0007] Chinese patent CN105819719A discloses a reinforced geopolymer and a preparation method thereof, which uses phosphate and / or polyphosphate, metakaolin, fly ash, water glass, alkaline compound, silicon dioxide, water and the like as raw materials, blends them according to their weight fractions, grinds and mixes them into a uniform slurry, pours the slurry into a mold, and cures at room temperature or low temperature (20-80℃) to obtain the product. The geopolymer product obtained by the formula and preparation method has high temperature resistance, chemical resistance, and excellent mechanical properties, with a compressive strength of 150 MPa or more, meeting the use requirements of building materials and high-temperature coatings.

[0008] And CN116395998A discloses a 3D-printable alkali-activated cementitious material slurry, an article comprising the same, and a preparation method and application thereof, wherein the alkali-activated cementitious material slurry comprises an aluminosilicate precursor; an alkali activator comprising MOH, M2O·nSiO2, and H2O, wherein M is an alkali metal; and a modifier.

[0009] And CN111548039A provides a red mud alkali-activated cementitious material aggregate and a preparation method thereof, wherein the raw materials of the red mud alkali-activated cementitious material aggregate include the following components in weight fractions: red mud 50-100 parts; activator 1-10 parts; fly ash 0-40 parts; and water 20-60 parts. The red mud alkali-activated cementitious material aggregate has high mechanical properties and compressive strength, and has a wider engineering application.

[0010] And US9,266,783 discloses a customized precursor material composition in solid form of a geopolymer material comprising fly ash (59-91%), sodium hydroxide (11-15%), rice husk (0.8-11%), and optionally sodium silicate (0-29%), however, its mechanical properties need to be improved.

[0011] US2009 / 0229493A1 discloses a high compressive silica mortar consisting of 30-70 wt% of silica, 40-70 wt% of blast furnace slag and 100 parts by weight of dry mortar powder of these silicas with 15-35 parts by weight of condensation regulator, furnace slag, and by the generation of C-S-H, CAH, amorphous Geopolymeric Matrix {Al 2 O 3.mSiO 2.nM 2 O.xH 2 O (M = K, Na, Ca)} and zeolite properties are high strength silica mortar after vibration molding solidification for 12-48 hours at 25-80°C, showing a compressive strength of 70.0 MPa or more, and before removing the form and aging for 28 days, solidification for 12-48 hours, can save energy. However, it contains a large amount of silica, which is very costly.

[0012] and US8,440,016B2 discloses a ground granulated blast furnace slag for sulfate-resistant cement, which comprises a mixture of ground granulated blast furnace slag having an alumina content of 12 to 17.5 mass% and 2 to 6 mass% of high-solubility gypsum, which can be used for concrete mortar.

[0013] and US20130081557A1 discloses a system, method and / or composition of an environmentally friendly composite building material. In one aspect, a method includes providing a mixture of a pozzolan material and / or a kaolin clay with an activator solution to form a silico-aluminate cementitious material through a resulting geopolymerization process. The alumino-silicate cementitious material is in a paste form. The method also includes processing the silico-aluminate cementitious material to transform the silico-aluminate cementitious material into a powder form of the alumino-silicate cementitious material. The method further includes mixing the alumino-silicate cementitious material in the powder form with water to control the processability of the silico-aluminate cementitious material.

[0014] The above-mentioned alkali-activated cementitious materials based on slag-based high calcium system and fly ash-based low calcium system have certain defects in mechanical properties and high content of silica, resulting in high cost, which cannot truly realize the low cost of concrete. The present application uses silica fume (SFU) as an admixture, which is widely used in the concrete industry due to its good insulation and corrosion resistance. However, as far as the present application is concerned, there is almost no research on its application as a water reducing agent in alkali-activated cementitious materials. Therefore, the present application uses SFU as a water reducing agent to explore its effect, application and preparation method in alkali-activated cementitious materials based on slag-based high calcium system and fly ash-based low calcium system. SUMMARY

[0015] The present application aims to provide the use of silica fume as a water reducing agent and the corresponding alkali-activated cementitious material to solve the problems in the above background.

[0016] The object of the present application can be achieved by the following technical solutions.

[0017] In a first aspect, the present application provides a use of silica fume as a water reducing agent, the silica fume being used as a water reducing agent for a low calcium alkali activated cementitious material system and / or a high calcium alkali activated cementitious material system.

[0018] Further, the low calcium alkali activated cementitious material system is a fly ash based low calcium alkali activated cementitious material system and / or the high calcium alkali activated cementitious material system is a slag based high calcium alkali activated cementitious material system.

[0019] Further, the use of the silica fume as a water reducing agent in a fly ash based low calcium system alkali activated cementitious material and a slag based high calcium system alkali activated cementitious material.

[0020] Further, the silica fume (Silica fume) is amorphous (non-crystalline) SiO2, and the average particle size of the silica fume (Silica fume) is about 0.1-0.3 μm, and the specific surface area is in the range of 15-30 m 2 / g.

[0021] At room temperature, the silica fume (Silica fume) is insoluble in water but soluble in alkali, and can react with an aqueous hydrofluoric acid solution, and the differential thermal analysis curve of the silica fume shows that amorphous SiO2 is converted into crystalline SiO2 when heated to above 500℃, and the crystalline SiO2 is cristobalite and / or tridymite.

[0022] In a second aspect, the present application discloses a fly ash based low calcium system alkali activated cementitious material; the alkali activated cementitious material is prepared from a water reducing agent, an alkali activated cementitious material precursor material-F fly ash, and an alkali solution.

[0023] Further, the water reducing agent can be selected from one or more of a naphthalene series water reducing agent, borax, sodium hexametaphosphate, polycarboxylic acid, silica sand, and silica fume.

[0024] Further, the water reducing agent is silica fume, the silica fume (Silica fume) is amorphous (non-crystalline) SiO2, and the average particle size of the silica fume (Silica fume) is about 0.1-0.3 μm, and the specific surface area is in the range of 15-30 m 2 / g.

[0025] At room temperature, the silica fume (Silica fume) is insoluble in water but soluble in alkali, and can react with an aqueous hydrofluoric acid solution, and the differential thermal analysis curve of the silica fume shows that amorphous SiO2 is converted into crystalline SiO2 when heated to above 500℃, and the crystalline SiO2 is cristobalite and / or tridymite.

[0026] The silica fume particle size distribution is shown in Figure 5, and the silica fume is active silica fume.

[0027] Further, the alkali solution includes a sodium silicate solution and a sodium hydroxide solution.

[0028] Further, the water reducing agent is 0.01-12 parts, the alkali-activated cementitious precursor material-F class fly ash is 80-150 parts, the sodium silicate solution is 20-35 parts, and the sodium hydroxide solution is 8-15 parts, in terms of mass parts; preferably, the water reducing agent is 0.5-8 parts, the alkali-activated cementitious precursor material-F class fly ash is 95-105 parts, the sodium silicate solution is 25-30 parts, and the sodium hydroxide solution is 9-12 parts; more preferably, the water reducing agent is 0.5-6 parts, the alkali-activated cementitious precursor material-F class fly ash is 100 parts, the sodium silicate solution is 27.1 parts, and the sodium hydroxide solution is 10.9 parts; more preferably, the water reducing agent is 2-5 parts, the alkali-activated cementitious precursor material-F class fly ash is 100 parts, the sodium silicate solution is 27.1 parts, and the sodium hydroxide solution is 10.9 parts; more preferably, the water reducing agent is 3-4 parts, the alkali-activated cementitious precursor material-F class fly ash is 100 parts, the sodium silicate solution is 27.1 parts, and the sodium hydroxide solution is 10.9 parts.

[0029] Further, the F class fly ash is the only precursor material for preparing the alkali-activated cementitious material, and the mass percentage of each oxide in the chemical composition of the F class fly ash is: SiO2(54.17%), Al2O3(31.57%), Fe2O3(3.48%), CaO(2.98%), K2O(1.90%), TiO2(1.37%), MgO(1.22%), and others(3.31%), and the F class fly ash has a particle size distribution as shown in Figure 4 of the specification.

[0030] Further, the sodium silicate solution is used to configure an alkali-activated solution, and the sodium silicate solution has a SiO2 content of 27.3% and a Na2O content of 8.54% in the chemical composition, and a modulus of 3.3; the sodium hydroxide solution is used to configure an alkali-activated solution, and is a liquid with a concentration of 10-20M, which is configured by using sodium hydroxide solid particles with a purity of ≥96%; preferably, the concentration is 14M.

[0031] Further, the sodium hydroxide solution can be replaced by other alkali metal hydroxides such as potassium hydroxide and other high-solubility alkali metal hydroxides.

[0032] Further, the fly ash-based low-calcium system alkali-activated cementitious material has a spreadability of not less than 200mm, and has a compressive strength of up to 58MPa; and the compressive strength of the alkali-activated cementitious material can be increased without reducing the flowability.

[0033] In a third aspect, the application discloses a preparation method of a fly ash-based low-calcium system alkali-activated cementitious material, comprising the following steps:

[0034] (1) respectively according to the mass fraction, 0.01-12 parts of water reducing agent, 80-150 parts of alkali-activated cementitious precursor material-F fly ash, an electronic balance is used to weigh the materials, and the weighing balance accuracy of the materials is ±0.01 g;

[0035] (2) the weighed water reducing agent and alkali-activated cementitious precursor material-F fly ash are mixed and placed into a stirrer, and stirring is performed until uniform;

[0036] (3) according to 20-35 parts of sodium silicate solution, 8-15 parts of 10-20M sodium hydroxide solution, the materials are weighed, an electronic balance is used to weigh the materials, and the weighing balance accuracy of the materials is ±0.01 g; the chemical composition of the sodium silicate solution comprises 27.3% of SiO2 and 8.54% of Na2O, and the modulus is 3.3;

[0037] (4) the alkaline solution is prepared, the sodium silicate solution in step (3) and the 10-20M sodium hydroxide solution are mixed and stirred uniformly;

[0038] (5) the alkaline solution prepared in step (4) is poured into the mixed fly ash and powdered water reducing agent in step (2), and a stirrer is used to stir at a speed of 5 levels for 3 min until a completely uniform paste appears.

[0039] Further, after step (5), the following steps are further included:

[0040] (6) a cement mortar fluidity tester (referred to as a jump table) is used to test the fluidity of the paste alkali-activated cementitious material prepared in step (5) according to the ASTM C230 cement mortar fluidity determination method;

[0041] (7) the alkali-activated cementitious material test block is prepared by selecting the best fluidity content, and the compressive strength is tested.

[0042] Further, the water reducing agent is silica fume, the silica fume powder is spherical white powder, the purity is >99%, and the particle size distribution is as shown in FIG. 5.

