A concrete mortar for repairing bridge expansion joints and its preparation process

Abstract

The present invention relates to the technical field of bridge building materials, and specifically to a concrete mortar for repairing bridge expansion joints and its preparation process. The concrete mortar comprises the following weight components: 350-450 parts of portland cement, 20-50 parts of sulfoaluminate cement, 5-15 parts of mineral powder, 10-25 parts of silica fume, 20-50 parts of fly ash, 450-550 parts of quartz sand, 10-30 parts of thickener, 4-8 parts of composite fiber, 2-4 parts of water reducing agent, 0.5-1.0 part of retarder, 0.3-0.5 part of defoamer, and 80-120 parts of water. The present invention uses a composite cementitious material of portland cement and rapid hardening sulfoaluminate cement as the main body, uses mineral powder, silica powder, and fly ash as admixtures, uses quartz sand as a filler, and then adds a thickener, composite fiber, and other additives. The prepared concrete mortar has excellent early and late strength performance and excellent impact resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge building materials, and specifically to a concrete mortar for repairing bridge expansion joints and its preparation process. Background Technique

[0002] As one of the important components of the upper structure of a bridge, the bridge expansion joint is an important accessory structure that ensures the free deformation of the bridge deck and plays a role in strengthening both ends and filling the gap. The concrete of the bridge expansion joint often suffers from wear, broken slabs, impact and fatigue damage, and the probability of repeated damage after repair is very high. Therefore, the repair of the expansion joint has always been a difficult problem to solve.

[0003] At present, there are mainly the following forms of repairing bridge expansion joints: filling with ordinary concrete, filling with fiber concrete, filling with modified asphalt, and filling with polymer (resin) concrete. However, some filling materials may have problems such as cracking and deformation during long-term use, which will affect the repair effect and service life. In addition, the adhesion of the filling material to the bridge surface is not good, which may cause the filling layer to delaminate or peel off from the base material, thus affecting the repair effect.

[0004] Therefore, we propose a concrete mortar for repairing bridge expansion joints and its preparation process. Summary of the Invention

[0005] The purpose of the present invention is to provide a concrete mortar for repairing bridge expansion joints and its preparation process to solve the problems raised in the above background technique.

[0006] To solve the above technical problems, the present invention provides the following technical solutions:

[0007] A preparation process of a concrete mortar for repairing bridge expansion joints includes the following steps:

[0008] Mix portland cement, sulfoaluminate cement, mineral powder, silica fume, fly ash, quartz sand, thickening agent, composite fiber, water reducing agent, setting retarder and defoaming agent evenly, add water, and stir for 1 - 5 minutes to obtain the concrete mortar.

[0009] Further, the concrete mortar includes the following weight components: 350 - 450 parts of portland cement, 20 - 50 parts of sulfoaluminate cement, 5 - 15 parts of mineral powder, 10 - 25 parts of silica fume, 20 - 50 parts of fly ash, 450 - 550 parts of quartz sand, 10 - 30 parts of thickening agent, 4 - 8 parts of composite fiber, 2 - 4 parts of water reducing agent, 0.5 - 1.0 part of setting retarder, 0.3 - 0.5 part of defoaming agent, and 80 - 120 parts of water.

[0010] Further, the preparation method of the thickening agent is as follows:

[0011] Step 1: Heat absolute ethanol, deionized water, 3-glycidoxypropylmethyldimethoxysilane, and dimethyldimethoxysilane to 70 - 80 °C, add dibutyltin dilaurate, react for 4 - 6 h, then add vinyldimethylethoxysilane, and perform end-capping reaction for 3 - 5 h. After rotary evaporation under reduced pressure, a double-bond-containing compound is obtained.

[0012] Step 2: Mix acrylic acid, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, the double-bond-containing compound, and deionized water evenly. Add sodium dodecyl sulfate and fatty alcohol polyoxyethylene ether and mix evenly. Perform ultrasonic emulsification for 10 - 20 min. Use sodium hydroxide solution to adjust the pH of the system to 7 - 8. Pass in nitrogen, heat to 65 - 75 °C, dropwise add the initiator aqueous solution, finish dropping in 40 - 60 min, keep the temperature for reaction for 3 - 5 h, cool to room temperature, and after demulsification, filtration, washing, and drying, a tackifier is obtained.

