Preparation and application of a composite air entraining agent for roller compacted concrete

Abstract

The application discloses a preparation and application of a roller compacted concrete composite air entraining agent and belongs to the field of concrete admixtures. The preparation method of the double maleic acid modified rosin air entraining agent comprises the following steps: mixing rosin acid, epoxy chloropropane, tetrabutylammonium bromide and a solvent, reacting, and obtaining an intermediate product A; mixing the intermediate product A, diethanolamine, an acid binding agent and a solvent, carrying out a nucleophilic substitution reaction, and obtaining an intermediate product B; mixing the intermediate product B, maleic anhydride, a catalyst and a polymerization inhibitor, carrying out an addition reaction, and obtaining the double maleic acid modified rosin air entraining agent. The double maleic anhydride modification of rosin acid is carried out, the hydrophilic structure is changed into a Y-shaped structure, the liquid film layer of the hydrophilic part is beneficial to be stabilized, and therefore the air entraining agent stability is improved. Meanwhile, the two carboxylic acid groups introduced enhance the hydrophilicity of the molecule, and the air entraining capacity is further improved.

Description

Technical Field

[0001] This invention relates to the field of concrete admixtures, and in particular to the preparation and application of a composite air-entraining agent for roller-compacted concrete. Background Technology

[0002] Roller-compacted concrete (RCC) is a special type of concrete characterized by its dry hardness and zero slump. Its construction technology draws upon mature and efficient filling techniques used in earth-rock dam engineering. Unlike traditional concrete, which relies on fluid pouring and vibration compaction, RCC requires layered compaction using a high-frequency vibratory roller after being placed by a paver. Due to its fast construction speed and low overall cost, this material is widely used in large-volume or large-area structural projects such as dams, heavy road base courses, large airport pavements, and port storage yards. RCC breaks through the traditional concrete cementitious material system, allowing for the incorporation of industrial byproducts such as fly ash and granulated blast furnace slag as admixtures, typically reaching 50% to 70% of the total cementitious material. This not only significantly reduces material costs but also plays a crucial role in improving the compactability of the concrete, enhancing interlayer bonding, and reducing temperature cracking.

[0003] Air-entraining agents are crucial admixtures for regulating the performance of roller-compacted concrete (RCC). Their function is to stably introduce a large number of uniform, independent, and closed microbubbles (typically with pore sizes of 20-200 micrometers) into the concrete mixture through physical or chemical means, thereby significantly improving the concrete's freeze-thaw resistance, workability, and rollability. The mechanism of these microbubbles is similar to that in ordinary concrete. However, because the admixture particles in RCC are usually finer and have a larger specific surface area than cement, they strongly adsorb air-entraining agent molecules. Simultaneously, the unburned carbon particles remaining in some admixtures (such as high-carbon fly ash) have a porous structure and extremely strong adsorption capacity, resulting in a significant reduction in the effective molecular concentration for foaming in the liquid phase, thus lowering the air content. Typically, the dosage of air-entraining agent needs to be increased to 2-5 times the conventional amount to achieve the desired effect, leading to a significant increase in cost and poor practicality.

[0004] Therefore, in order to address the problem of adsorption of air-entraining agents by admixtures, it is urgent to develop an air-entraining agent solution suitable for roller-compacted concrete. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing and applying a composite air-entraining agent for roller-compacted concrete, so as to solve the above-mentioned problems in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: One of the technical solutions of this invention is to provide a method for preparing a bismaleic acid modified rosin air-entraining agent, comprising the following steps: (1) A rosin acid, epichlorohydrin, tetrabutylammonium bromide and solvent are mixed and reacted to obtain intermediate product A; (2) The intermediate product A, diethanolamine, acid-binding agent and solvent are mixed and subjected to nucleophilic substitution reaction to obtain intermediate product B; (3) The intermediate product B, maleic anhydride, catalyst and polymerization inhibitor are mixed and subjected to an addition reaction to obtain the bismaleic acid modified rosin air-entraining agent.

[0007] Preferably, in step (1): the mass ratio of rosin acid, epichlorohydrin, tetrabutylammonium bromide and solvent is 20-50:10-25:0.001-5:40-60; the reaction temperature is 50-80℃ and the time is 4-8h.