[0043] Further, the water reducing agent is 0.5-8 parts, the alkali-activated cementitious precursor material-F fly ash is 95-105 parts, the sodium silicate solution is 25-30 parts, and the sodium hydroxide solution is 9-12 parts.

[0044] Further, the water reducing agent is 0.5-6 parts, the alkali-activated cementitious precursor material-F class fly ash is 100 parts, the sodium silicate solution is 27.1 parts, and the 10-20M sodium hydroxide solution is 10.9 parts.

[0045] Further, the F class fly ash is the only precursor material for preparing the alkali-activated cementitious material, and the mass percentage of each oxide in the chemical composition of the F class fly ash is: SiO2(54.17%), Al2O3(31.57%), Fe2O3(3.48%), CaO(2.98%), K2O(1.90%), TiO2(1.37%), MgO(1.22%), and others(3.31%), and the F class fly ash has a particle size distribution as shown in FIG. 4 of the specification.

[0046] Further, the sodium silicate solution is used to configure an alkali-activated solution, and the sodium silicate solution has a SiO2 content of 27.3% and a Na2O content of 8.54% in the chemical composition, and a modulus of 3.3; the sodium hydroxide solution is used to configure an alkali-activated solution, and is a liquid with a concentration of 10-20M, which is configured by using solid particles of sodium hydroxide with a purity of ≥96%; preferably, the concentration is 14M.

[0047] In a fourth aspect, the application claims the use of silica fume as a water reducing agent for a fly ash-based low-calcium system alkali-activated cementitious material, and the fly ash in the fly ash-based low-calcium system alkali-activated cementitious material is a F class fly ash.

[0048] Further, the fly ash-based low-calcium system alkali-activated cementitious material is the fly ash-based low-calcium system alkali-activated cementitious material of the second aspect of the application.

[0049] In a fifth aspect, the application provides a slag-based high-calcium system alkali-activated cementitious material using silica fume as a water reducing agent; the alkali-activated cementitious material is prepared from the following materials: a water reducing agent, an alkali-activated cementitious precursor material-S95 grade slag, and an alkali solution.

[0050] Further, the water reducing agent is silica fume, the silica fume (Silica fume) is amorphous (non-crystalline) SiO2, the average particle size of the silica fume (Silica fume) is about 0.1-0.3μm, and the specific surface area is in the range of 15-30m 2 / g;

[0051] At room temperature, the silica fume (Silica fume) is insoluble in water but soluble in alkali, and can react with an aqueous hydrofluoric acid solution, and the differential thermal analysis curve of the silica fume shows that the amorphous SiO2 is converted into crystalline SiO2 when heated to higher than 500℃, and the crystalline SiO2 is cristobalite and / or tridymite.

[0052] The silica fume particle size distribution is shown in Figure 5, and the silica fume is active silica fume.

[0053] Further, the alkali solution comprises a sodium silicate solution and a sodium hydroxide solution.

[0054] Further, the water reducing agent is 0.01-12 parts, the alkali-activated cementitious precursor material-S95 grade slag is 80-150 parts, the sodium silicate solution is 8-20 parts, and the sodium hydroxide solution is 14-28 parts, in terms of mass parts.

[0055] Preferably, the water reducing agent is 0.5-8 parts, the alkali-activated cementitious precursor material-S95 grade slag is 95-105 parts, the sodium silicate solution is 10-16 parts, and the sodium hydroxide solution is 16-22 parts.

[0056] More preferably, the water reducing agent is 0.5-6 parts, the alkali-activated cementitious precursor material-S95 grade slag is 100 parts, the sodium silicate solution is 14.6 parts, and the sodium hydroxide solution is 20.4 parts.

[0057] More preferably, the water reducing agent is 2-5 parts, the alkali-activated cementitious precursor material-S95 grade slag is 100 parts, the sodium silicate solution is 14.6 parts, and the sodium hydroxide solution is 20.4 parts.

[0058] More preferably, the water reducing agent is 3-4 parts, the alkali-activated cementitious precursor material-S95 grade slag is 100 parts, the sodium silicate solution is 14.6 parts, and the sodium hydroxide solution is 20.4 parts.

[0059] Further, the alkali-activated cementitious precursor material-S95 grade slag is the only precursor material for preparing the alkali-activated cementitious material, and the mass percentage of each oxide in the chemical composition is: CaO (40.43%), SiO2 (30.46%), Al2O3 (15.81%), MgO (9.42%), Fe2O3 (0.281%), K2O (0.423%), TiO2 (0.673%), MnO (0.52%), Na2O (0.499%), S (1.16%), SrO (0.0549%), Cl (0.0467%), ZrO2 (0.0391%), BaO (0.0389%), P2O5 (0.017%), V2O5 (0.0084%), Y2O3 (0.0083%), CeO2 (0.0069%), and CuO (0.0012%).

[0060] Further, the sodium silicate solution is used to configure the alkali-activated solution, the chemical composition of the sodium silicate solution is that SiO2 accounts for 27.3%, Na2O accounts for 8.54%, and the modulus is 3.3; the sodium hydroxide solution is used to configure the alkali-activated solution, and is configured by using sodium hydroxide solid particles with a purity of ≥96%, wherein the sodium hydroxide particles are 1.8 parts, and the distilled water is 18.6 parts.

[0061] Further, the sodium hydroxide solution can be replaced by other alkali metal hydroxides such as potassium hydroxide and other high-solubility alkali metal hydroxides.

[0062] Further, the fluidity of the slag-based high-calcium system alkali-activated cementitious material has an expansion degree of not less than 236 mm, and the compressive strength can reach 104.6 MPa; the compressive strength of the alkali-activated cementitious material can be improved without reducing the fluidity.

[0063] In a sixth aspect, the application discloses a preparation method of a slag-based high-calcium system alkali-activated cementitious material using silica fume as a water reducing agent, comprising the following steps:

[0064] (1) The water reducing agent, the alkali-activated cementitious material precursor material-S95 grade slag, and the sodium hydroxide solution are weighed according to the mass fraction, respectively, 0.01-12 parts, 80-150 parts, and 14-28 parts, respectively, and an electronic balance is used to weigh the materials, and the weighing balance accuracy of the materials is ±0.01 g;

[0065] (2) The weighed water reducing agent and alkali-activated cementitious material precursor material-S95 grade slag are mixed and put into a stirrer, and stirred until uniform;

[0066] (3) The sodium silicate solution and the sodium hydroxide solution are weighed according to the mass fraction, respectively, 8-20 parts and 14-28 parts, respectively, and an electronic balance is used to weigh the materials, and the weighing balance accuracy of the materials is ±0.01 g; the chemical composition of the sodium silicate solution is that SiO2 accounts for 27.3%, Na2O accounts for 8.54%, and the modulus is 3.3;

[0067] (4) The alkali solution is prepared, and the sodium silicate solution and the sodium hydroxide solution in step (3) are mixed and stirred uniformly;

[0068] (5) The alkali solution configured in step (4) is poured into the mixed alkali-activated cementitious material precursor material-S95 grade slag and the powdered water reducing agent in step (2), and a stirrer is used to stir at a speed of 5 for 3 min until a completely uniform paste appears.

[0069] Further, the following steps are further included after step (5):

[0070] (6) Using a cement mortar flow tester (referred to as a jump table), the paste-like alkali-activated cementitious material prepared in step (5) is tested for flowability according to the ASTM C230 cement mortar flow test method;

[0071] (7) The alkali-activated cementitious material with the best flowability is selected to prepare a test block, and the compressive strength is tested.

[0072] Further, the water reducing agent is silica fume, which is a spherical white powder with a purity of > 99%, and a particle size distribution as shown in FIG. 5. The silica fume is active silica fume.

[0073] Further, the water reducing agent is 0.01-12 parts by mass, the alkali-activated cementitious material precursor material-S95 grade slag is 80-150 parts by mass, the sodium silicate solution is 8-20 parts by mass, and the sodium hydroxide solution is 14-28 parts by mass.

[0074] Preferably, the water reducing agent is 0.5-8 parts, the alkali-activated cementitious material precursor material-S95 grade slag is 95-105 parts, the sodium silicate solution is 10-16 parts, and the sodium hydroxide solution is 16-22 parts.

[0075] More preferably, the water reducing agent is 0.5-6 parts, the alkali-activated cementitious material precursor material-S95 grade slag is 100 parts, the sodium silicate solution is 14.6 parts, and the sodium hydroxide solution is 20.4 parts.

[0076] More preferably, the water reducing agent is 2-5 parts, the alkali-activated cementitious material precursor material-S95 grade slag is 100 parts, the sodium silicate solution is 14.6 parts, and the sodium hydroxide solution is 20.4 parts.

[0077] More preferably, the water reducing agent is 3-4 parts, the alkali-activated cementitious material precursor material-S95 grade slag is 100 parts, the sodium silicate solution is 14.6 parts, and the sodium hydroxide solution is 20.4 parts.

[0078] Further, the alkali-activated cementitious material precursor material-S95 grade slag is the only precursor material for preparing the alkali-activated cementitious material, and the mass percentage of each oxide in the chemical composition is: CaO (40.43%), SiO2 (30.46%), Al2O3 (15.81%), MgO (9.42%), Fe2O3 (0.281%), K2O (0.423%), TiO2 (0.673%), MnO (0.52%), Na2O (0.499%), S (1.16%), SrO (0.0549%), Cl (0.0467%), ZrO2 (0.0391%), BaO (0.0389%), P2O5 (0.017%), V2O5 (0.0084%), Y2O3 (0.0083%), CeO2 (0.0069%), CuO (0.0012%), and the alkali-activated cementitious material precursor material-S95 grade slag has a particle size distribution as shown in FIG. 4 of the specification.

[0079] Further, the sodium silicate solution is used to configure an alkali-activated solution, and the mass percentage of SiO2 in the chemical composition of the sodium silicate solution is 27.3%, and the mass percentage of Na2O is 8.54%, and the modulus is 3.3; the sodium hydroxide solution is used to configure an alkali-activated solution, and the sodium hydroxide solution is configured by using sodium hydroxide solid particles with a purity of ≥96%, and the concentration of the sodium hydroxide particles is 1.8 parts, and the concentration of the distilled water is 18.6 parts.

[0080] In a seventh aspect, the application discloses a use of silica ash as a water reducing agent of a slag-based high-calcium system alkali-activated cementitious material, and the slag in the slag-based high-calcium system alkali-activated cementitious material is S95 grade slag.

[0081] Further, the slag-based high-calcium system alkali-activated cementitious material is the slag-based high-calcium system alkali-activated cementitious material of the fifth aspect of the application.

[0082] Advantages of the application:

[0083] (1) Silica ash is found to be used as a water reducing agent of a fly ash-based low-calcium system alkali-activated cementitious material and a slag-based high-calcium system alkali-activated cementitious material for the first time.