[0013] In the above technical solution, using 3-glycidoxypropylmethyldimethoxysilane, dimethyldimethoxysilane, and vinyldimethylethoxysilane as raw materials, a double-bond-containing compound with epoxy groups is prepared by hydrolysis and condensation method; selecting acrylic acid, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and the double-bond-containing compound as comonomers can introduce a large number of polar hydrophilic groups such as carboxyl groups, amide groups, and sulfonic acid groups into the polymer molecular chain. The hydrophilic groups form hydrogen bonds by combining with water molecules, adsorb and fix free water molecules on the polymer molecular chain, thereby playing a certain role in increasing viscosity and retaining water.

[0014] Further, in Step 1, the double-bond-containing compound includes the following weight components: 13 - 14 parts of absolute ethanol, 2 - 3 parts of deionized water, 5 - 6 parts of 3-glycidoxypropylmethyldimethoxysilane, 5.5 - 6.5 parts of dimethyldimethoxysilane, 6 - 7 parts of vinyldimethylethoxysilane, and 0.01 - 0.03 parts of dibutyltin dilaurate.

[0015] Further, in Step 2, the tackifier includes the following weight components: 1 - 4 parts of acrylic acid, 4 - 12 parts of acrylamide, 3 - 8 parts of 2-acrylamido-2-methylpropanesulfonic acid, 2 - 6 parts of the double-bond-containing compound, 100 - 200 parts of deionized water, 1.4 - 2.0 parts of sodium dodecyl sulfate, 0.1 - 0.5 parts of fatty alcohol polyoxyethylene ether, and 5 - 15 parts of the initiator aqueous solution.

[0016] Further, the concentration of the initiator aqueous solution is 2 - 5 wt%, and the initiator is 2,2'-azobis(2-methylpropionamidine) dihydrochloride.

[0017] Further, the composite fiber is composed of 1 - 3 parts by mass of polypropylene fiber and 3 - 5 parts by mass of basalt fiber.

[0018] Further, the composite fiber is subjected to a modification treatment, and the specific modification process is as follows:

[0019] Step (1): Under nitrogen protection, polypropylene fiber and xylene are mixed evenly, swollen at 70 - 80 °C for 1 - 2 h, and after suction filtration, acetone washing, and drying, pretreated polypropylene fiber is obtained; basalt fiber is heated at 250 - 300 °C for 1 - 2 h, cooled to room temperature, immersed in an acetone solution for 1 - 2 h, and after washing and drying, pretreated basalt fiber is obtained;

[0020] Step (2): The pretreated polypropylene fiber and pretreated basalt fiber are mixed evenly, a mixed solution of anhydrous ethanol, deionized water, and 3 - aminopropyltrimethoxysilane is added, and then nano - silica is added, and the reaction is carried out at 55 - 65 °C for 4 - 6 h. After filtration, washing, and drying, amino - functionalized composite fiber is obtained;

[0021] Step (3): Under nitrogen protection, the amino - functionalized composite fiber, succinic anhydride, and diethanolamine are mixed evenly, and the reaction is carried out at 115 - 125 °C for 6 - 8 h. Then diethylenetriamine is added, and the reaction is carried out at 105 - 115 °C for 10 - 12 h to obtain the modified composite fiber.

[0022] In the above - mentioned technical solution, by pretreating polypropylene fiber and basalt fiber, the surface micro - roughness of the fiber is improved; then, the surfaces of the pretreated polypropylene fiber and pretreated basalt fiber are synergistically modified by nano - silica and 3 - aminopropyltrimethoxysilane to obtain amino - functionalized composite fiber. Due to the small particle size and large surface activity of nano - silica, introducing it into the composite fiber modification system can further increase the surface roughness of the fiber, improve the wetting effect between the fiber and the cement - based material, promote the stress transfer between the fiber and the cement - based material, and thus increase the bonding force at the interface between the fiber and the cement - based material; finally, by reacting succinic anhydride and diethanolamine to form hyperbranched macromolecules, grafting hyperbranched molecules onto the amino - functionalized composite fiber, the toughness of the hyperbranched macromolecules is used to improve the impact resistance of the material; at the same time, the secondary amine of diethylenetriamine reacts with the terminal hydroxyl group of the hyperbranched molecule to form terminal - amino hyperbranched composite fiber, that is, the modified fiber, so that chemical reaction anchor points are formed on the fiber, which can further react with the epoxy group in the tackifier, enhancing the binding force between the two, thereby improving the mechanical properties of the concrete mortar.

