Steam-curing-free early strength agent for sleeper concrete and preparation method of steam-curing-free early strength agent

Abstract

The invention relates to the field of concrete, and particularly discloses a steam-curing-free early strength agent for sleeper concrete and a preparation method thereof.The steam-curing-free early strength agent for sleeper concrete is prepared from a polymeric macromonomer, a polymeric micromonomer and a functional micromonomer according to the molar ratio of 1: (3.5-4): (0.4-0.7), the polymeric macromonomer comprises one or more of TPEG, EPEG and HEPG, the polymeric micromonomer comprises acrylic acid, sodium methallyl sulfonate, hydroxyethyl acrylate and butyl acrylate, the acid-ester ratio in the polymeric micromonomer is (3-4): (6-7), and the functional micromonomer is prepared from cellulose and maleic anhydride. According to the steam-curing-free early strength agent, the 3d compressive strength of concrete can be improved by 129.6% or above, the 28d compressive strength of the concrete can be improved by 75.8% or above, the concrete has good early strength and durability, and the competitive advantages of sleeper concrete in the field of sleepers are improved.

Description

Technical Field

[0001] The present application relates to the technical field of concrete, and in particular to a steam-free early strength agent for sleeper concrete and a preparation method thereof. Background Art

[0002] Sleepers are key components that secure rails in place on railway tracks. They support the rails and transmit train pressure to the trackbed. They must be flexible and resilient to cushion train impacts and recover from deformation, ensuring the stability of the track's geometry. Concrete sleepers are currently the mainstream material due to their long lifespan and low maintenance costs. Steam curing is typically used in concrete sleeper production to enhance the early strength of the sleeper concrete, allowing for early release of prestressing and improving sleeper production efficiency.

[0003] However, steam curing has adverse effects on the durability and brittleness of concrete. Research has shown that steam curing increases the internal porosity of concrete, resulting in lower durability than standard-cured concrete. Consequently, researchers have conducted a series of studies on how to achieve demolding strength within a specified timeframe without steam curing. For example, researchers have employed inorganic and / or organic early-strength agents to improve the early strength of concrete. Examples include calcium chloride, sodium chloride, and other inorganic early-strength agents, and alcoholamines. While these early-strength agents can improve the early strength of concrete, they often result in reduced strength and durability in the later stages of the concrete's development. Consequently, researchers have turned their attention to polycarboxylate superplasticizers, which have become the preferred early-strength agent for concrete due to their low dosage, high water-reduction rate, environmental friendliness, and adjustable molecular structure. Consequently, researchers are conducting further research on polycarboxylate superplasticizers, hoping to develop agents that can further enhance the early strength of concrete and thereby further enhance the competitive advantage of sleeper concrete in the sleeper industry. Summary of the Invention

[0004] In order to solve the above technical problems, the present application provides a steam-free early strength agent for sleeper concrete and a preparation method thereof.

[0005] In the first aspect, the present application provides a steam-free early strength agent for sleeper concrete, the raw materials used include a polymer macromonomer, a polymer small monomer and a functional small monomer in a molar ratio of 1: (3.5-4): (0.4-0.7), the polymer macromonomer includes one or more of TPEG, EPEG and HEPG, the polymer small monomer includes acrylic acid, sodium methacrylic acid, hydroxyethyl acrylate and butyl acrylate, the acid ester ratio in the polymer small monomer is (3-4): (6-7), and the functional small monomer is made of cellulose and maleic anhydride.

[0006] By adopting the above technical solution, the present application first uses cellulose and maleic anhydride to prepare a functional small monomer. Maleic anhydride hydrolyzes in an alkaline environment to form a dicarboxyl structure, which forms a composite polar group with the hydroxyl group in the cellulose molecule, thereby improving the adsorption density of the early strength agent molecules on the surface of cement particles, significantly enhancing the synergistic dispersion effect of electrostatic repulsion and steric hindrance; the physical wrapping effect of the cellulose network on maleic anhydride can slow down its hydrolysis rate and form a gradient release characteristic. Therefore, the functional small monomer effectively enhances the dispersion and adsorption performance of the early strength agent in the concrete system through its own synergistic effect. Subsequently, the present application uses acrylic acid, sodium methacrylic acid, hydroxyethyl acrylate and butyl acrylate as polymerization small monomers, controls the acid ester ratio, and adjusts the molecular spatial structure of the polycarboxylic acid so that it has both early strength ability and concrete slump retention.

