Early strength agent for improving strength and durability of concrete and method for preparing the same

Abstract

The application relates to the field of concrete materials, and particularly discloses an early strength agent for improving the strength and durability of concrete and a preparation method thereof. The early strength agent for improving the strength and durability of concrete comprises the following raw materials in parts by weight: 20-30 parts of nano silicon dioxide, 10-20 parts of calcium bromide, 5-10 parts of silica fume, 2-4 parts of triethanolamine, 5-10 parts of ethylene glycol and 8-15 parts of an expansive agent. The early strength agent for improving the strength and durability of concrete reduces the corrosion and damage of chlorides and sulfates to concrete steel bars, the nano silicon dioxide, the silica fume and the calcium bromide are combined with each other to synergistically improve the strength and durability of concrete, the invasion and corrosion of chloride ions are reduced, and the impermeability of the concrete is improved.

Description

Technical Field

[0001] This application relates to the field of concrete materials, and more specifically, to an early-strength agent for improving the strength and durability of concrete and a method for preparing the same. Background Technology

[0002] Concrete accelerators are admixtures that improve the early strength of concrete without significantly affecting its later strength. They accelerate cement hydration and promote the development of early concrete strength. The demand for concrete accelerators is particularly high during winter construction or emergency repairs.

[0003] Commonly used early strength agents include chloride early strength agents and sulfate early strength agents. However, chloride early strength agents have a certain corrosive effect on the steel bars in concrete and will also reduce the strength of cement mortar in the later stage. Sulfate early strength agents also have the problems of excessive strength loss in the later stage, poor compatibility with cement, and easy whitening and blooming on the surface of concrete, thus affecting the normal use of concrete. Summary of the Invention

[0004] In order to reduce the harm of chloride and sulfate salts in traditional early strength agents to concrete, this application provides an early strength agent that improves the strength and durability of concrete and its preparation method.

[0005] In the first aspect, this application provides an early-strength agent for improving the strength and durability of concrete, which adopts the following technical solution: an early-strength agent for improving the strength and durability of concrete, comprising the following raw materials in parts by weight: 20-30 parts of nano-silica, 10-20 parts of calcium bromide, 5-10 parts of silica fume, 2-4 parts of triethanolamine, 5-10 parts of ethylene glycol, and 8-15 parts of expansion agent.

[0006] By employing the above technical solution, a compound of nano-silica, calcium bromide, and silica fume is used to form an early-strength agent. This agent is free of chloride ions and sulfates, reducing the corrosion of steel reinforcement by chlorides and sulfates in the early-strength agent, thus affecting the later-stage strength and durability of concrete. The silicon-oxygen bonds in nano-silica can react with calcium hydroxide produced during concrete hydration to form a gel, promoting the direct growth of hydration products on the surface of nano-silica particles, further accelerating concrete hydration and thus improving early-stage strength. In the later stages of concrete hydration, the pozzolanic effect of nano-silica can further enhance the degree of hydration, improving later-stage strength and thus enhancing durability. Calcium bromide promotes the crystallization of calcium hydroxide in concrete, accelerating C3S hydration, thereby accelerating concrete hydration and hardening, and improving early-stage strength. Silica fume can fill the space around concrete particles, making the internal structure of concrete more compact, increasing density, and thus improving strength. Silica fume effectively improves the concrete's resistance to chloride ion penetration and reduces the intrusion and corrosion of acid ions by increasing the concrete's density and silica content, thereby enhancing the concrete's chemical corrosion resistance and impermeability.

[0007] Adding a small amount of triethanolamine to early-strength agents can form a hydrophilic film on the surface of cement particles in concrete, promoting the hydration of C3S, increasing the early strength of concrete, and promoting the full and dense growth of later hydration products, thereby improving the later strength and durability of concrete. Simultaneously, triethanolamine can also form covalent bonds with metal cations to produce complexes, thus protecting the reinforcing steel in the concrete and improving its corrosion resistance.

