Slag-containing anti-cracking cement mortar and preparation method thereof

Abstract

The invention discloses an anti-cracking cement mortar containing slag and a preparation method thereof, and relates to the technical field of slag cement mortars.The anti-cracking cement mortar is prepared from, by mass, 100 parts of a slag cement raw material, 39-44.5 parts of water, 0.6-1 part of a polycarboxylic acid water reducing agent, 0.3-0.5 part of a super absorbent polymer, 4-5 parts of an exciting agent and 0.03-0.05 part of multi-walled carbon nanotubes; the preparation method of the anti-cracking cement mortar comprises the following steps: premixing the slag cement raw material, the super absorbent polymer and the multi-walled carbon nanotubes for 1-2 minutes, sequentially adding the water, the polycarboxylic acid water reducing agent and the exciting agent, mixing at a low speed for 1-2 minutes, and mixing at a high speed for 3-5 minutes to obtain the anti-cracking cement mortar.

Description

Technical Field

[0001] The present invention relates to the technical field of slag cement mortar, and specifically to a crack - resistant cement mortar containing slag and its preparation method. Background Technique

[0002] With the rapid development of the construction industry, traditional cement mortar has gradually become difficult to meet the green environmental protection requirements due to problems such as high energy consumption and high carbon emissions. The production of ordinary Portland cement requires high - temperature calcination, which not only consumes a large amount of energy but also is accompanied by significant greenhouse gas emissions, conflicting with the current trend of low - carbon economic development. As an important part of industrial waste residue, the active components of slag can replace part of the cement clinker. While improving the mechanical properties of mortar and reducing production costs, it can also reduce environmental pollution.

[0003] Research shows that the incorporation of slag can optimize the structure of cement stone, improve the density of materials, and effectively inhibit the generation of cracks. However, in the existing technology, the synergistic mechanism between the slag content and the crack - resistance performance of mortar has not been fully clarified, and some products have problems such as insufficient early strength, high dry - shrinkage rate, or unstable construction performance. In addition, key technical links such as the control of slag particle size distribution, the compatibility of activators, and the optimization of production process parameters still need to be broken through, restricting the large - scale application of slag in crack - resistant mortar.

[0004] Under this background, developing a preparation technology for slag - based crack - resistant cement mortar with both environmental protection and functionality has important practical significance for promoting the transformation and upgrading of the building materials industry and realizing the green development of construction projects. Summary of the Invention

[0005] The purpose of the present invention is to provide a crack - resistant cement mortar containing slag and its preparation method to solve the problems raised in the existing technology.

[0006] To achieve the above purpose, the present invention provides the following technical solutions: A crack - resistant cement mortar containing slag, the proportion of each component in the crack - resistant cement mortar, by mass fraction, includes: 100 parts of slag cement raw material, 39 - 44.5 parts of water, 0.6 - 1 part of polycarboxylate water - reducing agent, 0.3 - 0.5 part of superabsorbent polymer, 4 - 5 parts of activator, and 0.03 - 0.05 part of multi - walled carbon nanotubes.

[0007] Further, the proportion of each component in the slag cement raw material, by mass percentage, includes: 70wt% alkali slag, 5 - 20wt% cement, and 10 - 25wt% gypsum.

[0008] Further, the proportion of each component in the alkali-activated slag, by mass percentage, includes: 32.46 wt% SiO2, 15.96 wt% Al2O3, 38.63 wt% CaO, 0.34 wt% Fe2O3, 7.51 wt% MgO, 0.30 wt% Na2O, 0.40 wt% K2O, 2.55 wt% SO3, and 1.29 wt% of other components.

[0009] Further, the particle sizes of the alkali-activated slag, cement, and gypsum are ≤ 70 μm.

[0010] Further, the proportion of each component in the activator, by mass percentage, includes: 33 - 56 wt% NaOH, 40 - 55% Na2SO4, and 5 - 17 wt% Na2O·1.5SiO2.

[0011] Further, the preparation method of the polycarboxylate water reducer includes the following steps: S1: After vacuum-drying the reaction vessel, nitrogen is introduced, n-butanol and sodium methoxide are added, and the mixture is heated to 90 - 95 °C for 20 - 25 min. Then it is heated to 120 - 121 °C, ethylene oxide is added, and it is heated to 130 - 160 °C and reacted under a pressure of 0.1 - 0.6 MPa for 2 - 4 h. It is cooled to 120 - 121 °C for aging for 30 - 35 min, and the material is discharged under reduced pressure. The product is neutralized with acetic acid to neutrality, and the product is filtered under vacuum using activated carbon to obtain polyether; S2: The polyether, acrylic acid, p-toluenesulfonic acid, phenothiazine, and toluene are added to the reaction vessel, and the mixture is heated to 140 - 145 °C for 12 - 13 h. It is cooled to 90 - 92 °C, and toluene is removed using a circulating water vacuum pump to obtain the esterified monomer; S3: The esterified monomer, acrylic acid, and mercaptopropionic acid are added to deionized water and stirred evenly to obtain solution A; ammonium persulfate is added to deionized water and stirred evenly to obtain solution B; sodium bisulfite is added to deionized water and stirred evenly to obtain solution C; solution A, solution B, and solution C are sequentially added to the reaction vessel, and the mixture is heated to 60 - 65 °C for 2 - 2.5 h, cooled to room temperature, and the pH of the product is adjusted to 6 - 7 to obtain the polycarboxylate water reducer.