[0023] Further, in step (1), the mass ratio of polypropylene fiber to xylene is 1:(30 - 40).

[0024] Further, in the step (2), the aminated composite fiber comprises the following weight components: 1-3 parts of pretreated polypropylene fiber, 3-5 parts of pretreated basalt fiber, 14-22 parts of absolute ethanol, 1.5-2.5 parts of deionized water, 0.5-1.0 part of 3-aminopropyltrimethoxysilane, and 0.10-0.25 part of nano-silica.

[0025] Further, in the step (3), the modified composite fiber comprises the following weight components: 4-8 parts of aminated composite fiber, 6-12 parts of succinic anhydride, 8-16 parts of diethanolamine, and 12-24 parts of diethylenetriamine.

[0026] Further, the water reducing agent is a polycarboxylate water reducing agent.

[0027] Further, the setting retarder is boric acid.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. For the concrete mortar for repairing bridge expansion joints and its preparation process of the present invention, the surfaces of pretreated polypropylene fiber and pretreated basalt fiber are synergistically modified by nano-silica and 3-aminopropyltrimethoxysilane to obtain aminated composite fiber, enhancing the interfacial adhesion between the composite fiber and the cement-based material; by grafting hyperbranched macromolecules onto the aminated composite fiber, the impact resistance of the material is improved. At the same time, the secondary amine of diethylenetriamine reacts with the terminal hydroxyl group of the hyperbranched molecule to introduce amino groups, obtaining hyperbranched composite fiber with terminal amino groups, that is, modified fiber, so that chemical reaction anchor points are formed on the fiber, which can react with the epoxy groups in the tackifier, enhancing the binding force between the two, so as to improve the bonding strength and impact resistance of the concrete mortar, ensuring that the repaired bridge expansion joint can withstand the loads of vehicles and pedestrians.

[0030] 2. For the concrete mortar for repairing bridge expansion joints and its preparation process of the present invention, acrylic acid, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and double bond-containing compounds are used as copolymerization monomers to obtain a tackifier containing epoxy groups. The molecular chain of the tackifier contains a large number of polar hydrophilic groups such as carboxyl groups, amide groups, and sulfonic acid groups. These groups can form hydrogen bonds with water molecules, effectively adsorbing and fixing free water molecules, thereby improving the water retention performance of the concrete mortar. At the same time, the introduction of the tackifier realizes good bonding between the polymer and the cement-based material, increasing the adhesion between the repaired concrete and the raw materials, improving the mechanical properties and stability of the repaired mortar; by fixing free water molecules, the hydrophilic groups improve the fluidity and plasticity of the repaired mortar, which is beneficial to full filling in the bridge expansion joint, thereby improving the repair effect.

[0031] 3. A concrete mortar for repairing bridge expansion joints and its preparation process according to the present invention, with a composite cementitious material of portland cement and rapid hardening sulphoaluminate cement as the main body, mineral powder, silica fume, and fly ash as admixtures, quartz sand as filler, and by adding a thickening agent, composite fibers, and other additives, the prepared concrete mortar has excellent early and late strength performance, and at the same time has excellent impact resistance, and can meet the requirements of rapid repair and long-term use of the anchor concrete of bridge expansion joints. Detailed implementation manners