[0008] When added to concrete, ethylene glycol is miscible with water. The hydroxide ions in ethylene glycol can form hydrogen bonds with water molecules, thereby locking in water molecules, reducing evaporation, lowering the freezing point of water, improving the frost resistance of concrete, reducing brittleness and cracking at low temperatures, and further enhancing the durability of concrete. On the other hand, ethylene glycol can also reduce the slump of concrete, further improving its durability. Adding expansive agents to concrete can reduce its internal porosity, increase its density, and further improve its strength and durability.

[0009] Preferably, the early strength agent raw material also includes 3-7 parts of calcium lignosulfonate.

[0010] By adopting the above technical solution, calcium lignosulfonate, an anionic surfactant, can improve the dispersion uniformity of various components in the accelerator in concrete, enhance the fluidity of the concrete, and simultaneously adsorb onto the surface of cement particles, causing the like-charged cement particles to repel each other, thereby reducing the agglomeration of cement particles. On the other hand, calcium lignosulfonate can reduce the surface tension of gas and liquid, and has a certain air-entraining effect in concrete, thereby improving the workability of concrete.

[0011] Preferably, the early strength agent raw materials further include 5-8 parts of ethylene glycol monovinyl polyethylene glycol ether, 10-15 parts of acrylic acid, 8-12 parts of hydroxyethyl acrylate, 0.1-0.3 parts of sodium hypophosphite, 0.1-0.3 parts of ascorbic acid, and 0.02-0.04 parts of initiator.

[0012] By employing the above-mentioned technical solution, the polycarboxylate superplasticizer formed by polymerizing ethylene glycol monovinyl polyethylene glycol ether, acrylic acid, and hydroxyethyl acrylate can disperse cement particles in concrete, promoting better fluidity of the concrete paste. Simultaneously, the polycarboxylate superplasticizer can be grafted with nano-silica, creating a coupling effect that reduces the flocculation and agglomeration of nano-silica particles, improving the adsorption and dispersion performance between the early-strength agent and concrete particles. Furthermore, the side chains of the polycarboxylate superplasticizer are also grafted with calcium lignosulfonate. Through the electrostatic repulsion of calcium lignosulfonate and the steric hindrance of the polycarboxylate superplasticizer, the dispersion of cement particles in concrete is further promoted, improving the fluidity of the concrete paste. At the same time, the polycarboxylate superplasticizer can also reduce the flash setting problem of calcium lignosulfonate, shorten the final setting time of concrete, increase the water reduction rate, and make the concrete paste structure more compact, further improving the strength of the concrete.

[0013] Preferably, the early strength agent raw material also includes 3-5 parts of basalt fiber.

[0014] By adopting the above technical solutions, basalt fiber can improve the strength and corrosion resistance of concrete, while reducing freeze-thaw damage, improving impermeability, and reducing shrinkage, thereby enhancing the low-temperature resistance and durability of concrete.

[0015] Preferably, the early strength agent raw material further includes 5-10 parts of γ-glycidyl etheroxypropyltrimethoxysilane.

[0016] By adopting the above technical solution, γ-glycidyl etheroxypropyltrimethoxysilane is used to modify the surface of basalt fibers, forming a protective film on the surface of the basalt fibers. This improves the corrosion resistance, oxidation resistance and surface activity of the basalt fibers, promotes the compatibility and dispersibility of the basalt fibers in the early strength agent system, and promotes better bonding of the basalt fibers with the concrete matrix, thereby improving the strength and corrosion resistance of the concrete.

[0017] Preferably, the expanding agent is a mixture of calcium oxide and magnesium oxide in a mass ratio of 1:0.6-0.8.

[0018] By employing the above technical solutions, calcium oxide and magnesium oxide react with the hydration products of concrete to form expansive products, reducing the internal porosity of the concrete and increasing its density. Magnesium oxide has a certain delayed expansion effect, and calcium oxide can reduce the consumption of calcium hydroxide in concrete, thereby improving its durability. Magnesium oxide and calcium oxide can fill the pores in concrete, reducing the further expansion of concrete cracks, refining the internal pore structure of concrete, and reducing the intrusion and corrosion of sulfates and chlorides, thus improving the durability and strength of concrete.

[0019] Preferably, the silica fume particle size is 0.1μm-0.3μm.