[0008] Preferably, in step (2): the mass ratio of intermediate product A, diethanolamine, acid-binding agent and solvent is 20-60:20-70:0.001-5:40-60; the acid-binding agent is sodium bicarbonate; the temperature of the nucleophilic substitution reaction is 50-80℃ and the time is 2-6h.

[0009] Preferably, in step (3): the mass ratio of intermediate product B, maleic anhydride, catalyst and polymerization inhibitor is 20-80:20-80:0.0001-2:0.0001-5; the catalyst is p-toluenesulfonic acid; the polymerization inhibitor is hydroquinone; the temperature of the addition reaction is 80-110℃ and the time is 2-6h.

[0010] Preferably, the solvent is one of ethanol, acetone and isopropanol.

[0011] The second technical solution of the present invention provides a bismaleic acid modified rosin air-entraining agent obtained according to the above preparation method.

[0012] The third technical solution of this invention: provides a composite air-entraining agent for roller-compacted concrete, the raw materials comprising, by mass parts: The above-mentioned bismaleic acid modified rosin air-entraining agent consists of 20-50 parts, sacrificial agent 5-50 parts, and water.

[0013] Preferably, the sacrificial agent is one or two of sulfated isopropanolamine salt, ammonium bromide, and ammonium chloride.

[0014] Fourth technical solution of the present invention: A method for preparing the above-mentioned composite air-entraining agent for roller-compacted concrete, comprising the following steps: By weight, 20-50 parts of the bismaleic acid modified rosin air-entraining agent, 30-50 parts of water and 5-50 parts of the sacrificial agent are mixed to obtain the composite air-entraining agent for roller-compacted concrete.

[0015] The fifth technical solution of the present invention provides an application of the above-mentioned bismaleic acid modified rosin air-entraining agent or the above-mentioned composite air-entraining agent for roller-compacted concrete in the field of air-entraining agents for roller-compacted concrete.

[0016] The beneficial technical effects of the present invention are as follows: This invention modifies rosin acid with bismaleic anhydride, transforming its hydrophilic structure into a Y-type structure. This facilitates the stabilization of the liquid film layer in the hydrophilic portion, thereby enhancing the gas-entraining agent's gas-stabilizing ability. Simultaneously, the two introduced carboxylic acid groups enhance the molecule's hydrophilicity, further improving its gas-entraining capacity.

[0017] To address the negatively charged surface characteristics of admixture particles such as fly ash, and to prevent the anionic air-entraining agent from complexing and adsorbing onto the particle surface through calcium ion bridging, this invention adds a cationic amino salt as a sacrificial agent to the formulation of the composite air-entraining agent. This sacrificial agent preferentially adsorbs onto the surface of admixture particles in roller-compacted concrete and can also bind to anionic air-entraining agent molecules, thereby reducing the adsorption of the air-entraining agent on calcium-containing particles and preventing the formation of calcium soap precipitates between calcium ions and the air-entraining agent.

[0018] Through the synergistic effect of the two components of the bismaleic acid modified rosin air-entraining agent and the sacrificial agent in this invention, the air-entraining ability and bubble stability of the product can be effectively improved while reducing the amount of air-entraining agent used. Detailed Implementation

[0019] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0020] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0021] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. It should be noted that any aspects of this invention not described in detail are conventional practices in the art and are not the focus of this invention.

[0022] The terms “comprising,” “including,” “having,” “containing,” etc., used in this invention are all open-ended terms, meaning that they include but are not limited to.