[0007] In summary, the steam-free early strength agent finally obtained in this application can further improve the later strength of concrete without affecting the early strength of concrete. Experimental data show that adding 0.5wt% of the steam-free early strength agent can increase the 3d compressive strength of concrete by more than 129.6% and the 28d compressive strength by more than 75.8%. Preferably, the polymerizable macromonomer comprises TPEG and HEPG.

[0008] By adopting the above technical solution, the present application utilizes TPEG and HEPG as polymerization macromonomers, wherein TPEG has good dispersion properties, can effectively reduce the water consumption of concrete and improve the fluidity of concrete, while HEPG has excellent collapse retention performance, can maintain the working performance of concrete stable for a long time, and the two work together to effectively optimize the molecular structure of the early strength agent, enhance its dispersion and adsorption properties in sleeper concrete, not only improve the later strength and durability of concrete, but also further improve the early strength of concrete, meeting the high performance requirements of sleeper concrete in practical applications.

[0009] Preferably, the molar ratio of TPEG to HEPG is (7-8):(2-3).

[0010] By adopting the above technical solution, this application sets the molar ratio of TPEG and HEPG to (7-8): (2-3), further optimizing the ratio of the polymerized macromonomer, achieving a more optimal balance between the dispersibility and adsorption properties of the steam-free early strength agent in the sleeper concrete. The polymerized macromonomer at this ratio can effectively improve the early strength of the concrete while ensuring that the later strength and durability are not significantly affected, thereby better meeting the strength development requirements of the sleeper concrete under steam-free curing conditions.

[0011] Preferably, the acid ester ratio in the polymerized small monomer is 3.8:6.2.

[0012] By adopting the above-mentioned technical solution, the present application precisely controls the acid ester ratio in the polymerized small monomer to 3.8:6.2, further optimizes the molecular structure of the steam-free early strength agent, improves its dispersibility and adsorption performance in the sleeper concrete, helps to enhance the dispersion effect of the early strength agent on cement particles, promotes the hydration reaction, thereby effectively improving the early strength of concrete while avoiding adverse effects on the later strength and durability.

[0013] Preferably, in the polymerizable small monomers, the molar ratio of acrylic acid to sodium methacrylic acid sulfonate is (90-95):(5-10), and the molar ratio of hydroxyethyl acrylate to butyl acrylate is (70-90):(10-30).

[0014] By adopting the above technical solution, the present application regulates the molar ratio of acrylic acid to sodium methacrylic acid sulfonate in the polymerized small monomer to be (90-95):(5-10), and the molar ratio of hydroxyethyl acrylate to butyl acrylate to be (70-90):(10-30), thereby effectively improving the water reduction rate and dispersibility of the early strength agent, ensuring that the concrete has higher fluidity and stability under steam-free curing conditions, further optimizing the molecular structure of the early strength agent, and enhancing the compatibility of the steam-free curing early strength agent with other components in the concrete, thereby significantly improving the early strength of the concrete and meeting the demolding strength requirements of the sleeper production.

[0015] Preferably, in the polymerizable small monomers, the molar ratio of acrylic acid to sodium methacrylic acid sulfonate is 92:8, and the molar ratio of hydroxyethyl acrylate to butyl acrylate is 75:25.

[0016] By adopting the above technical solution, the early strength of concrete can be significantly improved, its compressive resistance can be enhanced, the molecular structure of the early strength agent can be further optimized, and the fluidity and collapse resistance of concrete can be improved, thereby ensuring that the sleeper concrete can quickly reach the demolding strength under steam-free curing conditions and meet production efficiency requirements.