[0020] By adopting the above technical solutions and controlling the particle size of silica fume within a suitable range, it is possible to effectively replenish silica fume into the pores of concrete, while reducing the agglomeration of silica fume particles, thereby further improving the strength and durability of concrete.

[0021] Secondly, this application provides a method for preparing an early-strength agent to improve the strength and durability of concrete, using the following technical solution:

[0022] A method for preparing an early-strength agent that improves the strength and durability of concrete includes the following specific steps: mixing and stirring nano-silica, calcium bromide, silica fume, triethanolamine, ethylene glycol and an expansion agent to obtain the early-strength agent that improves the strength and durability of concrete.

[0023] By adopting the above technical solution, the prepared early strength agent is free of chloride ions and sulfate compounds, reducing the corrosion and damage of concrete by chlorides and sulfates. Under the synergistic effect of the various components in this application, the prepared early strength agent can significantly improve the early strength and durability of concrete.

[0024] Preferably, acrylic acid, hydroxyethyl acrylate, ascorbic acid, and water are mixed in advance to form a mixture A. Then, ethylene glycol monovinyl polyethylene glycol ether is heated and dissolved in water to form an ethylene glycol monovinyl polyethylene glycol ether solution. The ethylene glycol monovinyl polyethylene glycol ether solution is then mixed with an initiator and sodium hypophosphite to form a composite solution. Finally, the composite solution and nano-silica are added to mixture A and mixed to react, thus obtaining a nano-silica-polycarboxylic acid composite.

[0025] By adopting the above technical solution, nano-silica is modified during the polymerization process of polycarboxylate superplasticizer, which promotes the uniform dispersion of nano-silica in the early strength agent system and the uniform filling of nano-silica in the pores of concrete, thereby improving the early strength of concrete. In addition, the prepared polycarboxylate superplasticizer has the advantages of being environmentally friendly and having a high water reduction rate, and promotes good fluidity and durability of concrete paste.

[0026] In summary, this application has the following beneficial effects:

[0027] 1. Because this application uses nano-silica, calcium bromide, silica fume and a small amount of triethanolamine to make a concrete early strength agent, it reduces the corrosion and damage of chloride and sulfate to concrete steel bars. Furthermore, the combination of nano-silica and calcium bromide improves the early strength of concrete, and silica fume can improve the density of concrete, thereby improving the strength and durability of concrete.

[0028] 2. This application preferably uses a polycarboxylate superplasticizer formed by polymerizing ethylene glycol monovinyl polyethylene glycol ether, acrylic acid, and hydroxyethyl acrylate to improve the density of concrete. Simultaneously, the polycarboxylate superplasticizer surface-modifies nano-silica, promoting uniform dispersion of nano-silica in the concrete and improving the dispersibility of the early-strength agent system. Furthermore, the polycarboxylate superplasticizer surface-grafts calcium lignosulfonate, reducing flash setting of calcium lignosulfonate, shortening the final setting time of concrete, and promoting better bonding between calcium lignosulfonate and concrete, thereby improving the early strength and durability of the concrete. Detailed Implementation

[0029] The present application will be further described in detail below with reference to the embodiments.

[0030] In this specific embodiment, there are no other special circumstances, and the components used are as follows:

[0031] The basalt fibers are 5 mm in length and 15 μm-16 μm in diameter.

[0032] The particle size of nano-silica is 14nm-15nm.

[0033] The particle size of calcium oxide is 2μm-3μm.

[0034] The particle size of magnesium oxide is 50nm-60nm.

[0035] Example

[0036] Example 1

[0037] An early-strength agent for improving the strength and durability of concrete comprises the following raw materials in parts by weight: 25 kg of nano-silica, 15 kg of calcium bromide, 8 kg of silica fume, 3 kg of triethanolamine, 8 kg of ethylene glycol, and 12 kg of expansive agent. The silica fume has a particle size of 0.2 μm, and the expansive agent is a mixture of calcium oxide and magnesium oxide in a mass ratio of 1:0.7.

[0038] A method for preparing an early-strength agent to improve the strength and durability of concrete includes the following specific steps:

[0039] The early-strength agent that improves the strength and durability of concrete is obtained by mixing nano-silica, calcium bromide, silica fume, triethanolamine, ethylene glycol and an expansion agent, and stirring at 500 r / min for 30 min.

