Early strength type freeze-thaw cycle resistant cementing material and preparation method thereof

Abstract

The invention relates to the technical field of cementing materials, in particular to an early-strength type freeze-thaw cycle-resistant cementing material and a preparation method thereof. The cementing material comprises the following raw materials in parts by mass: 50 parts of steel slag, 32-42 parts of blast furnace slag, 11-17 parts of desulfurized gypsum, 22-30 parts of fly ash, 3-5 parts of calcium chloride, 4-7 parts of a composite alkali activator and 11-17 parts of an interface treating agent. Through the combined action of the composite alkali activator and the interface treating agent, the mechanical strength and the freeze-thaw cycle resistance of the cementing material are improved at the same time, and particularly, the early strength and the freeze-thaw cycle resistance are improved at the same time, so that the cementing material can be applied to high-humidity and cold regions.

Description

Technical Field

[0001] The invention relates to the technical field of gelling materials, and in particular to an early-strength freeze-thaw cycle resistant gelling material and a preparation method thereof. Background Art

[0002] With the rapid development of urban infrastructure, the demand for concrete is increasing. The primary raw material for concrete is Portland cement, and its production is associated with significant energy consumption and carbon emissions. Reportedly, due to outdated technology, producing one ton of Portland cement generates significant amounts of carbon dioxide. The Portland cement production process, which converts raw materials into clinker, consumes significant amounts of energy and produces significant amounts of carbon dioxide. If the carbon dioxide generated by electricity consumption is included, the amount of carbon dioxide produced is even higher. With increasingly stringent environmental protection requirements, the development of low-carbon alternatives to cement is becoming increasingly important. Among these, the development of cementitious materials has garnered the most attention. Their primary raw materials are industrial waste residues and tailings, such as steel slag and blast furnace slag, combined with desulfurized gypsum and other raw materials. The composition of steel slag and blast furnace slag is similar to that of cement clinker, forming the theoretical basis for cementitious materials to replace cement. The preparation process for this new generation of cementitious materials is much simpler, requiring only grinding rather than high-temperature calcination. Therefore, cementitious materials are currently a hot topic in research as cement replacements.

[0003] However, cementitious materials made from industrial solid waste have poor freeze-thaw cycle resistance. This is because the network structure formed by the alkali-induced reaction is not as dense as the gel network of cement hydration products, and the pore size distribution is uneven. The expansion pressure of water in the pores can tear the pore wall structure. Therefore, cementitious materials made from industrial solid waste as raw materials often have weak freeze-thaw cycle resistance. In addition, although the CaO content of slag and furnace slag is close to that of cement, they lack the active C3S / C2S mineral phase, resulting in insufficient structural toughness. Literature reports that after 50 freeze-thaw cycles, the mechanical strength loss rate of cementitious materials can reach over 20%. This results in a significant loss of mechanical strength in the application of cementitious materials, especially in cold and humid areas during the winter.

[0004] CN114477806A discloses a low-carbon cementitious material comprising the following components: 20-70 parts steel slag, 20-60 parts blast furnace slag, 5-40 parts fly ash, 3-30 parts desulfurized gypsum, 5-50 parts lime, and 3-20 parts activator. Using bulk solid wastes such as steel slag, blast furnace slag, and fly ash as the main raw materials, a roller press is used to create microcracks and steam-wetting technology is used to partially decompose free calcium oxide and magnesium oxide. RO phase separation technology and microstructure distortion technology are used to enhance material activity, eliminate stability issues, and improve grindability. At the same time, activation energy is stimulated to achieve the preparation of a low-carbon emission cementitious material. However, the mechanical strength is relatively low and it cannot replace high-strength cement. Furthermore, common disadvantages of cementitious materials include slow early strength growth and poor freeze-thaw cycle resistance, which limits their use in cold regions.

[0005] CN117049850A discloses a cementitious material using steel slag as raw material. The cementitious material is composed of the following components: 100 parts of powder material, 0.5-1 parts of dimethyl carbonate, 0.05-0.15 parts of retarder, 0.2-0.5 parts of water reducer, and 38-50 parts of water. The powder material is composed, by weight, of the following components: 30-45 parts of ground steel slag powder, 20-30 parts of granulated blast furnace slag powder, 5-10 parts of calcium aluminate, 15-20 parts of gypsum, and 5-10 parts of fly ash. This cementitious material also suffers from a weak freeze-thaw cycle resistance.