[0084] (2) Compared with several other relatively mature high-efficiency water reducing agents (naphthalene series, polycarboxylic acid, borax, and sodium hexametaphosphate), silica ash shows better effects in improving the flow performance of a fly ash-based alkali-activated cementitious material, and the flowability can be improved by 40.8% compared with other water reducing agents.

[0085] (3) Compared with several other relatively mature high-efficiency water reducing agents (naphthalene series, polycarboxylic acid, borax, and sodium hexametaphosphate), silica ash shows better effects in improving the mechanical properties of a fly ash-based alkali-activated cementitious material, and the compressive strength can reach 68.3 MPa.

[0086] (4) Compared with other several relatively mature high-efficient water-reducing agents (naphthalene series, polycarboxylic acid, borax, sodium hexametaphosphate), the silica ash shows better effect in improving the flowability of the slag-based high-calcium system alkali-activated cementitious material. The flowability can be improved by 50% at 3% addition amount of the other water-reducing agents.

[0087] (5) Compared with other several relatively mature high-efficient water-reducing agents (naphthalene series, polycarboxylic acid, borax, sodium hexametaphosphate), the silica ash shows better effect in improving the mechanical property of the slag-based high-calcium system alkali-activated cementitious material. The compressive strength can be improved to 70.7 MPa at a suitable addition amount. BRIEF DESCRIPTION OF DRAWINGS

[0088] The application will be further described below in combination with the drawings.

[0089] Fig. 1 is a preparation flow chart of the fly ash-based low-calcium system alkali-activated cementitious material of the application;

[0090] Fig. 2 is a flowability test result chart of the fly ash-based low-calcium system alkali-activated cementitious material of the application;

[0091] Fig. 3 is a compressive strength test result chart of the fly ash-based low-calcium system alkali-activated cementitious material of the application;

[0092] Fig. 4 is a fly ash particle size distribution chart of the application;

[0093] Fig. 5 is a scanning electron microscope image of each raw material of the application;

[0094] Fig. 6 is a preparation flow chart of the slag-based high-calcium system alkali-activated cementitious material of the application;

[0095] Fig. 7 is a flowability test result chart of the slag-based high-calcium system alkali-activated cementitious material of the application;

[0096] Fig. 8 is a compressive strength test result chart of the slag-based high-calcium system alkali-activated cementitious material of the application;

[0097] Fig. 9 is a S95 grade slag particle size distribution chart of the application. DETAILED DESCRIPTION

[0098] The technical solutions in the embodiments of the application will be apparently and completely described below in combination with the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0099] In specific embodiments, the silica fume is amorphous (non-crystalline) SiO2, the average particle size of the silica fume is about 0.1-0.3 μm, and the specific surface area is in the range of 15-30 m 2 / g.

[0100] At room temperature, the silica fume is insoluble in water but soluble in alkali, and can react with aqueous hydrofluoric acid. The differential thermal analysis curve of the silica fume shows that the amorphous SiO2 is converted into crystalline SiO2 when heated to above 500℃, and the crystalline SiO2 is cristobalite and / or tridymite.

[0101] The particle size distribution of the silica fume is shown in FIG. 5. The silica fume is active silica fume, which is purchased from Kefeng Metallurgical Company and is a spherical white powder with a purity of >99%.

[0102] The silica sand is inert silica sand, which is purchased from Bishui New Material Company and is a white spherical powder with a purity of >99%.

[0103] A fly ash-based low-calcium system alkali-activated cementitious material is formulated according to the following mass parts: (1) F-class fly ash 100 parts; (2) sodium silicate solution 27.1 parts; (3) sodium hydroxide solution (14M) 10.9 parts.

[0104] The particle size distribution of the F-class fly ash is shown in FIG. 4. The mass percentages of oxides in the chemical composition of the F-class fly ash are: SiO2 (54.17%), Al2O3 (31.57%), Fe2O3 (3.48%), CaO (2.98%), K2O (1.90%), TiO2 (1.37%), MgO (1.22%), and others (3.31%).

[0105] The sodium silicate solution is produced by Jiashan County Yourui Refractory Material Co., Ltd., and the chemical composition of the sodium silicate solution contains 27.3% SiO2 and 8.54% Na2O, and the modulus is 3.3.

[0106] The sodium hydroxide solution is a liquid with a concentration of 14M, which is configured by using sodium hydroxide solid particles with a purity of ≥96%.

[0107] A preparation method of a fly ash-based low-calcium system alkali-activated cementitious material is shown in FIG. 1, which includes the following steps:

[0108] (1) According to 100 parts of fly ash, the materials are weighed using an electronic balance, and the weighing accuracy of the balance is ±0.01 g;

[0109] (2) 27.1 parts of sodium silicate solution, 10.9 parts of sodium hydroxide solution (14M) were weighed, the materials were weighed using an electronic balance, and the balance accuracy of the materials was ±0.01 g;

[0110] (3) An alkaline solution was prepared by mixing 27.1 parts of sodium silicate solution and 10.9 parts of sodium hydroxide solution (14M) and stirring uniformly;

[0111] (4) The alkaline solution prepared in step (3) was poured into the fly ash weighed in step (1), and a blender was used to stir at a speed of 5 for 3 min until a completely uniform paste appeared;

[0112] (5) The paste of alkaline-activated cementitious material prepared in step (5) was tested for fluidity using a cement mortar fluidity tester (referred to as a jump table) according to the ASTM C230 cement mortar fluidity test method.

[0113] Since the material used in the blank example is a fly ash-based low calcium system alkaline-activated cementitious material, it is named AAF.

[0114] Example 1: The components of the water reducing agent used in the low calcium system alkaline-activated cementitious material and their mass parts, test methods, and blank example are the same, except that silica fume is added as a water reducing agent, and the silica fume is 0.5 parts.

[0115] Among them, the silica fume is purchased from Kegong Metallurgical Company, which is a spherical white powder with a purity of >99%.

[0116] The above materials were tested according to the following steps to obtain a water reducing agent suitable for low calcium system alkaline-activated cementitious material, as shown in FIG. 1, which includes the following steps:

[0117] (1) 0.5 parts of silica fume and 100 parts of fly ash were weighed, and the materials were weighed using an electronic balance, and the balance accuracy of the materials was ±0.01 g;

[0118] (2) The weighed powdered water reducing agent was mixed with the alkaline-activated cementitious material precursor material-fly ash in a blender, and stirred at a speed of 2 for 1 min until uniform;

[0119] (3) 27.1 parts of sodium silicate solution, 10.9 parts of sodium hydroxide solution (14M) were weighed, the materials were weighed using an electronic balance, and the balance accuracy of the materials was ±0.01 g;

[0120] (4) An alkaline solution was prepared by mixing 27.1 parts of sodium silicate solution and 10.9 parts of sodium hydroxide solution (14M) and stirring uniformly;

[0121] (5) Pour the alkaline solution prepared in step (4) into the fly ash and powdered water-reducing agent mixed in step (2), and stir using a blender at a speed of 5 for 3 minutes until a completely uniform paste is obtained;

[0122] (6) The paste of the alkali-activated cementitious material prepared in step (5) is tested for fluidity using a cement mortar fluidity tester (referred to as a "jump table") according to the ASTM C230 cement mortar fluidity test method.

[0123] Since the water-reducing agent used in Example 1 is silica fume, and the dosage is 0.5%, it is named SFU-0.5%.

[0124] Example 2: The components of the water-reducing agent used in the low-calcium system alkali-activated cementitious material and their mass parts, test methods, and blank example are the same as in Example 1, and the test steps are the same as in Example 1, except that silica fume is added as a water-reducing agent, and the silica fume is 1 part.

[0125] Since the water-reducing agent used in Example 2 is silica fume, and the dosage is 1%, it is named SFU-1%.

[0126] Example 3: The components of the water-reducing agent used in the low-calcium system alkali-activated cementitious material and their mass parts, test methods, and blank example are the same as in Example 1, and the test steps are the same as in Example 1, except that silica fume is added as a water-reducing agent, and the silica fume is 2 parts.

[0127] Since the water-reducing agent used in Example 3 is silica fume, and the dosage is 2%, it is named SFU-2%.

[0128] Example 4: The components of the water-reducing agent used in the low-calcium system alkali-activated cementitious material and their mass parts, test methods, and blank example are the same as in Example 1, and the test steps are the same as in Example 1, except that silica fume is added as a water-reducing agent, and the silica fume is 3 parts.

[0129] Since the water-reducing agent used in Example 4 is silica fume, and the dosage is 3%, it is named SFU-3%.

[0130] Example 5: The components of the water-reducing agent used in the low-calcium system alkali-activated cementitious material and their mass parts, test methods, and blank example are the same as in Example 1, and the test steps are the same as in Example 1, except that silica fume is added as a water-reducing agent, and the silica fume is 4 parts.

[0131] Since the water-reducing agent used in Example 5 is silica fume, and the dosage is 4%, it is named SFU-4%.

[0132] Example 6: The components of the water reducing agent used in the low calcium system alkali-activated cementitious material and its mass parts, test method and blank example are the same as those in Example 1, and the test steps are the same as those in Example 1, the difference is that silica fume is added as a water reducing agent, and the silica fume is 5 parts.

[0133] Since the water reducing agent used in Example 6 is silica fume, the dosage is 5%, so it is named SFU-5%.

[0134] Example 7: The components of the water reducing agent used in the low calcium system alkali-activated cementitious material and its mass parts, test method and blank example are the same as those in Example 1, and the test steps are the same as those in Example 1, the difference is that silica fume is added as a water reducing agent, and the silica fume is 6 parts.

[0135] Since the water reducing agent used in Example 7 is silica fume, the dosage is 6%, so it is named SFU-6%.

[0136] Comparative Example 1: The mass parts of the water reducing agent used in the low calcium system alkali-activated cementitious material and the test steps and methods are the same as those in Example 1, the difference is that the silica fume is replaced by a naphthalene-based water reducing agent.

[0137] Among them, the naphthalene-based water reducing agent is purchased from Shanghai Chenqi Chemical Technology Co., Ltd., the model is CQJ-NX, and the appearance is brown yellow powder.

[0138] Since the water reducing agent used in Comparative Example 1 is a naphthalene-based water reducing agent, the dosage is 0.5%, so it is named N-0.5%.

[0139] Comparative Example 2: The mass parts of the water reducing agent used in the low calcium system alkali-activated cementitious material and the test steps and methods are the same as those in Example 2, the difference is that the silica fume is replaced by a naphthalene-based water reducing agent.

[0140] Since the water reducing agent used in Comparative Example 2 is a naphthalene-based water reducing agent, the dosage is 1%, so it is named N-1%.