[0040] Example 2-3

[0041] The difference between Examples 2-3 and Example 1 is that the content of each component in the early strength agent raw material is different, as shown in Table 1.

[0042] Table 1: Content of each component in Examples 1-3

[0043]

[0044]

[0045] Example 4

[0046] The difference between Example 4 and Example 1 is that the expanding agent in the early strength agent raw material is a mixture of calcium oxide and magnesium oxide in a mass ratio of 1:0.6, and the silica fume particle size is 0.1μm.

[0047] Example 5

[0048] The difference between Example 5 and Example 1 is that the expanding agent in the early strength agent raw material is a mixture of calcium oxide and magnesium oxide in a mass ratio of 1:0.8, and the silica fume particle size is 0.3μm.

[0049] Example 6

[0050] The difference between Example 6 and Example 1 is that the early strength agent raw material also includes 5 kg of calcium lignosulfonate.

[0051] A method for preparing an early-strength agent to improve the strength and durability of concrete includes the following specific steps:

[0052] The early-strength agent that improves the strength and durability of concrete is obtained by mixing nano-silica, calcium bromide, silica fume, triethanolamine, calcium lignosulfonate, ethylene glycol and an expansion agent, and stirring at 500 r / min for 30 min.

[0053] Example 7

[0054] The difference between Example 7 and Example 6 is that the amount of calcium lignosulfonate used in the early strength agent raw material is 3 kg.

[0055] Example 8

[0056] The difference between Example 8 and Example 6 is that the amount of calcium lignosulfonate used in the early strength agent raw material is 7 kg.

[0057] Example 9

[0058] The difference between Example 9 and Example 6 is that the early strength agent raw materials also include 7 kg of ethylene glycol monovinyl polyethylene glycol ether, 12 kg of acrylic acid, 10 kg of hydroxyethyl acrylate, 0.2 kg of ascorbic acid, 0.2 kg of sodium hypophosphite, and 0.03 kg of initiator, wherein the initiator is ammonium persulfate.

[0059] A method for preparing an early-strength agent to improve the strength and durability of concrete includes the following specific steps:

[0060] S1: Acrylic acid and water are mixed at a mass ratio of 10:1. Then, hydroxyethyl acrylate and ascorbic acid are added and mixed. The mixture is stirred at 200 rpm for 10 min to form mixture A. Then, ethylene glycol monovinyl polyethylene glycol ether is mixed and dissolved in water at a mass ratio of 1:1. The mixture is heated to 30°C to form an ethylene glycol monovinyl polyethylene glycol ether solution. The ethylene glycol monovinyl polyethylene glycol ether solution is then mixed with an initiator and sodium hypophosphite and stirred at 200 rpm for 10 min to form a composite solution. Then, nano-silica, calcium lignosulfonate, the composite solution, and silica fume are added to mixture A and stirred at 200 rpm for 10 min. The mixture is then reacted at a constant temperature of 30°C for 2 h to obtain the nano-silica-polycarboxylic acid composite.

[0061] S2: Mix nano-silica-polycarboxylic acid composite, calcium bromide, triethanolamine, ethylene glycol and expansion agent, and stir at 500 r / min for 30 min to obtain an early strength agent that improves the strength and durability of concrete.

[0062] Example 10

[0063] The difference between Example 10 and Example 9 is that the amount of ethylene glycol monovinyl polyethylene glycol ether used in the early strength agent raw materials is 5 kg, the amount of acrylic acid is 10 kg, the amount of hydroxyethyl acrylate is 12 kg, the amount of ascorbic acid is 0.1 kg, the amount of sodium hypophosphite is 0.1 kg, and the amount of initiator is 0.02 kg.

[0064] Example 11

[0065] The difference between Example 11 and Example 9 is that the amount of ethylene glycol monovinyl polyethylene glycol ether used in the early strength agent raw materials is 8 kg, the amount of acrylic acid is 15 kg, the amount of hydroxyethyl acrylate is 8 kg, the amount of ascorbic acid is 0.3 kg, the amount of sodium hypophosphite is 0.3 kg, and the amount of initiator is 0.04 kg.