[0006] CN118637884A discloses a hydrophobic gel material for regulating roadbed moisture in high-altitude cold regions. The material is composed of the following raw materials by weight: 0.5-1 part of a nano-type hydrophobic material and 90-95 parts of a steel slag-based rock and soil curing agent; the nano-type hydrophobic material is composed of the following raw materials by weight: 5-8 parts of a sodium methyl silicate solution, 6-20 parts of a silane modifier, 0.5-1 part of ethylene glycol, and 50-100 parts of a nano-silica sol; the steel slag-based rock and soil curing agent is composed of the following raw materials by weight: 14-16 parts of steel slag micropowder, 5-7 parts of slag, and 7-9 parts of desulfurized gypsum. The nano-type super-hydrophobic material provided in this patent forms a super-hydrophobic film when it comes into contact with soil particles. The steel slag-based rock and soil curing agent tightly connects the film to the soil particles to form a dense and stable structure. The dense and stable structure not only reduces downward seepage from the road surface, but also reduces the rise of capillary water at the bottom of the roadbed; thereby effectively controlling the internal moisture content of the roadbed in the region. Ensure the fluctuation range of the moisture content inside the material and improve the freeze-thaw cycle resistance of the cementitious material.

[0007] CN115180842A discloses a low-carbon, low-emission solid waste-based cementitious material, comprising 20-40 parts of steel slag, 40-60 parts of slag, 5-10 parts of desulfurized gypsum, 15-20 parts of tailings, and 3-8 parts of slag. The steel slag is pretreated with a dopant, and the dopant includes the following components: ammonium tungstate, attapulgite, lithium aluminum silicate, and sodium heavy alkylbenzene sulfonate.

[0008] However, existing technologies for improving freeze-thaw cycle resistance in gelling materials struggle to maintain mechanical strength, particularly early-stage strength. The early-stage strength of gelling materials relies on high alkalinity, which rapidly forms a network. However, this gel network has defects, resulting in a degraded pore structure. These often become weak points that tear the network apart during freeze-thaw cycles. In other words, high alkalinity often impairs freeze-thaw stability. Summary of the Invention

[0009] In order to solve the shortcomings of existing cementitious materials based on steel slag and slag in that it is difficult to balance early strength and freeze-thaw cycle resistance. The present invention proposes an early-strength freeze-thaw cycle resistant cementitious material and a preparation method thereof. Steel slag, blast furnace slag, and desulfurized gypsum are used as the main raw materials, making full use of large amounts of industrial solid waste. By compounding a composite alkali activator and an interface treatment agent, the early strength and freeze-thaw cycle resistance of the obtained cementitious material are improved at the same time. Specifically, the present invention achieves the above-mentioned purpose through the following technical solutions:

[0010] An early-strength freeze-thaw cycle resistant cementitious material comprises the following raw materials in parts by mass: 50 parts of steel slag, 32-42 parts of blast furnace slag, 11-17 parts of desulfurized gypsum, 22-30 parts of fly ash, 3-5 parts of calcium chloride, 4-7 parts of a composite alkali activator, and 11-17 parts of an interface treatment agent; the composite alkali activator comprises water glass, sulfate, and hydroxides of alkali metals / alkaline earth gold; and the interface treatment agent is a compound of modified nano-silica sol and vinyl acetate copolymer emulsion.

[0011] Preferably, the modified nano-silica sol is nano-silica sol that has been treated with Silane-PEG-(CH2) a -NH2 modified, Silane is a group containing trialkoxysilane, the chemical expression is -O(CH2) b -NHCONH-(CH2) c-Si(OR1)(OR2)(OR3), wherein R1, R2, and R3 are independently selected from at least one of methyl, ethyl, propyl, butyl, pentyl, and phenyl; and a, b, and c are independently integers from 0 to 3, such as 0, 1, 2, and 3. Also preferably, the raw materials for preparing the vinyl acetate copolymer include: 100 parts by mass of vinyl acetate, 7-10 parts by mass of polyvinyl alcohol, 22-35 parts by mass of C4-6 alkyl (meth)acrylate, 6-10 parts by mass of an alkenyl silane coupling agent, 4-6 parts by mass of an epoxy-containing acrylate derivative, and 2-4 parts by mass of a persulfate.

[0012] Furthermore, the composite alkaline activator is a mixture of water glass, sulfate, and hydroxide of alkali metal / alkaline earth gold in a mass ratio of 100:30-40:10-17.

[0013] Furthermore, in the composite alkali activator, the water glass is Na2O·nSiO2, where n is 1.8-2.6; the sulfate is selected from at least one of sodium sulfate, potassium sulfate, and calcium sulfate; and the alkali metal / alkaline earth gold hydroxide is selected from at least one of sodium hydroxide, potassium hydroxide, and calcium hydroxide. The inventors have discovered that using a composite alkali activator in conjunction with an interface treatment agent can synergistically improve the early strength and freeze-thaw cycle resistance of cementitious materials.

[0014] Furthermore, the solid contents of the modified nano-silica sol and the vinyl acetate copolymer emulsion are independently 25-40%; and the mass ratio of the modified nano-silica sol and the vinyl acetate copolymer emulsion is 1-2:1-2.

