Alkali-activated cementing material and preparation method therefor

Abstract

The present invention relates to the technical field of cement-based materials, and particularly relates to an alkali-activated cementing material and a preparation method therefor. Provided is an alkali-activated cementing material, which comprises the following preparation raw materials in parts by mass: 50-70 parts of calcined coal gangue, 50-70 parts of mineral slag, 5-16 parts of steel fibers, 1-1.5 parts of barium chloride, 40-55 parts of a sodium silicate solution, 5-10 parts of sodium hydroxide and 15-25 parts of water, wherein the steel fibers are directionally arranged in the alkali-activated cementing material; and the composition of the sodium silicate solution comprises 27.58 wt% of SiO2, 8.75 wt% of Na2O and 63.67 wt% of H2O. The alkali-activated cementing material is low in cost and has excellent mechanical properties.

Description

Alkali-activated cementitious material and preparation method thereof

[0001] The present application claims priority to the Chinese patent application No. 202411124327.X, filed on August 15, 2024, and titled "Alkali-activated cementitious material and preparation method thereof", the content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of cement-based materials, in particular to an alkali-activated cementitious material and a preparation method thereof. BACKGROUND

[0003] Cement is one of the most widely used building cementitious materials in the world, and about 5% to 8% of the global carbon dioxide emissions are caused by cement. With the advent of a low-carbon economy, it is crucial to develop new, sustainable, and low-carbon building materials. The production process of alkali-activated cementitious material produces about 80% less carbon dioxide than cement concrete, significantly reducing carbon emissions. Alkali-activated cementitious material has the advantages of fast setting, early strength, high compressive strength, low density, acid and alkali corrosion resistance, high temperature resistance, low permeability, and excellent durability, and is a cementitious material with great development potential, which can be considered as the best substitute for cement.

[0004] Coal gangue is a solid waste generated during coal mining, and its main components are silicon dioxide and aluminum oxide. Slag is a byproduct of the blast furnace ironmaking process, and its main components are silicon dioxide, calcium oxide, and aluminum oxide. Since coal gangue has a low calcium content, and slag is a solid waste with a high calcium content, in order to better utilize solid waste such as coal gangue, slag can be added as a mineral admixture to alkali-activated coal gangue cementitious material, which not only realizes the resource utilization of coal gangue, but also improves its performance. Compared with Portland cement-based composites, alkali-activated coal gangue cementitious material is more brittle. SUMMARY

[0005] The present application aims to provide an alkali-activated cementitious material and a preparation method thereof, which has low cost and excellent mechanical properties.

[0006] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0007] The present application provides an alkali-activated cementitious material, which comprises the following preparation raw materials in mass fraction: calcined coal gangue 50-70 parts, slag 50-70 parts, steel fiber 5-16 parts, barium chloride 1-1.5 parts, sodium silicate solution 40-55 parts, sodium hydroxide 5-10 parts, and water 15-25 parts.

[0008] The steel fiber is arranged in the alkali-activated cementitious material.

[0009] The sodium silicate solution has a composition of 27.58wt% SiO2, 8.75wt% Na2O and 63.67wt% H2O.

[0010] Preferably, the preparation raw materials include, in parts by mass, 58 parts of calcined coal gangue, 58 parts of slag, 7-14 parts of steel fiber, 1.2 parts of barium chloride, 47 parts of sodium silicate solution, 8 parts of sodium hydroxide and 19 parts of water.

[0011] Preferably, the preparation method of the calcined coal gangue includes the following steps:

[0012] The coal gangue is calcined to obtain the calcined coal gangue.

[0013] The calcination temperature is 700-900℃, and the time is 1-3h.

[0014] Preferably, the steel fiber has a length of 8-16mm and a diameter of 0.18-0.26mm.

[0015] The application also provides a preparation method of the alkali-activated cementitious material.

[0016] The calcined coal gangue, slag, steel fiber, barium chloride, sodium silicate solution, sodium hydroxide and water are mixed, and then pouring, demolding and test block curing are sequentially performed to obtain the alkali-activated cementitious material.

[0017] The pouring is performed by using an L-shaped pouring device.

[0018] Preferably, the mixing includes the following steps:

[0019] The sodium hydroxide and water are mixed, the obtained sodium hydroxide solution and sodium silicate solution are mixed, and an alkali activator is obtained.