[0012] Further, the solid content of the polycarboxylate water reducer is 30%.

[0013] Further, in the preparation process of the polyether, the molar ratio of n-butanol:sodium methoxide:ethylene oxide is 1:(0.05 - 0.1):(6 - 10).

[0014] Furthermore, the proportions of the components in the preparation process of the esterification monomer include, by mass, 600-800 parts of polyether, 72-96 parts of acrylic acid, 20.2-26.9 parts of p-toluenesulfonic acid, 1.0-1.3 parts of phenothiazine, and 202-269 parts of toluene.

[0015] Furthermore, the proportions of the components in the preparation process of the polycarboxylate water-reducing agent include, by mass, 300-500 parts of esterification monomer, 36-60 parts of acrylic acid, 1.06-1.76 parts of mercaptopropionic acid, 3.36-5.6 parts of ammonium persulfate, and 3.06-5.1 parts of sodium bisulfite.

[0016] Furthermore, the method for preparing the highly water-absorbent polymer comprises the following steps: Add methacrylic acid, n-butyl methacrylate and acrylamide to N,N-dimethylformamide, stir evenly, add nano-silica suspension, N,N'-methylenebisacrylamide and azobisisobutyronitrile, stir evenly, heat to 60-65°C under argon atmosphere and react for 12-12.5h, add the product into deionized water to swell, dry in vacuum at 100-105°C, grind to obtain a highly absorbent polymer.

[0017] Furthermore, in the preparation process of the highly absorbent polymer, the molar ratio of methacrylic acid: n-butyl methacrylate: acrylamide is 1:1:1; the amount of N,N'-methylenebisacrylamide added is 0.4 mol% of the total monomer concentration; the amount of azobisisobutyronitrile added is 0.5 mol% of the total monomer concentration; and the amount of nano-silicon dioxide added is 5-10 wt% of the total monomer mass.

[0018] A method for preparing anti-cracking cement mortar containing slag, comprising the following steps: premixing slag cement raw materials, highly absorbent polymers, and multi-walled carbon nanotubes for 1-2 minutes, sequentially adding water, polycarboxylate water reducer, and activator, mixing at a low speed for 1-2 minutes, and mixing at a high speed for 3-5 minutes, to obtain anti-cracking cement mortar; Furthermore, the low-speed mixing rate is 100-300 rpm, and the high-speed mixing rate is 500-1200 rpm.

[0019] Furthermore, the multi-walled carbon nanotubes have a thickness of 30 nm, a diameter of 5-15 nm, and a length of 48-78 nm.

[0020] Furthermore, the particle size of the nano-silicon dioxide is 50 nm. Compared with the prior art, the present invention has the following beneficial effects: 1. Through the water retention regulation of nano-silica composite superabsorbent polymer, the present invention utilizes the silicon-oxygen framework of nano-silica to improve the structural rigidity of the superabsorbent polymer, and its surface hydroxyl groups adsorb water through hydrogen bonds. At the same time, the pozzolanic reaction of nano-particles generates C-S-H gel, which is tightly connected to the matrix to form capillary channels, realizing continuous release under the drive of water gradient, maintaining the internal humidity, and reducing autogenous shrinkage stress.

[0021] 2. Through the self-made shrinkage-reducing polycarboxylate superplasticizer, the present invention utilizes the unreacted esterified macromonomer and the unadsorbed polycarboxylate superplasticizer molecules to enrich in the pore solution, reducing the capillary stress; the hydrophobic modification of the side chain reduces the adsorption of C3A, inhibits the excessive generation of early AFt, and optimizes the pore structure.

[0022] 3. The present invention further optimizes the ratio of the slag-gypsum-clinker system and the activator. On the one hand, it plays the synergistic effect of nano-silica composite superabsorbent polymer and the slag-gypsum-clinker system. Nano-silica is embedded in the SAP network through physical adsorption and chemical grafting, enhancing its water absorption rate in the alkaline environment, and stabilizing the SAP structure through the rigidity of the silicon-oxygen framework. At the same time, the pozzolanic reaction of nano-silica generates C-S-H gel, which reacts with the active Al2O3 and CaO in the slag to form stable ettringite (AFt), filling the pores and improving the matrix density. On the other hand, it utilizes the synergistic effect of the shrinkage-reducing polycarboxylate superplasticizer and the slag-gypsum system. The unreacted esterified macromonomer and the unadsorbed molecules of the polycarboxylate superplasticizer enrich in the pore solution, reducing the surface tension and significantly reducing the capillary stress. In the slag system, the low adsorption characteristics of the polycarboxylate superplasticizer enable it to be more retained in the liquid phase, forming a dynamic equilibrium with the Ca 2+ 、Al 3+ released from the slag, inhibiting the explosive crystallization of AFt, delaying the accumulation of shrinkage stress, prolonging the hydration induction period of the polycarboxylate superplasticizer, delaying the rapid reaction of C3A, and reducing the excessive generation of early AFt. The retarding characteristics of the slag and the polycarboxylate superplasticizer cooperate to form a "double retarding effect", optimizing the hydration heat release curve and reducing the risk of temperature stress cracking. Specific Embodiments