[0015] Furthermore, the vinyl acetate copolymer emulsion is prepared by a preparation method comprising the following steps:

[0016] (P1) uniformly mixing vinyl acetate, a C4-6 alkyl (meth)acrylate, an alkenyl silane coupling agent, and an epoxy group-containing acrylate derivative to obtain a mixed monomer;

[0017] (P2) dissolving polyvinyl alcohol in water under heating conditions (85-95° C.), adding an emulsifier and 20-30% of an initiator, and mixing uniformly, slowly adding 20-30% of a mixed monomer under reflux, and reacting for 0.5-1 hour to obtain a seed emulsion; slowly adding the remaining mixed monomer and initiator in 3-5 batches, and after all the materials have been added, continuing the reflux reaction, cooling, filtering, discharging, adjusting the solid content, and discharging.

[0018] Furthermore, in step (S2), the slow addition is completed within 10-15 minutes, the interval between each addition is 1-2 hours, the reflux reaction time is continued for 1-2 hours, and the temperature is lowered to 20-40°C.

[0019] Furthermore, the number average molecular weight of the polyvinyl alcohol polymer is 1000-2000, preferably 1500-1900; the C4-6 alkyl (meth)acrylate is selected from at least one of butyl (meth)acrylate, pentyl (meth)acrylate, and hexyl (meth)acrylate; the alkenyl silane coupling agent is selected from at least one of vinyltriethoxysilane and vinyltriisopropoxysilane; the epoxy-containing acrylate derivative is selected from glycidyl (meth)acrylate; the persulfate is selected from at least one of ammonium persulfate, sodium persulfate, and potassium persulfate; the emulsifier is not particularly limited and is well known to those skilled in the art, such as anionic surfactants (SDS) and nonionic surfactants (Tween, Span, etc.). In one embodiment of the present invention, the emulsifier is a mixture of SDS and Tween in a mass ratio of 1-3:1-3, preferably a mixture of SDS and Tween-20 in a mass ratio of 1-2:1-2.

[0020] Furthermore, the size of silica in the nano-silica sol is 100-200 nm, and the silica and Silane-PEG-(CH2) a -NH2 mass ratio is 100:30-45; further, the solid content of the modified nano-silica sol is 25-40%.

[0021] Furthermore, Silane-PEG-(CH2) a In -NH2, the number average molecular weight of the PEG segment is 1200-2000, and Silane- represents -OCH2CH2-NHCONH-CH2CH2CH2-Si(OCH3)3, -OCH2CH2-NHCONH-CH2CH2CH2-Si(OCH2CH3)3, or -OCH2CH2-NHCONH-CH2CH2CH2-Si(OCH2CH2CH3)3. For example, Where n=1000, its trade name is Silane-PEG 1000 -NH2, also known as Silane-PEG 1000 -CH2-NH2; n = 1200, its trade name is Silane-PEG 1200 -CH2-NH2, also known as Silane-PEG 1200 -CH2-NH2; n = 2000, its trade name is Silane-PEG 2000 -CH2-NH2, also known as Silane-PEG 2000 -CH2-NH2; n = 3000, its trade name is Silane-PEG 3000 -NH2, also known as Silane-PEG 3000-CH2-NH2.

[0022] The inventors discovered that using a silane coupling agent with a specific PEG length can significantly improve the freeze-thaw cycle resistance of the cementitious material while maintaining its mechanical properties. The inventors also attempted to use small-molecule aminosilane coupling agents such as γ-aminopropyltriethoxysilane, but the results were not significant. This suggests that the PEG segment plays a significant role in adhesive materials. This is likely due to the long chain preventing premature condensation of silanol groups after silane hydrolysis; secondly, it acts as a flexible spacer, providing some toughness; and finally, PEG improves the hydrophilicity of silica nanoparticles and enhances the dispersibility of the entire molecule in polar systems. However, the PEG segment length needs to be appropriately limited; a number-average molecular weight of 1200-2000 is sufficient to achieve these objectives.

[0023] Furthermore, the modified nano-silica sol is prepared by the following preparation method: heating the nano-silica sol with a solid content of 25-40% to 50-65° C., adding Silane-PEG-(CH2) a -NH2, keep warm and continue the reaction for 2-5h to obtain modified nano-silica sol.

[0024] Calcium chloride supplements soluble calcium sources, promotes the formation of CASH gel, compensates for the defects of active calcium components in slag, and accelerates the development of early strength. However, the amount of calcium chloride must be strictly limited. Too little calcium chloride cannot play a corresponding role in improving material properties. However, the amount should not be too much, otherwise the chloride ion concentration will be too high, which will cause corrosion. However, a certain chloride ion concentration is required to increase the conductivity of the liquid phase between pores and accelerate the formation of metal ions (such as Na + , K + , Ca 2+ ) migrate to the active aggregate, triggering the alkali-induced reaction.