[0066] Example 12

[0067] The difference between Example 12 and Example 9 is that the early strength agent raw material also includes 4 kg of basalt fiber.

[0068] A method for preparing an early-strength agent to improve the strength and durability of concrete includes the following specific steps:

[0069] S1: Acrylic acid and water are mixed at a mass ratio of 10:1. Then, hydroxyethyl acrylate and ascorbic acid are added and mixed. The mixture is stirred at 200 rpm for 10 min to form mixture A. Then, ethylene glycol monovinyl polyethylene glycol ether is mixed and dissolved in water at a mass ratio of 1:1. The mixture is heated to 30°C to form an ethylene glycol monovinyl polyethylene glycol ether solution. The ethylene glycol monovinyl polyethylene glycol ether solution is then mixed with an initiator and sodium hypophosphite and stirred at 200 rpm for 10 min to form a composite solution. Then, nano-silica, calcium lignosulfonate, the composite solution, and silica fume are added to mixture A and stirred at 200 rpm for 10 min. The mixture is then reacted at a constant temperature of 30°C for 2 h to obtain the nano-silica-polycarboxylic acid composite.

[0070] S2: Mix nano-silica-polycarboxylic acid composite, calcium bromide, basalt fiber, triethanolamine, ethylene glycol and expansion agent, and stir at 500 r / min for 30 min to obtain an early strength agent that improves the strength and durability of concrete.

[0071] Example 13

[0072] The difference between Example 13 and Example 12 is that the amount of basalt fiber used in the early strength agent raw material is 3 kg.

[0073] Example 14

[0074] The difference between Example 14 and Example 12 is that the amount of basalt fiber used in the early strength agent raw material is 3 kg.

[0075] Example 15

[0076] The difference between Example 15 and Example 12 is that the early strength agent raw material also includes 8 kg of γ-glycidoxypropyltrimethoxysilane.

[0077] A method for preparing an early-strength agent to improve the strength and durability of concrete includes the following specific steps:

[0078] S1: Acrylic acid and water are mixed at a mass ratio of 10:1. Then, hydroxyethyl acrylate and ascorbic acid are added and mixed. The mixture is stirred at 200 rpm for 10 min to form mixture A. Then, ethylene glycol monovinyl polyethylene glycol ether is mixed and dissolved in water at a mass ratio of 1:1. The mixture is heated to 30°C to form an ethylene glycol monovinyl polyethylene glycol ether solution. The ethylene glycol monovinyl polyethylene glycol ether solution is then mixed with an initiator and sodium hypophosphite and stirred at 200 rpm for 10 min to form a composite solution. Then, nano-silica, calcium lignosulfonate, the composite solution, and silica fume are added to mixture A and stirred at 200 rpm for 10 min. The mixture is then reacted at a constant temperature of 30°C for 2 h to obtain the nano-silica-polycarboxylic acid composite.

[0079] S2: Soak basalt fibers in acetone for 1 hour, wash with tap water, and then dry the washed basalt fibers at 110°C. Then soak the basalt fibers in a mixture of γ-glycidyl etheroxypropyltrimethoxysilane and water at a mass ratio of 1:10 at 45°C for 6 hours. Remove the basalt fibers, wash with tap water, and dry at 110°C to obtain modified basalt fibers.

[0080] S3: Mix nano-silica-polycarboxylic acid composite, calcium bromide, modified basalt fiber, triethanolamine, ethylene glycol and expansion agent, and stir at 500 r / min for 30 min to obtain an early strength agent that improves the strength and durability of concrete.

[0081] Example 16

[0082] The difference between Example 16 and Example 15 is that the amount of γ-glycidoxypropyltrimethoxysilane used in the early strength agent raw material is 5 kg.

[0083] Example 17

[0084] The difference between Example 17 and Example 15 is that the amount of γ-glycidoxypropyltrimethoxysilane used in the early strength agent raw material is 10 kg.