[0020] The calcined coal gangue, slag and barium chloride are mixed, and then the alkali activator and steel fiber are sequentially added.

[0021] Preferably, after the pouring is completed, the method further includes standing.

[0022] The standing temperature is 20±2℃, the relative humidity is 95±1%, and the time is 24h.

[0023] Preferably, the test block curing temperature is 20±2℃, and the time is 28 days.

[0024] The application provides an alkali-activated cementitious material, which comprises the following preparation raw materials in mass fraction: calcined coal gangue 50-70 parts, slag 50-70 parts, steel fiber 5-16 parts, barium chloride 1-1.5 parts, sodium silicate solution 40-55 parts, sodium hydroxide 5-10 parts and water 15-25 parts; the steel fiber is directionally arranged in the alkali-activated cementitious material; the composition of the sodium silicate solution is 27.58wt% of SiO2, 8.75wt% of Na2O and 63.67wt% of H2O.

[0025] Compared with common cement materials and alkali-activated materials, the technical scheme has the following advantages:

[0026] 1) The solid waste such as coal gangue and slag is recycled and utilized, the use of cement is avoided, the emission of carbon dioxide is significantly reduced, and the sustainable development of the environment is important;

[0027] 2) The sodium silicate solution and sodium hydroxide in the alkali-activated cementitious material are combined with the steel fiber, the brittleness of the alkali-activated cementitious material is effectively reduced, the mechanical properties are improved, and the cracking of the material is delayed;

[0028] 3) The directional arrangement of the steel fiber can further improve the toughness and ductility of the alkali-activated cementitious material, improve the problem of large drying shrinkage caused by the alkali-activated cementitious material, and maximize the saving of steel fiber material, so that the alkali-activated cementitious material with lower preparation cost is prepared. BRIEF DESCRIPTION OF DRAWINGS

[0029] Fig. 1 is a preparation flowchart of the alkali-activated cementitious material. DETAILED DESCRIPTION

[0030] The application provides an alkali-activated cementitious material, which comprises the following preparation raw materials in mass fraction: calcined coal gangue 50-70 parts, slag 50-70 parts, steel fiber 5-16 parts, barium chloride 1-1.5 parts, sodium silicate solution 40-55 parts, sodium hydroxide 5-10 parts and water 15-25 parts;

[0031] The steel fiber is directionally arranged in the alkali-activated cementitious material;

[0032] The composition of the sodium silicate solution is 27.58wt% of SiO2, 8.75wt% of Na2O and 63.67wt% of H2O.

[0033] In the application, all the preparation raw materials are commercially available products well known by those skilled in the art without special instructions.

[0034] The alkali-activated cementitious material described in the present application comprises 50-70 parts by mass of calcined coal gangue, preferably 55-65 parts, and more preferably 58-62 parts. In the present application, the preparation method of the calcined coal gangue preferably comprises the following steps: calcining coal gangue to obtain the calcined coal gangue; the calcination temperature is preferably 700-900℃, more preferably 700-800℃, and most preferably 800℃; the time is preferably 1-3h, more preferably 2-3h, and most preferably 2h. In the present application, the coal gangue is preferably obtained from solid waste generated during coal mining.

[0035] In the present application, the role of the calcined coal gangue is to prepare an alkali-activated cementitious material, which has strong secondary hydration reactivity compared to uncalcined coal gangue.

[0036] The alkali-activated cementitious material described in the present application comprises 50-70 parts by mass of slag, preferably 55-65 parts, and more preferably 58-62 parts, based on the mass fraction of the calcined coal gangue. In the present application, the slag is preferably S95 slag and / or S105 slag. In the present application, the slag is preferably obtained from by-products generated during the blast furnace ironmaking process.

[0037] In the present application, the role of the slag is to combine with the calcined coal gangue, which can significantly improve the strength of the coal gangue-based geopolymer.

[0038] The alkali-activated cementitious material described in the present application comprises 5-16 parts by mass of steel fiber, preferably 8-13 parts, and more preferably 9-10 parts, based on the mass fraction of the calcined coal gangue. In the present application, the length of the steel fiber is preferably 8-16mm, more preferably 8-13mm, and most preferably 13mm; the diameter is preferably 0.18-0.26mm, more preferably 0.18-0.20mm, and most preferably 0.20mm.