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0024] Example 1: A preparation method of crack-resistant cement mortar containing slag, comprising the following steps: S1: After vacuum drying the reaction vessel, introduce nitrogen, add 1 mmol of n-butanol and 0.05 mmol of sodium methoxide, heat to 90 °C and react for 20 min, then heat to 120 °C, add 6 mmol of ethylene oxide, heat to 130 °C, and react under a pressure of 0.2 MPa for 3 h. Cool to 120 °C and age for 30 min. Release the pressure and discharge the material. Neutralize the product with acetic acid to neutrality, and vacuum filter the product with activated carbon to obtain polyether; S2: Add 600 g of polyether, 36 g of acrylic acid, 1.06 g of p-toluenesulfonic acid, 3.36 g of phenothiazine, and 202 g of toluene into the reaction vessel, heat to 140 °C and react for 12 h, then cool to 90 °C, and remove toluene using a circulating water vacuum pump to obtain an esterified monomer; S3: Add 300 g of the esterified monomer, 36 g of acrylic acid, and 1.06 g of mercaptopropionic acid into 100 g of deionized water, stir evenly to obtain solution A; add 3.36 g of ammonium persulfate into 200 g of deionized water, stir evenly to obtain solution B; add 3.06 g of sodium bisulfite into 166 g of deionized water, stir evenly to obtain solution C; add solution A, solution B, and solution C into the reaction vessel in sequence, heat to 60 °C and react for 2 h, cool to room temperature, and adjust the pH of the product to 6 to obtain a polycarboxylate superplasticizer; S4: Add 1 mmol of methacrylic acid, 1 mmol of n-butyl methacrylate, and 1 mmol of acrylamide into N,N-dimethylformamide, stir evenly, add a nano-silica suspension containing 1.5 g of nano-silica, 0.012 mmol of N,N'-methylenebisacrylamide, and 0.015 mmol of azobisisobutyronitrile, stir evenly, and heat to 60 °C under an argon atmosphere and react for 12 h. Add the product into deionized water to swell, dry under vacuum at 100 °C, and grind to obtain a superabsorbent polymer; S5: Premix 70 g of alkali-activated slag, 5 g of cement, 25 g of gypsum, 0.3 g of superabsorbent polymer, and 0.03 g of multi-walled carbon nanotubes for 1 min, then add 44.5 g of water, 0.6 g of polycarboxylate superplasticizer, and 4 g of activator in sequence, mix at low speed for 1 min, and mix at high speed for 3 min to obtain crack-resistant cement mortar.

[0025] Example 2: A preparation method of crack-resistant cement mortar containing slag, comprising the following steps: A preparation method of crack-resistant cement mortar containing slag, comprising the following steps: S1: After vacuum drying the reaction vessel, introduce nitrogen, add 1 mmol of n-butanol and 0.05 mmol of sodium methoxide, heat to 90 °C and react for 20 min, then heat to 120 °C, add 6 mmol of ethylene oxide, heat to 130 °C, and react under a pressure of 0.2 MPa for 3 h. Cool to 120 °C and age for 30 min. Release the pressure and discharge the material. Neutralize the product with acetic acid to neutrality, and vacuum filter the product with activated carbon to obtain polyether; S2: Add 600 g of polyether, 36 g of acrylic acid, 1.06 g of p-toluenesulfonic acid, 3.36 g of phenothiazine, and 202 g of toluene into a reaction vessel, heat to 140 °C and react for 12 h, cool to 90 °C, and remove toluene using a circulating water vacuum pump to obtain an esterification monomer; S3: Add 300 g of the esterification monomer, 36 g of acrylic acid, and 1.06 g of mercaptopropionic acid into 100 g of deionized water, stir evenly to obtain solution A; add 3.36 g of ammonium persulfate into 200 g of deionized water, stir evenly to obtain solution B; add 3.06 g of sodium bisulfite into 166 g of deionized water, stir evenly to obtain solution C; add solution A, solution B, and solution C into the reaction vessel in sequence, heat to 60 °C and react for 2 h, cool to room temperature, adjust the pH of the product to 6 to obtain a polycarboxylate water reducer; S4: Add 1 mmol of methacrylic acid, 1 mmol of n-butyl methacrylate, and 1 mmol of acrylamide into N,N-dimethylformamide, stir evenly, add a nano-silica suspension containing 1.5 g of nano-silica, 0.012 mmol of N,N'-methylenebisacrylamide, and 0.015 mmol of azobisisobutyronitrile, stir evenly, heat to 60 °C and react for 12 h under an argon atmosphere, add the product into deionized water to swell, dry in vacuum at 100 °C, and grind to obtain a superabsorbent polymer; S5: Premix 70 g of alkali-activated slag, 20 g of cement, 10 g of gypsum, 0.3 g of the superabsorbent polymer, and 0.03 g of multi-walled carbon nanotubes for 1 min, then add 44.5 g of water, 0.6 g of the polycarboxylate water reducer, and 4 g of an activator in sequence, mix at low speed for 1 min, and mix at high speed for 3 min to obtain crack-resistant cement mortar.

