Early-strength low-shrinkage polymer repair mortar, preparation method and application thereof

Abstract

The application relates to the technical field of building materials and special engineering repair materials, in particular to early-strength low-shrinkage polymer repair mortar as well as a preparation method and application thereof. The early-strength low-shrinkage polymer repair mortar contains the following raw materials in parts by weight: ternary cementing material 100 parts, polymer powder 5-10 parts, aggregate 150-200 parts, water reducing agent 0.1-1 part, water-retaining thickening agent 0.01-0.1 part, defoaming agent 0.05-0.5 part, retarder 0.3-1 part and water 35-55 parts; wherein the ternary cementing material contains the following raw materials in 100% by mass percentage: first cementing component 30-40%, second cementing component 40-50% and the balance being a third cementing component. The early-strength low-shrinkage polymer repair mortar prepared by the application has high early compressive strength and low shrinkage rate and is stable in volume.

Description

Technical Field

[0001] This invention relates to the field of building materials and special engineering repair materials, specifically to an early-strength, low-shrinkage polymer repair mortar, its preparation method, and its application. Background Technology

[0002] In the field of building construction, concrete structures are highly susceptible to surface damage, cracks, sandblasting, and voids due to environmental erosion, load-bearing effects, construction defects, and aging wear during long-term service. These defects not only affect the aesthetics of the building structure but also reduce its load-bearing capacity, durability, and safety. If not repaired and reinforced in a timely manner, these defects may worsen, potentially leading to structural safety accidents and causing significant economic losses and safety hazards. Therefore, developing high-performance repair materials for timely and effective repair of damaged concrete structures, extending the service life of buildings, and reducing maintenance costs has significant engineering application value and practical significance.

[0003] Patent CN102826813B discloses a low-temperature rapid repair mortar for pavement and its preparation method. The low-temperature rapid repair mortar comprises the following components in parts by weight: silicate cement: 25-35 parts, aluminate cement: 5-10 parts, anhydrite: 3-6 parts, quartz sand: 30-60 parts, steel slag sand: 8-15 parts, latex powder: 0.8-1.5 parts, cellulose ether: 0.1-0.3 parts, lithium carbonate: 0.2-0.4 parts, and defoamer: 0.05-0.1 parts. This low-temperature rapid repair mortar possesses excellent physical and mechanical properties, exhibits rapid strength development at low temperatures, and demonstrates high strength. It also exhibits high bonding strength with the existing pavement substrate, good wear resistance, and durability. When applied to road repair, especially in low-temperature environments, it significantly shortens the construction period and ensures high mechanical strength within a short period under low-temperature conditions, improving construction efficiency, ensuring project quality, and reducing road maintenance costs.

[0004] In recent years, ternary cementitious systems have been increasingly applied to the modification research of cement-based materials. By compounding different types of cementitious materials, the synergistic effect between the components is utilized to optimize the hydration characteristics and macroscopic properties of the materials. Patent CN111087204B discloses a mineral admixture ternary cementitious system and its preparation method. The preparation method includes the following steps: placing raw material SAP in NaCl solution and soaking for 1-2 days to obtain water-absorbing and swellable SAP; weighing lithium acetate: sodium acetate: sodium octanoate: sodium hydroxide: calcium hydroxide according to the ratio, placing it at 300-350℃, keeping it at that temperature for 20-40 minutes, cooling it, and then grinding it to obtain slow-release glass; weighing mineral powder, fly ash, slow-release glass, and water-absorbing and swellable SAP according to the mass ratio, mixing them, and stirring until uniform to obtain ternary cementitious material; pouring the ternary cementitious material into a mold, curing it, demolding it, and obtaining the final product; this cementitious system can meet the needs of water-scarce areas, with a short preparation cycle and good repeatability.

[0005] However, the application of existing ternary cementitious systems in polymer repair mortars still faces many technical bottlenecks: the proportion of ternary cementitious components lacks scientific optimization, the synergistic effect between components is not fully utilized, and it is difficult to achieve a balance between early strength and low shrinkage performance at the same time. Therefore, there is an urgent need in the market for a polymer repair mortar based on early strength and low shrinkage. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention provides an early-strength, low-shrinkage polymer repair mortar and its preparation method. The early-strength, low-shrinkage polymer repair mortar disclosed in this invention has high early compressive strength, low shrinkage rate, and volume stability.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides an early-strength, low-shrinkage polymer repair mortar, comprising, by weight, the following raw materials: 100 parts of ternary cementitious material, 5-10 parts of polymer powder, 150-200 parts of aggregate, 0.1-1 parts of water-reducing agent, 0.01-0.1 parts of water-retaining and thickening agent, 0.05-0.5 parts of defoamer, 0.1-0.3 parts of retarder, and 35-55 parts of water; wherein, the ternary cementitious material, by mass percentage, comprises the following raw materials: 30-40% of a first cementitious component, 40-50% of a second cementitious component, and the remainder being a third cementitious component.