[0025] The present invention also provides a method for preparing the above-mentioned early-strength freeze-thaw cycle resistant gelling material, comprising the following steps:

[0026] (S1) ball milling steel slag, blast furnace slag, and fly ash to obtain a mixed material A;

[0027] (S2) mixing the desulfurized gypsum and the composite alkali activator uniformly, aging, and drying to obtain a mixed material B;

[0028] (S3) Mixed material A and mixed material B are evenly mixed by ball milling, calcium chloride and an interface treatment agent are added, and mixed evenly by a high-speed mixer to obtain an early-strength freeze-thaw cycle resistant gelling material.

[0029] Furthermore, in step (S1), the ball milling speed is 200-400 rpm, the ball milling time is 3-5 h, and the specific surface area of ​​the mixed material A is 300-500 m 2 / kg; in step (S2), the mixture is evenly mixed in a high-speed mixer, aged for 1-3 days, and dried to a moisture content of ≤0.7%; in step (S3), the ball milling speed is 100-150rpm, and the ball milling time is 10-20h.

[0030] In the present invention, the composite alkali activator and the compounded interface treatment agent have a synergistic effect. Conventional alkali activators are used to improve early strength, but they lead to coarse pores and uneven dispersion. The present invention adopts a composite alkali activator, and the main component of water glass is sodium silicate, which provides silicate ions and an alkaline environment to promote the dissolution and reaction of slag. Sulfates such as sodium sulfate may participate in the formation of ettringite, which contributes to early strength and structural densification. Hydroxides such as sodium hydroxide provide a high alkaline environment to accelerate the decomposition of slag. Hydroxides provide the high alkalinity required for rapid startup, while water glass continues to provide an alkaline environment and a key silicon source in the middle and late stages of the reaction, maintaining the continuous progress of the reaction and avoiding reaction stagnation due to a rapid decrease in alkalinity. The formation rate of ettringite is usually faster than that of CSH gel, and its needle-shaped crystals can form an interwoven structure in the early stage, providing a significant contribution to early strength. The presence of sulfate accelerates this process. The composite alkali activator can quickly obtain sufficient strength and form an extremely dense, fine microstructure with few pores, thereby giving the material excellent resistance to damage caused by repeated freeze-thaw cycles. However, the composite alkali activator of the present invention needs to be used in conjunction with an interface treatment agent to maximize its effect. The interface treatment agent forms an interface between the unhydrated / partially hydrated cementitious material particles and between them and the hydration products, improving interfacial bonding, filling / closing pores and microcracks, and improving toughness. The ultrafine nanoparticles of the modified nano-silica sol can fill in the pores between the unhydrated particles and the early hydration products, playing a physical filling role and increasing the density. The surface silanols can react with the dissolved Ca in an alkaline environment. 2+The reaction generates additional CSH gel, which accelerates and strengthens the connection between particles and directly contributes to the early strength. There are also modified amino groups on the surface, which react with the epoxy groups on the side chains of the vinyl acetate copolymer, further strengthening this effect. During the stirring and early hydration process of the vinyl acetate copolymer emulsion, the polymer particles are dispersed in the slurry. As the water evaporates or is consumed by hydration, the polymer particles gradually condense into a film. This continuous or discontinuous flexible polymer film wraps and bridges around the unhydrated particles, hydration products and pores, providing additional adhesion and cohesion. The presence of the copolymer has flexibility. When the internal water freezes and generates expansion pressure, it can absorb and buffer part of the stress and reduce damage to the rigid hydration product skeleton. The synergistic mechanism of the composite alkali activator and the interface treatment agent is still unclear. The inventor speculates that the possible reason is that the alkali-activated cementitious material has weak areas compared to the cement material, such as larger pores and uneven pores. The interface treatment agent can penetrate these weak areas and significantly improve the toughness and crack resistance of these weak areas. The combined effect of these two factors makes the previously relatively weak ITZ region denser, more bonded, and more resilient, significantly increasing the strength of the weak region against damage caused by freeze-thaw cycles. Together, they optimize the interface and microstructure of the cementitious material, resulting in a highly homogeneous, defect-free, and balancedly rigid and flexible whole.

[0031] Through extensive research on steel slag and blast furnace slag, both bulk industrial solid wastes, and a certain proportion of desulfurized gypsum, the inventors have simultaneously improved the mechanical strength and freeze-thaw cycle resistance of cementitious materials through the combined action of a composite alkali activator and an interface treatment agent. In particular, they have simultaneously improved the early strength and freeze-thaw cycle resistance of these materials. This allows the cementitious materials to be used in high-humidity and cold regions. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is an SEM photograph of the cementitious material of Example 1 after curing for 28 days and undergoing 100 freeze-thaw cycles.