[0026] Example 3: A method for preparing crack-resistant cement mortar containing slag, comprising the following steps: A method for preparing crack-resistant cement mortar containing slag, comprising the following steps: S1: After vacuum-drying the reaction vessel, introduce nitrogen, add 1 mmol of n-butanol and 1 mmol of sodium methoxide, heat to 90 °C and react for 20 min, heat to 120 °C, add 10 mmol of ethylene oxide, heat to 145 °C, react under a pressure of 0.4 MPa for 3 h, cool to 120 °C and age for 30 min, discharge under reduced pressure, neutralize the product to neutral with acetic acid, and filter the product using activated carbon under vacuum to obtain polyether; S2: Add 600 g of polyether, 36 g of acrylic acid, 1.06 g of p-toluenesulfonic acid, 3.36 g of phenothiazine, and 202 g of toluene into a reaction vessel, heat to 140 °C and react for 12 h, cool to 90 °C, and remove toluene using a circulating water vacuum pump to obtain an esterification monomer; S3: Add 300 g of esterified monomer, 36 g of acrylic acid, and 1.06 g of mercaptopropionic acid to 100 g of deionized water, stir evenly to obtain solution A; add 3.36 g of ammonium persulfate to 200 g of deionized water, stir evenly to obtain solution B; add 3.06 g of sodium bisulfite to 166 g of deionized water, stir evenly to obtain solution C; add solution A, solution B, and solution C to the reaction vessel in sequence, heat to 60 °C and react for 2 h, cool to room temperature, adjust the pH of the product to 6 to obtain a polycarboxylate water reducer; S4: Add 1 mmol of methacrylic acid, 1 mmol of n-butyl methacrylate, and 1 mmol of acrylamide to N,N-dimethylformamide, stir evenly, add a nano-silica suspension containing 1.5 g of nano-silica, 0.012 mmol of N,N'-methylenebisacrylamide, and 0.015 mmol of azobisisobutyronitrile, stir evenly, heat to 60 °C under an argon atmosphere and react for 12 h, add the product to deionized water to swell, dry in vacuum at 100 °C, and grind to obtain a superabsorbent polymer; S5: Premix 70 g of alkali-activated slag, 20 g of cement, 10 g of gypsum, 0.3 g of superabsorbent polymer, and 0.03 g of multi-walled carbon nanotubes for 1 min, then add 44.5 g of water, 0.6 g of polycarboxylate water reducer, and 4 g of activator in sequence, mix at low speed for 1 min, and mix at high speed for 3 min to obtain crack-resistant cement mortar.

[0027] Example 4: A preparation method of crack-resistant cement mortar containing slag, comprising the following steps: A preparation method of crack-resistant cement mortar containing slag, comprising the following steps: S1: After vacuum-drying the reaction vessel, introduce nitrogen, add 1 mmol of n-butanol and 1 mmol of sodium methoxide, heat to 90 °C and react for 20 min, heat to 120 °C, add 10 mmol of ethylene oxide, heat to 145 °C, and react for 3 h under a pressure of 0.4 MPa, cool to 120 °C and age for 30 min, release the pressure and discharge the material, neutralize the product with acetic acid to neutrality, and filter the product with activated carbon under vacuum to obtain polyether; S2: Add 600 g of polyether, 36 g of acrylic acid, 1.06 g of p-toluenesulfonic acid, 3.36 g of phenothiazine, and 202 g of toluene to the reaction vessel, heat to 140 °C and react for 12 h, cool to 90 °C, and remove toluene using a circulating water vacuum pump to obtain an esterified monomer; S3: Add 300 g of esterified monomer, 36 g of acrylic acid, and 1.06 g of mercaptopropionic acid to 100 g of deionized water, stir evenly to obtain solution A; add 3.36 g of ammonium persulfate to 200 g of deionized water, stir evenly to obtain solution B; add 3.06 g of sodium bisulfite to 166 g of deionized water, stir evenly to obtain solution C; add solution A, solution B, and solution C to the reaction vessel in sequence, heat to 60 °C and react for 2 h, cool to room temperature, adjust the pH of the product to 6 to obtain a polycarboxylate water reducer; S4: Add 1 mmol of methacrylic acid, 1 mmol of n-butyl methacrylate, and 1 mmol of acrylamide to N,N-dimethylformamide, stir evenly, add a nano-silica suspension containing 3 g of nano-silica, 0.012 mmol of N,N'-methylenebisacrylamide, and 0.015 mmol of azobisisobutyronitrile, stir evenly, heat to 60 °C under an argon atmosphere and react for 12 h, add the product to deionized water to swell, dry under vacuum at 100 °C, and grind to obtain a superabsorbent polymer; S5: Premix 70 g of alkali-activated slag, 20 g of cement, 10 g of gypsum, 0.3 g of superabsorbent polymer, and 0.03 g of multi-walled carbon nanotubes for 1 min, then add 44.5 g of water, 0.6 g of polycarboxylate water reducer, and 4 g of activator in sequence, mix at low speed for 1 min, and mix at high speed for 3 min to obtain crack-resistant cement mortar.