[0017] In the second aspect, the present application provides a method for preparing a steam-free early strength agent for sleeper concrete, comprising the following steps: dispersing a small polymer monomer and a functional small monomer in water to obtain material A, then dispersing a reducing agent and a chain transfer agent in water to obtain material B, dispersing a large polymer monomer in water and fully dissolving it, then adding 50-60wt% of material A, then adding an oxidant and an initiator, heating to 45-55°C, adding all the remaining materials A and B, keeping the temperature for reaction for 2-4h, and finally adjusting the pH to neutral, and adjusting the solid content in the system to 35-40wt% to obtain a steam-free early strength agent.

[0018] By adopting the above technical solution, the present application uses a specific molar ratio of polymer macromonomer, polymer small monomer and functional small monomer as raw materials, disperses the polymer small monomer and functional small monomer in water to form material A, disperses the reducing agent and chain transfer agent in water to form material B, and adds the polymer macromonomer, oxidant and initiator step by step to react, and finally adjusts the pH value and solid content to complete the preparation. The early strength agent prepared by the present application can significantly improve the early strength of the sleeper concrete and meet the requirements of quickly reaching the demolding strength under the condition of no steaming; the synergistic effect of the polymer macromonomer, polymer small monomer and functional small monomer in a certain ratio not only ensures the early strength effect, but also takes into account the later strength and durability of the concrete; by precisely controlling the reaction conditions, such as temperature, reaction time and feeding ratio, the performance stability and repeatability of the early strength agent are ensured; the introduction of functional small monomers further optimizes the compatibility of the early strength agent with concrete, and improves the overall performance of concrete.

[0019] Preferably, the functional small monomer is prepared by the following method: hydrolyzing cellulose to obtain a cellulose hydrolyzate, then blending the cellulose hydrolyzate with maleic anhydride in a weight ratio of (4-8): (2-6), and reacting at a temperature of 75-90°C for 3.5-4.5h to obtain a functional small monomer.

[0020] By adopting the above-mentioned technical solution, the method for preparing the functional small monomer of the present application effectively improves the reactivity and stability of the functional small monomer by reacting a cellulose hydrolyzate with maleic anhydride at a specific temperature and ratio. The functional small monomer produced by this method synergizes with the polymerized macromonomer and polymerized small monomer, further improving the water reduction rate and early strength performance of the steam-free early strength agent, while also ensuring the later strength and durability of the concrete.

[0021] Preferably, the weight ratio of the cellulose hydrolysate to maleic anhydride is 5:5.

[0022] By adopting the above technical solution, this application controls the weight ratio of cellulose hydrolyzate to maleic anhydride to 5:5, precisely regulating the structural characteristics of the functional small monomer, which helps to improve the compatibility and reactivity of the functional small monomer with the polymerized macromonomer and the polymerized small monomer, thereby further improving the dispersion and adsorption properties of the final steam-free early strength agent. The functional small monomer at this ratio can effectively enhance the dispersion uniformity of the early strength agent in the sleeper concrete, promote the full hydration of cement particles, and significantly improve the early strength of the concrete while avoiding adverse effects on later strength and durability.

[0023] In summary, this application has the following beneficial technical effects: 1. This application utilizes a specific molar ratio of a polymer macromonomer, a polymer micromonomer, and a functional micromonomer to significantly enhance the early strength of sleeper concrete under steam-free curing conditions, meeting the requirement for achieving demolding strength within a specified timeframe. The functional micromonomer is made from cellulose and maleic anhydride, optimizing the compatibility of the early strength agent with concrete, further enhancing the strength development performance of the concrete while also balancing late-stage strength and durability. Experimental data show that the addition of 0.5 wt% of the steam-free curing early strength agent can increase the 3-day compressive strength of concrete by over 129.6% and the 28-day compressive strength by over 75.8%. 2. The preparation method of the present application can effectively improve the reactivity and stability of the functional small monomer by reacting the cellulose hydrolysis product with maleic anhydride at a specific temperature and ratio. The functional small monomer prepared by this method synergizes with the polymerized large monomer and the polymerized small monomer, further improving the water reduction rate and early strength performance of the steam-free early strength agent, while ensuring the later strength and durability of the concrete. DETAILED DESCRIPTION