[0023] This invention discloses a method for preparing a bismaleic acid modified rosin air-entraining agent, comprising the following steps: By mass, 20-50 parts of rosin acid, 0.001-5 parts of tetrabutylammonium bromide, and 40-60 parts of solvent were added to a four-necked flask equipped with a magnetic stir bar, a reflux condenser, and a thermometer. 10-25 parts of epichlorohydrin were added dropwise through a constant-pressure funnel over 5-30 minutes. The mixture was magnetically stirred at 50-80°C for 4-8 hours. After the reaction was complete, the solvent was removed by rotary evaporation, followed by washing with hot distilled water 1-10 times and drying to obtain intermediate product A. The reaction is as follows: Add 20-60 parts of the intermediate product A, 20-70 parts of diethanolamine, 0.001-5 parts of sodium bicarbonate (an acid-binding agent), and 40-60 parts of solvent to a four-necked flask equipped with a magnetic stir bar, reflux condenser, and thermometer. Stir magnetically at 50-80°C for 2-6 hours. After the reaction, wash 1-10 times with distilled water, then remove water and solvent by vacuum distillation, and dry to obtain intermediate product B. The reaction is as follows: Add 20-80 parts of the intermediate product B, 20-80 parts of maleic anhydride, 0.0001-2 parts of catalyst, and 0.0001-5 parts of polymerization inhibitor to a four-necked flask equipped with a magnetic stir bar, a water separator, a reflux condenser, and a thermometer. Stir and heat to 80-110°C, react for 2-6 hours to obtain the bismaleic acid modified rosin air-entraining agent. The reaction is as follows; Furthermore, the solvent is one of ethanol, acetone, and isopropanol.

[0024] Furthermore, the catalyst is p-toluenesulfonic acid.

[0025] Furthermore, the polymerization inhibitor is hydroquinone.

[0026] The added polymerization inhibitor is designed to suppress the ring-opening homopolymerization of maleic anhydride and prevent it from forming byproducts such as polymaleic anhydride, thereby ensuring the efficient addition reaction between maleic anhydride and intermediate product B to obtain a structurally well-defined bismaleic acid modified rosin air-entraining agent.

[0027] The present invention also discloses a bismaleic acid modified rosin air-entraining agent obtained according to the above preparation method.

[0028] This invention also discloses a composite air-entraining agent for roller-compacted concrete, wherein the raw materials, by mass parts, include: The above-mentioned bismaleic acid modified rosin air-entraining agent consists of 20-50 parts, sacrificial agent 5-50 parts, and water.

[0029] Furthermore, the sacrificial agent is one or two of sulfated isopropanolamine salt, ammonium bromide, and ammonium chloride.

[0030] This invention also discloses a method for preparing the above-mentioned composite air-entraining agent for roller-compacted concrete, comprising the following steps: By mass, at room temperature, 20-50 parts of the bismaleic acid modified rosin air-entraining agent are added to 30-50 parts of water and stirred at 300 rpm for 10-30 min. Then, 5-50 parts of the sacrificial agent are added and stirred at 300 rpm for another 10-30 min. The mixture is then diluted to a concentration (referring to the total concentration of air-entraining agent and sacrificial agent in the solution) of 1-10 wt% to obtain the composite air-entraining agent for roller-compacted concrete.

[0031] The present invention also discloses the application of the above-mentioned bismaleic acid modified rosin air-entraining agent or the above-mentioned composite air-entraining agent for roller-compacted concrete in the field of air-entraining agents for roller-compacted concrete.

[0032] Unless otherwise specified, "room temperature" in this invention refers to 10-30°C. Unless otherwise specified, "parts" in this invention refers to parts by weight.

[0033] All raw materials used in the following embodiments and comparative examples of the present invention are commercially available products.

[0034] In the examples and comparative examples, "parts" refers to "parts by weight".

[0035] Example 1 A method for preparing a bismaleic acid-modified rosin air-entraining agent, comprising the following steps: By mass fraction, 50 parts of rosin acid, 0.02 parts of tetrabutylammonium bromide, and 40 parts of isopropanol were added to a four-necked flask equipped with a magnetic stir bar, a reflux condenser, and a thermometer. 25 parts of epichlorohydrin were added dropwise through a constant pressure funnel over a period of 10 minutes. The mixture was magnetically stirred at 80°C for 4 hours. After the reaction was completed, the solvent was removed by rotary evaporation, and the product was washed five times with hot distilled water and dried to obtain intermediate product A.

