Early setting promoting repair mortar and preparation method thereof
Through the repair mortar raw materials and activation treatment with specific ratios, a three-dimensional network is formed, which solves the problem of easy damage to existing repair mortars in harsh environments, and achieves the early repair effect with high strength and strong self-repair ability.
Patent Information
- Application Number
- CN202510577843.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-07
- Publication Date
- 2025-07-25
AI Technical Summary
The existing repair mortar is prone to damage in harsh environments such as humid, salty, and large temperature changes, resulting in the expansion of concrete cracks and high repair costs. The traditional repair method has a long construction period, making it difficult to quickly condense and lack of bonding with old concrete.
The three-dimensional network is formed by using silicate cement, nano-calcium carbonate, fly ash, expansion agent, polyol-based shrinkage agent, polycarboxylic acid-based water reducing agent and activated polyvinyl alcohol by activating polyvinyl alcohol, which synergistically shortens the initial settling time and enhances interface bonding performance and early strength.
It has achieved high early strength and fast initial setting, can self-repair microcracks, improve the overall strength of the system, enhance the bonding performance with old concrete, reduce the porosity after cement solidification, and has good construction convenience.
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Figure CN120365004A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of mortar, and particularly relates to a quick-setting repair mortar and a preparation method thereof. Background Art
[0002] Concrete is widely used in various fields. During its long-term service, especially under harsh environmental conditions such as humidity, high salt content, and large temperature variations, it is often subjected to erosion from natural or human factors. These will accelerate the expansion of concrete cracks, leading to a further decline in structural performance and even threatening the safe use of buildings. At the same time, as the service time increases, the surface of the concrete will show damage or cracks exposing stones and sand, which will cause the surface to be unsightly, and the road surface depression will cause problems such as unsafe driving. At the same time, the damage to the concrete is not limited to surface cracks and spalling, but may also penetrate into the steel bar layer, causing steel bar corrosion and expansion, further exacerbating the deterioration of the structure.
[0003] Facing such severe problems of concrete structure damage, the traditional demolition and reconstruction plan is no longer the first choice due to its high cost, long construction period, and huge consumption of environmental resources. Instead, repair mortar is often used to repair the damaged parts separately. The repair mortar used needs to have excellent adhesion, durability, and permeability, be able to closely fit the original concrete surface, effectively fill cracks and defects, and resist subsequent environmental erosion. However, the existing repair mortar is prone to re-damage, and if it is a large-area renovation, the cost is too high.
[0004] Therefore, there is an urgent need for a quick-setting repair mortar to repair the damaged parts, improve its bonding strength with the old concrete, enhance the bonding force of the repair interface, and be able to cure quickly, which has become a technical problem to be solved at present. Summary of the Invention
[0005] The purpose of the present invention is to solve the deficiencies existing in the prior art, and to provide a quick-setting repair mortar and a preparation method thereof.
[0006] A quick-setting repair mortar, the raw materials of which by mass include: 100 parts of portland cement, 250 - 300 parts of standard sand, 1 - 5 parts of nano calcium carbonate, 1 - 5 parts of fly ash, 6 - 10 parts of expansive agent, 1 - 6 parts of polyol shrinkage reducing agent, 0.1 - 0.2 parts of polycarboxylate superplasticizer, 2 - 4 parts of activated polyvinyl alcohol, and 1 - 3 parts of rheology regulator.
[0007] Among them, the activated polyvinyl alcohol is prepared by the following steps: adding polyvinyl alcohol into a mixed solvent, standing at 70 - 75°C for 10 - 30 min, adding maleic anhydride and an initiator thereto, stirring at 70 - 80°C for 5 - 10 h under nitrogen protection, cooling to 40 - 50°C, adding water thereto and stirring evenly, adding borax thereto, stirring at 40 - 50°C for 1 - 2 h, and spray drying.
[0008] Preferably, the particle size D of the activated polyvinyl alcohol 50 = 5 - 8 μm.
[0009] Preferably, the mixed solvent is obtained by mixing tetrahydrofuran and water in a mass ratio of 2 - 5:1.
[0010] Preferably, the initiator is at least one of potassium persulfate, sodium persulfate, and ammonium persulfate.
[0011] Preferably, the mass ratio of polyvinyl alcohol, maleic anhydride, initiator, and borax is 1 - 5:1 - 4:0.01 - 0.1:0.1 - 1.
[0012] Preferably, the expansive agent includes: microencapsulated calcium oxide expansive agent and calcium sulfoaluminate expansive agent.
[0013] More preferably, the mass ratio of the microencapsulated calcium oxide expansive agent to the calcium sulfoaluminate expansive agent is 1 - 2:1.