[0028] Example 5: A preparation method of crack-resistant cement mortar containing slag, comprising the following steps: A preparation method of crack-resistant cement mortar containing slag, comprising the following steps: S1: After vacuum-drying the reaction vessel, introduce nitrogen, add 1 mmol of n-butanol and 1 mmol of sodium methoxide, heat to 90 °C and react for 20 min, heat to 120 °C, add 10 mmol of ethylene oxide, heat to 145 °C, react under a pressure of 0.4 MPa for 3 h, cool to 120 °C and age for 30 min, release the pressure and discharge the material, neutralize the product with acetic acid to neutrality, and vacuum-filter the product with activated carbon to obtain polyether; S2: Add 600 g of polyether, 36 g of acrylic acid, 1.06 g of p-toluenesulfonic acid, 3.36 g of phenothiazine, and 202 g of toluene to the reaction vessel, heat to 140 °C and react for 12 h, cool to 90 °C, and remove toluene using a circulating water vacuum pump to obtain an esterified monomer; S3: Add 300 g of esterified monomer, 36 g of acrylic acid, and 1.06 g of mercaptopropionic acid to 100 g of deionized water, stir evenly to obtain solution A; add 3.36 g of ammonium persulfate to 200 g of deionized water, stir evenly to obtain solution B; add 3.06 g of sodium bisulfite to 166 g of deionized water, stir evenly to obtain solution C; add solution A, solution B, and solution C to the reaction vessel in sequence, heat to 60 °C and react for 2 h, cool to room temperature, adjust the pH of the product to 6 to obtain a polycarboxylate water reducer; S4: Add 1 mmol of methacrylic acid, 1 mmol of n-butyl methacrylate, and 1 mmol of acrylamide to N,N-dimethylformamide, stir evenly, add a nano-silica suspension containing 3 g of nano-silica, 0.012 mmol of N,N'-methylenebisacrylamide, and 0.015 mmol of azobisisobutyronitrile, stir evenly, heat to 60 °C under an argon atmosphere and react for 12 h, add the product to deionized water to swell, dry under vacuum at 100 °C, and grind to obtain a superabsorbent polymer; S5: Pre-mix 70 g of alkali slag, 20 g of cement, 10 g of gypsum, 0.4 g of superabsorbent polymer, and 0.04 g of multi-walled carbon nanotubes for 1 min, then add 42.2 g of water, 0.8 g of polycarboxylate water reducer, and 4 g of activator in sequence, mix at low speed for 1 min, and mix at high speed for 3 min to obtain crack-resistant cement mortar.

[0029] Example 6: A method for preparing crack-resistant cement mortar containing slag, comprising the following steps: A method for preparing crack-resistant cement mortar containing slag, comprising the following steps: S1: After vacuum-drying the reaction vessel, introduce nitrogen, add 1 mmol of n-butanol and 1 mmol of sodium methoxide, heat to 90 °C and react for 20 min, heat to 120 °C, add 10 mmol of ethylene oxide, heat to 145 °C, react under a pressure of 0.4 MPa for 3 h, cool to 120 °C and age for 30 min, release the pressure and discharge the material, neutralize the product with acetic acid to neutrality, and filter the product through activated carbon under vacuum to obtain polyether; S2: Add 600 g of polyether, 36 g of acrylic acid, 1.06 g of p-toluenesulfonic acid, 3.36 g of phenothiazine, and 202 g of toluene to the reaction vessel, heat to 140 °C and react for 12 h, cool to 90 °C, and remove toluene using a circulating water vacuum pump to obtain an esterified monomer; S3: Add 300 g of esterified monomer, 36 g of acrylic acid, and 1.06 g of mercaptopropionic acid to 100 g of deionized water, stir evenly to obtain solution A; add 3.36 g of ammonium persulfate to 200 g of deionized water, stir evenly to obtain solution B; add 3.06 g of sodium bisulfite to 166 g of deionized water, stir evenly to obtain solution C; add solution A, solution B, and solution C to the reaction vessel in sequence, heat to 60 °C and react for 2 h, cool to room temperature, adjust the pH of the product to 6 to obtain a polycarboxylate water reducer; S4: Add 1 mmol of methacrylic acid, 1 mmol of n-butyl methacrylate, and 1 mmol of acrylamide to N,N-dimethylformamide, stir evenly, add a nano-silica suspension containing 3 g of nano-silica, 0.012 mmol of N,N'-methylenebisacrylamide, and 0.015 mmol of azobisisobutyronitrile, stir evenly, heat to 60 °C under an argon atmosphere and react for 12 h, add the product to deionized water for swelling, vacuum dry at 100 °C, and grind to obtain a superabsorbent polymer; S5: Premix 70 g of alkali-activated slag, 20 g of cement, 10 g of gypsum, 0.5 g of superabsorbent polymer, and 0.05 g of multi-walled carbon nanotubes for 1 min, then add 39 g of water, 1 g of polycarboxylate water reducer, and 4 g of activator in sequence, mix at low speed for 1 min, and mix at high speed for 3 min to obtain crack-resistant cement mortar.