[0008] This invention constructs a ternary cementitious system. The first cementitious component rapidly generates ettringite during the early hydration stage, quickly building a structural framework and achieving high early strength in a short period, meeting the urgent need for timeliness in rapid repair projects. Simultaneously, the reaction of the second cementitious component in-situ fills and compensates for the chemical shrinkage caused by early hydration, effectively suppressing the concentrated release of self-shrinkage. The third cementitious component continues to hydrate in the later stages, generating CSH gel, further enhancing density and long-term strength. The differentiated design of the reaction sequence of the three cementitious components transforms the hydration process from a "concentrated burst" to a "staged and controllable" process, avoiding the volume instability problem caused by excessively rapid hydration in traditional early-strength mortars from the outset.

[0009] In some embodiments, the first cementing component is sulfoaluminate cement, the second cementing component is one or more of slag powder, fly ash, metakaolin, and natural volcanic ash, and the third cementing component is silicate cement.

[0010] In some embodiments, the method for preparing the polymer powder includes the following steps: (1) Add ethylene-vinyl acetate to the solvent, heat to 60-80℃ and stir for 10-20 min, then add sodium hydroxide solution and react for 2-4 h. After post-treatment, EVA-OH is obtained; add silane to methanol solution, adjust pH=4-5, stir at room temperature for 20-30 min to obtain silane hydrolysate; (2) Add the EVA-OH obtained in step (1) to toluene, then add the silane hydrolysate and catalyst obtained in step (1), heat to 80-90℃ and stir for 2-3 hours, then process and ball mill to obtain polymer powder.

[0011] In existing polymer-modified repair mortars, polymers are mainly used to improve flexibility and adhesion, but they fail to form a synergistic volume control mechanism with the multi-gelling system. This invention first introduces hydroxyl active groups into the polymer molecular chain through the alkaline alcoholysis reaction of ethylene-vinyl acetate, obtaining the EVA-OH intermediate. Simultaneously, silane is pre-hydrolyzed under acidic conditions to generate reactive silanol groups. Subsequently, under the action of a catalyst, the hydroxyl groups in EVA-OH undergo a condensation reaction with the silanol groups in the silane hydrolysate, chemically grafting a silane coupling structure onto the EVA molecular chain via Si-OC covalent bonds. One side of the grafted silane coupling structure… During cement hydration, the silane structure can chemically bond with the silanol groups on the surface of CSH gel or ettringite, transforming the organic polymer phase and inorganic hydration product phase from simple physical blending to "chemical anchoring," significantly improving the interfacial bonding strength between the organic and inorganic phases. On the other hand, the introduction of the silane structure reduces the hydrophilicity of the polymer film, delaying its premature demulsification and film formation in an alkaline environment, making it more time-matched with the formation process of ettringite and CSH gel. This truly achieves synchronous coupling between polymer film formation and hydration product generation, avoiding the volume instability problem of "early expansion and later shrinkage" that easily occurs when relying solely on expansion agents to compensate for shrinkage.

[0012] In some embodiments, the silane coupling agent is vinyltrimethoxysilane.

[0013] In some embodiments, the mass ratio of EVA-OH to silane in the silane hydrolysate in step (2) is 1:(0.05-0.15).

[0014] In some embodiments, the aggregate is one or more of natural river sand, manufactured sand, and quartz sand.

[0015] In some embodiments, the water-reducing agent is a polycarboxylate water-reducing agent.

[0016] In some embodiments, the water-retaining and thickening agent is hydroxypropyl methylcellulose ether.

[0017] A second aspect of this invention provides a method for preparing early-strength, low-shrinkage polymer repair mortar, comprising the following steps: S1. Add the ternary cementitious material, aggregate, water-reducing agent, water-retaining thickener, defoamer, and retarder to the mixer and mix for 5-10 minutes to obtain a dry mix; S2. Mix the polymer powder with water for 20-30 minutes, add it to the dry mixture obtained in step S1, and stir for 5-10 minutes to obtain early-strength, low-shrinkage polymer repair mortar.