[0085] Comparative Example

[0086] Comparative Example 1

[0087] The difference between Comparative Example 1 and Example 1 is that magnesium oxide in the expanding agent of the early strength agent raw material is replaced with an equal amount of calcium oxide.

[0088] Comparative Example 2

[0089] The difference between Comparative Example 2 and Example 1 is that silica ash is not used in the early strength agent raw material.

[0090] Comparative Example 3

[0091] The difference between Comparative Example 3 and Example 1 is that the calcium bromide in the early strength agent raw material is replaced by an equal amount of nano-calcium carbonate, wherein the particle size of the nano-calcium carbonate is 20nm-30nm.

[0092] Performance testing

[0093] The early-strength agents for improving concrete strength and durability provided in Examples 1-17 and Comparative Examples 1-3 of this application were subjected to the following performance tests, and the performance test results are shown in Table 2.

[0094] Detection methods

[0095] I. Compressive Strength

[0096] Referring to the compressive strength test in GB / T50081—2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", the dosage of early strength agent in concrete is 1%, and the compressive strength of concrete is tested on the 1st, 7th and 28th days of curing.

[0097] II. Flowability

[0098] Referring to GB / T8077-2012 "Test Method for Homogeneity of Concrete Admixtures", the early strength agent prepared in this application was added to concrete at a dosage of 0.18%, and the fluidity of the concrete paste was determined.

[0099] III. Durability

[0100] Referring to the chloride ion penetration test in GB / T50082--2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete", the early strength agent prepared in this application was added to the concrete at a dosage of 1%, and the chloride ion penetration resistance of the concrete was tested after 28 days of curing.

[0101] Table 2: Performance Test Data Table

[0102]

[0103]

[0104] The performance test results of Examples 1-5 show that the early-strength agent prepared in this application can significantly improve the early strength and durability of concrete. Furthermore, this application uses a compound of nano-silica, calcium bromide, and silica fume to form the early-strength agent, and incorporates a small amount of triethanolamine to synergistically promote the early strength of concrete. Simultaneously, it avoids the corrosion and strength damage to concrete reinforcement caused by chloride ions and sulfate compounds. The use of silica fume to fill around concrete particles improves the compactness of the concrete structure, reduces the intrusion and corrosion of acid ions and chloride ions, thereby improving the impermeability and durability of concrete. The usage amounts of each component differ in Examples 1-3; the performance test results show that the early-strength agent prepared in Example 1 has superior overall performance.

[0105] In Examples 6-8, different amounts of calcium lignosulfonate were added to the early-strength agent. The performance test results showed that the fluidity and durability of the concrete were significantly improved. Calcium lignosulfonate can promote the uniform dispersion of each component in the early-strength agent in the concrete. At the same time, calcium lignosulfonate is adsorbed on the surface of the concrete, reducing the agglomeration of concrete particles. Calcium lignosulfonate can also improve the workability of the concrete, has a certain water-reducing effect, and further improve the durability of the concrete.

[0106] In Examples 9-11, a polycarboxylate superplasticizer made with acrylic monomers was added to the early-strength agent. This polycarboxylate superplasticizer improved the workability and fluidity of concrete, reducing the impact of moisture on the concrete. Performance tests showed a significant increase in the concrete's strength, durability, and fluidity. Simultaneously, the polycarboxylate superplasticizer could graft-modify nano-silica and calcium lignosulfonate, promoting more uniform dispersion of nano-silica in the concrete, reducing the agglomeration of nano-silica particles, and also reducing the flash setting of calcium lignosulfonate, resulting in a denser concrete paste structure, reducing chloride ion intrusion and corrosion, and further improving concrete strength and durability. Furthermore, the polycarboxylate superplasticizer could improve the self-dispersibility of silica fume, promoting its uniform filling of the concrete voids, thereby increasing the concrete's density and further enhancing its strength and durability.

[0107] In Examples 12-14, different amounts of basalt fiber were added to the early strength agent. The test results showed that the resistance to chloride ion penetration and the durability of concrete were significantly improved, further demonstrating the promoting effect of basalt fiber on the impermeability of concrete. At the same time, basalt fiber can also improve the low temperature resistance of concrete and reduce the phenomenon of freeze-thaw damage in winter.