[0141] Comparative Example 3: The mass parts of the water reducing agent used in the low calcium system alkali-activated cementitious material and the test steps and methods are the same as those in Example 3, the difference is that the silica fume is replaced by a naphthalene-based water reducing agent.

[0142] Since the water reducing agent used in Comparative Example 3 is a naphthalene-based water reducing agent, the dosage is 2%, so it is named N-2%.

[0143] Comparative Example 4: The mass parts of the water reducing agent used in the low calcium system alkali-activated cementitious material and the test steps and methods are the same as those in Example 4, the difference is that the silica fume is replaced by a naphthalene-based water reducing agent.

[0144] Since the water reducing agent used in Comparative Example 4 is a naphthalene series water reducing agent, and the dosage is 3%, it is named N-3%.

[0145] Comparative Example 5: The water reducing agent used in the low calcium system alkali activated cementitious material in this example is the same as in Example 5, except that the silica ash is replaced by a naphthalene series water reducing agent.

[0146] Since the water reducing agent used in Comparative Example 5 is a naphthalene series water reducing agent, and the dosage is 4%, it is named N-4%.

[0147] Comparative Example 6: The water reducing agent used in the low calcium system alkali activated cementitious material in this example is the same as in Example 6, except that the silica ash is replaced by a naphthalene series water reducing agent.

[0148] Since the water reducing agent used in Comparative Example 6 is a naphthalene series water reducing agent, and the dosage is 5%, it is named N-5%.

[0149] Comparative Example 7: The water reducing agent used in the low calcium system alkali activated cementitious material in this example is the same as in Example 7, except that the silica ash is replaced by a naphthalene series water reducing agent.

[0150] Since the water reducing agent used in Comparative Example 7 is a naphthalene series water reducing agent, and the dosage is 6%, it is named N-6%.

[0151] Comparative Example 8: The water reducing agent used in the low calcium system alkali activated cementitious material in this example is the same as in Example 1, except that the silica ash is replaced by borax.

[0152] Among them, borax is purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd., and its chemical formula is Na2B4O7·10H2O, which is a colorless transparent crystalline powder.

[0153] Since the water reducing agent used in Comparative Example 8 is borax, and the dosage is 0.5%, it is named B-0.5%.

[0154] Comparative Example 9: The water reducing agent used in the low calcium system alkali activated cementitious material in this example is the same as in Example 2, except that the silica ash is replaced by borax.

[0155] Since the water reducing agent used in Comparative Example 9 is borax, and the dosage is 1%, it is named B-1%.

[0156] Comparative Example 10: The water reducing agent used in the low calcium system alkali activated cementitious material in this example is the same as in Example 3, except that the silica ash is replaced by borax.

[0157] Since the water reducing agent used in Comparative Example 10 is borax, and the dosage is 2%, it is named B-2%.

[0158] Comparative Example 11: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is borax, and the dosage is 3%, it is named B-3%.

[0159] Comparative Example 11: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is borax, and the dosage is 3%, it is named B-3%.

[0160] Comparative Example 12: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is borax, and the dosage is 4%, it is named B-4%.

[0161] Comparative Example 11: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is borax, and the dosage is 3%, it is named B-3%.

[0162] Comparative Example 13: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is borax, and the dosage is 5%, it is named B-5%.

[0163] Comparative Example 11: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is borax, and the dosage is 3%, it is named B-3%.

[0164] Comparative Example 14: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is borax, and the dosage is 6%, it is named B-6%.

[0165] Comparative Example 11: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is borax, and the dosage is 3%, it is named B-3%.

[0166] Comparative Example 15: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is sodium hexametaphosphate, and the dosage is 0.5%, it is named SH-0.5%.

[0167] Among them, sodium hexametaphosphate is produced by Xilong Chemical Co., Ltd., and is colorless transparent glass flake or microparticle crystal.

[0168] Comparative Example 11: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is borax, and the dosage is 3%, it is named B-3%.

[0169] Comparative Example 16: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is sodium hexametaphosphate, and the dosage is 1%, it is named SH-1%.

[0170] Since the water reducing agent used in Comparative Example 16 is sodium hexametaphosphate, the dosage is 1%, so it is named SH-1%.

[0171] Comparative Example 17: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is the same as in Example 3, except that the silica ash is replaced by sodium hexametaphosphate.

[0172] Since the water reducing agent used in Comparative Example 17 is sodium hexametaphosphate, the dosage is 2%, so it is named SH-2%.

[0173] Comparative Example 18: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is the same as in Example 4, except that the silica ash is replaced by sodium hexametaphosphate.

[0174] Since the water reducing agent used in Comparative Example 18 is sodium hexametaphosphate, the dosage is 3%, so it is named SH-3%.

[0175] Comparative Example 19: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is the same as in Example 5, except that the silica ash is replaced by sodium hexametaphosphate.

[0176] Since the water reducing agent used in Comparative Example 19 is sodium hexametaphosphate, the dosage is 4%, so it is named SH-4%.

[0177] Comparative Example 20: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is the same as in Example 6, except that the silica ash is replaced by sodium hexametaphosphate.

[0178] Since the water reducing agent used in Comparative Example 20 is sodium hexametaphosphate, the dosage is 5%, so it is named SH-5%.

[0179] Comparative Example 21: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is the same as in Example 7, except that the silica ash is replaced by sodium hexametaphosphate.

[0180] Since the water reducing agent used in Comparative Example 21 is sodium hexametaphosphate, the dosage is 6%, so it is named SH-6%.

[0181] Comparative Example 22: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is the same as in Example 1, except that the silica ash is replaced by polycarboxylic acid.

[0182] The polycarboxylic acid used in this example is a white solid powder, purchased from Shanghai Chenqi Chemical Technology Co., Ltd., with the brand name of Sika and the model number 540P.

[0183] Since the water reducing agent used in Comparative Example 22 is polycarboxylic acid, the dosage is 0.5%, and it is named PC-0.5%.

[0184] Comparative Example 23: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is polycarboxylic acid, and the dosage is 1%, and it is named PC-1%.

[0185] Since the water reducing agent used in Comparative Example 23 is polycarboxylic acid, the dosage is 1%, and it is named PC-1%.

[0186] Comparative Example 24: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is polycarboxylic acid, and the dosage is 2%, and it is named PC-2%.

[0187] Since the water reducing agent used in Comparative Example 24 is polycarboxylic acid, the dosage is 2%, and it is named PC-2%.

[0188] Comparative Example 25: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is polycarboxylic acid, and the dosage is 3%, and it is named PC-3%.

[0189] Since the water reducing agent used in Comparative Example 25 is polycarboxylic acid, the dosage is 3%, and it is named PC-3%.

[0190] Comparative Example 26: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is polycarboxylic acid, and the dosage is 4%, and it is named PC-4%.

[0191] Since the water reducing agent used in Comparative Example 26 is polycarboxylic acid, the dosage is 4%, and it is named PC-4%.

[0192] Comparative Example 27: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is polycarboxylic acid, and the dosage is 5%, and it is named PC-5%.

[0193] Since the water reducing agent used in Comparative Example 27 is polycarboxylic acid, the dosage is 5%, and it is named PC-5%.

[0194] Comparative Example 28: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is polycarboxylic acid, and the dosage is 6%, and it is named PC-6%.

[0195] Since the water reducing agent used in Comparative Example 28 is polycarboxylic acid, the dosage is 6%, and it is named PC-6%.

[0196] Comparative Example 29: The water reducing agent used in the low calcium system alkali-activated cementitious material of this example was prepared in the same manner as in Example 1, except that the silica fume was replaced with silica sand.

[0197] The silica sand was purchased from Bishui New Material Co. Ltd. and had a purity of >99% and was a white spherical powder.

[0198] The water reducing agent used in Comparative Example 29 was silica sand and was added at a dosage of 0.5% and was designated SFL-0.5%.

[0199] Comparative Example 30: The water reducing agent used in the low calcium system alkali-activated cementitious material of this example was prepared in the same manner as in Example 2, except that the silica fume was replaced with silica sand.

[0200] The water reducing agent used in Comparative Example 30 was silica sand and was added at a dosage of 1% and was designated SFL-1%.

[0201] Comparative Example 31 : The water reducing agent used in the low calcium system alkali-activated cementitious material of this example was prepared in the same manner as in Example 3, except that the silica fume was replaced with silica sand.

[0202] The water reducing agent used in Comparative Example 31 was silica sand and was added at a dosage of 2% and was designated SFL-2%.

[0203] Comparative Example 32: The water reducing agent used in the low calcium system alkali-activated cementitious material of this example was prepared in the same manner as in Example 4, except that the silica fume was replaced with silica sand.

[0204] The water reducing agent used in Comparative Example 32 was silica sand and was added at a dosage of 3% and was designated SFL-3%.

[0205] Comparative Example 33: The water reducing agent used in the low calcium system alkali-activated cementitious material of this example was prepared in the same manner as in Example 5, except that the silica fume was replaced with silica sand.

[0206] The water reducing agent used in Comparative Example 33 was silica sand and was added at a dosage of 4% and was designated SFL-4%.

[0207] Comparative Example 34: The water reducing agent used in the low calcium system alkali-activated cementitious material of this example was prepared in the same manner as in Example 6, except that the silica fume was replaced with silica sand.

[0208] The water reducing agent used in Comparative Example 34 was silica sand and was added at a dosage of 5% and was designated SFL-5%.

[0209] Comparative Example 35: The water reducing agent used in the low calcium system alkali-activated cementitious material in this example is silica sand, and the mass parts, test steps and methods are the same as those in Example 7, except that the silica ash is replaced by silica sand.

[0210] The water reducing agent used in Comparative Example 35 is silica sand, and the dosage is 6%, so it is named SFL-6%.

[0211] A fly ash-based low calcium system alkali-activated cementitious material is formulated according to the following mass parts: (1) F-class fly ash 100 parts; (2) sodium silicate solution 27.1 parts; (3) sodium hydroxide solution (14M) 10.9 parts.

[0212] The F-class fly ash has a particle size distribution as shown in Figure 4, and the mass percentages of oxides in its chemical composition are: SiO2 (54.17%), Al2O3 (31.57%), Fe2O3 (3.48%), CaO (2.98%), K2O (1.90%), TiO2 (1.37%), MgO (1.22%), and others (3.31%).

[0213] The sodium silicate solution is produced by Jiashan County Yourui Refractory Materials Co., Ltd., and its chemical composition contains 27.3% SiO2 and 8.54% Na2O, with a modulus of 3.3.

[0214] The sodium hydroxide solution is a liquid with a concentration of 14M, prepared from solid particles of sodium hydroxide with a purity of ≥96%.