[0014] More preferably, the microencapsulated calcium oxide is prepared by the following specific steps: adding ethylene - vinyl acetate copolymer into toluene and stirring evenly, adding benzoyl peroxide thereto and stirring for 5 - 10 min to obtain a mixed solution; adding calcium oxide particles into a fluidized bed coater, preheating to 50 - 60°C, setting the atomization pressure at 0.6 - 0.8 MPa, the inlet air temperature at 80 - 90°C, and the liquid spraying rate at 5 - 10 mL / min, atomizing and spraying the mixed solution onto the surface of the fluidized calcium oxide through a high - pressure spray gun to form a coating layer, curing at 152 - 158°C for 1 - 2 h under nitrogen protection, cooling to room temperature, and drying.
[0015] Even more preferably, the mass ratio of ethylene - vinyl acetate copolymer, benzoyl peroxide, and calcium oxide particles is 1 - 3:0.01 - 0.1:10 - 30.
[0016] Even more preferably, the particle size of the calcium oxide particles is 50 - 200 μm.
[0017] Preferably, the polyol shrinkage - reducing agent is polyethylene glycol or polyvinyl alcohol.
[0018] Preferably, the particle size D of the rheology regulator 90 < 10 μm.
[0019] Preferably, the rheology regulator is prepared by the following specific steps: adding hydroxypropyl methylcellulose into water and stirring evenly, adding lithium soapstone, nano-silica, and dispersant thereto, performing ultrasonic treatment for 1-2 h with an ultrasonic frequency of 40-60 kHz, adding calcium chloride solution thereto under stirring, continuing to stir for 1-3 h, performing ultrasonic treatment for 10-30 min with an ultrasonic frequency of 40-60 kHz, centrifuging, freeze-drying, and sieving after airflow pulverization.
[0020] In the present invention, the lamellar structure of lithium soapstone is dissociated under the action of ultrasonic waves, and nano-silica is loaded on the lamellar structure. The nano-silica forms hydrogen bonds with hydroxypropyl methylcellulose and can jointly construct a dynamic reversible network with the borate bond of activated polyvinyl alcohol. Subsequently, calcium ions are used to not only accelerate cement hydration but also act as a cationic cross-linking agent to promote the combination of lithium soapstone lamellae and hydroxypropyl methylcellulose, which can dissociate and reduce viscosity during stirring and recombine to increase structural strength when at rest, achieving the balance of construction rheological properties and anti-settling.
[0021] More preferably, the dispersant is sodium hexametaphosphate.
[0022] More preferably, the mass ratio of hydroxypropyl methylcellulose, lithium soapstone, nano-silica, dispersant, and calcium chloride is 5-10:1-5:1-4:0.01-0.1:0.001-0.008.
[0023] More preferably, the ultrasonic treatment frequency for both times is 40-60 kHz.
[0024] The preparation method of the above-mentioned early-setting repair mortar includes the following steps: premixing portland cement, standard sand, nano-calcium carbonate, and fly ash for 1-3 min, adding an expansive agent and dry-mixing for 1-2 min, adding a polycarboxylate superplasticizer, adjusting with water and stirring for 1-2 min, and sequentially adding a polyalcohol shrinkage-reducing agent, activated polyvinyl alcohol, and a rheology regulator and stirring for 1-4 min.
[0025] Beneficial effects: In the present invention, polyvinyl alcohol is activated and added to the mortar, which can not only reduce the surface tension of the mortar, but also the microporous structure therein can adsorb calcium ions to accelerate C-S-H nucleation. The sulfate radical provided by the calcium sulfoaluminate expansive agent reacts with tricalcium aluminate in the cement to generate ettringite, and the chloride ions in the rheology regulator shorten the initial setting time synergistically by accelerating the hydration of C3A minerals; In the rheology regulator used in the present invention, nano-silica and activated polyvinyl alcohol are compounded to form a three-dimensional network, effectively reducing the porosity of the system. Microencapsulated calcium oxide gradually dissolves and releases calcium ions in the alkaline environment of cement hydration, generating calcium hydroxide and producing volume expansion. At the same time, the flexible molecular chains of activated polyvinyl alcohol migrate under the action of water to jointly achieve crack filling, and self-healing of microcracks of 0.1-0.6 mm can be realized.
[0026] The mortar obtained by the present invention has good interfacial bonding performance with the concrete to be repaired, high early strength, fast initial setting, good construction convenience, and the curing process proceeds along with the cement hydration process to form a three-dimensional interpenetrating network of polymer-inorganic cement, effectively improving the strength after solidification. With the action of fly ash and activated polyvinyl alcohol, it can self-repair microcracks, effectively reduce the porosity after cement solidification, and effectively improve the overall strength of the system. Description of the Drawings
[0027] Figure 1 It is a comparison chart of the 7-day compressive strength and 28-day compressive strength of the repair mortars obtained in Example 5 and Comparative Examples 1-2.