[0030] Comparative Example 1: A method for preparing crack-resistant cement mortar containing slag, comprising the following steps: S1: After vacuum drying the reaction vessel, introduce nitrogen, add 1 mmol of n-butanol and 0.05 mmol of sodium methoxide, heat to 90 °C and react for 20 min, heat to 120 °C, add 6 mmol of ethylene oxide, heat to 130 °C, react under a pressure of 0.2 MPa for 3 h, cool to 120 °C and age for 30 min, release the pressure and discharge the material, neutralize the product with acetic acid to neutrality, and filter the product through activated carbon under vacuum to obtain polyether; S2: Add 600 g of polyether, 36 g of acrylic acid, 1.06 g of p-toluenesulfonic acid, 3.36 g of phenothiazine, and 202 g of toluene to the reaction vessel, heat to 140 °C and react for 12 h, cool to 90 °C, and remove toluene using a circulating water vacuum pump to obtain an esterified monomer; S3: Add 300 g of esterified monomer, 36 g of acrylic acid, and 1.06 g of mercaptopropionic acid to 100 g of deionized water, stir evenly to obtain solution A; add 3.36 g of ammonium persulfate to 200 g of deionized water, stir evenly to obtain solution B; add 3.06 g of sodium bisulfite to 166 g of deionized water, stir evenly to obtain solution C; add solution A, solution B, and solution C to the reaction vessel in sequence, heat to 60 °C and react for 2 h, cool to room temperature, adjust the pH of the product to 6 to obtain a polycarboxylate water reducer; S4: Add 1 mmol of methacrylic acid and 1 mmol of n-butyl methacrylate into N,N-dimethylformamide, stir evenly, then add 0.012 mmol of N,N'-methylenebisacrylamide and 0.015 mmol of azobisisobutyronitrile, stir evenly again. Heat the mixture to 60 °C under an argon atmosphere and react for 12 h. Add the product into deionized water for swelling, then dry it in vacuum at 100 °C and grind it to obtain a superabsorbent polymer. S5: Premix 70 g of alkali slag, 5 g of cement, 25 g of gypsum, 0.3 g of superabsorbent polymer, and 0.03 g of multi-walled carbon nanotubes for 1 min. Then add 44.5 g of water, 0.6 g of polycarboxylate superplasticizer, and 4 g of activator in sequence, mix at low speed for 1 min, and then mix at high speed for 3 min to obtain crack-resistant cement mortar.

[0031] Comparative Example 2: A preparation method of crack-resistant cement mortar containing slag, comprising the following steps: S1: After vacuum-drying the reaction vessel, introduce nitrogen, add 1 mmol of n-butanol and 0.05 mmol of sodium methoxide, heat to 90 °C and react for 20 min. Then heat to 120 °C, add 6 mmol of ethylene oxide, heat to 130 °C, and react under a pressure of 0.2 MPa for 3 h. Cool to 120 °C and age for 30 min. Release the pressure and discharge the material. Neutralize the product with acetic acid to neutrality, and filter the product through activated carbon under vacuum to obtain polyether. S2: Add 600 g of polyether, 36 g of acrylic acid, 1.06 g of p-toluenesulfonic acid, 3.36 g of phenothiazine, and 202 g of toluene into the reaction vessel, heat to 140 °C and react for 12 h. Cool to 90 °C and remove toluene using a circulating water vacuum pump to obtain an esterified monomer. S3: Add 300 g of esterified monomer, 36 g of acrylic acid, and 1.06 g of mercaptopropionic acid into 100 g of deionized water, stir evenly to obtain Solution A; add 3.36 g of ammonium persulfate into 200 g of deionized water, stir evenly to obtain Solution B; add 3.06 g of sodium bisulfite into 166 g of deionized water, stir evenly to obtain Solution C. Add Solution A, Solution B, and Solution C into the reaction vessel in sequence, heat to 60 °C and react for 2 h, cool to room temperature, and adjust the pH of the product to 6 to obtain a polycarboxylate superplasticizer. S4: Premix 70 g of alkali slag, 5 g of cement, 25 g of gypsum, and 0.03 g of multi-walled carbon nanotubes for 1 min. Then add 44.5 g of water, 0.6 g of polycarboxylate superplasticizer, and 4 g of activator in sequence, mix at low speed for 1 min, and then mix at high speed for 3 min to obtain crack-resistant cement mortar.

