A kind of fast-curing repair mortar and preparation method thereof

Abstract

The present invention belongs to the technical field of building materials, and specifically relates to a fast-curing repair mortar and a preparation method thereof. A fast-curing repair mortar comprises the following components by weight: 100 parts of silicate cement; 250-300 parts of standard sand; 6-10 parts of expansion agent; 1-6 parts of polyol shrinkage reducer; 0.1-0.2 parts of polycarboxylic acid water reducer; 2-4 parts of modified polyvinyl alcohol; the preparation of the modified polyvinyl alcohol comprises the following steps: taking polyether polyol, triphenylphosphine, diisopropyl azodicarboxylate and lactamide Trt in a solvent, stirring for 5-8 hours and treating to obtain the obtained product. The present invention adds modified polyvinyl alcohol to the mortar, reduces the surface tension of the mortar, promotes the dissolution of the expansion agent, accelerates the generation of a large number of expansive crystals by the volume stabilizer after hydration, can significantly promote the early setting of the mortar, and improves the early strength of the mortar. At the same time, the interaction between the modified polyvinyl alcohol and the polycarboxylic acid water reducer improves the early strength of the mortar.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and in particular relates to a fast-curing repair mortar and a preparation method thereof. Background Art

[0002] Concrete structures used in buildings are often subject to erosion from natural or human factors during long-term service, especially in harsh environmental conditions such as humidity, high salt content, and large temperature changes. Such factors include chloride ion penetration, carbonation, freeze-thaw cycles, and corrosion from chemicals, which accelerate the aging and damage of concrete, leading to a decline in structural performance and even threatening the safe use of buildings. This type of damage is not limited to surface cracks and spalling, but may also penetrate into the steel layer, causing steel corrosion and expansion, further exacerbating the deterioration of the structure.

[0003] Faced with such severe concrete structure damage problems, the traditional demolition and reconstruction solution is no longer the first choice due to its high cost, long construction period and huge consumption of environmental resources. Therefore, technicians and experts in the industry are increasingly inclined to adopt more economical, efficient and environmentally friendly repair and reinforcement technologies to extend the service life of buildings and ensure structural safety.

[0004] Repair technology covers two major areas: materials science and engineering technology. Its core lies in the development of high-performance repair mortars and the optimization of repair processes. Repair mortars must have excellent adhesion, durability and permeability, be able to fit tightly to the original concrete surface, effectively fill cracks and defects, and resist subsequent environmental erosion. In addition, for different types of damage, such as microcracks, large cracks, and spalling areas, targeted repair formulas and construction technologies need to be developed to ensure that the repair effect reaches or even exceeds the original structural performance.

[0005] In terms of repair technology, we emphasize refined operation and quality control. Before construction, the damaged parts need to be thoroughly cleaned and evaluated to ensure that the repair interface is clean and free of impurities; during the construction process, parameters such as material ratio, mixing time, and construction temperature need to be strictly controlled, and appropriate construction methods such as pressure grouting, spraying, and smearing should be used to ensure that the repair layer forms a good integrity with the original structure; after construction, necessary maintenance and testing are also required to evaluate the repair effect and ensure the quality of the repair.

[0006] Patent CN201510387307.6 discloses a modified cement slurry formula for rapid repair of concrete, which mainly includes basic materials such as cement, aggregate, fly ash, latex powder, etc., and innovatively adds early strength agent, expansion agent, defoamer and thickener to improve its performance. These additives are intended to accelerate the initial setting process of cement slurry, improve the water reduction performance of mortar, and may reduce shrinkage cracks through the expansion effect. However, although this formula has made breakthroughs in accelerating the repair speed and improving physical properties, there is a significant problem: the bonding performance with the concrete to be repaired is weak, resulting in insufficient bonding strength of the repair interface. This deficiency may directly affect the repair effect, reduce the overall strength and durability of the repaired concrete structure, and thus affect its long-term service life.

[0007] Therefore, there is an urgent need for a repair mortar that can improve its bonding strength with old concrete, enhance the bonding strength of the repair interface and can cure quickly. Summary of the invention

[0008] One of the purposes of the present invention is to provide a fast-curing repair mortar that can cure quickly.