[0215] A method for preparing a fly ash-based low calcium system alkali-activated cementitious material, as shown in Figure 1, includes the following steps:

[0216] (1) According to 100 parts of fly ash, weigh the materials using an electronic balance, and the weighing accuracy of the materials is ±0.01g;

[0217] (2) According to 27.1 parts of sodium silicate solution and 10.9 parts of sodium hydroxide solution (14M), weigh the materials using an electronic balance, and the weighing accuracy of the materials is ±0.01g;

[0218] (3) Prepare an alkaline solution by mixing and stirring 27.1 parts of sodium silicate solution and 10.9 parts of sodium hydroxide solution (14M) uniformly;

[0219] (4) Pour the alkaline solution prepared in step (3) into the fly ash weighed in step (1), and use a blender to stir at a speed of 5 for 3 minutes until a completely uniform paste is obtained;

[0220] (5) Put the paste of alkali-activated cementitious material stirred in step (4) into a plastic mold and manually vibrate to remove air bubbles.

[0221] (6) Put the alkali-activated cementitious material of step (5) into a high-low temperature test chamber for curing at a constant temperature of 75°C and 35% humidity for 72h.

[0222] (7) Use YAW-300C type automatic cement compressive and flexural strength tester to test the compressive strength of the alkali-activated cementitious material test block of step (6) according to the standard ASTM C 109-93. Select three test block strengths and take the average value.

[0223] Since the material used in the blank example is a fly ash-based low calcium system alkali-activated cementitious material, it is named AAF.

[0224] Example 8: The water reducing agent used in the low calcium system alkali-activated cementitious material of this example is the same as the blank example in terms of quality parts, test method and compressive strength test, the difference is that silica fume is added, and the amount of silica fume is 3 parts. This amount is selected according to the flowability test results to achieve the best flowability of silica fume (as shown in Figure 2).

[0225] Among them, the silica fume is purchased from Kegong Metallurgical Company, which is a spherical white powder with a purity of > 99%.

[0226] The above materials are prepared into a water reducing agent suitable for low calcium system alkali-activated cementitious material according to the following steps, as shown in Figure 1, including the following steps:

[0227] (1) According to the amount of 3 parts of silica fume and 100 parts of fly ash, the materials are weighed using an electronic balance, and the weighing accuracy of the materials is ± 0.01 g;

[0228] (2) Put the weighed powdered water reducing agent and alkali-activated cementitious material precursor material-fly ash into a blender and mix at 2 speed for 1 min until uniform;

[0229] (3) According to the amount of 27.1 parts of sodium silicate solution and 10.9 parts of sodium hydroxide solution (14M), the materials are weighed using an electronic balance, and the weighing accuracy of the materials is ± 0.01 g;

[0230] (4) Prepare an alkaline solution by mixing 27.1 parts of sodium silicate solution and 10.9 parts of sodium hydroxide solution (14M) and stirring evenly;

[0231] (5) Pour the alkaline solution prepared in step (4) into the fly ash + powdered water reducing agent mixed in step (2) and use a blender to stir at 5 speed for 3 min until a completely uniform paste appears;

[0232] (6) Put the paste-like alkali-activated cementitious material of step (4) into a plastic mold and manually vibrate to remove air bubbles.

[0233] (7) Put the alkali-activated cementitious material of step (5) into a high-low temperature test chamber for curing at a constant temperature of 75℃ and humidity of 35% for 72h.

[0234] (8) The cured alkali-activated cementitious material test blocks of step (6) are tested for compressive strength using a YAW-300C full-automatic cement compressive and flexural integrated machine according to the standard ASTM C 109-93. The strength of three test blocks is selected and averaged.

[0235] Since the water reducing agent used in the example is silica fume, the dosage is 3%, so it is named SFU-3%.

[0236] Comparative Example 36: The water reducing agent used in the low calcium system alkali-activated cementitious material of this example is the same as the blank example. The test steps are the same as the example, and the difference is that the silica fume is replaced by a naphthalene-based water reducing agent, and the naphthalene-based water reducing agent is 4 parts. This dosage is selected according to the fluidity test results to achieve the best fluidity of the naphthalene-based water reducing agent (as shown in Figure 2).

[0237] Among them, the naphthalene-based water reducing agent is purchased from Shanghai Chenqi Chemical Technology Co., Ltd., the model is CQJ-NX, and the appearance is brownish yellow powder.

[0238] Since the water reducing agent used in Comparative Example 36 is a naphthalene-based water reducing agent, the dosage is 4%, so it is named N-4%.

[0239] Comparative Example 37: The water reducing agent used in the low calcium system alkali-activated cementitious material of this example is the same as the blank example. The test steps are the same as the example, and the difference is that the silica fume is replaced by borax, and the borax is 4 parts. This dosage is selected according to the fluidity test results to achieve the best fluidity of the borax (as shown in Figure 2).

[0240] Among them, the borax is purchased from the National Pharmaceutical Group Chemical Reagent Co., Ltd., the chemical formula is Na2B4O7·10H2O, and it is a colorless transparent crystalline powder.

[0241] Since the water reducing agent used in Comparative Example 37 is borax, the dosage is 4%, so it is named B-4%.

[0242] Comparative Example 38: The water reducing agent used in the low calcium system alkali-activated cementitious material of this example is the same as the blank example. The test steps are the same as the example, and the difference is that the silica fume is replaced by sodium hexametaphosphate, and the sodium hexametaphosphate is 4 parts. This dosage is selected according to the fluidity test results to achieve the best fluidity of the sodium hexametaphosphate (as shown in Figure 2).

[0243] Among them, the sodium hexametaphosphate is produced by Xilong Chemical Co., Ltd., and it is anhydrous, colorless and transparent glass flake or microparticle crystal.

[0244] Since the water reducing agent used in Comparative Example 38 is sodium hexametaphosphate, the dosage is 4%, so it is named SH-4%.

[0245] Comparative Example 39: This embodiment relates to the water reducing agent used in the low calcium system alkali activated cementitious material, the dosage of each part, the test method and the blank example are the same. The test steps are the same as the examples, and the difference is that the silica ash is replaced by polycarboxylic acid, and the polycarboxylic acid is 0.5 parts. This dosage is selected according to the fluidity test results to select the polycarboxylic acid dosage to achieve the best fluidity (as shown in Figure 2).

[0246] Among them, the polycarboxylic acid is purchased from Shanghai Chenqi Chemical Technology Co., Ltd., Xica brand, model 540P, white solid powder.

[0247] Since the water reducing agent used in Comparative Example 39 is polycarboxylic acid, the polycarboxylic acid is 0.5%, so it is named PC-0.5%.

[0248] Figure 2 is the fluidity test result. As shown in Figure 2, the incorporation of silica ash as a high-efficiency water reducing agent makes the alkali-activated cementitious material exhibit the most obvious improvement in workability. At a dosage of 3%, it reaches the best spreadability of the alkali-activated cementitious material modified by the water reducing agent in the present application—222.5 mm, which is 40.8% higher than the alkali-activated cementitious material without the water reducing agent, which only has 158 mm. In comparison, the naphthalene-based water reducing agent, borax, sodium hexametaphosphate and polycarboxylic acid respectively increased by 40.2%, 37.6%, 13.3% and 0.8% at 4%, 4%, 4% and 0.5%. Silica sand has no effect at all.

[0249] According to the compressive strength test result of Figure 3, the incorporation of silica ash as a high-efficiency water reducing agent makes the alkali-activated cementitious material exhibit the most obvious improvement in mechanical properties. The compressive strength reaches 58 MPa at a dosage of 3%, which is 17.3% higher than the alkali-activated cementitious material without the water reducing agent. While the naphthalene-based water reducing agent only improves the mechanical properties by 11.7% at the best fluidity dosage. The rest all make the compressive strength of the alkali-activated cementitious material decrease.

[0250] A slag-based high-calcium system alkali-activated cementitious material is formulated according to the following mass parts: (1) S95 grade slag 100 parts; (2) sodium silicate solution 14.6 parts; (3) sodium hydroxide particles 1.8 parts; (4) distilled water 18.6 parts.

[0251] The S95 grade slag is the only precursor material for preparing the alkali-activated cementitious material, and the particle size distribution is shown in FIG. 4. The mass percentage of each oxide in the chemical composition is: CaO (40.43%), SiO2 (30.46%), Al2O3 (15.81%), MgO (9.42%), Fe2O3 (0.281%), K2O (0.423%), TiO2 (0.673%), MnO (0.52%), Na2O (0.499%), S (1.16%), SrO (0.0549%), Cl (0.0467%), ZrO2 (0.0391%), BaO (0.0389%), P2O5 (0.017%), V2O5 (0.0084%), Y2O3 (0.0083%), CeO2 (0.0069%), and CuO (0.0012%).

[0252] The sodium silicate solution is produced by Jiashan County Yourui Refractory Material Co., Ltd., and the chemical composition contains 27.3% of SiO2 and 8.54% of Na2O, and the modulus is 3.3.

[0253] The sodium hydroxide solution is prepared by using sodium hydroxide solid particles with a purity of ≥96%.

[0254] A preparation method of a slag-based high-calcium system alkali-activated cementitious material, as shown in FIG. 1, includes the following steps:

[0255] (1) According to 100 parts of fly ash, the materials are weighed using an electronic balance, and the weighing balance accuracy of the materials is ±0.01 g;

[0256] (2) According to 14.6 parts of sodium silicate solution, 1.8 parts of sodium hydroxide particles, and 18.6 parts of distilled water, the materials are weighed using an electronic balance, and the weighing balance accuracy of the materials is ±0.01 g;

[0257] (3) Prepare an alkaline solution by mixing and stirring 14.6 parts of sodium silicate solution, 1.8 parts of sodium hydroxide particles, and 18.6 parts of distilled water uniformly;

[0258] (4) Pour the alkaline solution prepared in step (3) into the slag weighed in step (1), and use a blender to stir at a speed of 5 for 1 min until a completely uniform paste appears;

[0259] (5) Use a cement mortar flow test instrument (referred to as a jump table) to test the flow of the paste alkali-activated cementitious material prepared in step (5) according to the ASTM C230 cement mortar flow test method.

[0260] Since the material used in this blank example is a slag-based high-calcium system alkali-activated cementitious material, it is named AAS.

[0261] Example 2-1

[0262] The components of the water reducing agent used in the high calcium system alkali-activated cementitious material of this example and their mass parts are the same as those of the blank example, and the difference lies in that silica fume is added as a water reducing agent. The silica fume is 0.5 parts.

[0263] The silica fume used in this example is purchased from the Metallurgical Company, which is a spherical white powder with a purity of > 99%.