[0018] The third aspect of this invention provides an application of early-strength, low-shrinkage polymer repair mortar in the repair of concrete structures such as bridges, roads, industrial floors, or prefabricated structural nodes.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention constructs a ternary cementitious system and utilizes the differences in hydration reactivity and reaction time of different cementitious components to form a phased hydration process of "early rapid reaction - mid-term compensation and regulation - late-term continuous densification". This ensures that the repair mortar can quickly obtain load-bearing capacity in the early stage, while suppressing self-shrinkage and volume instability caused by uneven hydration or excessive reaction, thus achieving a unity of early strength and low shrinkage performance.

[0020] 2. This invention prepares polymer powder by grafting silane onto ethylene-vinyl acetate, which is then embedded in the hydration product network as an "organic crosslinking phase," significantly reducing the pore connectivity of the hardened slurry, effectively mitigating drying shrinkage strain, improving bonding strength, and preventing shrinkage. Detailed Implementation

[0021] The present invention will be described below with reference to specific embodiments. It should be noted that the examples and comparative examples below are for illustrative purposes only and are not intended to limit the invention. Other combinations and various modifications within the scope of the invention can be made without departing from its spirit or scope.

[0022] To facilitate implementation of this invention by those skilled in the art, some raw materials and manufacturers of the embodiments and comparative examples are described below: The compounds and related reagents used in the following specific embodiments are all commercially available. The average particle size of the quartz sand is 140 mesh; the polycarboxylate superplasticizer is PCA-Ⅰ, purchased from Jiangsu Subote New Material Co., Ltd.; the hydroxypropyl methylcellulose ether is HPMC 150000S, purchased from Shandong Heda Group Co., Ltd.; the polyether-modified silicone defoamer is TS-603, purchased from Nanjing Tianshi New Material Technology Co., Ltd.; the S95 grade granulated blast furnace slag powder is purchased from Shanghai Baotian New Building Materials Co., Ltd.; and the ethylene-vinyl acetate is Vinnapas® RE5010N, purchased from Wacker Chemie (China) Co., Ltd.

[0023] It should be noted that the post-processing steps such as "filtration", "washing" and "drying" mentioned in the following embodiments are routine operations for those skilled in the art, and should be selected according to actual operation.

[0024] Preparation Example 1 The preparation method of polymer powder-1# includes the following steps: (1) Add 20g of ethylene-vinyl acetate to 500ml of toluene, heat to 70℃ and stir for 15min, then add 100ml of 20wt% sodium hydroxide solution dropwise. The addition is completed in 40min. After that, react for 3h, cool to room temperature and add 1mol / L dilute hydrochloric acid. Stir to neutralize to pH 7. Add 1000mL of deionized water to the neutralized mixture, stir for 10min, let stand for 30min, pour off the supernatant, filter, collect the lower white precipitate, wash with deionized water and dry to obtain EVA-OH; add 1g of vinyltrimethoxysilane to 10ml of 95wt% methanol solution, adjust pH=4 with 1mol / L dilute hydrochloric acid, stir at room temperature for 25min to obtain silane hydrolysate; (2) Add 10g of EVA-OH obtained in step (1) to 100ml of toluene, then add all the silane hydrolysate obtained in step (1) and 0.1g of dibutyltin dilaurate. Heat to 85℃ and stir for 2.5h. Cool to room temperature and pour into methanol while stirring. Let stand for 30min, filter, collect the precipitate, wash with methanol, dry, and ball mill for 30min. The ball-to-material ratio is (5-8):1 and the rotation speed is 300-400r / min to obtain polymer powder-1#.

[0025] Preparation Example 2 The specific implementation method of polymer powder-2# is the same as that of preparation example 1, except that the amount of vinyltrimethoxysilane added is 2g.

[0026] Preparation Example 3 The specific implementation method of polymer powder-3# is the same as that of preparation example 1, except that vinyltrimethoxysilane is replaced by γ-aminopropyltriethoxysilane in equal amounts.

[0027] Preparation Example 4 The specific implementation method of polymer powder-4# is the same as that of preparation example 1, except that vinyltrimethoxysilane is replaced by γ-glycidoxypropyltrimethoxysilane in equal amounts.

[0028] Example 1 An early-strength, low-shrinkage polymer repair mortar, by weight, comprises the following raw materials: 100 parts of ternary cementitious material, 8 parts of polymer adhesive powder-1#, 180 parts of quartz sand, 0.5 parts of polycarboxylate superplasticizer, 0.05 parts of hydroxypropyl methylcellulose ether, 0.1 parts of polyether-modified silicone defoamer, 0.2 parts of sodium gluconate, and 45 parts of water; wherein, the ternary cementitious material, by mass percentage (100%), comprises the following raw materials: 35% of 42.5R rapid-hardening sulfoaluminate cement, 45% of S95 grade granulated blast furnace slag powder, and the balance being 42.5R ordinary Portland cement.