[0036] 50 parts of intermediate product A, 25 parts of diethanolamine, 0.05 parts of sodium bicarbonate (an acid-binding agent), and 40 parts of isopropanol were added to a four-necked flask equipped with a magnetic stir bar, a reflux condenser, and a thermometer. The mixture was magnetically stirred at 80°C for 4 hours. After the reaction was completed, the mixture was washed five times with distilled water, and the water and solvent were removed by vacuum distillation. The mixture was then dried to obtain intermediate product B.

[0037] 50 parts of maleic anhydride, 0.01 parts of catalyst p-toluenesulfonic acid, 0.001 parts of polymerization inhibitor hydroquinone, and 20 parts of intermediate product B were added to a four-necked flask equipped with a magnetic stir bar, a water separator, a reflux condenser, and a thermometer. The mixture was stirred and heated to 110°C and reacted for 6 hours to obtain a bismaleic acid modified rosin air-entraining agent.

[0038] Preparation of composite air-entraining agents for roller-compacted concrete: At room temperature, 40 parts of bismaleic acid modified rosin air-entraining agent were added to 50 parts of water and stirred at 300 rpm for 10 min. Then, 10 parts of sacrificial agent sulfated isopropanolamine salt were added and stirred at 300 rpm for 10 min. Then, water was added to dilute to a concentration of 10 wt% to obtain a composite air-entraining agent for roller-compacted concrete.

[0039] Example 2 A method for preparing a bismaleic acid-modified rosin air-entraining agent, comprising the following steps: By mass fraction, 40 parts of rosin acid, 0.01 parts of tetrabutylammonium bromide, and 40 parts of ethanol were added to a four-necked flask equipped with a magnetic stir bar, a reflux condenser, and a thermometer. 25 parts of epichlorohydrin were added dropwise through a constant pressure funnel over a period of 20 minutes. The mixture was magnetically stirred at 80°C for 5 hours. After the reaction was completed, the solvent was removed by rotary evaporation, and the product was washed 10 times with hot distilled water and dried to obtain intermediate product A.

[0040] 40 parts of intermediate product A, 32 parts of diethanolamine, 0.01 parts of sodium bicarbonate (an acid-binding agent), and 50 parts of ethanol were added to a four-necked flask equipped with a magnetic stir bar, a reflux condenser, and a thermometer. The mixture was magnetically stirred at 80°C for 6 hours. After the reaction was completed, the mixture was washed 10 times with distilled water, and the water and solvent were removed by vacuum distillation. The mixture was then dried to obtain intermediate product B.

[0041] 30 parts of maleic anhydride, 0.01 parts of catalyst p-toluenesulfonic acid, 0.04 parts of polymerization inhibitor hydroquinone, and 80 parts of intermediate product B were added to a four-necked flask equipped with a magnetic stir bar, a water separator, a reflux condenser, and a thermometer. The mixture was stirred and heated to 110°C and reacted for 6 hours to obtain a bismaleic acid modified rosin air-entraining agent.

[0042] Preparation of composite air-entraining agents for roller-compacted concrete: At room temperature, 50 parts of bismaleic acid modified rosin air-entraining agent were added to 30 parts of water and stirred at 300 rpm for 30 min. Then, 10 parts of ammonium chloride and 10 parts of sulfated isopropanolamine salt were added and stirred at 300 rpm for 10 min. Then, water was added to dilute to a concentration of 5 wt% to obtain a composite air-entraining agent for roller-compacted concrete.

[0043] Example 3 A method for preparing a bismaleic acid-modified rosin air-entraining agent, comprising the following steps: By mass fraction, 40 parts of rosin acid, 0.01 parts of tetrabutylammonium bromide, and 40 parts of ethanol were added to a four-necked flask equipped with a magnetic stir bar, a reflux condenser, and a thermometer. 25 parts of epichlorohydrin were added dropwise through a constant pressure funnel over a period of 20 minutes. The mixture was magnetically stirred at 80°C for 5 hours. After the reaction was completed, the solvent was removed by rotary evaporation, and the product was washed five times with hot distilled water and dried to obtain intermediate product A.