[0032] 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 embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] In this embodiment, the portland cement: P·O 42.5 grade, sourced from Hunan Xindingli New Material Technology Co., Ltd.; sulphoaluminate cement: R.SAC 42.5 grade, sourced from Henan Haonai Building Materials Co., Ltd.; mineral powder: S95 grade mineral powder, sourced from Shandong Kefa Building Materials Co., Ltd.; silica fume: product number GWF13, particle size 350 - 400 mesh, sourced from Hebei Siruite Mineral Products Co., Ltd.; fly ash: first-class fly ash, particle size 200 - 300 mesh, sourced from Jining Hengzhi New Building Materials Co., Ltd.; quartz sand: particle size 40 - 70 mesh, sourced from Changxing Qingsheng Calcium Industry Co., Ltd.; water reducing agent: powder polycarboxylate water reducing agent, model PC-1030, sourced from Suzhou Xingbang Chemical Building Materials Co., Ltd.; defoaming agent: silicone defoaming agent BYK-088; polypropylene fiber: fiber diameter 2.5μm, length 5mm, sourced from Shanghai Lingyu Building Materials Co., Ltd.; basalt fiber: chopped fiber, length 6mm, single filament diameter 15μm, sourced from Tai'an Songze Composite Materials Co., Ltd.; nano-silica: water-based nano-SiO2, particle size 20 - 30nm, sourced from Shanghai Xiaohuang Nano Technology Co., Ltd.; fatty alcohol polyoxyethylene ether: AEO-9, sourced from BASF (China) Co., Ltd.

[0034] In the following examples and comparative examples, 1 part is equal to 10g.

[0035] Example 1: A preparation process of a concrete mortar for repairing bridge expansion joints, including the following processes:

[0036] Mix 350 parts of portland cement, 20 parts of sulfoaluminate cement, 5 parts of mineral powder, 10 parts of silica fume, 20 parts of fly ash, 450 parts of quartz sand, 10 parts of thickener, 4 parts of composite fiber (composed of 1 part of polypropylene fiber and 3 parts of basalt fiber), 2 parts of water reducer, 0.5 part of retarder and 0.3 part of defoamer evenly, add 80 parts of water, and stir for 1 min to obtain concrete mortar;

[0037] The preparation method of the thickener is as follows:

[0038] Step 1: Heat 13 parts of absolute ethanol, 2 parts of deionized water, 5 parts of 3-glycidoxypropylmethyldimethoxysilane and 5.5 parts of dimethyldimethoxysilane to 70 °C, add 0.01 part of dibutyltin dilaurate, react for 4 h, then add 6 parts of vinyldimethylethoxysilane, and carry out capping reaction for 3 h. After rotary evaporation under reduced pressure, a double bond-containing compound is obtained;

[0039] Step 2: Mix 1 part of acrylic acid, 4 parts of acrylamide, 3 parts of 2-acrylamido-2-methylpropanesulfonic acid, 2 parts of the double bond-containing compound and 100 parts of deionized water evenly, add 1.4 parts of sodium dodecyl sulfate and 0.1 part of fatty alcohol polyoxyethylene ether and mix evenly. Carry out ultrasonic emulsification for 10 min, adjust the pH of the system to 7 with sodium hydroxide solution, introduce nitrogen, heat to 65 °C, dropwise add 5 parts of 2 wt% initiator aqueous solution, finish dropping in 40 min, keep the temperature for reaction for 3 h, cool to room temperature, and after demulsification, filtration, washing and drying, a thickener is obtained.

[0040] Example 2: A preparation process of concrete mortar for repairing bridge expansion joints, including the following processes:

[0041] Compared with Example 1, the composite fiber in Example 2 is modified, and other steps are the same as those in Example 1;

[0042] The composite fiber is modified, and the specific modification process is as follows:

[0043] Step (1): Under nitrogen protection, mix 1 part of polypropylene fiber and 30 parts of xylene evenly, swell at 70 °C for 1 h, and after suction filtration, washing with acetone and drying, obtain pretreated polypropylene fiber; heat 3 parts of basalt fiber at 250 °C for 1 h, cool to room temperature, soak in acetone solution for 1 h, and after washing and drying, obtain pretreated basalt fiber;

[0044] Step (2): Mix 1 part of the pretreated polypropylene fiber and 3 parts of the pretreated basalt fiber evenly, add a mixed solution of 14 parts of absolute ethanol, 1.5 parts of deionized water and 0.5 part of 3-aminopropyltrimethoxysilane, and then add 0.10 part of nano-silica, react at 55 °C for 4 h, and after filtration, washing and drying, obtain amino-functionalized composite fiber;

[0045] Step (3): Under nitrogen protection, 4 parts of amino-functionalized composite fiber, 6 parts of succinic anhydride and 8 parts of diethanolamine were mixed evenly, reacted at 115 °C for 6 h, then 12 parts of diethylenetriamine was added and reacted at 105 °C for 10 h to obtain the modified composite fiber.