[0039] In the present application, the role of the steel fiber is to improve the performance of the alkali-activated cementitious material, reduce its brittleness, improve its mechanical properties, and delay its cracking.

[0040] The alkali-activated cementitious material described in the present application comprises 1-1.5 parts by mass of barium chloride, preferably 1.1-1.3 parts, and more preferably 1.1-1.2 parts, based on the mass fraction of the calcined coal gangue.

[0041] In the present application, the role of the barium chloride is to prolong the hydration and hardening time, so that it remains plastic for a longer period of time, facilitating pouring.

[0042] The alkali-activated cementitious material of the present application comprises 40-55 parts by mass of sodium silicate solution, preferably 43-52 parts, and more preferably 46-50 parts, based on the mass of the calcined coal gangue.

[0043] In the present application, the sodium silicate solution serves to activate the calcined coal gangue and slag and improve the performance of the alkali-activated coal gangue-slag material.

[0044] The alkali-activated cementitious material of the present application comprises 5-10 parts by mass of sodium hydroxide, preferably 6-9 parts, and more preferably 7-8 parts, based on the mass of the calcined coal gangue.

[0045] In the present application, the sodium hydroxide serves to reduce the modulus of the sodium silicate solution.

[0046] The alkali-activated cementitious material of the present application comprises 15-25 parts by mass of water, preferably 16-23 parts, and more preferably 18-21 parts, based on the mass of the calcined coal gangue. In the examples of the present application, the water is distilled water.

[0047] The present application also provides a method for preparing the alkali-activated cementitious material described in the above technical solution, comprising the following steps:

[0048] After the calcined coal gangue, slag, steel fiber, barium chloride, sodium silicate solution, sodium hydroxide and water are mixed, pouring, demolding and test block curing are performed in sequence to obtain the alkali-activated cementitious material.

[0049] The pouring is performed using an L-shaped pouring device.

[0050] In the present application, the mixing preferably comprises the following steps:

[0051] The sodium hydroxide and water are mixed, the obtained sodium hydroxide solution and sodium silicate solution are mixed to obtain an alkali activator.

[0052] After the calcined coal gangue, slag and barium chloride are mixed, the alkali activator and steel fiber are added in sequence.

[0053] The present application mixes sodium hydroxide and water, mixes the obtained sodium hydroxide solution and sodium silicate solution to obtain an alkali activator.

[0054] The present application does not have any special limitation on the mixing of the sodium hydroxide and water, which can be performed using processes well known to those skilled in the art.

[0055] The mixing process of the sodium hydroxide solution and the sodium silicate solution is not particularly limited in the present application, and can be carried out using a process known to those skilled in the art.

[0056] After the mixing of the sodium hydroxide solution and the sodium silicate solution is completed, the present application also preferably comprises cooling, and the cooling process is not particularly limited in the present application, and can be carried out using a process known to those skilled in the art to ensure cooling for 24 h to room temperature.

[0057] In the present application, the modulus of the alkali activator is preferably 1.2-1.4, more preferably 1.2-1.3, and most preferably 1.3.

[0058] After obtaining the alkali activator, the calcined coal gangue, the slag and the barium chloride are mixed, and then the alkali activator and the steel fiber are sequentially added.

[0059] In the present application, the mixing is preferably carried out under stirring, and the stirring speed is 75 r / min; the stirring time is 1 min. The mixing preferably comprises first mixing the calcined coal gangue and the slag, and then adding the barium chloride.

[0060] After adding the alkali activator, the present application also preferably comprises sequentially carried out first stirring and second stirring; the temperature of the first stirring is preferably 20±2℃, the speed is preferably 75 r / min, and the time is preferably 2 min; the temperature of the second stirring is preferably 20±2℃, the speed is preferably 285 r / min, and the time is preferably 1 min.

[0061] After adding the steel fiber, the present application also preferably comprises third stirring, and the temperature of the third stirring is preferably 20±2℃, the speed is preferably 285 r / min, and the time is preferably 2 min.

[0062] In the present application, the pouring is carried out using an L-shaped pouring device. In the present application, the L-shaped pouring device can ensure that the velocity difference of the shear velocity field is large enough when the base material is flowing, so that the fibers can be oriented faster to achieve the purpose of steel fiber orientation.