[0009] To achieve one of the purposes of the present invention, the technical solution adopted by the present invention is:

[0010] A fast-curing repair mortar comprises the following components by weight: 100 parts of silicate cement; 250-300 parts of standard sand; 6-10 parts of expansion agent; 1-6 parts of polyol shrinkage reducer; 0.1-0.2 parts of polycarboxylic acid water reducer; 2-4 parts of modified polyvinyl alcohol; the preparation of the modified polyvinyl alcohol comprises the following steps: taking polyether polyol, triphenylphosphine, diisopropyl azodicarboxylate and lactamide Trt in a solvent, stirring for 5-8 hours and then treating to obtain the modified polyvinyl alcohol.

[0011] Furthermore, the preparation process of the lactamide Trt comprises the following steps:

[0012]

[0013] Lactamide, trityl chloride and triethylamine are reacted in dichloromethane for 1 to 3 hours and then treated to obtain lactamide Trt.

[0014] Furthermore, the mass ratio of the polyether polyol, triphenylphosphine, diisopropyl azodicarboxylate and lactamide Trt is 1: (0.15-0.2): (0.12-0.18): (0.07-0.1).

[0015] Furthermore, the molar ratio of lactamide, trityl chloride and triethylamine is 1:(1-1.2):(1-1.2).

[0016] Furthermore, the expansion agent is one of a calcium oxide expansion agent and a calcium sulfoaluminate expansion agent.

[0017] Furthermore, the solvent is one of tetrahydrofuran and dioxane.

[0018] Furthermore, the following components are included by weight: 100 parts of silicate cement; 260 parts of standard sand; 7 parts of expansion agent; 4 parts of polyol shrinkage reducer; 0.1 parts of polycarboxylic acid water reducer; and 3 parts of modified polyvinyl alcohol.

[0019] Furthermore, the polyether polyol is polyvinyl alcohol.

[0020] A second object of the present invention is to provide a method for preparing a fast-curing repair mortar.

[0021] To achieve the second purpose of the present invention, the technical solution adopted by the present invention is:

[0022] Take silicate cement, standard sand, expansion agent, polyol shrinkage reducer, polycarboxylic acid water reducer, modified polyvinyl alcohol and 180-200 parts of water, stir and mix to obtain fast-curing repair mortar.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention adds modified polyvinyl alcohol to the mortar, reduces the surface tension of the mortar, promotes the dissolution of the expansion agent, accelerates the volume stabilizer to generate a large number of expansion crystals after hydration, can significantly promote the early setting of the mortar, and improves the early strength of the mortar. At the same time, the modified polyvinyl alcohol interacts with the polycarboxylate water reducer to improve the early strength of the mortar.

[0025] The mortar of the present invention has good interface bonding performance with the concrete to be repaired through the selection of raw materials and content adjustment, and has high early strength, fast initial setting and good construction convenience. DETAILED DESCRIPTION

[0026] The technical scheme of the present invention is further described below in conjunction with specific embodiments. However, it should be understood by those skilled in the art that the following examples are only used to illustrate the present invention and should not be regarded as limiting the present invention. The specific conditions not specified in the examples are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, unless otherwise specified, are conventional products obtained through commercial channels.

[0027] Example 1

[0028] A fast-curing repair mortar comprises the following components by weight: 100 parts of silicate cement; 260 parts of standard sand; 7 parts of expansion agent; 4 parts of polyol shrinkage reducer; 0.1 part of polycarboxylic acid water reducer; and 3 parts of modified polyether polyol.

[0029] Wherein, the preparation process of the modified polyvinyl alcohol comprises the following steps:

[0030] Take 10g of polyvinyl alcohol, 1.8g of triphenylphosphine and 0.85g of lactamide Trt and disperse them in 50mL of tetrahydrofuran at 20°C, then add 1.5g of diisopropyl azodicarboxylate dropwise to the mixture, heat to 25°C and stir for 6h; add 80mL of deionized water to the reaction solution, stir at 100°C for 10min, separate the mixed solution while hot; concentrate the lower layer of liquid, add 20mL of glacial acetic acid, stir at 60°C for 1h, and distill the mixed liquid to obtain modified polyvinyl alcohol.