[0264] The above materials are tested according to the following steps to obtain a water reducing agent suitable for high calcium system alkali-activated cementitious material, as shown in Figure 6, which includes the following steps:

[0265] (1) According to the active silica fume 0.5 parts, the slag 100 parts, the materials are weighed, and the electronic balance is used to weigh the materials, and the weighing balance accuracy of the materials is ± 0.01 g;

[0266] (2) The weighed powdered water reducing agent is mixed with the alkali-activated cementitious material precursor material-slag into a blender, and stirred at 2 levels for 1 min to be uniform;

[0267] (3) According to the sodium silicate solution 14.6 parts, the sodium hydroxide particles 1.8 parts, the distilled water 18.6 parts, the materials are weighed, and the electronic balance is used to weigh the materials, and the weighing balance accuracy of the materials is ± 0.01 g;

[0268] (4) Prepare the alkaline solution, mix and stir the sodium silicate solution 14.6 parts, the sodium hydroxide particles 1.8 parts, and the distilled water 18.6 parts uniformly;

[0269] (5) Pour the alkaline solution prepared in step (4) into the mixed slag + powdered water reducing agent in step (2), and use a blender to stir at level 5 for 3 min to obtain a completely uniform paste;

[0270] (6) Use the cement mortar fluidity tester (referred to as the jump table) to test the fluidity of the paste alkali-activated cementitious material prepared in step (5) according to the ASTM C230 cement mortar fluidity test method.

[0271] Since the water reducing agent used in Example 2-1 is silica fume, the dosage is 0.5%, so it is named 2-SFU-0.5%.

[0272] Example 2-2: The components of the water reducing agent used in the high calcium system alkali-activated cementitious material of this example and their mass parts are the same as those of the blank example, and the test steps are the same as those of Example 2-1, and the difference lies in that silica fume is added as a water reducing agent. The silica fume is 1 part.

[0273] Since the water reducing agent used in Example 2-2 is silica fume, and the dosage is 1%, it is named 2-SFU-1%.

[0274] Example 2-3: The components of the water reducing agent used in high calcium system alkali activated cementitious materials and their mass parts, test methods, and blank examples are the same as in Example 2-1, and the test steps are the same as in Example 2-1, except that silica fume is added as a water reducing agent, and the silica fume is 2 parts.

[0275] Since the water reducing agent used in Example 2-3 is silica fume, and the dosage is 2%, it is named 2-SFU-2%.

[0276] Example 2-4: The components of the water reducing agent used in high calcium system alkali activated cementitious materials and their mass parts, test methods, and blank examples are the same as in Example 2-1, and the test steps are the same as in Example 2-1, except that silica fume is added as a water reducing agent, and the silica fume is 3 parts.

[0277] Since the water reducing agent used in Example 2-4 is silica fume, and the dosage is 3%, it is named 2-SFU-3%.

[0278] Example 2-5: The components of the water reducing agent used in high calcium system alkali activated cementitious materials and their mass parts, test methods, and blank examples are the same as in Example 2-1, and the test steps are the same as in Example 2-1, except that silica fume is added as a water reducing agent, and the silica fume is 4 parts.

[0279] Since the water reducing agent used in Example 2-5 is silica fume, and the dosage is 4%, it is named 2-SFU-4%.

[0280] Example 2-6: The components of the water reducing agent used in high calcium system alkali activated cementitious materials and their mass parts, test methods, and blank examples are the same as in Example 2-1, and the test steps are the same as in Example 2-1, except that silica fume is added as a water reducing agent, and the silica fume is 5 parts.

[0281] Since the water reducing agent used in Example 2-6 is silica fume, and the dosage is 5%, it is named 2-SFU-5%.

[0282] Example 2-7: The components of the water reducing agent used in high calcium system alkali activated cementitious materials and their mass parts, test methods, and blank examples are the same as in Example 2-1, and the test steps are the same as in Example 2-1, except that silica fume is added as a water reducing agent, and the silica fume is 6 parts.

[0283] Since the water reducing agent used in Example 2-7 is silica fume, and the dosage is 6%, it is named 2-SFU-6%.

[0284] Comparative Example 2-1: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example is the same as in Example 2-1, except that the silica fume is replaced by a naphthalene-based water reducing agent.

[0285] The naphthalene-based water reducing agent is commercially available from Shanghai Chenqi Chemical Technology Co., Ltd. and has a model number of CQJ-NX and an appearance of brownish yellow powder.

[0286] The water reducing agent used in Comparative Example 2-1 is a naphthalene-based water reducing agent with an addition amount of 0.5%, and is therefore designated as 2-N-0.5%.

[0287] Comparative Example 2-2: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example is the same as in Example 2-2, except that the silica fume is replaced by a naphthalene-based water reducing agent.

[0288] The water reducing agent used in Comparative Example 2-2 is a naphthalene-based water reducing agent with an addition amount of 1%, and is therefore designated as 2-N-1%.

[0289] Comparative Example 2-3: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example is the same as in Example 2-3, except that the silica fume is replaced by a naphthalene-based water reducing agent.

[0290] The water reducing agent used in Comparative Example 2-3 is a naphthalene-based water reducing agent with an addition amount of 2%, and is therefore designated as 2-N-2%.

[0291] Comparative Example 2-4: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example is the same as in Example 2-4, except that the silica fume is replaced by a naphthalene-based water reducing agent.

[0292] The water reducing agent used in Comparative Example 2-4 is a naphthalene-based water reducing agent with an addition amount of 3%, and is therefore designated as 2-N-3%.

[0293] Comparative Example 2-5: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example is the same as in Example 2-5, except that the silica fume is replaced by a naphthalene-based water reducing agent.

[0294] The water reducing agent used in Comparative Example 2-5 is a naphthalene-based water reducing agent with an addition amount of 4%, and is therefore designated as 2-N-4%.

[0295] Comparative Example 2-6: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example is the same as in Example 2-6, except that the silica fume is replaced by a naphthalene-based water reducing agent.

[0296] Since the water reducing agent used in Comparative Example 2-6 is a naphthalene series water reducing agent, and the dosage is 5%, it is named 2-N-5%.

[0297] Comparative Example 2-7: The water reducing agent used in high calcium system alkali activated cementitious material in this embodiment is the same as in Example 2-7, the difference is that the silica ash is replaced by a naphthalene series water reducing agent.

[0298] Since the water reducing agent used in Comparative Example 2-7 is a naphthalene series water reducing agent, and the dosage is 6%, it is named 2-N-6%.

[0299] Comparative Example 2-8: The water reducing agent used in high calcium system alkali activated cementitious material in this embodiment is the same as in Example 2-1, the difference is that the silica ash is replaced by borax.

[0300] Among them, borax is purchased from National Pharmaceutical Group Chemical Reagent Co., Ltd., the chemical formula is Na2B4O7·10H2O, and it is a colorless transparent crystalline powder.

[0301] Since the water reducing agent used in Comparative Example 2-8 is borax, and the dosage is 0.5%, it is named 2-B-0.5%.

[0302] Comparative Example 2-9: The water reducing agent used in high calcium system alkali activated cementitious material in this embodiment is the same as in Example 2-2, the difference is that the silica ash is replaced by borax.

[0303] Since the water reducing agent used in Comparative Example 2-9 is borax, and the dosage is 1%, it is named 2-B-1%.

[0304] Comparative Example 2-10: The water reducing agent used in high calcium system alkali activated cementitious material in this embodiment is the same as in Example 2-3, the difference is that the silica ash is replaced by borax.

[0305] Since the water reducing agent used in Comparative Example 2-10 is borax, and the dosage is 2%, it is named 2-B-2%.

[0306] Comparative Example 2-11: The water reducing agent used in high calcium system alkali activated cementitious material in this embodiment is the same as in Example 2-4, the difference is that the silica ash is replaced by borax.

[0307] Since the water reducing agent used in Comparative Example 2-11 is borax, and the dosage is 3%, it is named 2-B-3%.

[0308] Comparative Example 2-12: The water reducing agent used in high calcium system alkali-activated cementitious material in this example is the same as that in Example 2-5, except that the silica fume is replaced by borax.

[0309] Since the water reducing agent used in Comparative Example 2-12 is borax, the dosage is 4%, and it is named 2-B-4%.

[0310] Comparative Example 2-13: The water reducing agent used in high calcium system alkali-activated cementitious material in this example is the same as that in Example 2-6, except that the silica fume is replaced by borax.

[0311] Since the water reducing agent used in Comparative Example 2-13 is borax, the dosage is 5%, and it is named 2-B-5%.

[0312] Comparative Example 2-14: The water reducing agent used in high calcium system alkali-activated cementitious material in this example is the same as that in Example 2-7, except that the silica fume is replaced by borax.

[0313] Since the water reducing agent used in Comparative Example 2-14 is borax, the dosage is 6%, and it is named 2-B-6%.

[0314] Comparative Example 2-15: The water reducing agent used in high calcium system alkali-activated cementitious material in this example is the same as that in Example 2-1, except that the silica fume is replaced by sodium hexametaphosphate.

[0315] Among them, sodium hexametaphosphate is produced by Xilong Chemical Company, and is colorless transparent glass flake or microparticle crystal.

[0316] Since the water reducing agent used in Comparative Example 2-15 is sodium hexametaphosphate, the dosage is 0.5%, and it is named 2-SH-0.5%.

[0317] Comparative Example 2-16: The water reducing agent used in high calcium system alkali-activated cementitious material in this example is the same as that in Example 2-2, except that the silica fume is replaced by sodium hexametaphosphate.

[0318] Since the water reducing agent used in Comparative Example 2-16 is sodium hexametaphosphate, the dosage is 1%, and it is named 2-SH-1%.

[0319] Comparative Example 2-17: The water reducing agent used in high calcium system alkali-activated cementitious material in this example is the same as that in Example 2-3, except that the silica fume is replaced by sodium hexametaphosphate.

[0320] Since the water reducing agent used in Comparative Example 2-17 is sodium hexametaphosphate, and the dosage is 2%, it is named 2-SH-2%.

[0321] Comparative Example 2-18: The water reducing agent used in high calcium system alkali activated cementitious material in this example is the same as in Example 2-4, except that the silica ash is replaced by sodium hexametaphosphate.

[0322] Since the water reducing agent used in Comparative Example 2-18 is sodium hexametaphosphate, and the dosage is 3%, it is named 2-SH-3%.

[0323] Comparative Example 2-19: The water reducing agent used in high calcium system alkali activated cementitious material in this example is the same as in Example 2-5, except that the silica ash is replaced by sodium hexametaphosphate.

[0324] Since the water reducing agent used in Comparative Example 2-19 is sodium hexametaphosphate, and the dosage is 4%, it is named 2-SH-4%.

[0325] Comparative Example 2-20: The water reducing agent used in high calcium system alkali activated cementitious material in this example is the same as in Example 2-6, except that the silica ash is replaced by sodium hexametaphosphate.