[0029] The preparation method of early-strength, low-shrinkage polymer repair mortar in this embodiment includes the following steps: S1. Add the ternary cementitious material, quartz sand, polycarboxylate superplasticizer, hydroxypropyl methylcellulose ether, polyether-modified silicone defoamer, and sodium gluconate to a mixer and mix for 8 minutes to obtain a dry mix. S2. Mix polymer powder-1# with water for 25 minutes, add it to the dry mixture obtained in step S1, and stir for 8 minutes to obtain early-strength, low-shrinkage polymer repair mortar.

[0030] Example 2 An early-strength, low-shrinkage polymer repair mortar, by weight, comprises the following raw materials: 100 parts of ternary cementitious material, 5 parts of polymer adhesive powder-1#, 150 parts of quartz sand, 0.1 parts of polycarboxylate superplasticizer, 0.01 parts of hydroxypropyl methylcellulose ether, 0.05 parts of polyether-modified silicone defoamer, 0.1 parts of sodium gluconate, and 35 parts of water; wherein, the ternary cementitious material, by mass percentage (100%), comprises the following raw materials: 30% of 42.5R rapid-hardening sulfoaluminate cement, 50% of S95 grade granulated blast furnace slag powder, and the balance being 42.5R ordinary Portland cement.

[0031] The preparation method of early-strength, low-shrinkage polymer repair mortar in this embodiment includes the following steps: S1. Add the ternary cementitious material, quartz sand, polycarboxylate superplasticizer, hydroxypropyl methylcellulose ether, polyether-modified silicone defoamer, and sodium gluconate to a mixer and mix for 5 minutes to obtain a dry mix. S2. Mix polymer powder-1# with water for 20 minutes, add it to the dry mixture obtained in step S1, and stir for 5 minutes to obtain early-strength, low-shrinkage polymer repair mortar.

[0032] Example 3 An early-strength, low-shrinkage polymer repair mortar, by weight, comprises the following raw materials: 100 parts of ternary cementitious material, 10 parts of polymer adhesive powder-1#, 200 parts of quartz sand, 1 part of polycarboxylate superplasticizer, 0.1 parts of hydroxypropyl methylcellulose ether, 0.15 parts of polyether-modified silicone defoamer, 0.3 parts of sodium gluconate, and 55 parts of water; wherein, the ternary cementitious material, by mass percentage (100%), comprises the following raw materials: 40% of 42.5R rapid-hardening sulfoaluminate cement, 40% of S95 grade granulated blast furnace slag powder, and the balance being 42.5R ordinary Portland cement.

[0033] The preparation method of early-strength, low-shrinkage polymer repair mortar in this embodiment includes the following steps: S1. Add the ternary cementitious material, quartz sand, polycarboxylate superplasticizer, hydroxypropyl methylcellulose ether, polyether-modified silicone defoamer, and sodium gluconate to a mixer and mix for 10 minutes to obtain a dry mix. S2. Mix polymer powder-1# with water for 30 minutes, add it to the dry mixture obtained in step S1, and stir for 10 minutes to obtain early strength low shrinkage polymer repair mortar.

[0034] Example 4 An early-strength, low-shrinkage polymer repair mortar and its preparation method are disclosed. The specific implementation method is the same as in Example 1, except that polymer powder-1# is replaced with polymer powder-2# in equal amounts.

[0035] Example 5 An early-strength, low-shrinkage polymer repair mortar and its preparation method are disclosed. The specific implementation method is the same as in Example 1, except that polymer powder-1# is replaced with polymer powder-3# in equal amounts.

[0036] Example 6 An early-strength, low-shrinkage polymer repair mortar and its preparation method are disclosed. The specific implementation method is the same as in Example 1, except that polymer powder-1# is replaced with polymer powder-4# in equal amounts.

[0037] Example 7 An early-strength, low-shrinkage polymer repair mortar and its preparation method are disclosed. The specific implementation method is the same as in Example 1, except that the polymer powder-1# is replaced with an equal amount of ethylene-vinyl acetate.

[0038] Performance testing The early-strength, low-shrinkage polymer repair mortars of the above embodiments were tested for 4-hour compressive strength and 28-day shrinkage rate under standard curing conditions according to the "Standard for Test Methods of Basic Performance of Building Mortar" JGJ / T 70-2009.