[0024] Material Source Unless otherwise specified, the raw materials used in this application are all commercially available products, specifically: Cellulose was purchased from Shandong Landu New Materials Co., Ltd.; Phosphoric acid was purchased from Jinan Xinjinshuo New Materials Co., Ltd., 85 wt% aqueous solution; Maleic anhydride, CAS number 108-31-6; Acrylic acid, CAS number 52255-49-9; Sodium methyl propylene sulfonate, CAS number 1561-92-8; Hydroxyethyl acrylate, CAS number 818-61-1; Butyl acrylate, CAS number 141-32-2; TPEG, HEPG, and EPEG were purchased from Hubei Langbowan Biopharmaceutical Co., Ltd., and all had a molecular weight of 2400.

[0025] The present application is further described in detail below with reference to preparation examples, embodiments and comparative examples.

[0026] Preparation Example 1.1 The preparation method of the functional small monomer comprises the following steps: Cellulose and phosphoric acid were dispersed in water at a solid-liquid ratio of 1:10, and hydrolyzed at a temperature of 160°C and a rotation speed of 400 r / min for 3 hours. Impurities in the hydrolyzate were filtered out, and then a saturated barium hydroxide solution was added. The mixture was allowed to stand for 24 hours, and the precipitate was removed by suction. The obtained solution was rotary evaporated to remove water to obtain a cellulose hydrolyzate. The cellulose hydrolyzate was then blended with maleic anhydride in a weight ratio of 4:6 and reacted at a temperature of 90°C for 3.5 hours to obtain a functional small monomer.

[0027] Preparation Example 1.2 The preparation method of the functional small monomer comprises the following steps: Cellulose and phosphoric acid were dispersed in water at a solid-liquid ratio of 1:10, and hydrolyzed at a temperature of 160°C and a rotation speed of 400 r / min for 3 hours. Impurities in the hydrolyzate were filtered out, and then a saturated barium hydroxide solution was added. The mixture was allowed to stand for 24 hours, and the precipitate was removed by suction. The obtained solution was rotary evaporated to remove water to obtain a cellulose hydrolyzate. The cellulose hydrolyzate was then blended with maleic anhydride at a weight ratio of 8:2 and reacted at a temperature of 75°C for 4.5 hours to obtain a functional small monomer.

[0028] Preparation Example 2.1 The preparation method of the functional small monomer is different from that of Preparation Example 1.1 in that the cellulose hydrolyzate and maleic anhydride are blended in a weight ratio of 5:5, and the rest are the same as those of Preparation Example 1.1.

[0029] Preparation Example 2.2 The preparation method of the functional small monomer is different from that of Preparation Example 1.1 in that the cellulose hydrolyzate and maleic anhydride are blended in a weight ratio of 6:4, and the rest are the same as those of Preparation Example 1.1.

[0030] Preparation Example 2.3 The preparation method of the functional small monomer is different from that of Preparation Example 1.1 in that the cellulose hydrolyzate and maleic anhydride are blended in a weight ratio of 7:3, and the rest are the same as those of Preparation Example 1.1.

[0031] Preparation Example 2.4 The preparation method of the functional small monomer is different from that of Preparation Example 1.1 in that the cellulose hydrolyzate and maleic anhydride are blended in a weight ratio of 8:2, and the rest are the same as those of Preparation Example 1.1.