[0033] Figure 2 This is an SEM photograph of the cementitious material of Comparative Example 5 after curing for 28 days and undergoing 100 freeze-thaw cycles. DETAILED DESCRIPTION

[0034] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] The mass percentages of fly ash components are as follows:

[0036] <![CDATA[SiO2]]> <![CDATA[Al2O3]]> CaO <![CDATA[Fe2O3]]> MgO <![CDATA[TiO2]]> <![CDATA[Na2O / K2O]]> <![CDATA[P2O5]]> 51.3％ 30.8％ 4.5％ 6.1％ 1.3％ 0.8％ 1.2％ 0.6％

[0037] The mass percentages of steel slag components are as follows:

[0038] CaO <![CDATA[SiO2]]> <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> MgO <![CDATA[TiO2]]> MnO 38.2％ 17.4％ 22.3％ 7.6％ 6.0％ 2.6％ 3.9％

[0039] The mass percentages of blast furnace slag components are as follows:

[0040] CaO <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> MgO <![CDATA[TiO2]]> MnO 34.5％ 25.8％ 17.2％ 2.6％ 8.3％ 1.3％ 9.4％

[0041] The structural formula of Silane-PEG-NH2 is as follows:

[0042] Where n=1000, Silane-PEG 1000 -NH2; n = 1200, Silane-PEG 1200 -NH2; n = 2000, Silane-PEG 2000 -NH2; n = 3000, Silane-PEG 3000 -NH2.

[0043] Preparation Example 1-1

[0044] 400 parts by mass of 25% solid content nano-silica sol (nano-SiO2 average particle size of 160nm) were heated to 60°C and added with stirring within 10 minutes 30 parts by mass of Silane-PEG 2000 -NH2, keep warm and continue the reaction for 3 hours, cool to room temperature to obtain modified nano-silica sol, and adjust the solid content to 30%.

[0045] Preparation Example 1-2

[0046] Other conditions were the same as those in Preparation Example 1-1, except that 30 parts by mass of Silane-PEG 2000 -NH2 is replaced by 45 parts by mass of Silane-PEG 1200 -NH2.

[0047] Preparation Examples 1-3

[0048] Other conditions are the same as those in Preparation Example 1-1, except that Silane-PEG 2000 -NH2 is replaced by Silane-PEG of equal mass 1000 -NH2.

[0049] Preparation Examples 1-4

[0050] Other conditions were the same as those in Preparation Example 1-1, except that 30 parts by mass of Silane-PEG 2000 -NH2 is replaced by Silane-PEG of equal mass 3000 -NH2.

[0051] Comparative Preparation Example 1

[0052] Other conditions were the same as those in Preparation Example 1-1, except that 30 parts by mass of Silane-PEG2000 -NH2 was replaced by 15 parts by mass of γ-aminopropyltriethoxysilane.

[0053] Preparation Example 2-1

[0054] The raw materials are 100 parts by mass of vinyl acetate, 35 parts by mass of butyl acrylate, 10 parts by mass of vinyltriethoxysilane, 6 parts by mass of glycidyl acrylate, 8 parts by mass of polyvinyl alcohol, 14 parts by mass of emulsifier (a mixture of SDS and Tween 20 in a mass ratio of 1:1), and 2.6 parts by mass of initiator ammonium persulfate.

[0055] (P1) mixing vinyl acetate, butyl acrylate, vinyl triethoxysilane, and glycidyl acrylate to obtain a mixed monomer;

[0056] (P2) Add polyvinyl alcohol (PVA) with a degree of polymerization of 1800 to 400 parts by mass of water, heat to 90°C, stir until completely dissolved, add an emulsifier and 25% of an initiator, mix well, slowly add 25% of the mixed monomer under reflux, and react for 1 hour to obtain a seed emulsion; slowly add the remaining mixed monomer and initiator in 3 batches, adding 25% of the mixed monomer and 25% of the initiator in each batch, and the addition time of each batch is 10 minutes. After the addition, continue to react for 30 minutes, add the next batch of raw materials, and after all the materials are added, continue to reflux and react for 1 hour, cool to 40°C, filter, discharge, adjust the solid content to 30%, and discharge to obtain a vinyl acetate copolymer emulsion.

[0057] Preparation Example 2-2

[0058] The rest is the same as Preparation Example 2-1, except that the raw materials are 100 parts by mass of vinyl acetate, 22 parts by mass of butyl acrylate, 6 parts by mass of vinyltriethoxysilane, 4 parts by mass of glycidyl acrylate, 7 parts by mass of polyvinyl alcohol, 14 parts by mass of emulsifier (the emulsifier is a mixture of SDS and Tween 20 in a mass ratio of 1:1), and 2.2 parts by mass of initiator ammonium persulfate.