[0028] Figure 2 It is a comparison chart of the initial setting time and 28-day bonding strength of the repair mortars obtained in Example 5 and Comparative Examples 1-2.
[0029] Figure 3 It is a comparison chart of the remaining crack widths during the self-repair test using the repair mortars obtained in Example 5 and Comparative Examples 1-2. Detailed Embodiments
[0030] The present invention will be further explained below in conjunction with specific embodiments.
[0031] Example 1 A kind of early-setting promoting repair mortar, whose raw materials include: 100 g of P.O.42.5 ordinary Portland cement, 250 g of standard sand, 1 g of nano calcium carbonate, 1 g of Class I fly ash, 6 g of expansive agent, 1 g of polyethylene glycol 400, 0.1 g of polycarboxylate-based water reducer, D 50 = 2 g of activated polyvinyl alcohol with D 90 1 g of rheology regulator with D <10 μm.
[0032] The activated polyvinyl alcohol is prepared by the following steps: Add 1 g of polyvinyl alcohol to 20 g of a mixed solvent (obtained by mixing tetrahydrofuran and water in a mass ratio of 2:1), let it stand at 70 °C for 10 min, add 1 g of maleic anhydride and 0.01 g of potassium persulfate thereto, under nitrogen protection, stir at 70 °C for 5 h, with a stirring speed of 100 r / min, cool to 40 °C, add 5 g of deionized water thereto and stir evenly, add 0.1 g of borax thereto, stir at 40 °C for 1 h, and spray dry.
[0033] The expansive agent is composed of a microencapsulated calcium oxide expansive agent and a calcium sulfoaluminate expansive agent in a mass ratio of 1:1. The microencapsulated calcium oxide expansive agent is prepared by the following specific steps: Add 1 g of ethylene-vinyl acetate copolymer to 10 g of toluene and stir evenly. Add 0.01 g of benzoyl peroxide thereto and stir for 5 min to obtain a mixed solution; Add 10 g of calcium oxide particles with a particle size of 50-200 μm to a fluidized bed coater, preheat to 50 °C, set the atomization pressure to 0.6 MPa, the inlet air temperature to 80 °C, and the liquid spraying rate to 5 mL / min. Atomize and spray the mixed solution onto the surface of the fluidized calcium oxide through a high-pressure spray gun to form a coating layer. Cure at a temperature of 152 °C for 1 h under nitrogen protection, cool to room temperature, and dry.
[0034] The rheology regulator is prepared by the following specific steps: Add 5 g of hydroxypropyl methylcellulose to 5 g of deionized water and stir evenly. Add 1 g of lithium soapstone, 1 g of nano-silica, and 0.01 g of sodium hexametaphosphate thereto, and perform ultrasonic treatment for 1 h with an ultrasonic frequency of 40 kHz. While stirring, add 1 g of a calcium chloride solution with a mass fraction of 0.1% thereto, continue to stir for 1 h with a stirring speed of 500 r / min, perform ultrasonic treatment for 10 min with an ultrasonic frequency of 40 kHz, centrifuge, freeze-dry, and screen after airflow pulverization.
[0035] The preparation method of the above-mentioned early-setting repair mortar includes the following steps: Premix P.O.42.5 ordinary Portland cement, standard sand, nano-calcium carbonate, and Class I fly ash for 1 min, add the expansive agent and dry-mix for 1 min, add a polycarboxylate-based water reducer, and adjust the water-binder ratio of the system to 0.18 by adding water. Stir at a speed of 500 r / min for 1 min, and sequentially add polyethylene glycol 400, activated polyvinyl alcohol, and the rheology regulator and stir for 1 min.
[0036] Example 2 An early-setting repair mortar, the raw materials of which include: 100 g of P.O.42.5 ordinary Portland cement, 300 g of standard sand, 5 g of nano-calcium carbonate, 5 g of Class I fly ash, 10 g of expansive agent, 6 g of polyethylene glycol 400, 0.2 g of polycarboxylate-based water reducer, 50 4 g of activated polyvinyl alcohol with D = 5-8 μm, 90 3 g of rheology regulator with <10 μm.
[0037] The activated polyvinyl alcohol is prepared by the following steps: Add 5 g of polyvinyl alcohol to 40 g of a mixed solvent (obtained by mixing tetrahydrofuran and water in a mass ratio of 5:1), let stand at a temperature of 75 °C for 30 min, add 4 g of maleic anhydride and 0.1 g of potassium persulfate thereto. Under nitrogen protection, stir at a temperature of 80 °C for 10 h with a stirring speed of 500 r / min. Cool to 50 °C, add 10 g of deionized water and stir evenly. Add 1 g of borax thereto and stir at a temperature of 50 °C for 2 h, and then perform spray drying.