[0063] After the pouring is completed, it is also preferably covered with plastic wrap and left to stand; the temperature of the standing is preferably 20±2℃; the relative humidity is preferably 95±1%; and the time is preferably 24 h.

[0064] The demolding process is not particularly limited in the present application, and can be carried out using a process known to those skilled in the art.

[0065] In the present application, the temperature for curing the test block is preferably 20±2℃, and the time is preferably 28 days; the curing of the test block preferably comprises strength test block curing or drying shrinkage test block curing; the relative humidity for the strength test block curing is preferably 95±1%, and the relative humidity for the drying shrinkage test block curing is preferably 60±5%; when the curing of the test block is the strength test block curing, the obtained alkali-activated cementitious material is a strength test block; when the curing of the test block is the drying shrinkage test block curing, the obtained alkali-activated cementitious material is a drying shrinkage test block.

[0066] The alkali-activated cementitious material and the preparation method thereof provided in the present application are described in detail below in combination with examples, but they cannot be understood as limiting the protection scope of the present application.

[0067] The source and preparation process of the raw materials in Examples 1-2 are as follows:

[0068] Preparation raw material: calcined coal gangue: solid waste produced in the process of coal mining in Shanxi, which is calcined at 800℃ for 120min;

[0069] Slag: solid waste produced in the process of blast furnace ironmaking (S95 slag);

[0070] Steel fiber: length 13mm, diameter 0.2mm;

[0071] Sodium silicate solution: modulus 3.25, composition: 27.58wt% SiO2, 8.75wt% Na2O and 63.67wt% H2O;

[0072] Sodium hydroxide: analytical pure;

[0073] Water: distilled water;

[0074] Preparation process:

[0075] As shown in Figure 1, after mixing sodium hydroxide and water, the obtained sodium hydroxide solution and sodium silicate solution are mixed (temperature 20℃, time 24h), and then cooled to room temperature to obtain an alkali activator;

[0076] After stirring and mixing the calcined coal gangue, slag and barium chloride (stirring speed 75r / min, time 1min), the alkali activator is added, followed by first stirring (temperature of the first stirring 20±2℃, stirring speed 75r / min, time 2min) and second stirring (20±2℃, stirring speed 285r / min, time 1min), and then steel fiber is added, and the mixture is stirred at a stirring speed of 285r / min for 2min to obtain a mixed slurry;

[0077] The mixed slurry is filled into a mold through an L-shaped pouring device to achieve the purpose of steel fiber orientation, then the mold is covered with plastic wrap, demolded after standard curing for 24 h in an environment with a temperature of 20±2℃ and a relative humidity of 95±1%, and the test piece obtained after demolding is placed in a standard curing chamber (temperature of 20±2℃) for curing for 28 d, to obtain an alkali-activated cementitious material (strength test block) when the relative humidity of curing is 95±1%, and an alkali-activated cementitious material (dry shrinkage test block) when the relative humidity of curing is 60±5%.

[0078] Example 1

[0079] Raw materials for preparing the alkali-activated cementitious material: 58 parts by weight of calcined coal gangue, 58 parts by weight of slag, 7 parts by weight of steel fiber, 1.2 parts of barium chloride, 47 parts by weight of sodium silicate solution, 8 parts by weight of sodium hydroxide, and 19 parts by weight of distilled water.

[0080] Example 2

[0081] Raw materials for preparing the alkali-activated cementitious material: 58 parts by weight of calcined coal gangue, 58 parts by weight of slag, 7 parts by weight of steel fiber, 1.2 parts of barium chloride, 47 parts by weight of sodium silicate solution, 8 parts by weight of sodium hydroxide, and 19 parts by weight of distilled water.

[0082] Comparative Example 1

[0083] Raw materials for preparing the alkali-activated cementitious material: 58 parts by weight of calcined coal gangue, 58 parts by weight of slag, 7 parts by weight of steel fiber, 1.2 parts of barium chloride, 47 parts by weight of sodium silicate solution, 8 parts by weight of sodium hydroxide, and 19 parts by weight of distilled water.

[0084] The preparation process is the same as that of Examples 1-2, except that no steel fiber orientation is performed (no L-shaped orientation mold is used during pouring).

[0085] Comparative Example 2

[0086] Raw materials for preparing the alkali-activated cementitious material: 58 parts by weight of calcined coal gangue, 58 parts by weight of slag, 7 parts by weight of steel fiber, 1.2 parts of barium chloride, 47 parts by weight of sodium silicate solution, 8 parts by weight of sodium hydroxide, and 19 parts by weight of distilled water.