[0032] Example 1.1 A method for preparing a steam-free hardening early strength agent for sleeper concrete comprises the following steps: Acrylic acid, sodium methacrylic acid sulfonate, hydroxyethyl acrylate and butyl acrylate were weighed and mixed in a ratio of 3:7 for the overall acid ester ratio, 85:15 for the molar ratio of acrylic acid and sodium methacrylic acid sulfonate, and 95:5 for the molar ratio of hydroxyethyl acrylate and butyl acrylate, to obtain a polymerizable small monomer; Subsequently, a polymerizable small monomer and the functional small monomer prepared in Preparation Example 1.1 at a molar ratio of 3.5:0.7 were dispersed in water to obtain Material A. Subsequently, a reducing agent (L-ascorbic acid) and a chain transfer agent (thiopropionic acid) were dispersed in water to obtain Material B. After the polymerizable macromonomer (TPEG) was dispersed in water and fully dissolved, 60 wt % of Material A was added. Subsequently, an oxidant (hydrogen peroxide) and an initiator (ammonium persulfate) were added. After the temperature was raised to 45° C., all the remaining Material A and Material B were added. The mixture was kept warm for 4 h. Finally, the pH was adjusted to neutral, and the solid content in the system was adjusted to 40 wt % to obtain a steam-free early strength agent. The molar ratio of the polymerized macromonomer, the polymerized small monomer and the functional small monomer is 1:3.5:0.7, the amount of the chain transfer agent is 0.48wt% of the polymerized macromonomer, the amount of the initiator is 0.06wt% of the polymerized macromonomer, the amount of the oxidant is 0.32wt% of the polymerized macromonomer, and the amount of the reducing agent is 0.025wt% of the polymerized macromonomer.

[0033] Example 1.2 A method for preparing a steam-free hardening early strength agent for sleeper concrete comprises the following steps: Acrylic acid, sodium methacrylate sulfonate, hydroxyethyl acrylate, and butyl acrylate were weighed and mixed in a ratio of 4:6 for the overall acid ester ratio, 97.5:2.5 for the molar ratio of acrylic acid and sodium methacrylate sulfonate, and 65:35 for the molar ratio of hydroxyethyl acrylate and butyl acrylate to obtain a polymerizable monomer; Subsequently, a polymerizable small monomer and the functional small monomer prepared in Preparation Example 1.1 at a molar ratio of 4:0.4 were dispersed in water to obtain Material A. Subsequently, a reducing agent (L-ascorbic acid) and a chain transfer agent (thiopropionic acid) were dispersed in water to obtain Material B. After the polymerizable macromonomer (TPEG, HEPG, and EPEG at a molar ratio of 5:4:1) was dispersed in water and fully dissolved, 50 wt% of Material A was added. Subsequently, an oxidant (hydrogen peroxide) and an initiator (ammonium persulfate) were added. After the temperature was raised to 55° C., the remaining Material A and Material B were added. The mixture was kept warm for 2 h. Finally, the pH was adjusted to neutral, and the solid content in the system was adjusted to 35 wt% to obtain a steam-free early strength agent. The molar ratio of the polymerized macromonomer, the polymerized small monomer and the functional small monomer is 1:4:0.4, the amount of the chain transfer agent is 0.48wt% of the polymerized macromonomer, the amount of the initiator is 0.06wt% of the polymerized macromonomer, the amount of the oxidant is 0.32wt% of the polymerized macromonomer, and the amount of the reducing agent is 0.025wt% of the polymerized macromonomer.

[0034] Example 2.1 A method for preparing a steam-free early strength agent for sleeper concrete, which differs from Example 1.1 in that the polymerized macromonomers are TPEG and HEPG in a molar ratio of 1:1, and the rest are the same as Example 1.1.

[0035] Example 2.2 A method for preparing a steam-free early strength agent for sleeper concrete, which differs from Example 1.1 in that the polymerized macromonomers are EPEG and HEPG in a molar ratio of 1:1, and the rest are the same as Example 1.1.

[0036] Example 2.3 A method for preparing a steam-free early strength agent for sleeper concrete, which differs from Example 1.1 in that the polymerized macromonomers are TPEG and EPEG in a molar ratio of 1:1, and the rest are the same as Example 1.1.

[0037] Example 3.1 A method for preparing a steam-free early strength agent for sleeper concrete, which is different from Example 2.1 in that the molar ratio of TPEG to HEPG is 7:3, and the rest is the same as Example 2.1.

[0038] Example 3.2 A method for preparing a steam-free early strength agent for sleeper concrete, which is different from Example 2.1 in that the molar ratio of TPEG to HEPG is 8:2, and the rest is the same as Example 2.1.