[0108] In Examples 15-17, different amounts of γ-glycidoxypropyltrimethoxysilane were added to the early strength agent. The performance test results showed that the overall performance of the concrete was improved. This indicates that the modification effect of γ-glycidoxypropyltrimethoxysilane on basalt fibers can increase the surface roughness of basalt fibers, promote better bonding between basalt fibers and the concrete matrix, and further improve the strength of concrete.

[0109] Comparing the performance test results of Comparative Example 1 and Example 1, it can be seen that without the use of magnesium oxide in Comparative Example 1, the durability and strength of the concrete both decrease. This further illustrates that the combination of calcium oxide and magnesium oxide as an expansive agent in this application can reduce the internal porosity of concrete, improve its strength and durability, and magnesium oxide has a certain delayed expansion effect, which can further fill the cracks in the concrete, thereby reducing the generation of concrete cracks and thus improving the durability and strength of the concrete.

[0110] Comparing the performance test results of Comparative Example 2 and Example 1, it can be seen that Comparative Example 2 does not use silica fume, and the overall performance of the concrete decreases, further illustrating the promoting effect of silica fume on the strength and durability of concrete.

[0111] Comparing the performance test results of Comparative Example 3 and Example 1, it can be seen that the use of calcium carbonate instead of calcium bromide in Comparative Example 3 significantly affected the durability of the concrete and caused a significant decrease in the later strength. This may be because although calcium carbonate promotes the early strength of concrete, it may cause the volume shrinkage of concrete, thereby reducing the later strength and durability of the concrete.

[0112] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing an early-strength agent to improve the strength and durability of concrete, characterized in that, The specific steps include the following: S1: Acrylic acid and water are mixed in a mass ratio of 10:

1. Then, hydroxyethyl acrylate and ascorbic acid are added and mixed. The mixture is stirred at 200 rpm for 10 min to form a mixture A. Then, ethylene glycol monovinyl polyethylene glycol ether is mixed and dissolved in water in a mass ratio of 1:

1. The mixture is heated to 30°C to form an ethylene glycol monovinyl polyethylene glycol ether solution. The ethylene glycol monovinyl polyethylene glycol ether solution is then mixed with an initiator and sodium hypophosphite and stirred at 200 rpm for 10 min to form a composite solution. Then, nano-silica, calcium lignosulfonate, the composite solution, and silica fume are added to mixture A and stirred at 200 rpm for 10 min. The mixture is then reacted at 30°C for 2 h to obtain a nano-silica-polycarboxylic acid composite. S2: Mix nano-silica-polycarboxylic acid composite, calcium bromide, triethanolamine, ethylene glycol and expansion agent, and stir at 500 r / min for 30 min to obtain an early strength agent that improves the strength and durability of concrete. The raw materials are as follows by weight: 20-30 parts nano silica, 10-20 parts calcium bromide, 5-10 parts silica fume, 2-4 parts triethanolamine, 5-10 parts ethylene glycol, 8-15 parts expanding agent, 5-8 parts ethylene glycol monovinyl polyethylene glycol ether, 10-15 parts acrylic acid, 8-12 parts hydroxyethyl acrylate, 0.1-0.3 parts sodium hypophosphite, 0.1-0.3 parts ascorbic acid, 0.02-0.04 parts initiator, and 3-7 parts calcium lignosulfonate.

2. The method for preparing the early-strength agent for improving the strength and durability of concrete according to claim 1, characterized in that: The early strength agent raw materials also include 3-5 parts of basalt fiber.

3. The method for preparing the early-strength agent for improving the strength and durability of concrete according to claim 2, characterized in that: The early strength agent raw materials also include 5-10 parts of γ-glycidyl etheroxypropyltrimethoxysilane.

4. The method for preparing the early-strength agent for improving the strength and durability of concrete according to claim 1, characterized in that: The expanding agent is a mixture of calcium oxide and magnesium oxide in a mass ratio of 1:0.6-0.

8.

5. The method for preparing the early-strength agent for improving the strength and durability of concrete according to claim 1, characterized in that: The silica fume has a particle size of 0.1μm-0.3μm.

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