[0059] Comparative Preparation Example 2-1

[0060] The other ingredients were the same as in Preparation Example 2-1, except that the raw materials were 100 parts by mass of vinyl acetate, 27 parts by mass of butyl acrylate, 6 parts by mass of glycidyl acrylate, 8 parts by mass of polyvinyl alcohol, 14 parts by mass of an emulsifier (a mixture of SDS and Tween 20 in a mass ratio of 1:1), and 2.6 parts by mass of ammonium persulfate as an initiator. Vinyltriethoxysilane was omitted.

[0061] Comparative Preparation Example 2-2

[0062] The other ingredients were the same as in Preparation Example 2-1, except that the raw materials were 100 parts by mass of vinyl acetate, 35 parts by mass of butyl acrylate, 10 parts by mass of vinyltriethoxysilane, 8 parts by mass of polyvinyl alcohol, 14 parts by mass of an emulsifier (a mixture of SDS and Tween 20 in a mass ratio of 1:1), and 2.6 parts by mass of an initiator, ammonium persulfate. That is, glycidyl acrylate was not added.

[0063] Example 1

[0064] (S1) 50 parts by mass of steel slag, 35 parts by mass of blast furnace slag, and 26 parts by mass of fly ash were ball-milled at a speed of 300 rpm for 5 h to obtain a mixed material A;

[0065] (S2) 15 parts by mass of desulfurized gypsum and 5 parts by mass of a composite alkali activator are uniformly mixed, wherein the composite alkali activator is a mixture of water glass (Na2O·nSiO2, where n is 2.4), sodium sulfate, and calcium hydroxide in a mass ratio of 100:35:15, aged, and dried to a moisture content of ≤1% to obtain a mixed material B;

[0066] (S3) Mixed material A and mixed material B are evenly mixed by ball milling, and 5 parts by mass of calcium chloride and 15 parts by mass of an interface treatment agent are added. The interface treatment agent is a compound of the modified nano-silica sol prepared in Preparation Example 1-1 and the vinyl acetate copolymer emulsion prepared in Preparation Example 2-1 in a mass ratio of 1:1. The mixture is evenly mixed in a high-speed mixer to obtain an early-strength freeze-thaw cycle-resistant gelling material.

[0067] Example 2

[0068] (S1) 50 parts by mass of steel slag, 32 parts by mass of blast furnace slag, and 30 parts by mass of fly ash were ball-milled at a speed of 300 rpm for 5 h to obtain a mixed material A;

[0069] (S2) 11 parts by mass of desulfurized gypsum and 4 parts by mass of a composite alkali activator are uniformly mixed, wherein the composite alkali activator is a mixture of water glass (Na2O·nSiO2, where n is 2.4), sodium sulfate, and calcium hydroxide in a mass ratio of 100:40:10, aged, and dried to a moisture content of ≤1% to obtain a mixed material B;

[0070] (S3) Mixed material A and mixed material B are evenly mixed by ball milling, and 3 parts by mass of calcium chloride and 11 parts by mass of an interface treatment agent are added. The interface treatment agent is a compound of the modified nano-silica sol prepared in Preparation Example 1-1 and the vinyl acetate copolymer emulsion prepared in Preparation Example 2-1 in a mass ratio of 2:1. The mixture is evenly mixed in a high-speed mixer to obtain an early-strength freeze-thaw cycle-resistant gelling material.

[0071] Example 3

[0072] (S1) 50 parts by mass of steel slag, 42 parts by mass of blast furnace slag, and 22 parts by mass of fly ash were ball-milled at a speed of 300 rpm for 5 h to obtain a mixed material A;

[0073] (S2) 17 parts by mass of desulfurized gypsum and 6 parts by mass of a composite alkali activator are uniformly mixed, wherein the composite alkali activator is a mixture of water glass (Na2O·nSiO2, where n is 2.4), sodium sulfate, and calcium hydroxide in a mass ratio of 100:30:17, aged, and dried to a moisture content of ≤1% to obtain a mixed material B;

[0074] (S3) Mixed material A and mixed material B are evenly mixed by ball milling, and 5 parts by mass of calcium chloride and 17 parts by mass of an interface treatment agent are added. The interface treatment agent is a compound of the modified nano-silica sol prepared in Preparation Example 1-1 and the vinyl acetate copolymer emulsion prepared in Preparation Example 2-1 in a mass ratio of 1:2. The mixture is evenly mixed in a high-speed mixer to obtain an early-strength freeze-thaw cycle-resistant gelling material.

[0075] Example 4

[0076] Other conditions were the same as those in Example 1, except that the modified nano-silica sol prepared in Preparation Example 1-1 was replaced by the modified nano-silica sol prepared in Preparation Example 1-2.