[0087] The preparation process is the same as that of Examples 1-2, except that no steel fiber orientation is performed (no L-shaped orientation mold is used during pouring).

[0088] Comparative Example 3

[0089] Reference Example 1, except that no steel fiber is added.

[0090] Comparative Example 4

[0091] Preparation raw materials of ordinary Portland cement material: cement 50 parts (42.5 grade ordinary Portland cement), distilled water 18 parts;

[0092] Preparation process: after the cement is dry-mixed for 1 min by a stirring planetary cement paste stirrer, distilled water is added and stirred for 5 min (at a speed of 285 r / min) to obtain cement neat paste;

[0093] After the obtained cement neat paste is loaded into a mold, covered with a preservative film, and placed in an environment with a temperature of 20±2℃ and a relative humidity of 95±1% for standard curing for 24 h, demolding is performed, and the obtained test piece after demolding is placed in a standard curing room (with a temperature of 20±2℃) for curing for 28 days, when the relative humidity of curing is 95±1%, an ordinary Portland cement material (strength test block) is obtained; when the relative humidity of curing is 60±5%, an ordinary Portland cement material (dry shrinkage test block) is obtained.

[0094] Test example

[0095] The alkali-activated cementitious materials described in Examples 1-2, the alkali-activated cementitious materials described in Comparative Examples 1-3, and the ordinary Portland cement material described in Comparative Example 4 are subjected to performance testing, and the test results are shown in Table 1:

[0096] Table 1 Performance test results of the alkali-activated cementitious materials described in Examples 1-2, the alkali-activated cementitious materials described in Comparative Examples 1-3, and the ordinary Portland cement material described in Comparative Example 4

[0097] The above only describes the preferred embodiments of the present application, and it should be noted that, for ordinary skilled persons in the technical field, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. An alkali-activated cementitious material, characterized in that, According to mass parts, the following raw materials are included: calcined coal gangue 50-70 parts, slag 50-70 parts, steel fiber 5-16 parts, barium chloride 1-1.5 parts, sodium silicate solution 40-55 parts, sodium hydroxide 5-10 parts, and water 15-25 parts; The steel fiber is arranged in the alkali-activated cementitious material in a directional manner; The sodium silicate solution has a composition of 27.58wt% SiO2, 8.75wt% Na2O, and 63.67wt% H2O.

2. The alkali-activated cementitious material of claim 1, wherein, According to mass parts, the following raw materials are included: calcined coal gangue 50-70 parts, slag 50-70 parts, steel fiber 5-16 parts, barium chloride 1-1.5 parts, sodium silicate solution 40-55 parts, sodium hydroxide 5-10 parts, and water 15-25 parts; 3. Alkali-activated cementitious material according to claim 1 or 2, c h a r a c t e r i z e d in that The preparation method of the calcined coal gangue includes the following steps: The coal gangue is calcined to obtain the calcined coal gangue; The calcining temperature is 700-900℃, and the calcining time is 1-3h.

4. Alkali-activated cementitious material according to claim 1 or 2, c h a r a c t e r i z e d in that The steel fiber has a length of 8-16mm and a diameter of 0.18-0.26mm.

5. Process for the production of an alkali-activated cementitious material according to any one of claims 1 to 4, characterized in that, The method includes the following steps: The calcined coal gangue, slag, steel fiber, barium chloride, sodium silicate solution, sodium hydroxide, and water are mixed, and then the pouring, demolding, and test block curing are sequentially performed to obtain the alkali-activated cementitious material; The pouring is performed by using an L-shaped pouring device.

6. The production method according to claim 5, wherein The mixing includes the following steps: The sodium hydroxide and water are mixed, the obtained sodium hydroxide solution and sodium silicate solution are mixed to obtain an alkali activator; The calcined coal gangue, slag, and barium chloride are mixed, and then the alkali activator and steel fiber are sequentially added.

7. The production method according to claim 5, wherein After the pouring is completed, the method further includes the following step: The temperature of the standing is 20±2℃, the relative humidity is 95±1%, and the time is 24h.

8. The production method according to claim 5, wherein The temperature of the test block curing is 20±2℃, and the time is 28 days.

Images