[0044] 40 parts of intermediate product A, 25 parts of diethanolamine, 0.01 parts of sodium bicarbonate (an acid-binding agent), and 50 parts of ethanol were added to a four-necked flask equipped with a magnetic stir bar, a reflux condenser, and a thermometer. The mixture was magnetically stirred at 80°C for 6 hours. After the reaction was completed, the mixture was washed five times with distilled water, and the water and solvent were removed by vacuum distillation. The mixture was then dried to obtain intermediate product B.

[0045] 50 parts of maleic anhydride, 0.02 parts of catalyst p-toluenesulfonic acid, 0.001 parts of polymerization inhibitor hydroquinone, and 20 parts of intermediate product B were added to a four-necked flask equipped with a magnetic stir bar, a water separator, a reflux condenser, and a thermometer. The mixture was stirred and heated to 110°C and reacted for 4 hours to obtain bismaleic acid modified rosin air-entraining agent.

[0046] Preparation of composite air-entraining agents for roller-compacted concrete: At room temperature, 50 parts of bismaleic acid modified rosin air-entraining agent were added to 30 parts of water and stirred at 300 rpm for 30 min. Then, 20 parts of sulfated isopropanolamine salt were added and stirred at 300 rpm for 10 min. Then, water was added to dilute to a concentration of 10 wt% to obtain a composite air-entraining agent for roller-compacted concrete.

[0047] Example 4 A method for preparing a bismaleic acid-modified rosin air-entraining agent, comprising the following steps: By mass fraction, 50 parts of rosin acid, 0.04 parts of tetrabutylammonium bromide, and 40 parts of acetone were added to a four-necked flask equipped with a magnetic stir bar, a reflux condenser, and a thermometer. 25 parts of epichlorohydrin were added dropwise through a constant pressure funnel over a period of 10 minutes. The mixture was magnetically stirred at 80°C for 5 hours. After the reaction was completed, the solvent was removed by rotary evaporation, and the product was washed five times with hot distilled water and dried to obtain intermediate product A.

[0048] 35 parts of intermediate product A, 20 parts of diethanolamine, 0.02 parts of sodium bicarbonate (an acid-binding agent), and 50 parts of ethanol were added to a four-necked flask equipped with a magnetic stir bar, a reflux condenser, and a thermometer. The mixture was magnetically stirred at 70°C for 4 hours. After the reaction was completed, the mixture was washed five times with distilled water, and the water and solvent were removed by vacuum distillation. The mixture was then dried to obtain intermediate product B.

[0049] 50 parts of maleic anhydride, 0.02 parts of catalyst p-toluenesulfonic acid, 0.001 parts of polymerization inhibitor hydroquinone, and 20 parts of intermediate product B were added to a four-necked flask equipped with a magnetic stir bar, a water separator, a reflux condenser, and a thermometer. The mixture was stirred and heated to 110°C and reacted for 4 hours to obtain bismaleic acid modified rosin air-entraining agent.

[0050] Preparation of composite air-entraining agents for roller-compacted concrete: At room temperature, 50 parts of bismaleic acid modified rosin air-entraining agent were added to 30 parts of water and stirred at 300 rpm for 30 min. Then, 10 parts of ammonium bromide and 10 parts of sulfated isopropanolamine salt were added and stirred at 300 rpm for 10 min. Then, water was added to dilute to a concentration of 10 wt% to obtain a composite air-entraining agent for roller-compacted concrete.

[0051] Example 5 A method for preparing a bismaleic acid-modified rosin air-entraining agent, comprising the following steps: By mass fraction, 40 parts of rosin acid, 0.04 parts of tetrabutylammonium bromide, and 30 parts of ethanol were added to a four-necked flask equipped with a magnetic stir bar, a reflux condenser, and a thermometer. 25 parts of epichlorohydrin were added dropwise through a constant pressure funnel over a period of 20 minutes. The mixture was magnetically stirred at 80°C for 6 hours. After the reaction was completed, the solvent was removed by rotary evaporation, and the product was washed 10 times with hot distilled water and dried to obtain intermediate product A.