[0326] Since the water reducing agent used in Comparative Example 2-20 is sodium hexametaphosphate, and the dosage is 5%, it is named 2-SH-5%.

[0327] Comparative Example 2-21: The water reducing agent used in high calcium system alkali activated cementitious material in this example is the same as in Example 2-7, except that the silica ash is replaced by sodium hexametaphosphate.

[0328] Since the water reducing agent used in Comparative Example 2-21 is sodium hexametaphosphate, and the dosage is 6%, it is named 2-SH-6%.

[0329] Comparative Example 2-22: The water reducing agent used in high calcium system alkali activated cementitious material in this example is the same as in Example 2-1, except that the silica ash is replaced by polycarboxylic acid.

[0330] The polycarboxylic acid used in this example is purchased from Shanghai Chenqi Chemical Technology Co., Ltd., with the brand of Sika and the model number of 540P, which is a white solid powder.

[0331] Since the water reducing agent used in Comparative Example 2-22 is polycarboxylic acid, and the dosage is 0.5%, it is named 2-PC-0.5%.

[0332] Comparative Example 2-23: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example is the same as in Example 2-2, except that the silica fume is replaced by polycarboxylic acid.

[0333] The water reducing agent used in Comparative Example 2-23 is polycarboxylic acid, and the dosage is 1%, so it is named 2-PC-1%.

[0334] Comparative Example 2-24: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example is the same as in Example 2-3, except that the silica fume is replaced by polycarboxylic acid.

[0335] The water reducing agent used in Comparative Example 2-24 is polycarboxylic acid, and the dosage is 2%, so it is named 2-PC-2%.

[0336] Comparative Example 2-25: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example is the same as in Example 2-4, except that the silica fume is replaced by polycarboxylic acid.

[0337] The water reducing agent used in Comparative Example 2-25 is polycarboxylic acid, and the dosage is 3%, so it is named 2-PC-3%.

[0338] Comparative Example 2-26: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example is the same as in Example 2-5, except that the silica fume is replaced by polycarboxylic acid.

[0339] The water reducing agent used in Comparative Example 2-26 is polycarboxylic acid, and the dosage is 4%, so it is named 2-PC-4%.

[0340] Comparative Example 2-27: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example is the same as in Example 2-6, except that the silica fume is replaced by polycarboxylic acid.

[0341] The water reducing agent used in Comparative Example 2-27 is polycarboxylic acid, and the dosage is 5%, so it is named 2-PC-5%.

[0342] Comparative Example 2-28: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example is the same as in Example 2-7, except that the silica fume is replaced by polycarboxylic acid.

[0343] The water reducing agent used in Comparative Example 2-28 is polycarboxylic acid, and the dosage is 6%, so it is named 2-PC-6%.

[0344] Comparative Example 2-29: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example was prepared according to the same procedure as Example 2-1, except that the silica fume was replaced with silica sand.

[0345] The silica sand was purchased from Bishui New Material Co., Ltd. and had a purity of >99% and was a white spherical powder.

[0346] The water reducing agent used in Comparative Example 2-29 was silica sand and was added at a dosage of 0.5%, and was therefore designated as 2-SFL-0.5%.

[0347] Comparative Example 2-30: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example was prepared according to the same procedure as Example 2-2, except that the silica fume was replaced with silica sand.

[0348] The water reducing agent used in Comparative Example 2-30 was silica sand and was added at a dosage of 1%, and was therefore designated as 2-SFL-1%.

[0349] Comparative Example 2-31: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example was prepared according to the same procedure as Example 2-3, except that the silica fume was replaced with silica sand.

[0350] The water reducing agent used in Comparative Example 2-31 was silica sand and was added at a dosage of 2%, and was therefore designated as 2-SFL-2%.

[0351] Comparative Example 2-32: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example was prepared according to the same procedure as Example 2-4, except that the silica fume was replaced with silica sand.

[0352] The water reducing agent used in Comparative Example 2-32 was silica sand and was added at a dosage of 3%, and was therefore designated as 2-SFL-3%.

[0353] Comparative Example 2-33: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example was prepared according to the same procedure as Example 2-5, except that the silica fume was replaced with silica sand.

[0354] The water reducing agent used in Comparative Example 2-33 was silica sand and was added at a dosage of 4%, and was therefore designated as 2-SFL-4%.

[0355] Comparative Example 2-34: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example was prepared according to the same procedure as Example 2-6, except that the silica fume was replaced with silica sand.

[0356] The water reducing agent used in Comparative Example 2-34 was silica sand and was added at a dosage of 5%, and was therefore designated as 2-SFL-5%.

[0357] Comparative Examples 2-35: The water-reducing agent used in this example for alkaline-activated cementitious materials in high-calcium systems, the mass fractions, test steps and methods are the same as those in Examples 2-7, except that silica fume is replaced with silica sand.

[0358] Since the water-reducing agent used in Comparative Example 2-35 was silica sand at a dosage of 6%, it was named 2-SFL-6.

[0359] A slag-based high-calcium system alkali-activated cementitious material is formulated according to the following mass parts: (1) 100 parts of S95 grade slag; (2) 14.6 parts of sodium silicate solution; (3) 1.8 parts of sodium hydroxide particles; (4) 18.6 parts of distilled water.

[0360] Among them, the S95 grade slag is the only precursor material for preparing alkali-activated cementitious materials, and its particle size distribution is shown in Figure 4. The mass percentage of each oxide in its chemical composition is as follows: CaO (40.43%), SiO2 (30.46%), Al2O3 (15.81%), MgO (9.42%), Fe2O3 (0.281%), K2O (0.423%), TiO2 (0.673%), MnO (0.52%), Na2O (0.499%), S (1.16%), SrO (0.0549%), Cl (0.0467%), ZrO2 (0.0391%), BaO (0. 0389%), P2O5 (0.017%), V2O5 (0.0084%), Y2O3 (0.0083%), CeO2 (0.0069%), CuO (0.0012%).

[0361] The sodium silicate solution is produced by Jiashan Yourui Refractory Materials Co., Ltd., and its chemical composition includes 27.3% SiO2, 8.54% Na2O, and a modulus of 3.3.

[0362] The sodium hydroxide particles, which are used to prepare the alkaline activation solution, have a purity of ≥96% and were purchased from Tianjin Wind and Ship Company.

[0363] Distilled water is used to prepare the alkaline activation solution, provided by Putian Yuxin Water Treatment Equipment Co., Ltd.

[0364] A method for preparing an alkali-activated cementitious material based on high calcium slag, as shown in Figure 6, includes the following steps:

[0365] (1) Weigh the material according to 100 parts of slag using an electronic balance. The weighing accuracy of the balance is ±0.01g.

[0366] (2) According to the sodium silicate solution 14.6 parts, sodium hydroxide particles 1.8 parts, distilled water 18.6 parts, the materials are weighed, the electronic balance is used to weigh the materials, and the balance accuracy of the materials is ±0.01 g;

[0367] (3) Preparation of alkaline solution, mix sodium silicate solution 14.6 parts, sodium hydroxide particles 1.8 parts, distilled water 18.6 parts and stir evenly;

[0368] (4) Pour the alkaline solution prepared in step (3) into the slag weighed in step (1), and use a blender to stir at a speed of 5 for 1 min until a completely uniform paste appears;

[0369] (5) Put the paste alkaline activated cementitious material stirred in step (4) into a plastic mold and manually vibrate to squeeze out air bubbles.

[0370] (6) According to European standard European standard EN 196-1, the alkaline activated cementitious material of step (5) is placed in a constant room temperature (20±2℃) and 99% humidity standard curing room for curing for 28d.

[0371] (7) The alkaline activated cementitious material test block cured in step (6) is tested for compressive strength according to the standard ASTM C 109-93 using YAW-300C full-automatic cement compressive and flexural strength tester. Select three test block strengths and take the average value.

[0372] Since the materials used in the blank example are slag-based alkaline activated cementitious materials, they are named AAS.

[0373] Example 2-8: The water reducing agent for high calcium system alkaline activated cementitious materials involved in this example has the same mass parts, test method as the blank example, and the difference is that silica fume is added, and the silica fume is 3 parts. This dosage is selected according to the flowability test results to achieve the best fluidity of silica fume (as shown in Figure 7).

[0374] Among them, the silica fume is purchased from Kegong Metallurgical Company, which is spherical white powder with purity >99%.

[0375] The above materials are prepared into a water reducing agent suitable for high calcium system alkaline activated cementitious materials according to the following steps, as shown in Figure 6, which includes the following steps:

[0376] (1) According to the silica fume 0.5 parts, the slag 100 parts, the materials are weighed, the electronic balance is used to weigh the materials, and the balance accuracy of the materials is ±0.01 g;

[0377] (2) Put the weighed powdered water reducing agent and alkaline activated cementitious material precursor material-slag into a blender, stir at a speed of 2 for 1 min until uniform;

[0378] (3) Weighing the materials, using an electronic balance to weigh the materials, the balance accuracy of the materials is ±0.01 g;

[0379] (4) Preparing the alkaline solution, mixing and stirring evenly sodium silicate solution 14.6 parts, sodium hydroxide particles 1.8 parts, distilled water 18.6 parts;

[0380] (5) Pouring the alkaline solution prepared in step (4) into the mixed slag + powdered water reducing agent in step (2), using a blender to stir at 5 level speed for 3 min until a completely uniform paste appears;

[0381] (6) The paste of alkali-activated cementitious material stirred in step (5) is loaded into a plastic mold and manually vibrated to squeeze out air bubbles.

[0382] (7) According to European standard European standard EN 196-1, the alkali-activated cementitious material of step (6) is placed in a constant room temperature (20±2℃) and 99% humidity standard curing room for curing for 28d.

[0383] (8) The alkali-activated cementitious material test block cured in step (7) is tested for compressive strength according to the standard ASTM C 109-93 using YAW-300C type full-automatic cement compressive and flexural integrated machine. Select three test block strengths and take the average value.

[0384] Since the water reducing agent used in the example is silica fume, the dosage is 3%, so it is named 2-SFU-3%.

[0385] Comparative Example 2-36: The water reducing agent used in the example is naphthalene series water reducing agent, the dosage is 2%, so it is named 2-N-2%.

[0386] Among them, the naphthalene series water reducing agent is purchased from Shanghai Chenqi Chemical Technology Co., Ltd., the model is CQJ-NX, and the appearance is brown yellow powder.

[0387] Comparative Example 2-36: The water reducing agent used in the example is naphthalene series water reducing agent, the dosage is 2%, so it is named 2-N-2%.