[0038] The expansive agent is composed of a microencapsulated calcium oxide expansive agent and a calcium sulfoaluminate expansive agent in a mass ratio of 2:1. The microencapsulated calcium oxide expansive agent is prepared by the following specific steps: Add 3 g of ethylene-vinyl acetate copolymer to 20 g of toluene and stir evenly. Add 0.1 g of benzoyl peroxide thereto and stir for 10 min to obtain a mixed solution. Add 30 g of calcium oxide particles with a particle size of 50-200 μm to a fluidized bed coater, preheat to 60 °C, set the atomization pressure to 0.8 MPa, the inlet air temperature to 90 °C, and the liquid spraying rate to 10 mL / min. Atomize and spray the mixed solution onto the surface of the fluidized calcium oxide through a high-pressure spray gun to form a coating layer. Cure at 158 °C for 2 h under nitrogen protection, cool to room temperature, and dry.
[0039] The rheology regulator is prepared by the following specific steps: Add 10 g of hydroxypropyl methylcellulose to 15 g of deionized water and stir evenly. Add 5 g of lithium soapstone, 4 g of nano-silica, and 0.1 g of sodium hexametaphosphate thereto, and perform ultrasonic treatment for 2 h at an ultrasonic frequency of 60 kHz. While stirring, add 2 g of a calcium chloride solution with a mass fraction of 0.4% thereto, continue stirring for 3 h at a stirring speed of 1000 r / min, perform ultrasonic treatment for 30 min at an ultrasonic frequency of 60 kHz, centrifuge, freeze-dry, and screen after airflow pulverization.
[0040] The preparation method of the above-mentioned early-setting repair mortar includes the following steps: Premix P.O. 42.5 ordinary Portland cement, standard sand, nano-calcium carbonate, and class I fly ash for 3 min, add the expansive agent and dry-mix for 2 min, add a polycarboxylate-based water reducer, add water to adjust the water-binder ratio of the system to 0.22, stir at a speed of 1000 r / min for 2 min, and sequentially add polyethylene glycol 400, activated polyvinyl alcohol, and the rheology regulator and stir for 4 min.
[0041] Example 3 An early-setting repair mortar, the raw materials of which include: 100 g of P.O. 42.5 ordinary Portland cement, 260 g of standard sand, 4 g of nano-calcium carbonate, 2 g of class I fly ash, 9 g of expansive agent, 2 g of polyethylene glycol 400, 0.17 g of polycarboxylate-based water reducer, 50 2.5 g of activated polyvinyl alcohol with D 90 <10 μm rheology regulator 2.5 g.
[0042] The activated polyvinyl alcohol is prepared by the following steps: Add 2 g of polyvinyl alcohol to 35 g of a mixed solvent (obtained by mixing tetrahydrofuran and water in a mass ratio of 3:1), let it stand at 73 °C for 15 min, add 3 g of maleic anhydride and 0.03 g of potassium persulfate thereto, under nitrogen protection, stir at 77 °C for 7 h, with a stirring speed of 400 r / min, cool to 42 °C, add 9 g of deionized water and stir evenly, add 0.3 g of borax thereto, stir at 48 °C for 80 min, and spray dry.
[0043] The expansive agent is composed of a microencapsulated calcium oxide expansive agent and a calcium sulfoaluminate expansive agent in a mass ratio of 1.8:1. The microencapsulated calcium oxide expansive agent is prepared by the following specific steps: Add 1.5 g of ethylene-vinyl acetate copolymer to 18 g of toluene and stir evenly, add 0.03 g of benzoyl peroxide thereto and stir for 9 min to obtain a mixed solution; Add 15 g of calcium oxide particles with a particle size of 50 - 200 μm to a fluidized bed coater, preheat to 58 °C, set the atomization pressure at 0.68 MPa, the inlet air temperature at 88 °C, and the liquid spraying rate at 7 mL / min, spray the mixed solution onto the surface of the fluidized calcium oxide through a high-pressure spray gun to form a coating layer, cure at 155 °C for 80 min under nitrogen protection, cool to room temperature, and dry.
[0044] The rheology regulator is prepared by the following specific steps: Add 9 g of hydroxypropyl methylcellulose to 8 g of deionized water and stir evenly, add 4 g of lithium soapstone, 2 g of nano-silica, and 0.07 g of sodium hexametaphosphate thereto, perform ultrasonic treatment for 80 min with an ultrasonic frequency of 55 kHz, add 1.2 g of a calcium chloride solution with a mass fraction of 0.3% thereto under stirring, continue to stir for 1.5 h with a stirring speed of 900 r / min, perform ultrasonic treatment for 15 min with an ultrasonic frequency of 55 kHz, centrifuge, freeze-dry, and screen after airflow pulverization.