[0052] 40 parts of intermediate product A, 25 parts of diethanolamine, 0.04 parts of sodium bicarbonate (an acid-binding agent), and 30 parts of ethanol were added to a four-necked flask equipped with a magnetic stir bar, a reflux condenser, and a thermometer. The mixture was magnetically stirred at 80°C for 6 hours. After the reaction was completed, the mixture was washed five times with distilled water, and the water and solvent were removed by vacuum distillation. The mixture was then dried to obtain intermediate product B.

[0053] Add 50 parts of maleic anhydride, 0.04 parts of catalyst p-toluenesulfonic acid, 0.001 parts of polymerization inhibitor hydroquinone, and 20 parts of intermediate product B to a four-necked flask equipped with a magnetic stir bar, a water separator, a reflux condenser, and a thermometer. Stir and heat to 100°C and react for 6 hours to obtain bismaleic acid modified rosin air-entraining agent.

[0054] Preparation of composite air-entraining agents for roller-compacted concrete: At room temperature, 40 parts of bismaleic acid modified rosin air-entraining agent were added to 30 parts of water and stirred at 300 rpm for 30 min. Then, 13 parts of ammonium bromide and 13 parts of ammonium chloride were added and stirred at 300 rpm for 30 min. Then, water was added to dilute the mixture to a concentration of 10 wt% to obtain a composite air-entraining agent for roller-compacted concrete.

[0055] Comparative Example 1 The only difference from Example 1 is that the bismaleic acid-modified rosin air-entraining agent in the composite air-entraining agent is replaced with an equal mass of commercially available rosin air-entraining agent GK-9. A .

[0056] Comparative Example 2 The only difference from Example 1 is that the addition of the sacrificial agent is omitted.

[0057] Comparative Example 3 The only difference from Example 1 is that maleic anhydride is omitted.

[0058] Effect verification 1. The performance of the composite air-entraining agents prepared in the above examples and comparative examples was tested according to the test methods in DL / T5150-2017 "Test Procedure for Hydraulic Concrete". Specifically, each sample was added to roller-compacted concrete for testing, and the amount of each sample added accounted for 0.05% of the mass of cementitious materials.

[0059] The raw material formula for the roller-compacted concrete described above is as follows: The cement used was Esheng PO42.5 cement, and the fly ash was Grade II; the fineness modulus of the sand was 2.5; the crushed stone consisted of 5-20mm and 20-40mm aggregates. A water-reducing agent, commercially available naphthalene-based water-reducing agent GK-A, was added to the concrete at a dosage of 1% of the cementitious material mass. The concrete mix design is shown in Table 1. The test results of the concrete performance are shown in Table 2.

[0060] Table 1. Experimental mix proportions (kg / m³) 3 ) Table 2 Concrete performance test results 2. The adsorption amount of the composite air-entraining agent in the concrete mortar was determined using a Total Organic Carbon (TOC) analyzer (TOC-L, Shimadzu, Japan). According to the mix proportion in Table 1, 50g of mortar and 50g of water were weighed into a beaker, stirred evenly, and centrifuged at 3000r / min for 10min in a centrifuge tube. 2mL of the supernatant was collected and filtered through a 0.22μm filter membrane. 1g of the filtrate (accurate to 0.0001g) was weighed and recorded as m1. The filtrate was acidified and diluted with 0.01mol / L hydrochloric acid to pH 2-4, and the reading was recorded as m2. The prepared solution was placed in an automatic sample tray, and the total organic carbon value was tested and recorded as C0. The organic carbon value C1 in the mortar was obtained according to the following formula (1).

[0061] (1) Since some sacrificial agents contain carbon (sulfated isopropanolamine salt), in order to eliminate the organic carbon value, it is necessary to test the organic carbon value of each sacrificial agent according to the above steps. According to formula (1), prepare a mortar system that omits only the air-entraining agent (specifically the corresponding air-entraining agent raw material in the composite air-entraining agent) to obtain the organic carbon value C2 of the sacrificial agent in the mortar. Similarly, test the organic carbon value of the air-entraining agent raw material and the sacrificial agent in the solution. The specific method is as follows: according to the corresponding admixture concentration in the mortar, replace 50g of mortar with an air-entraining agent aqueous solution or a sacrificial agent aqueous solution with the same admixture concentration to obtain the organic carbon value (C3) of the air-entraining agent in water and the organic carbon value (C4) of the sacrificial agent in the aqueous solution.