[0031] Wherein, the preparation process of the lactamide Trt comprises the following steps:

[0032] Take lactamide (10 mmol) and triethylamine (11 mmol) in 10 mL of dichloromethane, slowly add trityl chloride (11 mmol) to the mixed system, stir at room temperature for 2 hours, adjust the pH to 7.0, concentrate the reaction solution, and pass it through a column (eluent, n-hexane: ethyl acetate = 10:1) to obtain lactamide Trt.

[0033] Mix silicate cement, standard sand, expansion agent, polyol shrinkage reducer, polycarboxylic acid water reducer and modified polyvinyl alcohol evenly according to the proportion of each component, and stir and mix with 200 parts of water to obtain a fast-curing repair mortar.

[0034] Example 2

[0035] A fast-curing repair mortar comprises the following components by weight: 100 parts of silicate cement; 250 parts of standard sand; 6 parts of expansion agent; 1 part of polyol shrinkage reducer; 0.1 part of polycarboxylic acid water reducer; and 2 parts of modified polyether polyol.

[0036] Wherein, the preparation process of the modified polyvinyl alcohol comprises the following steps:

[0037] Take 10g of polyvinyl alcohol, 1.8g of triphenylphosphine and 0.85g of lactamide Trt and disperse them in 50mL of tetrahydrofuran at 20°C, then add 1.5g of diisopropyl azodicarboxylate dropwise to the mixture, heat to 25°C and stir for 6h; add 80mL of deionized water to the reaction solution, stir at 100°C for 10min, separate the mixed solution while hot; concentrate the lower layer of liquid, add 20mL of glacial acetic acid, stir at 60°C for 1h, and distill the mixed liquid to obtain modified polyvinyl alcohol.

[0038] Wherein, the preparation process of the lactamide Trt comprises the following steps:

[0039] Take lactamide (10 mmol) and triethylamine (11 mmol) in 10 mL of dichloromethane, slowly add trityl chloride (11 mmol) to the mixed system, stir at room temperature for 3 hours, adjust the pH to 7.0, concentrate the reaction solution, and pass it through a column (eluent, n-hexane: ethyl acetate = 10:1) to obtain lactamide Trt.

[0040] According to the proportion of each component, silicate cement, standard sand, expansion agent, polyol shrinkage reducer, polycarboxylic acid water reducer and modified polyvinyl alcohol are uniformly mixed, and 180 parts of water are stirred and mixed to obtain a fast-curing repair mortar.

[0041] Example 3

[0042] A fast-curing repair mortar comprises the following components by weight: 100 parts of silicate cement; 300 parts of standard sand; 10 parts of expansion agent; 10 parts of polyol shrinkage reducer; 0.2 parts of polycarboxylic acid water reducer; and 4 parts of modified polyether polyol.

[0043] Wherein, the preparation process of the modified polyvinyl alcohol comprises the following steps:

[0044] Take 10g of polyvinyl alcohol, 2g of triphenylphosphine and 1g of lactamide Trt and disperse them in 50mL of tetrahydrofuran at 20°C, then add 1.8g of diisopropyl azodicarboxylate dropwise to the mixture, heat to 25°C and stir for 5h; add 80mL of deionized water to the reaction solution, stir at 100°C for 10min, separate the mixed solution while hot; concentrate the lower layer of liquid, add 20mL of glacial acetic acid, stir at 60°C for 1h, and distill the mixed liquid to obtain modified polyvinyl alcohol.

[0045] Wherein, the preparation process of the lactamide Trt comprises the following steps:

[0046] Take lactamide (10 mmol) and triethylamine (12 mmol) in 10 mL of dichloromethane, slowly add trityl chloride (12 mmol) to the mixed system, stir at room temperature for 1 hour, adjust the pH to 7.0, concentrate the reaction solution, and pass it through a column (eluent, n-hexane: ethyl acetate = 10:1) to obtain lactamide Trt.

[0047] Mix silicate cement, standard sand, expansion agent, polyol shrinkage reducer, polycarboxylic acid water reducer and modified polyvinyl alcohol evenly according to the proportion of each component, and stir and mix with 200 parts of water to obtain a fast-curing repair mortar.

[0048] Comparative Example 1

[0049] A repair mortar, which is different from Example 1 in that: when preparing the repair mortar, the modified polyether polyol is replaced by an equal amount of polyether polyol.