[0046] Example 3: A preparation process of concrete mortar for repairing bridge expansion joints, including the following processes:

[0047] 400 parts of portland cement, 35 parts of sulfoaluminate cement, 10 parts of mineral powder, 15 parts of silica fume, 40 parts of fly ash, 500 parts of quartz sand, 20 parts of thickener, 6 parts of composite fiber (composed of 2 parts of polypropylene fiber and 4 parts of basalt fiber), 3 parts of water reducer, 0.8 part of retarder and 0.4 part of defoamer were mixed evenly, 100 parts of water was added, and stirred for 3 min to obtain the concrete mortar;

[0048] The preparation method of the thickener is as follows:

[0049] Step 1: 13.5 parts of absolute ethanol, 2.5 parts of deionized water, 5.5 parts of 3-glycidoxypropylmethyldimethoxysilane and 6 parts of dimethyldimethoxysilane were heated to 75 °C, 0.02 part of dibutyltin dilaurate was added, reacted for 4 - 6 h, then 6.5 parts of vinyldimethylethoxysilane was added for end-capping reaction for 4 h, and after reduced pressure rotary evaporation, a double bond-containing compound was obtained;

[0050] Step 2: 3 parts of acrylic acid, 8 parts of acrylamide, 5 parts of 2-acrylamido-2-methylpropanesulfonic acid, 4 parts of double bond-containing compound and 150 parts of deionized water were mixed evenly, 1.6 parts of sodium dodecyl sulfate and 0.4 part of fatty alcohol polyoxyethylene ether were added and mixed evenly, ultrasonic emulsification was carried out for 15 min, the pH of the system was adjusted to 7.5 with sodium hydroxide solution, nitrogen was introduced, the temperature was raised to 70 °C, 10 parts of 3 wt% initiator aqueous solution was added dropwise, and the addition was completed in 50 min, and the reaction was carried out under insulation for 4 h, cooled to room temperature, and after demulsification, filtration, washing and drying, the thickener was obtained;

[0051] The composite fiber was modified, and the specific modification process is as follows:

[0052] Step (1): Under nitrogen protection, 2 parts of polypropylene fiber and 70 parts of xylene were mixed evenly, swollen at 75 °C for 1.5 h, and after suction filtration, acetone washing and drying, pretreated polypropylene fiber was obtained; the basalt fiber was heated at 300 °C for 1.5 h, cooled to room temperature, immersed in acetone solution for 1.5 h, and after washing and drying, pretreated basalt fiber was obtained;

[0053] Step (2): Mix 2 parts of pretreated polypropylene fibers and 4 parts of pretreated basalt fibers evenly, add a mixed solution of 18 parts of absolute ethanol, 2 parts of deionized water and 0.8 part of 3-aminopropyltrimethoxysilane, then add 0.2 part of nano-silica, react at 60 °C for 5 h, and after filtration, washing and drying, obtain amino-functionalized composite fibers;

[0054] Step (3): Under nitrogen protection, mix 6 parts of amino-functionalized composite fibers, 8 parts of succinic anhydride and 12 parts of diethanolamine evenly, react at 120 °C for 7 h, then add 18 parts of diethylenetriamine, and react at 110 °C for 11 h to obtain modified composite fibers.

[0055] Example 4: A preparation process of concrete mortar for repairing bridge expansion joints, including the following processes:

[0056] Mix 450 parts of portland cement, 50 parts of sulfoaluminate cement, 15 parts of mineral powder, 25 parts of silica fume, 50 parts of fly ash, 550 parts of quartz sand, 30 parts of thickener, 8 parts of composite fibers (composed of 3 parts of polypropylene fibers and 5 parts of basalt fibers), 4 parts of water reducer, 1.0 part of retarder and 0.5 part of defoamer evenly, add 120 parts of water, and stir for 5 min to obtain concrete mortar;

[0057] The preparation method of the thickener is as follows:

[0058] Step 1: Heat 14 parts of absolute ethanol, 3 parts of deionized water, 6 parts of 3-glycidoxypropylmethyldimethoxysilane and 6.5 parts of dimethyldimethoxysilane to 80 °C, add 0.03 part of dibutyltin dilaurate, react for 6 h, then add 7 parts of vinyldimethylethoxysilane for capping reaction for 5 h, and obtain a double-bond-containing compound through rotary evaporation under reduced pressure;

[0059] Step 2: Mix 4 parts of acrylic acid, 12 parts of acrylamide, 8 parts of 2-acrylamido-2-methylpropanesulfonic acid, 6 parts of the double-bond-containing compound and 200 parts of deionized water evenly, add 2.0 parts of sodium dodecyl sulfate and 0.5 part of fatty alcohol polyoxyethylene ether and mix evenly, perform ultrasonic emulsification for 20 min, adjust the pH of the system to 8 with sodium hydroxide solution, introduce nitrogen, heat to 75 °C, dropwise add 15 parts of 5 wt% initiator aqueous solution, finish dropping in 60 min, keep the temperature for reaction for 5 h, cool to room temperature, and obtain the thickener after demulsification, filtration, washing and drying;

[0060] The composite fibers are subjected to modification treatment, and the specific modification process is as follows:

[0061] Step (1): Under nitrogen protection, 3 parts of polypropylene fibers and 120 parts of xylene were mixed evenly, swollen at 80 °C for 2 h, and after filtration, washing with acetone, and drying, pretreated polypropylene fibers were obtained; 5 parts of basalt fibers were heated at 300 °C for 2 h, cooled to room temperature, soaked in an acetone solution for 2 h, and after washing and drying, pretreated basalt fibers were obtained.

[0062] Step (2): 3 parts of pretreated polypropylene fibers and 5 parts of pretreated basalt fibers were mixed evenly, a mixed solution of 22 parts of absolute ethanol, 2.5 parts of deionized water, and 1.0 part of 3-aminopropyltrimethoxysilane was added, and then 0.25 part of nano-silica was added. The reaction was carried out at 65 °C for 6 h. After filtration, washing, and drying, amino-functionalized composite fibers were obtained.

[0063] Step (3): Under nitrogen protection, 8 parts of amino-functionalized composite fibers, 12 parts of succinic anhydride, and 16 parts of diethanolamine were mixed evenly, reacted at 125 °C for 8 h, then 24 parts of diethylenetriamine were added, and the reaction was carried out at 115 °C for 12 h to obtain modified composite fibers.

[0064] Comparative Example 1: A preparation process of concrete mortar for repairing bridge expansion joints, including the following process:

[0065] Compared with Example 3, Comparative Example 1 added 40 parts of tackifier, and other steps were the same as those in Example 3.

[0066] Comparative Example 2: A preparation process of concrete mortar for repairing bridge expansion joints, including the following process:

[0067] The preparation method of the tackifier is as follows:

[0068] Step two: 3 parts of acrylic acid, 8 parts of acrylamide, 5 parts of 2-acrylamido-2-methylpropanesulfonic acid, 4 parts of vinyldimethylethoxysilane, and 150 parts of deionized water were mixed evenly, 1.6 parts of sodium dodecyl sulfate and 0.4 part of fatty alcohol polyoxyethylene ether were added and mixed evenly, ultrasonic emulsification was carried out for 15 min, the pH of the system was adjusted to 7.5 using a sodium hydroxide solution, nitrogen was introduced, the temperature was raised to 70 °C, 10 parts of a 3 wt% initiator aqueous solution was added dropwise, and the dropping was completed in 50 min. The reaction was carried out under insulation for 4 h, cooled to room temperature, and after demulsification, filtration, washing, and drying, the tackifier was obtained.

[0069] Compared with Example 3, Comparative Example 2 did not include Step one, and the double-bond-containing compound in Step two was replaced with the same mass of vinyldimethylethoxysilane, and other steps were the same as those in Example 3.