[0039] Example 3.3 A method for preparing a steam-free early strength agent for sleeper concrete, which is different from Example 2.1 in that the molar ratio of TPEG to HEPG is 9:1, and the rest is the same as Example 2.1.

[0040] Example 4.1 A method for preparing a steam-free early strength agent for sleeper concrete, which is different from Example 1.1 in that the acid ester ratio in the polymerized small monomer is 3.2:6.8, and the rest is the same as Example 1.1.

[0041] Example 4.2 A method for preparing a steam-free early strength agent for sleeper concrete, which is different from Example 1.1 in that the acid ester ratio in the polymerized small monomer is 3.4:6.6, and the rest is the same as Example 1.1.

[0042] Example 4.3 A method for preparing a steam-free curing early strength agent for sleeper concrete, which is different from Example 1.1 in that the acid ester ratio in the polymerized small monomer is 3.6:6.4, and the rest is the same as Example 1.1.

[0043] Example 4.4 A method for preparing a steam-free curing early strength agent for sleeper concrete, which is different from Example 1.1 in that the acid ester ratio in the polymerized small monomer is 3.8:6.2, and the rest is the same as Example 1.1.

[0044] Example 5.1 A method for preparing a steam-free early strength agent for sleeper concrete, which differs from Example 4.4 in that, in the polymerized small monomers, the molar ratio of acrylic acid to sodium methacrylic acid sulfonate is 90:10, and the molar ratio of hydroxyethyl acrylate to butyl acrylate is 90:10; the rest is the same as Example 4.4.

[0045] Example 5.2 A method for preparing a steam-free early strength agent for sleeper concrete, which differs from Example 4.4 in that, in the polymerized small monomers, the molar ratio of acrylic acid to sodium methacrylic acid sulfonate is 95:5, and the molar ratio of hydroxyethyl acrylate to butyl acrylate is 70:30; the rest is the same as Example 4.4.

[0046] Example 5.3 A method for preparing a steam-free early strength agent for sleeper concrete, which differs from Example 4.4 in that, in the polymerized small monomers, the molar ratio of acrylic acid to sodium methacrylic acid sulfonate is 92:8, and the molar ratio of hydroxyethyl acrylate to butyl acrylate is 75:25. The rest is the same as Example 4.4.

[0047] Examples 6.1-6.4 A method for preparing a steam-free early strength agent for sleeper concrete, which differs from Example 1.1 in that the functional small monomers prepared in Preparation Example 1.1 are replaced by the functional small monomers prepared in Preparation Examples 2.1-2.4 respectively, and the rest are the same as Example 1.1.

[0048] Comparative Example 1.1 The difference from Example 1.1 is that sodium methacrylic acid sulfonate is removed from the polymerization monomer, while maintaining the overall acid ester ratio of 3:7 and the molar ratio of hydroxyethyl acrylate to butyl acrylate of 95:5. Acrylic acid, hydroxyethyl acrylate and butyl acrylate are weighed and mixed to obtain the polymerization monomer. The rest is the same as Example 1.1.

[0049] Comparative Example 1.2 The difference from Example 1.1 is that butyl acrylate is removed from the polymerizable monomer, while maintaining the overall acid ester ratio of 3:7 and the molar ratio of acrylic acid to sodium methacrylic acid sulfonate of 85:15. Acrylic acid, sodium methacrylic acid sulfonate and hydroxyethyl acrylate are weighed and mixed to obtain the polymerizable monomer. The rest is the same as Example 1.1.

[0050] Comparative Example 2 The difference from Example 1.1 is that the functional small monomer is removed, the molar ratio of the polymerized macromonomer to the polymerized small monomer is 1:4.2, and the rest is the same as Example 1.1.

[0051] Performance testing 0.5 wt% of the steam-free early strength agent prepared in the Examples and Comparative Examples was added to cement, and the mechanical properties of the cement were tested according to the "Test Method for Cement Mortar Strength (IOS)" (GB / T 8076-2008). The S / C ratio was 3, and the water consumption was controlled to achieve a mortar fluidity of 180 mm ± 5. The cement was placed in a 4 cm × 4 cm × 16 cm mold. The specimens were cured in a standard curing room for 24 hours before being removed from the mold and continued to cure. The compressive strength (MPa) of the specimens was measured at 3 and 28 days using a CMT5 105 electronic universal testing machine (loading rate 2400 N / s). A blank control was used for a cement specimen without any admixture. The improvement in the 3-day and 28-day compressive strengths of the cement obtained with the steam-free early strength agent prepared in the Examples and Comparative Examples was calculated.