[0032] Comparative Example 3: A preparation method of crack-resistant cement mortar containing slag, comprising the following steps: S1: Add 1 mmol of methacrylic acid, 1 mmol of n-butyl methacrylate, and 1 mmol of acrylamide into N,N-dimethylformamide, stir evenly, add a nano-silica suspension containing 1.5 g of nano-silica, 0.012 mmol of N,N'-methylenebisacrylamide, and 0.015 mmol of azobisisobutyronitrile, stir evenly, heat to 60 °C under an argon atmosphere and react for 12 h. Add the product into deionized water to swell, dry in vacuum at 100 °C, and grind to obtain a superabsorbent polymer; S2: Pre-mix 70 g of alkali slag, 5 g of cement, 25 g of gypsum, 0.3 g of superabsorbent polymer, and 0.03 g of multi-walled carbon nanotubes for 1 min, then add 44.5 g of water, 0.6 g of polycarboxylate superplasticizer PCA®-Ⅰ, and 4 g of activator in sequence, mix at low speed for 1 min, and mix at high speed for 3 min to obtain crack-resistant cement mortar.

[0033] Comparative Example 4: A preparation method of crack-resistant cement mortar containing slag, comprising the following steps: S1: After vacuum-drying the reaction vessel, introduce nitrogen, add 1 mmol of n-butanol and 0.05 mmol of sodium methoxide, heat to 90 °C and react for 20 min, heat to 120 °C, add 6 mmol of ethylene oxide, heat to 130 °C, and react for 3 h under a pressure of 0.2 MPa. Cool to 120 °C and age for 30 min, discharge under reduced pressure, neutralize the product with acetic acid to neutrality, and filter the product with activated carbon under vacuum to obtain polyether; S2: Add 600 g of polyether, 36 g of acrylic acid, 1.06 g of p-toluenesulfonic acid, 3.36 g of phenothiazine, and 202 g of toluene into the reaction vessel, heat to 140 °C and react for 12 h, cool to 90 °C, and remove toluene using a circulating water vacuum pump to obtain an esterified monomer; S3: Add 300 g of esterified monomer, 36 g of acrylic acid, and 1.06 g of mercaptopropionic acid into 100 g of deionized water, stir evenly to obtain Solution A; add 3.36 g of ammonium persulfate into 200 g of deionized water, stir evenly to obtain Solution B; add 3.06 g of sodium bisulfite into 166 g of deionized water, stir evenly to obtain Solution C; add Solution A, Solution B, and Solution C into the reaction vessel in sequence, heat to 60 °C and react for 2 h, cool to room temperature, and adjust the pH of the product to 6 to obtain a polycarboxylate superplasticizer; S4: Add 1 mmol of methacrylic acid, 1 mmol of n-butyl methacrylate, and 1 mmol of acrylamide into N,N-dimethylformamide, stir evenly, add a nano-silica suspension containing 1.5 g of nano-silica, 0.012 mmol of N,N'-methylenebisacrylamide, and 0.015 mmol of azobisisobutyronitrile, stir evenly, heat to 60 °C under an argon atmosphere and react for 12 h, add the product into deionized water to swell, dry in vacuum at 100 °C, and grind to obtain a superabsorbent polymer; S5: Premix 70 g of alkali slag, 5 g of cement, 25 g of gypsum, 0.3 g of superabsorbent polymer, and 0.03 g of multi-walled carbon nanotubes for 1 min, then add 44.5 g of water, 1.2 g of polycarboxylate superplasticizer, and 4 g of activator in sequence, mix at low speed for 1 min, and mix at high speed for 3 min to obtain crack-resistant cement mortar.

[0034] Experiment: Performance test of crack-resistant cement mortar: Test according to the method described in JC / T603-2004 "Test Method for Dry Shrinkage of Cement Mortar". Calculate the shrinkage rate ε i and the shrinkage reduction rate R.

[0035] ε i =L i -L0 / 250; where L0 is the initial length of the specimen, in mm; L i is the length of the specimen at different ages, in mm.

[0036] The experimental data are shown in Table 1 below.

[0037] Table 1 Data table of crack resistance performance test of crack-resistant cement mortar Shrinkage rate (7d) / % Shrinkage rate (28d) / % Example 1 0.09 0.16 Example 2 0.09 0.16 Example 3 0.08 0.16 Example 4 0.08 0.15 Example 5 0.07 0.15 Example 6 0.06 0.14 Comparative Example 1 0.11 0.19 Comparative Example 2 0.12 0.21 Comparative Example 3 0.14 0.23 Comparative Example 4 0.12 0.20 Conclusion: The crack-resistant cement mortar prepared by the present invention has excellent crack resistance performance.

[0038] In Comparative Example 1, nano-silica was not added to the superabsorbent polymer, resulting in a reduction in the crack resistance performance of the crack-resistant cement mortar; in Comparative Example 2, the superabsorbent polymer was not added, resulting in a reduction in the crack resistance performance of the crack-resistant cement mortar; in Comparative Example 3, a common commercially available polycarboxylate superplasticizer was used, resulting in a reduction in the crack resistance performance of the crack-resistant cement mortar; in Comparative Example 4, an excessive amount of polycarboxylate superplasticizer was used, resulting in a reduction in the crack resistance performance of the crack-resistant cement mortar.