[0045] The preparation method of the above-mentioned early-setting repair mortar includes the following steps: Premix P.O.42.5 ordinary Portland cement, standard sand, nano-calcium carbonate, and class I fly ash for 1.5 min, add the expansive agent and dry-mix for 1.5 min, add a polycarboxylate-based water reducer, add water to adjust the water-binder ratio of the system to 0.21, stir at a speed of 700 r / min for 1.5 min, and sequentially add polyethylene glycol 400, activated polyvinyl alcohol, and the rheology regulator and stir for 3 min.
[0046] Example 4 An early-setting repair mortar, the raw materials of which include: 100 g of P.O.42.5 ordinary Portland cement, 280 g of standard sand, 2 g of nano-calcium carbonate, 4 g of class I fly ash, 7 g of expansive agent, 5 g of polyethylene glycol 400, 0.13 g of polycarboxylate-based water reducer, D 50= 3.5 g of activated polyvinyl alcohol with a size of 5 - 8 μm, D 90 1.5 g of a rheology modifier with a size < 10 μm.
[0047] The activated polyvinyl alcohol is prepared by the following steps: Add 4 g of polyvinyl alcohol to 25 g of a mixed solvent (obtained by mixing tetrahydrofuran and water in a mass ratio of 4:1), let it stand at 71 °C for 25 min, add 2 g of maleic anhydride and 0.07 g of potassium persulfate to it, under nitrogen protection, stir at 73 °C for 9 h with a stirring speed of 200 r / min, cool to 48 °C, add 7 g of deionized water and stir evenly, add 0.7 g of borax to it, stir at 42 °C for 100 min, and then spray dry.
[0048] The expansive agent is composed of a microencapsulated calcium oxide expansive agent and a calcium sulfoaluminate expansive agent in a mass ratio of 1.2:1. The microencapsulated calcium oxide expansive agent is prepared by the following specific steps: Add 2.5 g of ethylene - vinyl acetate copolymer to 12 g of toluene and stir evenly, add 0.07 g of benzoyl peroxide to it and stir for 7 min to obtain a mixed solution; Add 25 g of calcium oxide particles with a particle size of 50 - 200 μm to a fluidized bed coater, preheat to 52 °C, set the atomization pressure at 0.75 MPa, the inlet air temperature at 82 °C, and the liquid spraying rate at 9 mL / min, spray the mixed solution onto the surface of the fluidized calcium oxide through a high - pressure spray gun to form a coating layer, cure at 155 °C for 100 min under nitrogen protection, cool to room temperature, and dry.
[0049] The rheology modifier is prepared by the following specific steps: Add 7 g of hydroxypropyl methylcellulose to 12 g of deionized water and stir evenly, add 2 g of lithium soapstone, 3 g of nano - silica, and 0.03 g of sodium hexametaphosphate to it, perform ultrasonic treatment for 100 min with an ultrasonic frequency of 45 kHz, add 1.8 g of a calcium chloride solution with a mass fraction of 0.2% to it under stirring, continue to stir for 2.5 h with a stirring speed of 700 r / min, perform ultrasonic treatment for 25 min with an ultrasonic frequency of 45 kHz, centrifuge, freeze - dry, and sieve after airflow pulverization.
[0050] The preparation method of the above - mentioned early - setting repair mortar includes the following steps: Premix P.O.42.5 ordinary Portland cement, standard sand, nano - calcium carbonate, and class I fly ash for 2.5 min, add the expansive agent and dry - mix for 1.5 min, add a polycarboxylate - based water - reducing agent, add water to adjust the water - binder ratio of the system to 0.19, stir at a speed of 900 r / min for 1.5 min, and then add polyethylene glycol 400, activated polyvinyl alcohol, and the rheology modifier in sequence and stir for 2 min.
[0051] Example 5 An early-setting repair mortar, the raw materials of which include: 100 g of P.O. 42.5 ordinary Portland cement, 270 g of standard sand, 3 g of nano calcium carbonate, 3 g of Class I fly ash, 8 g of expansive agent, 3.5 g of polyethylene glycol 400, 0.15 g of polycarboxylate superplasticizer, D 50 = 3 g of activated polyvinyl alcohol with a particle size of 5 - 8 μm, D 90 2 g of rheology regulator with a particle size < 10 μm.