[0070] Comparative Example 3: A preparation process of concrete mortar for repairing bridge expansion joints, including the following process:

[0071] The composite fiber is subjected to a modification treatment, and the specific modification process is as follows:

[0072] Step (1): Under nitrogen protection, 2 parts of polypropylene fiber and 70 parts of xylene are mixed evenly, swollen at 75°C for 1.5 h, and after suction filtration, acetone washing, and drying, pretreated polypropylene fiber is obtained; the basalt fiber is heated at 300°C for 1.5 h, cooled to room temperature, immersed in an acetone solution for 1.5 h, and after washing and drying, pretreated basalt fiber is obtained;

[0073] Step (2): 2 parts of the pretreated polypropylene fiber and 4 parts of the pretreated basalt fiber are mixed evenly, a mixed solution of 18 parts of absolute ethanol, 2 parts of deionized water, and 0.8 part of 3-aminopropyltrimethoxysilane is added, and then 0.2 part of nano-silica is added, and the reaction is carried out at 60°C for 5 h. After filtration, washing, and drying, amino-functionalized composite fiber is obtained;

[0074] Compared with Example 3, Comparative Example 3 does not include Step (3), and other steps are the same as those in Example 3.

[0075] Experiment: Take the concrete mortar obtained in Examples 1-4 and Comparative Examples 1-3, prepare specimens, and detect and record the test results of their properties respectively:

[0076] The compressive strength is measured in accordance with the provisions of GB / T 17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)". The size of the specimen is 160 mm × 40 mm × 40 mm. The compressive strength test is carried out on the specimens cured under standard conditions for 2 h and 28 d, and the data is recorded. The impact resistance is measured in accordance with the provisions of GB / T 21120-2018 "Synthetic Fibers for Cement Concrete and Mortar". The size of the specimen is 152 mm in diameter and 63.5 mm in thickness. After curing for 28 d, the impact test is carried out and the data is recorded.

[0077] Test Results

[0078]

[0079] According to the data in the above table, the following conclusions can be clearly obtained:

[0080] 1. Compared with Examples 2-4, the compressive strength and impact resistance of the product obtained in Example 1 have both decreased, indicating that by modifying the composite fiber in the present invention, the combination of the composite fiber and the matrix material can be enhanced, thereby improving the mechanical properties of the concrete mortar.

[0081] 2. Compared with Examples 2-4, the compressive strength of the product obtained in Comparative Example 1 has decreased, indicating that increasing the addition amount of the thickener will reduce the mechanical properties of the mortar.

[0082] 3. Compared with Examples 2-4, the compressive strength and impact resistance of the product obtained in Comparative Example 2 decreased. This indicates that when preparing the tackifier, the absence of double bond-containing compounds will lead to a lack of epoxy groups, thereby affecting its binding with the modified composite fiber. The impact resistance of the product obtained in Comparative Example 3 decreased, indicating that compared with the aminated composite fiber, the modified fiber prepared in the present invention is grafted with hyperbranched macromolecules, thereby improving the impact resistance of the material.

[0083] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0084] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation process of concrete mortar for repairing bridge expansion joints, characterized in that: It includes the following steps: Mix portland cement, sulfoaluminate cement, mineral powder, silica fume, fly ash, quartz sand, thickening agent, composite fiber, water reducing agent, setting retarder and defoamer evenly, add water, and stir for 1 - 5 min to obtain concrete mortar; The concrete mortar includes the following weight components: 350 - 450 parts of portland cement, 20 - 50 parts of sulfoaluminate cement, 5 - 15 parts of mineral powder, 10 - 25 parts of silica fume, 20 - 50 parts of fly ash, 450 - 550 parts of quartz sand, 10 - 30 parts of thickening agent, 4 - 8 parts of composite fiber, 2 - 4 parts of water reducing agent, 0.5 - 1.0 part of setting retarder, 0.3 - 0.5 part of defoamer, and 80 - 120 parts of water; The preparation method of the thickening agent is as follows: Step 1: Heat anhydrous ethanol, deionized water, 3 - glycidoxypropylmethyldimethoxysilane and dimethyldimethoxysilane to 70 - 80 °C, add dibutyltin dilaurate, react for 4 - 6 h, then add vinyldimethylethoxysilane, and carry out end - capping reaction for 3 - 5 h. After rotary evaporation under reduced pressure, a double - bond - containing compound is obtained; Step 2: Mix acrylic acid, acrylamide, 2 - acrylamido - 2 - methylpropanesulfonic acid, the double - bond - containing compound and deionized water evenly, add sodium dodecyl sulfate and fatty alcohol polyoxyethylene ether and mix evenly, carry out ultrasonic emulsification for 10 - 20 min, adjust the pH of the system to 7 - 8 with sodium hydroxide solution, introduce nitrogen, heat to 65 - 75 °C, dropwise add an aqueous initiator solution, finish dropping in 40 - 60 min, keep the temperature for reaction for 3 - 5 h, cool to room temperature, and after demulsification, filtration, washing and drying, a thickening agent is obtained.