[0039] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention.

Claims

1. A crack-proof cement mortar containing slag, characterized in that: The proportions of the individual components in the anti-cracking cement mortar, by mass, include: 100 parts of slag cement raw materials, 39-44.5 parts of water, 0.6-1 parts of polycarboxylic acid water-reducing agent, 0.3-0.5 parts of highly absorbent polymer, 4-5 parts of activator, and 0.03-0.05 parts of multi-walled carbon nanotubes.

2. The anti-cracking cement mortar containing slag according to claim 1, characterized in that: The proportions of the components in the slag cement raw materials, by weight percentage, include: 70wt% alkali slag, 5-20wt% cement, and 10-25wt% gypsum.

3. The anti-cracking cement mortar containing slag according to claim 1, characterized in that: The proportions of the components in the activator, by mass percentage, include: 33-56wt% NaOH, 40-55% Na2SO4, and 5-17wt% Na2O·1.5SiO2.

4. The anti-cracking cement mortar containing slag according to claim 1, characterized in that: The preparation method of the polycarboxylate water-reducing agent comprises the following steps: S1: After vacuum drying the reaction container, nitrogen is introduced, n-butanol and sodium methoxide are added, heated to 90-95°C for reaction for 20-25min, heated to 120-121°C, ethylene oxide is added, heated to 130-160°C, reacted at a pressure of 0.1-0.6MPa for 2-4h, cooled to 120-121°C for aging for 30-35min, discharged under reduced pressure, neutralized the product with acetic acid to neutrality, and vacuum filtered the product with activated carbon to obtain polyether; S2: Add polyether, acrylic acid, p-toluenesulfonic acid, phenothiazine and toluene into a reaction vessel, heat to 140-145° C. for reaction for 12-13 hours, cool to 90-92° C., remove toluene using a circulating water vacuum pump, and obtain an esterification monomer; S3: Add esterification monomer, acrylic acid and mercaptopropionic acid into deionized water, stir evenly to obtain solution A; add ammonium persulfate into deionized water, stir evenly to obtain solution B; add sodium bisulfite into deionized water, stir evenly to obtain solution C; add solution A, solution B and solution C into a reaction vessel in sequence, heat to 60-65°C for reaction for 2-2.5h, cool to room temperature, adjust the pH of the product to 6-7, and obtain a polycarboxylate water reducer.

5. The anti-cracking cement mortar containing slag according to claim 4, characterized in that: In the preparation process of the polyether, the molar ratio of n-butanol: sodium methoxide: ethylene oxide is 1: (0.05-0.1): (6-10).

6. The anti-cracking cement mortar containing slag according to claim 4, characterized in that: The proportions of the various components in the preparation process of the esterification monomer include, by mass, 600-800 parts of polyether, 72-96 parts of acrylic acid, 20.2-26.9 parts of p-toluenesulfonic acid, 1.0-1.3 parts of phenothiazine, and 202-269 parts of toluene.

7. The anti-cracking cement mortar containing slag according to claim 4, characterized in that: The proportions of the various components in the preparation process of the polycarboxylic acid water-reducing agent include, by mass, 300-500 parts of esterification monomer, 36-60 parts of acrylic acid, 1.06-1.76 parts of mercaptopropionic acid, 3.36-5.6 parts of ammonium persulfate, and 3.06-5.1 parts of sodium bisulfite.

8. The anti-cracking cement mortar containing slag according to claim 1, characterized in that: The method for preparing the highly water-absorbent polymer comprises the following steps: Add methacrylic acid, n-butyl methacrylate and acrylamide to N,N-dimethylformamide, stir evenly, add nano-silica suspension, N,N'-methylenebisacrylamide and azobisisobutyronitrile, stir evenly, heat to 60-65°C under argon atmosphere and react for 12-12.5h, add the product into deionized water to swell, dry in vacuum at 100-105°C, grind to obtain a highly absorbent polymer.

9. The anti-cracking cement mortar containing slag according to claim 8, characterized in that: During the preparation of the highly absorbent polymer, the molar ratio of methacrylic acid: n-butyl methacrylate: acrylamide is 1:1:1; the amount of N,N'-methylenebisacrylamide added is 0.4 mol% of the total monomer concentration; the amount of azobisisobutyronitrile added is 0.5 mol% of the total monomer concentration; and the amount of nano-silica added is 5-10 wt% of the total monomer mass.

10. The method for preparing a crack-resistant cement mortar containing slag according to any one of claims 1 to 9, characterized in that: The following steps are involved: The slag cement raw materials, highly absorbent polymer and multi-walled carbon nanotubes are premixed for 1-2 minutes, and water, polycarboxylic acid water reducer and activator are added in sequence, mixed at a low speed for 1-2 minutes and at a high speed for 3-5 minutes to obtain anti-cracking cement mortar.