[0077] Example 5

[0078] Other conditions were the same as those in Example 1, except that the modified nano-silica sol prepared in Preparation Example 1-1 was replaced by the modified nano-silica sol prepared in Preparation Example 1-3.

[0079] Example 6

[0080] Other conditions were the same as those in Example 1, except that the modified nano-silica sol prepared in Preparation Example 1-1 was replaced by the modified nano-silica sol prepared in Preparation Example 1-4.

[0081] Example 7

[0082] Other conditions were the same as those in Example 1, except that the vinyl acetate copolymer emulsion prepared in Preparation Example 2-1 was replaced by the vinyl acetate copolymer emulsion prepared in Preparation Example 2-2.

[0083] Comparative Example 1

[0084] Other conditions were the same as those in Example 1, except that the modified nano-silica sol prepared in Preparation Example 1-1 was replaced by the vinyl acetate copolymer emulsion prepared in Comparative Preparation Example 1.

[0085] Comparative Example 2

[0086] Other conditions were the same as those in Example 1, except that the vinyl acetate copolymer emulsion prepared in Preparation Example 2-1 was replaced by the vinyl acetate copolymer emulsion prepared in Comparative Preparation Example 2-1.

[0087] Comparative Example 3

[0088] Other conditions were the same as those in Example 1, except that the vinyl acetate copolymer emulsion prepared in Preparation Example 2-1 was replaced by the vinyl acetate copolymer emulsion prepared in Comparative Preparation Example 2-2.

[0089] Comparative Example 4

[0090] Other conditions were the same as those in Example 1, except that the interface treatment agents were all modified nano-silica sols prepared in Preparation Example 1-1.

[0091] Comparative Example 5

[0092] Other conditions were the same as those in Example 1, except that the interface treatment agents were all vinyl acetate copolymer emulsions prepared in Preparation Example 2-1.

[0093] Application Examples

[0094] The cementitious materials of the above examples and comparative examples were prepared into 50 mm × 50 mm × 100 mm test blocks at a water-binder ratio of 0.32. Performance testing was conducted under the test conditions described in GB / T 17671-2021. The results are shown in Table 1 below. After 28 days of curing, the freeze-thaw cycles were repeated 100 times at temperatures ranging from -20±2°C / 4 hours to 25±2°C / 8 hours. The compressive and flexural strengths were then retested. The strength retention was calculated using the 28-day compressive and flexural strengths as the baseline.

[0095] Figure 1 This is an SEM photograph of the cementitious material of Example 1 after curing for 28 days and undergoing 100 freeze-thaw cycles. Figure 2 This is an SEM photograph of the cementitious material of Comparative Example 5 after 28 days of curing and 100 freeze-thaw cycles. It can be seen that the cementitious material of the Example maintains its pre-freeze-thaw microstructure after freeze-thaw cycles, while the cementitious material of Comparative Example 5 exhibits poor freeze-thaw cycle resistance, exhibiting numerous cracks and resulting in a loss of mechanical properties.

[0096] Table 1 Cementitious material performance test

[0097]

[0098]

[0099] It can be seen from the data in Table 1 that the cementitious material provided by the present invention, through the coordinated action of the composite alkali activator and the interface treatment agent, takes into account both early strength and freeze-thaw cycle resistance, and expands the use of such cementitious materials that utilize bulk industrial solid waste in cold regions.

Claims

1. An early-strength freeze-thaw cycle resistant gelling material, characterized in that: The method comprises the following raw materials in parts by weight: 50 parts of steel slag, 32-42 parts of blast furnace slag, 11-17 parts of desulfurized gypsum, 22-30 parts of fly ash, 3-5 parts of calcium chloride, 4-7 parts of composite alkali activator, and 11-17 parts of interface treatment agent; The composite alkali activator includes water glass, sulfate, and hydroxide of alkali metal / alkaline earth gold; The interface treatment agent is a compound of modified nano silica sol and vinyl acetate copolymer emulsion.

2. The early strength freeze-thaw cycle resistant gelling material according to claim 1, characterized in that: The modified nano silica sol is nano silica sol that has been treated with Silane-PEG-(CH2) a -NH2 modified, the chemical expression of Silane is -O(CH2) b -NHCONH-(CH2) c -Si(OR1)(OR2)(OR3), wherein R1, R2, and R3 are independently selected from at least one of methyl, ethyl, propyl, butyl, pentyl, and phenyl; a, b, and c are independently integers from 0 to 3; and / or The raw materials for preparing the vinyl acetate copolymer include: 100 parts by mass of vinyl acetate, 7-10 parts by mass of polyvinyl alcohol, 22-35 parts by mass of (meth)acrylate C4-6 alkyl ester, 6-10 parts by mass of alkenyl silane coupling agent, 4-6 parts by mass of epoxy-containing acrylate derivative, and 2-4 parts by mass of persulfate.