2. The preparation process of a concrete mortar for repairing bridge expansion joints according to claim 1, characterized in that: In the said Step 1, the double - bond - containing compound includes the following weight components: 13 - 14 parts of anhydrous ethanol, 2 - 3 parts of deionized water, 5 - 6 parts of 3 - glycidoxypropylmethyldimethoxysilane, 5.5 - 6.5 parts of dimethyldimethoxysilane, 6 - 7 parts of vinyldimethylethoxysilane, and 0.01 - 0.03 part of dibutyltin dilaurate.

3. The preparation process of a concrete mortar for repairing bridge expansion joints according to claim 1, characterized in that: In the said Step 2, the thickening agent includes the following weight components: 1 - 4 parts of acrylic acid, 4 - 12 parts of acrylamide, 3 - 8 parts of 2 - acrylamido - 2 - methylpropanesulfonic acid, 2 - 6 parts of the double - bond - containing compound, 100 - 200 parts of deionized water, 1.4 - 2.0 parts of sodium dodecyl sulfate, 0.1 - 0.5 part of fatty alcohol polyoxyethylene ether, and 5 - 15 parts of the aqueous initiator solution.

4. The preparation process of a concrete mortar for repairing bridge expansion joints according to claim 1, characterized in that: The composite fiber is composed of 1 - 3 mass parts of polypropylene fiber and 3 - 5 mass parts of basalt fiber by compounding.

5. The preparation process of a concrete mortar for repairing bridge expansion joints according to claim 4, characterized in that: The composite fiber is subjected to modification treatment, and the specific modification process is as follows: Step (1): Under nitrogen protection, mix polypropylene fiber and xylene evenly, swell at 70 - 80 °C for 1 - 2 h, and after suction filtration, washing with acetone and drying, pretreated polypropylene fiber is obtained; heat basalt fiber at 250 - 300 °C for 1 - 2 h, cool to room temperature, soak it in acetone solution for 1 - 2 h, and after washing and drying, pretreated basalt fiber is obtained; Step (2): Mix the pretreated polypropylene fibers and pretreated basalt fibers evenly, add a mixed solution of absolute ethanol, deionized water and 3-aminopropyltrimethoxysilane, then add nano-silica, and react at 55 - 65 °C for 4 - 6 h. After filtration, washing and drying, amino-functionalized composite fibers are obtained. Step (3): Under nitrogen protection, mix the amino-functionalized composite fibers, succinic anhydride and diethanolamine evenly, react at 115 - 125 °C for 6 - 8 h, then add diethylenetriamine and react at 105 - 115 °C for 10 - 12 h to obtain modified composite fibers.

6. The preparation process of the concrete mortar for repairing bridge expansion joints according to claim 5, characterized in that: In the said step (2), the amino-functionalized composite fibers include the following weight components: 1 - 3 parts of pretreated polypropylene fibers, 3 - 5 parts of pretreated basalt fibers, 14 - 22 parts of absolute ethanol, 1.5 - 2.5 parts of deionized water, 0.5 - 1.0 part of 3-aminopropyltrimethoxysilane, and 0.10 - 0.25 part of nano-silica.

7. The preparation process of a concrete mortar for repairing bridge expansion joints according to claim 5, characterized in that: In the said step (3), the modified composite fibers include the following weight components: 4 - 8 parts of amino-functionalized composite fibers, 6 - 12 parts of succinic anhydride, 8 - 16 parts of diethanolamine, and 12 - 24 parts of diethylenetriamine.

8. A concrete mortar for repairing bridge expansion joints prepared by the preparation process according to any one of claims 1 - 7.

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