[0062] The adsorption rate S of the air-entraining agent in the mortar suf The results are shown in Table 3, calculated according to formula (2).

[0063] (2) Table 3 Adsorption rate of air-entraining agent in mortar As can be seen from the data in Table 2 regarding Examples 1-5 and Comparative Examples 1-3, the initial gas content and 1-hour gas content of the five composite air-entraining agents prepared in each example of the present invention are higher than those in Comparative Examples 1-3, and the 1-hour gas loss is smaller, and the 28-day compressive strength is higher than that in Comparative Examples 1-3. Combined with Comparative Examples 1-3, it can be seen that the foaming properties of the modified air-entraining agent designed in the present invention are significantly better than those of the air-entraining agents in the comparative examples.

[0064] The data in Table 3 shows that the sacrificial agent added to the composite air-entraining agent specified in this invention can prevent the air-entraining agent from adsorbing onto the surface of fly ash and increase the concentration of the air-entraining agent in the slurry.

[0065] The above data demonstrate that the composite air-entraining agent specified in this invention has excellent foaming and foam-stabilizing properties, and has a promising application prospect in roller-compacted concrete.

[0066] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a bismaleic acid-modified rosin air-entraining agent, characterized in that, Includes the following steps: (1) A rosin acid, epichlorohydrin, tetrabutylammonium bromide and solvent are mixed and reacted to obtain intermediate product A; (2) The intermediate product A, diethanolamine, acid-binding agent and solvent are mixed and subjected to nucleophilic substitution reaction to obtain intermediate product B; (3) The intermediate product B, maleic anhydride, catalyst and polymerization inhibitor are mixed and subjected to an addition reaction to obtain the bismaleic acid modified rosin air-entraining agent.

2. The preparation method according to claim 1, characterized in that, In step (1): the mass ratio of rosin acid, epichlorohydrin, tetrabutylammonium bromide and solvent is 20-50:10-25:0.001-5:40-60; the reaction temperature is 50-80℃ and the time is 4-8h.

3. The preparation method according to claim 1, characterized in that, In step (2): the mass ratio of intermediate product A, diethanolamine, acid-binding agent and solvent is 20-60:20-70:0.001-5:40-60; the acid-binding agent is sodium bicarbonate; the temperature of the nucleophilic substitution reaction is 50-80℃ and the time is 2-6h.

4. The preparation method according to claim 1, characterized in that, In step (3): the mass ratio of intermediate product B, maleic anhydride, catalyst and polymerization inhibitor is 20-80:20-80:0.0001-2:0.0001-5; the catalyst is p-toluenesulfonic acid; the polymerization inhibitor is hydroquinone; the temperature of the addition reaction is 80-110℃ and the time is 2-6h.

5. The preparation method according to claim 1, characterized in that, The solvent is one of ethanol, acetone and isopropanol.

6. A bismaleic acid modified rosin air-entraining agent obtained by the preparation method according to any one of claims 1-5.

7. A composite air-entraining agent for roller-compacted concrete, characterized in that, Raw materials, by mass parts, include: The ingredients of claim 6 are 20-50 parts of the bismaleic acid modified rosin air-entraining agent, 5-50 parts of the sacrificial agent, and water.

8. The composite air-entraining agent for roller-compacted concrete according to claim 7, characterized in that, The sacrificial agent is one or two of sulfated isopropanolamine salt, ammonium bromide, and ammonium chloride.

9. A method for preparing a composite air-entraining agent for roller-compacted concrete according to any one of claims 7-8, characterized in that, Includes the following steps: By weight, 20-50 parts of the bismaleic acid modified rosin air-entraining agent, 30-50 parts of water and 5-50 parts of the sacrificial agent are mixed to obtain the composite air-entraining agent for roller-compacted concrete.

10. The application of the bismaleic acid modified rosin air-entraining agent of claim 6 or the composite air-entraining agent for roller-compacted concrete of any one of claims 7-8 in the field of air-entraining agents for roller-compacted concrete.

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