[0050] Comparative Example 2

[0051] A repair mortar is different from Example 1 in that the modified polyether polyol is omitted when preparing the repair mortar.

[0052] Test example

[0053] The repair mortars prepared in Examples 1-5 and Comparative Examples 1-2 were respectively tested for compressive strength, interfacial flexural strength, initial setting time, and bonding strength. The specific test methods are as follows: Compressive strength test: refer to GB / T 17671-2021 "Test method for strength of cement mortar (ISO method)"; Initial setting time test: measured by GB / T1346-2019 method, wherein the ambient temperature during the test is -20°C; Bonding strength test: measured by SJG11-2004 method, wherein the 28d bonding strength is the bonding strength measured after the sample is exposed to the air for 28 days. The comparative test results of each embodiment and comparative example are shown in Table 1.

[0054] As can be seen from Table 1, Examples 1 to 3 show a significant improvement in compressive strength compared to Comparative Examples 1 to 2, which directly reflects the excellent performance of the fast-curing repair mortar of the present invention in enhancing the bearing capacity of the structure. At the same time, the initial setting time is significantly shortened, which is due to the synergistic effect of the special additives in the formula, which accelerates the cement hydration reaction process, so that the repair material can reach sufficient hardening strength in a shorter time to meet emergency repair needs. In addition, the enhancement of bonding strength further confirms that the repair mortar can not only solidify quickly, but also form a strong bond with the existing structure, thereby improving the stability and durability of the overall structure. In summary, the fast-curing repair mortar of the present invention achieves the dual advantages of efficient solidification and excellent bonding while improving the compressive strength.

[0055] The above are only preferred embodiments of the present invention, and are not limited to the above examples. For those skilled in the art, various changes and variations are possible under the principle of the present invention. Any modifications and improvements made should be considered within the scope of protection of the present invention.

Claims

1. A fast-curing repair mortar, characterized in that: The composition includes the following components by weight: 100 parts of Portland cement; 250-300 parts of standard sand; 6-10 parts of expansion agent; 1-6 parts of polyol shrinkage reducer; 0.1-0.2 parts of polycarboxylic acid water reducer; 2-4 parts of modified polyvinyl alcohol; the preparation of the modified polyvinyl alcohol comprises the following steps: taking polyether polyol, triphenylphosphine, diisopropyl azodicarboxylate and lactamide Trt in a solvent, stirring for 5-8 hours and treating to obtain the modified polyvinyl alcohol.

2. The fast-curing repair mortar according to claim 1, characterized in that: The preparation process of the lactamide Trt comprises the following steps: Lactamide, trityl chloride and triethylamine are reacted in dichloromethane for 1 to 3 hours and then treated to obtain lactamide Trt.

3. The fast-curing repair mortar according to claim 1, characterized in that: The mass ratio of the polyether polyol, triphenylphosphine, diisopropyl azodicarboxylate and lactamide Trt is 1: (0.15-0.2): (0.12-0.18): (0.07-0.1).

4. The fast-curing repair mortar according to claim 2, characterized in that: The molar ratio of lactamide, trityl chloride and triethylamine is 1:(1-1.2):(1-1.2).

5. The fast-curing repair mortar according to claim 1, characterized in that: The expansion agent is one of a calcium oxide expansion agent and a calcium sulphoaluminate expansion agent.

6. The fast-curing repair mortar according to claim 1, characterized in that: The solvent is one of tetrahydrofuran and dioxane.

7. The fast-curing repair mortar according to claim 1, characterized in that: The following components are included by weight: 100 parts of silicate cement; 260 parts of standard sand; 7 parts of expansion agent; 4 parts of polyol shrinkage reducing agent; 0.1 part of polycarboxylic acid water reducing agent; 3 parts of modified polyvinyl alcohol.

8. The method for preparing the fast-curing repair mortar according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: taking silicate cement, standard sand, expansion agent, polyol shrinkage reducer, polycarboxylic acid water reducer, modified polyvinyl alcohol and 180-200 parts of water, stirring and mixing to obtain fast-curing repair mortar.

9. The fast-curing repair mortar according to claim 1, characterized in that: The polyether polyol is polyvinyl alcohol.

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