[0052] The activated polyvinyl alcohol is prepared by the following steps: Add 3 g of polyvinyl alcohol to 30 g of a mixed solvent (obtained by mixing tetrahydrofuran and water in a mass ratio of 3.5:1), let it stand at 72 °C for 20 min, add 2.5 g of maleic anhydride and 0.05 g of potassium persulfate thereto, under nitrogen protection, stir at 75 °C for 8 h, with a stirring speed of 300 r / min, cool to 45 °C, add 8 g of deionized water and stir evenly, add 0.5 g of borax thereto, stir at 45 °C for 90 min, and then spray dry.
[0053] The expansive agent is composed of microencapsulated calcium oxide expansive agent and calcium sulfoaluminate expansive agent in a mass ratio of 1.5:1. The microencapsulated calcium oxide expansive agent is prepared by the following specific steps: Add 2 g of ethylene-vinyl acetate copolymer to 15 g of toluene and stir evenly, add 0.05 g of benzoyl peroxide and stir for 8 min to obtain a mixed solution; Add 20 g of calcium oxide particles with a particle size of 50 - 200 μm to a fluidized bed coater, preheat to 55 °C, set the atomization pressure at 0.7 MPa, the inlet air temperature at 85 °C, and the liquid spraying rate at 8 mL / min, spray the mixed solution onto the surface of the fluidized calcium oxide through a high-pressure spray gun to form a coating layer, cure at 155 °C for 90 min under nitrogen protection, cool to room temperature, and dry.
[0054] The rheology regulator is prepared by the following specific steps: Add 8 g of hydroxypropyl methylcellulose to 10 g of deionized water and stir evenly, add 3 g of lithium soapstone, 2.5 g of nano silica, and 0.05 g of sodium hexametaphosphate thereto, perform ultrasonic treatment for 90 min with an ultrasonic frequency of 50 kHz, add 1.5 g of a calcium chloride solution with a mass fraction of 0.25% thereto under stirring, continue to stir for 2 h with a stirring speed of 800 r / min, perform ultrasonic treatment for 20 min with an ultrasonic frequency of 50 kHz, centrifuge, freeze-dry, and sieve after airflow pulverization.
[0055] The preparation method of the above-mentioned early-setting repair mortar includes the following steps: premix P.O. 42.5 ordinary Portland cement, standard sand, nano calcium carbonate, and class I fly ash for 2 min, add an expansion agent and dry mix for 1.5 min, add a polycarboxylate superplasticizer, add water to adjust the water-binder ratio of the system to 0.20, stir at a speed of 800 r / min for 1.5 min, and sequentially add polyethylene glycol 400, activated polyvinyl alcohol, and a rheology regulator and stir for 2.5 min.
[0056] Comparative Example 1 An early-setting repair mortar, the raw materials of which include: 100 g of P.O. 42.5 ordinary Portland cement, 270 g of standard sand, 3 g of nano calcium carbonate, 3 g of class I fly ash, 8 g of an expansion agent, 3.5 g of polyethylene glycol 400, 0.15 g of a polycarboxylate superplasticizer, D 50 = 2.75 g of activated polyvinyl alcohol with a particle size of 5 - 8 μm, 0.25 g of borax, D 90 2 g of a rheology regulator with a particle size < 10 μm.
[0057] The activated polyvinyl alcohol is prepared by the following steps: add 3 g of polyvinyl alcohol to 30 g of a mixed solvent (obtained by mixing tetrahydrofuran and water in a mass ratio of 3.5:1), let it stand at a temperature of 72 °C for 20 min, add 2.5 g of maleic anhydride and 0.05 g of potassium persulfate thereto, under nitrogen protection, stir at a temperature of 75 °C for 8 h, with a stirring speed of 300 r / min, cool to 45 °C, add 8 g of deionized water thereto and stir evenly, stir at a temperature of 45 °C for 90 min, and spray dry.
[0058] The expansion agent is composed of a microencapsulated calcium oxide expansion agent and a calcium sulfoaluminate expansion agent in a mass ratio of 1.5:1. The microencapsulated calcium oxide expansion agent is prepared by the following specific steps: add 2 g of ethylene-vinyl acetate copolymer to 15 g of toluene and stir evenly, add 0.05 g of benzoyl peroxide thereto and stir for 8 min to obtain a mixed solution; add 20 g of calcium oxide particles with a particle size of 50 - 200 μm to a fluidized bed coater, preheat to 55 °C, set the atomization pressure at 0.7 MPa, the inlet air temperature at 85 °C, and the liquid spraying rate at 8 mL / min, atomize and spray the mixed solution onto the surface of the fluidized calcium oxide through a high-pressure spray gun to form a coating layer, cure at a temperature of 155 °C for 90 min under nitrogen protection, cool to room temperature, and dry.