[0052] Table 1 Performance test table Data Analysis: As can be seen from Table 1, the steam-free early strength agent of Examples 1.1-1.2 can increase the 3d compressive strength of cement by 129.6%-130.5%, and the 28d compressive strength by 75.8%-76.1%, which proves that the steam-free early strength agent finally obtained in this application can further improve the later strength of concrete without affecting the early strength of concrete.

[0053] In Examples 2.1-2.3, the present application changes the type of polymerized macromonomer, among which the 3d compressive strength improvement rate of Example 2.1 is significantly improved, proving that the present application utilizes TPEG and HEPG together as polymerized macromonomers, among which TPEG has good dispersion properties, can effectively reduce the water consumption of concrete and improve the fluidity of concrete, while HEPG has excellent collapse retention properties, and can maintain the working performance of concrete stable for a long time. The two work together to effectively optimize the molecular structure of the early strength agent and enhance its dispersion and adsorption properties in the sleeper concrete, which not only improves the later strength and durability of the concrete, but also further improves the early strength of the concrete, meeting the high performance requirements of the sleeper concrete in practical applications.

[0054] In Examples 3.1-3.3, the present application changes the molar ratio of the polymerized macromonomer, wherein the 3d compressive strength improvement rate and the 28d compressive strength improvement rate of Examples 3.1-3.2 are both increased, proving that the present application further optimizes the ratio of the polymerized macromonomer, which can achieve a better balance between the dispersibility and adsorption performance of the steam-free early strength agent in the sleeper concrete. The polymerized macromonomer under this ratio can effectively improve the early strength of the concrete while ensuring that the later strength and durability are not significantly affected, thereby better meeting the strength development requirements of the sleeper concrete under steam-free curing conditions.

[0055] In Examples 4.1-4.4, the present application changes the acid ester ratio in the polymerized small monomer, among which the 3d compressive strength improvement rate of Example 4.4 is significantly increased, proving that the present application further optimizes the molecular structure of the steam-free early strength agent by precisely controlling the acid ester ratio in the polymerized small monomer at 3.8:6.2, thereby improving its dispersibility and adsorption properties in the sleeper concrete, helping to enhance the dispersion effect of the early strength agent on cement particles and promote the hydration reaction, thereby effectively improving the early strength of concrete while avoiding adverse effects on the later strength and durability.

[0056] In Examples 5.1-5.3, the present application changes the molar ratio of acrylic acid and sodium methacrylic acid sulfonate and the molar ratio of hydroxyethyl acrylate and butyl acrylate in the polymerized small monomers. Among them, Example 5.2 has the highest 3d compressive strength improvement rate, and the overall 3d compressive strength improvement rate of Examples 5.1-5.3 is also higher than that of Example 4.4. This proves that the present application effectively improves the water reduction rate and dispersibility of the early strength agent by regulating the molar ratio of acrylic acid and sodium methacrylic acid sulfonate and the molar ratio of hydroxyethyl acrylate and butyl acrylate in the polymerized small monomers, ensuring that the concrete has higher fluidity and stability under steam-free curing conditions, further optimizing the molecular structure of the early strength agent, and enhancing the compatibility of the steam-free curing early strength agent with other components in the concrete, thereby significantly improving the early strength of the concrete and meeting the requirements of the demolding strength for sleeper production.

[0057] In Examples 6.1-6.4, the present application changed the weight ratio of cellulose hydrolysis product and maleic anhydride in the functional small monomer, among which the 3d compressive strength improvement rate and 28d compressive strength improvement rate of Example 6.1 both increased, proving that the present application precisely regulated the structural characteristics of the functional small monomer by controlling the weight ratio of cellulose hydrolysis product and maleic anhydride, which helped to improve the compatibility and reactivity between the functional small monomer and the polymerized macromonomer and the polymerized small monomer, thereby further improving the dispersion and adsorption properties of the final steam-free early strength agent.