3. The early strength freeze-thaw cycle resistant gelling material according to claim 1 or 2, characterized in that: The composite alkali activator is a mixture of water glass, sulfate, and hydroxide of alkali metal / alkaline earth gold in a mass ratio of 100:30-40:10-17.

4. The early strength freeze-thaw cycle resistant gelling material according to claim 1, characterized in that: In the composite alkali activator, the water glass is Na2O·nSiO2, where n is 1.8-2.6; the sulfate is selected from at least one of sodium sulfate, potassium sulfate, and calcium sulfate; the hydroxide of alkali metal / alkaline earth gold is selected from at least one of sodium hydroxide, potassium hydroxide, and calcium hydroxide; and / or The solid contents of the modified nano-silica sol and the vinyl acetate copolymer emulsion are independently 30-40%; the mass ratio of the modified nano-silica sol and the vinyl acetate copolymer emulsion is 1-2:1-2.

5. The early strength freeze-thaw cycle resistant gelling material according to claim 1, characterized in that: The vinyl acetate copolymer emulsion is prepared by a preparation method comprising the following steps: (P1) uniformly mixing vinyl acetate, a C4-6 alkyl (meth)acrylate, an alkenyl silane coupling agent, and an epoxy group-containing acrylate derivative to obtain a mixed monomer; (P2) dissolving polyvinyl alcohol in water under heating conditions, adding an emulsifier and 20-30% of an initiator, and mixing uniformly, slowly adding 20-30% of a mixed monomer under reflux, and reacting for 0.5-1 hour to obtain a seed emulsion; slowly adding the remaining mixed monomer and initiator in 3-5 batches, and after all materials have been added, continuing the reflux reaction, cooling, filtering, discharging, adjusting the solid content, and discharging; Furthermore, in step (S2), the slow addition is completed within 10-15 minutes, the interval between each addition is 1-2 hours, the reflux reaction time is continued for 1-2 hours, and the temperature is lowered to 20-40°C.

6. The early strength freeze-thaw cycle resistant gelling material according to claim 2, characterized in that: The number average molecular weight of the polyvinyl alcohol polymer is 1000-2000, preferably 1500-1900; the C4-6 alkyl (meth)acrylate is selected from at least one of butyl (meth)acrylate, pentyl (meth)acrylate, and hexyl (meth)acrylate; the alkenyl silane coupling agent is selected from at least one of vinyl triethoxysilane and vinyl triisopropoxysilane; the epoxy-containing acrylate derivative is selected from glycidyl (meth)acrylate; and the persulfate is selected from at least one of ammonium persulfate, sodium persulfate, and potassium persulfate.

7. The early strength freeze-thaw cycle resistant gelling material according to claim 2, characterized in that: The size of silica in nano-silica sol is 100-200nm, silica and Silane-PEG-(CH2) a -NH2 mass ratio is 100:30-45; further, the solid content of the modified nano-silica sol is 25-40%.

8. The early strength freeze-thaw cycle resistant gelling material according to claim 2, characterized in that: Silane-PEG-(CH2) a -NH2, the number average molecular weight of the PEG segment is 1200-2000, Silane- represents -OCH2CH2-NHCONH-CH2CH2CH2-Si(OCH3)3, -OCH2CH2-NHCONH-CH2CH2CH2-Si(OCH2CH3)3, or -OCH2CH2-NHCONH-CH2CH2CH2-Si(OCH2CH2CH3)3.

9. The early strength freeze-thaw cycle resistant gelling material according to claim 2, characterized in that The modified nano-silica sol is prepared by the following preparation method: heating the nano-silica sol with a solid content of 30-40% to 50-65°C, adding Silane-PEG-(CH2) a -NH2, keep warm and continue the reaction for 2-5h to obtain modified nano-silica sol.

10. The method for preparing the early-strength freeze-thaw cycle resistant gelling material according to any one of claims 1 to 9, characterized in that: The following steps are involved: (S1) ball milling steel slag, blast furnace slag, and fly ash to obtain a mixed material A; (S2) mixing the desulfurized gypsum and the composite alkali activator uniformly, aging, and drying to obtain a mixed material B; (S3) mixing the mixed material A and the mixed material B by ball milling, adding calcium chloride and an interface treatment agent, and mixing them evenly with a high-speed mixer to obtain an early-strength freeze-thaw cycle-resistant gelling material; Furthermore, in step (S1), the ball milling speed is 200-400 rpm, the ball milling time is 3-5 h, and the specific surface area of ​​the mixed material A is 300-500 m 2 / kg; in step (S2), the mixture is evenly mixed in a high-speed mixer, aged for 1-3 days, and dried to a moisture content of ≤0.7%; in step (S3), the ball milling speed is 100-150rpm, and the ball milling time is 10-20h.

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