[0059] The rheological regulator is prepared by the following specific steps: Add 8 g of hydroxypropyl methylcellulose to 10 g of deionized water and stir evenly. Add 3 g of lithium soapstone, 2.5 g of nano-silica, and 0.05 g of sodium hexametaphosphate thereto, and perform ultrasonic treatment for 90 min at an ultrasonic frequency of 50 kHz. While stirring, add 1.5 g of a calcium chloride solution with a mass fraction of 0.25%, continue to stir for 2 h at a stirring speed of 800 r / min, perform ultrasonic treatment for 20 min at an ultrasonic frequency of 50 kHz, centrifuge, freeze-dry, and screen after airflow pulverization.
[0060] The preparation method of the early-setting repair mortar described above includes the following steps: Premix P.O. 42.5 ordinary Portland cement, standard sand, nano-calcium carbonate, and class I fly ash for 2 min, add an expansion agent and dry-mix for 1.5 min, add a polycarboxylate-based water reducer, and adjust the water-binder ratio of the system to 0.20 by adding water. Stir at a speed of 800 r / min for 1.5 min, and sequentially add polyethylene glycol 400, activated polyvinyl alcohol, borax, and the rheological regulator and stir for 2.5 min.
[0061] Comparative Example 2 An early-setting repair mortar, the raw materials of which include: 100 g of P.O. 42.5 ordinary Portland cement, 270 g of standard sand, 3 g of nano-calcium carbonate, 3 g of class I fly ash, 8 g of expansion agent, 3.5 g of polyethylene glycol 400, 0.15 g of polycarboxylate-based water reducer, 50 3 g of activated polyvinyl alcohol with D 90 = 5 - 8 μm, and 2 g of a rheological regulator with <10 μm.
[0062] The activated polyvinyl alcohol is prepared by the following steps: Add 3 g of polyvinyl alcohol to 30 g of a mixed solvent (obtained by mixing tetrahydrofuran and water in a mass ratio of 3.5:1), let it stand at a temperature of 72 °C for 20 min, add 2.5 g of maleic anhydride and 0.05 g of potassium persulfate thereto, and under nitrogen protection, stir at a temperature of 75 °C for 8 h at a stirring speed of 300 r / min. Cool to 45 °C, add 8 g of deionized water and stir evenly, add 0.5 g of borax, stir at a temperature of 45 °C for 90 min, and perform spray drying.
[0063] The expansion agent is composed of calcium oxide expansion agent and calcium sulfoaluminate expansion agent in a mass ratio of 1.5:1. The rheology control agent is prepared by the following specific steps: 8g of hydroxypropyl methylcellulose is added to 10g of deionized water and stirred evenly, 3g of hectorite, 2.5g of nano-silicon dioxide, and 0.05g of sodium hexametaphosphate are added thereto, ultrasonic treatment is performed for 90min at an ultrasonic frequency of 50kHz, 1.5g of calcium chloride solution with a mass fraction of 0.25% is added thereto under stirring, stirring is continued for 2h at a stirring speed of 800r / min, ultrasonic treatment is performed for 20min at an ultrasonic frequency of 50kHz, centrifugation, freeze drying, air flow crushing and screening.
[0064] The preparation method of the above-mentioned early-setting repair mortar comprises the following steps: premixing PO42.5 ordinary Portland cement, standard sand, nano calcium carbonate and grade I fly ash for 2 minutes, adding an expansion agent and dry mixing for 1.5 minutes, adding a polycarboxylic acid-based water reducer, adding water to adjust the water-cement ratio of the system to 0.20, stirring at a speed of 800 r / min for 1.5 minutes, and successively adding polyethylene glycol 400, activated polyvinyl alcohol and a rheology control agent and stirring for 2.5 minutes.
[0065] The 7d compressive strength and 28d compressive strength of the repair mortar obtained in Example 5 and Comparative Examples 1-2 were measured with reference to GB / T 17671-2021 "Test Method for Cement Mortar Strength (ISO Method)". The initial setting time of the repair mortar obtained in Example 5 and Comparative Examples 1-2 was measured with reference to GB / T 1346-2019 "Test Method for Cement Standard Consistency Water Amount, Setting Time and Stability". The 28d bonding strength of the repair mortar obtained in Example 5 and Comparative Examples 1-2 was measured with reference to Shenzhen SJG11-2004 "Technical Specifications for Production and Application of Dry Powder Mortar".
[0066] like Figure 1 and Figure 2 As shown, the repair mortar obtained in Example 5 has the highest 7d compressive strength, 28d compressive strength and 28d bonding strength, and the shortest initial setting time, which is better than that of Comparative Examples 1-2 (P < 0.05).