[0039] The specific test results are shown in Table 1: Table 1

[0040] A comparison of the experimental data from Examples 1-3 in Table 1 shows that the early-strength, low-shrinkage polymer repair mortar obtained by this invention has high early compressive strength, low shrinkage, and good volume stability. A comparison of Example 4 and Example 1 shows that changing the ratio of silane in the EVA-OH and silane hydrolysate inhibits the early hydration reaction of sulfoaluminate cement, resulting in a decrease in early compressive strength. A comparison of Example 5 and Example 1 shows that replacing vinyltrimethoxysilane with an equal amount of γ-aminopropyltriethoxysilane results in the amino group being primarily bonded to the inorganic phase by hydrogen and ionic bonds, with bond energies lower than covalent bonds, thus reducing the constraint energy on shrinkage stress. The weaker force leads to increased shrinkage and decreased volume stability. Comparing Example 6 with Example 1, it can be seen that replacing vinyltrimethoxysilane with γ-glycidoxypropyltrimethoxysilane in equal amounts results in better flexibility of the COC bond formed after the epoxy group ring-opening, but the chemical bonding strength is slightly lower than that of the Si-O-Si covalent bond, leading to increased shrinkage and decreased volume stability. Comparing Example 7 with Example 1, it can be seen that directly using ethylene-vinyl acetate results in only physical mixing with the inorganic phase, without chemical bonding, which cannot effectively constrain shrinkage stress, leading to decreased compressive strength, increased shrinkage, and decreased volume stability.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A high-strength, low-shrinkage polymer repair mortar, characterized in that, The product comprises, by weight, the following raw materials: 100 parts of ternary cementitious material, 5-10 parts of polymer powder, 150-200 parts of aggregate, 0.1-1 parts of water-reducing agent, 0.01-0.1 parts of water-retaining thickener, 0.05-0.5 parts of defoamer, 0.1-0.3 parts of retarder, and 35-55 parts of water; wherein, the ternary cementitious material, by mass percentage, comprises the following raw materials: 30-40% of the first cementitious component, 40-50% of the second cementitious component, and the balance being the third cementitious component.

2. The early-strength, low-shrinkage polymer repair mortar according to claim 1, characterized in that, The first cementitious component is sulfoaluminate cement, the second cementitious component is one or more of slag powder, fly ash, metakaolin, and natural volcanic ash, and the third cementitious component is silicate cement.

3. The early-strength, low-shrinkage polymer repair mortar according to claim 1, characterized in that, The method for preparing the polymer powder includes the following steps: (1) Add ethylene-vinyl acetate to the solvent, heat to 60-80℃ and stir for 10-20 min, then add sodium hydroxide solution and react for 2-4 h. After post-treatment, EVA-OH is obtained; add silane to methanol solution, adjust pH=4-5, stir at room temperature for 20-30 min to obtain silane hydrolysate; (2) Add the EVA-OH obtained in step (1) to toluene, then add the silane hydrolysate and catalyst obtained in step (1), heat to 80-90℃ and stir for 2-3 hours, then process and ball mill to obtain polymer powder.

4. The early-strength, low-shrinkage polymer repair mortar according to claim 3, characterized in that, The silane coupling agent is vinyltrimethoxysilane.

5. The early-strength, low-shrinkage polymer repair mortar according to claim 3, characterized in that, The mass ratio of EVA-OH to silane in the silane hydrolysate in step (2) is 1:(0.05-0.15).

6. The early-strength, low-shrinkage polymer repair mortar according to claim 1, characterized in that, The aggregate is one or more of natural river sand, manufactured sand, and quartz sand.

7. The early-strength, low-shrinkage polymer repair mortar according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate water-reducing agent.

8. The early-strength, low-shrinkage polymer repair mortar according to claim 1, characterized in that, The water-retaining and thickening agent is hydroxypropyl methylcellulose ether.

9. A method for preparing the early-strength, low-shrinkage polymer repair mortar according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Add the ternary cementitious material, aggregate, water-reducing agent, water-retaining thickener, defoamer, and retarder to the mixer and mix for 5-10 minutes to obtain a dry mix; S2. Mix the polymer powder with water for 20-30 minutes, add it to the dry mixture obtained in step S1, and stir for 5-10 minutes to obtain early-strength, low-shrinkage polymer repair mortar.

10. The application of the early-strength low-shrinkage polymer repair mortar according to any one of claims 1-8 or the early-strength low-shrinkage polymer repair mortar obtained by the preparation method according to claim 9 in the repair of concrete structures such as bridges, roads, industrial floors or prefabricated structural nodes.

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