[0388] Comparative Example 2-37: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example is the same as that of the blank example. The test steps are the same as those of the examples, except that the silica fume is replaced by borax, and the borax is 5 parts. This dosage is selected according to the fluidity test results to achieve the best fluidity of borax (as shown in FIG. 7).

[0389] The borax used in Comparative Example 2-37 is purchased from the National Pharmaceutical Group Chemical Reagent Co., Ltd., and its chemical formula is Na2B4O7·10H2O, which is a colorless transparent crystalline powder.

[0390] Since the water reducing agent used in Comparative Example 2-37 is borax, and the dosage is 5%, it is named 2-B-5%.

[0391] Comparative Example 2-38: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example is the same as that of the blank example. The test steps are the same as those of the examples, except that the silica fume is replaced by sodium hexametaphosphate, and the sodium hexametaphosphate is 2 parts. This dosage is selected according to the fluidity test results to achieve the best fluidity of sodium hexametaphosphate (as shown in FIG. 7).

[0392] The sodium hexametaphosphate used in Comparative Example 2-38 is produced by Xilong Chemical Co., Ltd., and is anhydrous, colorless, transparent glass flakes or microcrystalline particles.

[0393] Since the water reducing agent used in Comparative Example 2-38 is sodium hexametaphosphate, and the dosage is 2%, it is named 2-SH-2%.

[0394] Comparative Example 2-39: The water reducing agent used in the high calcium system alkali-activated cementitious material of this example is the same as that of the blank example. The test steps are the same as those of the examples, except that the silica fume is replaced by polycarboxylic acid, and the polycarboxylic acid is 1 part. This dosage is selected according to the fluidity test results to achieve the best fluidity of polycarboxylic acid (as shown in FIG. 7).

[0395] The polycarboxylic acid used in Comparative Example 2-39 is purchased from Shanghai Chenqi Chemical Technology Co., Ltd., and is a white solid powder with a brand of Xica and a model number of 540P.

[0396] Since the water reducing agent used in Comparative Example 2-39 is polycarboxylic acid, and the dosage is 1%, it is named 2-PC-1%.

[0397] Figure 7 is the fluidity test results. As can be seen from the figure, the incorporation of silica fume as a high efficiency water reducing agent makes the alkali activated cementitious material exhibit the most obvious performance improvement. At 2% dosage, it reached the best spread of 236 mm in the invention about the water reducing agent modified alkali activated cementitious material, compared with the alkali activated cementitious material without water reducing agent only 181.5 mm, increased by 30%. In contrast, naphthalene series water reducing agent, borax, sodium hexametaphosphate and polycarboxylic acid increased by 9.7%, 15.7%, 5.8% and 1.9% respectively at 2%, 3%, 1% and 1%. Silica sand has no effect at all.

[0398] According to the compressive strength test results of Figure 8, the incorporation of silica fume as a high efficiency water reducing agent makes the high calcium system alkali activated cementitious material not only maintain the original mechanical properties, but also have a small amount of improvement. At 2% dosage, although the compressive strength is lower than that of slag alkali activated cementitious material at 1 day of curing, the compressive strength after 3 days is slightly improved compared with that of slag alkali activated cementitious material. The final 28d compressive strength reaches 104.6MPa. The rest all make the compressive strength of alkali activated cementitious material decrease.

[0399] The above has carried out the detailed description to one embodiment of the present application, but the content described is only the preferred embodiment of the present application, cannot be considered for limiting the scope of the present application. All equivalent changes and improvements made according to the scope of the present application should still belong to the patent coverage range of the present application.

Claims

1. Use of silica fume as a water reducing agent, characterized in that: The water reducing agent is used in a low calcium alkali activated cementitious material system and / or a high calcium alkali activated cementitious material system.

2. Use of silica fume as a water reducing agent according to claim 1, characterized in that: The low calcium alkali activated cementitious material system is a fly ash based low calcium alkali activated cementitious material system and / or the high calcium alkali activated cementitious material system is a slag based high calcium alkali activated cementitious material system.

3. Use of silica fume as a water reducing agent according to claim 2, wherein the fly ash in the low calcium system is a Class F fly ash, the Class F fly ash is the only precursor material for preparing the low calcium system alkali activated cementitious material, and the mass percentage of each oxide in the chemical composition of the Class F fly ash is: SiO2 is 54.17%, Al2O3 is 31.57%, Fe2O3 is 3.48%, CaO is 2.98%, K2O is 1.90%, TiO2 is 1.37%, MgO is 1.22%, and the rest is 3.31%.

4. Use of silica fume as a water reducing agent according to claim 2, wherein the S95 grade slag is the only precursor material for preparing the high calcium system alkali activated cementitious material, and the mass percentage of each oxide in the chemical composition of the S95 grade slag is: CaO is 40.43%, SiO2 is 30.46%, Al2O3 is 15.81%, MgO is 9.42%, Fe2O3 is 0.281%, K2O is 0.423%, TiO2 is 0.673%, MnO is 0.52%, Na2O is 0.499%, S is 1.16%, SrO is 0.0549%, Cl is 0.0467%, ZrO2 is 0.0391%, BaO is 0.0389%, P2O5 is 0.017%, V2O5 is 0.0084%, Y2O3 is 0.0083%, CeO2 is 0.0069%, and CuO is 0.0012%.

5. A fly ash-based low calcium system alkali-activated cementitious material with silica fume as a water-reducing agent, characterized in that: The alkali activated cementitious material is prepared from a water reducing agent, a Class F fly ash which is the only precursor material for the alkali activated cementitious material, and an alkali solution; the water reducing agent is silica fume.

6. A fly ash based low calcium system alkali activated cementitious material according to claim 5, characterised in that, The alkali solution comprises a sodium silicate solution and a sodium hydroxide solution, the water reducing agent is 0.01-12 parts by mass, the Class F fly ash which is the only precursor material for the alkali activated cementitious material is 80-150 parts, the sodium silicate solution is 20-35 parts, and the sodium hydroxide solution is 8-15 parts.

7. A fly ash based low calcium system alkali activated cementitious material with silica fume as a water reducing agent according to claim 6, characterised in that, The sodium silicate solution has a SiO2 content of 27.3% and a Na2O content of 8.54%, and a modulus of 3.3; the sodium hydroxide solution is a liquid with a concentration of 10-20M, which is prepared by using sodium hydroxide solid particles with a purity of ≥96%.

8. A fly ash based low calcium system alkali activated cementitious material with silica fume as a water reducing agent according to claim 6, characterised in that, The Class F fly ash is the only precursor material for preparing the alkali activated cementitious material, and the mass percentage of each oxide in the chemical composition of the Class F fly ash is: SiO2 is 54.17%, Al2O3 is 31.57%, Fe2O3 is 3.48%, CaO is 2.98%, K2O is 1.90%, TiO2 is 1.37%, MgO is 1.22%, and the rest is 3.31%.

9. A fly ash based low calcium system alkali activated cementitious material according to any one of claims 5-8 as a water reducer, characterised in that, The alkali activated cementitious material has an expansion degree of not less than 200mm.

10. A method of producing a fly ash based low calcium system alkali activated cementitious material as claimed in any one of claims 5 to 9 characterised in that, The method comprises the following steps: The method comprises the following steps: (1) according to the mass fraction of water reducing agent, alkali-activated cementitious material unique precursor material-F fly ash; (2) the water reducing agent and alkali-activated cementitious material precursor material-F fly ash mixed into the blender, stirring to uniform; (3) according to the mass fraction of sodium silicate solution, sodium hydroxide solution; the chemical composition of the sodium silicate solution is 27.3% of SiO2, 8.54% of Na2O, and a modulus of 3.3; (4) preparation of alkaline solution, mixing and stirring uniformly the sodium silicate solution and sodium hydroxide solution in step (3); (5) the alkaline solution prepared in step (4) is poured into the mixed fly ash and silica ash in step (2), and stirred uniformly using a blender.

11. A slag-based high calcium system alkali-activated cementitious material with silica fume as a water-reducing agent, characterized in that, The alkali-activated cementitious material is prepared from the following materials: water reducing agent, alkali-activated cementitious material unique precursor material-S95 grade slag, and alkali solution; the water reducing agent is silica ash.

12. A slag-based high calcium system alkali-activated cementitious material according to claim 11 using silica fume as a water-reducing agent, characterised in that, The alkali solution includes sodium silicate solution and sodium hydroxide solution, and according to the mass fraction, the water reducing agent is 0.01-12 parts, the alkali-activated cementitious material precursor material-S95 grade slag is 80-150 parts, the sodium silicate solution is 10-25 parts, the sodium hydroxide solid particles are 4-10 parts, and the distilled water is 10-16 parts.

13. A slag-based high calcium system alkali activated cementitious material according to claim 11, characterised in that, The sodium silicate solution is 27.3% of SiO2, 8.54% of Na2O, and a modulus of 3.3; the purity of the sodium hydroxide solid particles is ≥96%.

14. A slag-based high calcium system alkali activated cementitious material according to claim 11, characterised in that, The S95 grade slag is the only precursor material for preparing slag-based high calcium system alkali-activated cementitious material, and the mass percentage of each oxide in the chemical composition of the S95 grade slag is: CaO is 40.43%, SiO2 is 30.46%, Al2O3 is 15.81%, MgO is 9.42%, Fe2O3 is 0.281%, K2O is 0.423%, TiO2 is 0.673%, MnO is 0.52%, Na2O is 0.499%, S is 1.16%, SrO is 0.0549%, Cl is 0.0467%, ZrO2 is 0.0391%, BaO is 0.0389%, P2O5 is 0.017%, V2O5 is 0.0084%, Y2O3 is 0.0083%, CeO2 is 0.0069%, and CuO is 0.0012%.

15. A silicious ash as a water reducing agent in a slag-based high calcium system alkali-activated cementitious material according to any one of claims 11-14, characterized in that: The alkali-activated cementitious material has an expansion of 190-200 mm.

16. A method of producing a slag-based high calcium system alkali-activated cementitious material with silica fume as a water-reducing agent according to any one of claims 11-14, characterized in that, The method comprises the following steps: (1) according to the mass fraction of water reducing agent, alkali-activated cementitious material precursor material-S95 grade slag is weighed; (2) the water reducing agent and alkali-activated cementitious material precursor material-S95 grade slag are mixed into the blender, and stirred to uniform; (3) according to the mass fraction of sodium silicate solution, sodium hydroxide solution; the chemical composition of the sodium silicate solution is 27.3% of SiO2, 8.54% of Na2O, and a modulus of 3.3; (4) preparation of alkaline solution, mixing and stirring uniformly the sodium silicate solution and sodium hydroxide solution in step (3); (5) the alkaline solution prepared in step (4) is poured into the mixed fly ash and silica ash in step (2), and stirred uniformly using a blender.

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