[0058] In Comparative Examples 1.1-1.2, the present application removed sodium methacrylic acid and butyl acrylate respectively. The results showed that the 3d compressive strength improvement rate and the 28d compressive strength improvement rate both decreased. This proves that the present application uses acrylic acid, sodium methacrylic acid, hydroxyethyl acrylate and butyl acrylate as polymerization monomers, controls the molar ratio, and effectively adjusts the molecular spatial structure of the polycarboxylic acid, so that it has both early strength ability and concrete slump retention.

[0059] In Comparative Example 2, the present application removed the functional small monomer, and the results showed that the 3d compressive strength improvement rate and the 28d compressive strength improvement rate both decreased, proving that the present application utilized the functional small monomer through its own synergistic effect to effectively enhance the dispersion and adsorption performance of the early strength agent in the concrete system.

[0060] The embodiments of this specific implementation method are all preferred embodiments of the present application and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A steam-free hardening early strength agent for sleeper concrete, characterized in that: The raw materials used include a polymeric macromonomer, a polymeric small monomer and a functional small monomer in a molar ratio of 1:(3.5-4):(0.4-0.7), wherein the polymeric macromonomer includes one or more of TPEG, EPEG and HEPG, the polymeric small monomer includes acrylic acid, sodium methacrylic acid sulfonate, hydroxyethyl acrylate and butyl acrylate, the acid ester ratio in the polymeric small monomer is (3-4):(6-7), and the functional small monomer is prepared from cellulose and maleic anhydride.

2. The non-steaming early strength agent for sleeper concrete according to claim 1, characterized in that: The polymeric macromonomers include TPEG and HEPG.

3. The non-steaming early strength agent for sleeper concrete according to claim 2, characterized in that: The molar ratio of TPEG to HEPG is (7-8): (2-3).

4. The non-steaming early strength agent for sleeper concrete according to claim 1, characterized in that: The acid ester ratio in the polymerized small monomer is 3.8:6.

2.

5. The non-steaming early strength agent for sleeper concrete according to claim 4, characterized in that: In the polymerizable monomers, the molar ratio of acrylic acid to sodium methacrylic acid sulfonate is (90-95):(5-10), and the molar ratio of hydroxyethyl acrylate to butyl acrylate is (70-90):(10-30).

6. The autoclave-free early strength agent for sleeper concrete according to claim 5, characterized in that: In the polymerizable monomers, the molar ratio of acrylic acid to sodium methacrylic acid sulfonate is 92:8, and the molar ratio of hydroxyethyl acrylate to butyl acrylate is 75:

25.

7. A method for preparing the steam-curing-free early strength agent for sleeper concrete according to any one of claims 1 to 6, characterized in that: The following steps are involved: The polymer small monomer and the functional small monomer are dispersed in water to obtain material A, and then the reducing agent and the chain transfer agent are dispersed in water to obtain material B. The polymer large monomer is dispersed in water and fully dissolved, and then 50-60wt% of material A is added, and then the oxidant and the initiator are added. After heating to 45-55°C, all the remaining materials A and B are added, and the reaction is kept warm for 2-4 hours. Finally, the pH is adjusted to neutral, and the solid content in the system is adjusted to 35-40wt% to obtain a steaming-free early strength agent.

8. The method for preparing a non-steaming early strength agent for sleeper concrete according to claim 7, characterized in that: The functional small monomer is prepared by the following method: The cellulose is hydrolyzed to obtain a cellulose hydrolyzate, which is then blended with maleic anhydride in a weight ratio of (4-8):(2-6), and reacted at a temperature of 75-90°C for 3.5-4.5 hours to obtain a functional small monomer.

9. The method for preparing a non-steaming early strength agent for sleeper concrete according to claim 8, characterized in that: The weight ratio of the cellulose hydrolysate to maleic anhydride is 5:5.

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