[0067] Place a 200mm×200mm×5mm mold on an insulation board, and then insert crack inducers on both sides of the mold. The height of the crack inducer is about 2 / 3 of the height of the mold to make a simple crack induction device. Then pour the repair mortar obtained in Example 5 and Comparative Examples 1-2 into the mold and smooth it. Finally, place a fan near the mold with a wind speed of about 3m / s. After cracks appear in the mortar, stop blowing. After measuring the initial crack width, place the specimen together with the mold in a standard curing room for curing. The temperature and relative humidity are controlled at 20±2℃ and 95±5%, respectively.
[0068] The cracks prefabricated by the flat plate cracking method are surface cracks, with a width of about 0.10 - 0.60 mm and a depth of only 3 - 5 mm.
[0069] After 21 days of curing, the cracks were measured again. The self - healing performance of each group of repair mortars was evaluated by the change in crack width. The cracks were divided into three groups: 0.1 - 0.3 mm, 0.3 - 0.5 mm, and 0.5 - 0.6 mm, and the remaining crack widths were recorded respectively.
[0070] As Figure 3 shown, the remaining crack width of the repair mortar obtained in Example 5 was the smallest in each group, which was better than that of Comparative Examples 1 - 2 (P < 0.05).
[0071] As described above, it is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.
Claims
1. An early-setting repair mortar, characterized in that, Its raw materials by mass fraction include: 100 parts of portland cement, 250 - 300 parts of standard sand, 1 - 5 parts of nano calcium carbonate, 1 - 5 parts of fly ash, 6 - 10 parts of expansion agent, 1 - 6 parts of polyol shrinkage reducing agent, 0.1 - 0.2 parts of polycarboxylate superplasticizer, 2 - 4 parts of activated polyvinyl alcohol, 1 - 3 parts of rheology regulator; Among them, the activated polyvinyl alcohol is prepared by the following steps: adding polyvinyl alcohol into a mixed solvent, standing at 70 - 75 °C for 10 - 30 min, adding maleic anhydride and an initiator thereto, stirring at 70 - 80 °C for 5 - 10 h under nitrogen protection, cooling to 40 - 50 °C, adding water thereto and stirring evenly, adding borax thereto, stirring at 40 - 50 °C for 1 - 2 h, and spray drying.
2. The early-setting repair mortar according to claim 1, characterized in that, D of Activated Polyvinyl Alcohol 50 = 5 - 8 μm.
3. The early-setting repair mortar according to claim 1, characterized in that, The mixed solvent is obtained by mixing tetrahydrofuran and water in a mass ratio of 2 - 5:
1.
4. The early-setting repair mortar according to claim 1, characterized in that, The initiator is at least one of potassium persulfate, sodium persulfate, and ammonium persulfate.
5. The early-setting repair mortar according to claim 1, characterized in that, The mass ratio of polyvinyl alcohol, maleic anhydride, initiator, and borax is 1 - 5:1 - 4:0.01 - 0.1:0.1 - 1.
6. The early-setting repair mortar according to claim 1, wherein The expansion agent includes: Microencapsulated calcium oxide expansion agent, calcium sulfoaluminate expansion agent.
7. The early-setting repair mortar according to claim 6, characterized in that, The mass ratio of the microencapsulated calcium oxide expansion agent to the calcium sulfoaluminate expansion agent is 1 - 2:
1.
8. The early-setting repair mortar according to claim 6, characterized in that, The microencapsulated calcium oxide is prepared by the following specific steps: adding ethylene - vinyl acetate copolymer into toluene and stirring evenly, adding benzoyl peroxide thereto and stirring for 5 - 10 min to obtain a mixed solution; adding calcium oxide particles into a fluidized bed coater, preheating to 50 - 60 °C, setting the atomization pressure at 0.6 - 0.8 MPa, the inlet air temperature at 80 - 90 °C, and the liquid spraying rate at 5 - 10 mL / min, atomizing and spraying the mixed solution onto the surface of the fluidized calcium oxide through a high - pressure spray gun to form a coating layer, curing at 152 - 158 °C for 1 - 2 h under nitrogen protection, cooling to room temperature, and drying.
9. The early-setting repair mortar according to claim 6, characterized in that, The polyol shrinkage reducing agent is polyethylene glycol or polyvinyl alcohol.
10. A method for preparing an early-setting repair mortar according to any one of claims 1-9, characterized in that, It includes the following steps: premixing portland cement, standard sand, nano calcium carbonate, and fly ash for 1 - 3 min, adding the expansion agent and dry - mixing for 1 - 2 min, adding the polycarboxylate superplasticizer, adjusting with water and stirring for 1 - 2 min, and successively adding the polyol shrinkage reducing agent, activated polyvinyl alcohol, and rheology regulator and stirring for 1 - 4 min.