Novel water reducing agent and its preparation method and application

Abstract

This invention discloses a novel water-reducing agent, its preparation method, and its application. The preparation method includes: pouring an unsaturated polyether macromonomer solution into a reaction vessel; adding an oxidant and stirring at 50℃~60℃; simultaneously adding an unsaturated carboxylic acid small monomer solution and a mixed solution of a reducing agent and a chain transfer agent dropwise into the reaction vessel and stirring; maintaining the temperature and then cooling to room temperature to obtain a mother liquor; adding a lignin solution to the mother liquor to adjust the pH of the material in the reaction vessel to 11~12 to obtain the novel water-reducing agent. The novel water-reducing agent of this invention can improve the effect of residual flocculants in manufactured sand on concrete performance.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, and in particular to a novel water-reducing agent, its preparation method, and its application. Background Technology

[0002] In recent years, natural sand mining in some areas has reached saturation. The use of manufactured sand to replace natural sand in engineering construction has become an inevitable trend. However, the actual use of manufactured sand in concrete formulation requires a corresponding increase in the amount of water-reducing agent due to its manufacturing process, leading to numerous problems such as poor concrete workability, poor durability, and insufficient volume stability. Currently, the crushing equipment used in manufactured sand production cannot effectively control the morphology and gradation of sand particles, resulting in a product with a high content of coarse particles, a large fineness modulus, and a relatively high stone powder content. Effective control of the stone powder content in manufactured sand is necessary; otherwise, its performance will be significantly reduced. This necessitates the use of large amounts of water for washing the manufactured sand, easily leading to resource waste.

[0003] For dust removal in manufactured sand, wet sand making is more effective than dry sand making. However, wet sand making has disadvantages such as huge water consumption, difficult wastewater treatment, high water content in manufactured sand, and fewer fine particles. To save water resources, wastewater needs to be treated multiple times to achieve higher yields. Currently, a mature treatment process involves adding a well-stirred polymeric flocculant to a high-efficiency thickener to accelerate the settling of solid particles, causing the wastewater to stratify. The overflow from the upper layer is then introduced into a production water storage tank for recycling. The remaining wastewater is treated with chemical flocculants such as PAC (polyaluminum chloride) or APAM (anionic polyacrylamide) to accelerate sludge settling and facilitate final recycling. As a result, a significant amount of flocculant inevitably remains in the manufactured sand. This residual flocculant can affect the workability of concrete during subsequent mixing.

[0004] Concrete, as the most important construction material in current engineering projects, directly impacts the safety of bridge construction. Higher-grade bridge concrete demands higher workability: it requires good workability and pumpability. Furthermore, concrete mixed with poorly sized manufactured sand requires even higher performance from admixtures. However, the market offers a wide variety of admixtures, with significant differences in mother liquor production, leading to vastly different water-reducing agents with varying effects. Moreover, residual flocculants from the manufactured sand production process can cause flocculent precipitation of solutes, colloids, or suspended particles in aqueous solutions, resulting in admixture failure. This is particularly challenging for projects with large concrete volumes, such as approximately 100,000 cubic meters, where high-grade concrete is predominant. Ensuring a large supply of high-strength concrete with high strength, high performance, good workability, and excellent economic indicators, while enhancing pumpability stability, presents a significant challenge in concrete construction.

[0005] Currently, research on the impact of flocculants on concrete is still limited among construction companies. Often, their laboratories only understand the composition of flocculants but lack the ability to degrade or further utilize them. When manufactured sand is used to produce concrete, if the flocculant content exceeds the limit, it may affect the effect of admixtures, thereby impacting the workability and strength of the concrete. However, most construction companies do not consider the impact of polyacrylamide flocculants in manufactured sand on concrete mixing. The only solution is to adjust the admixture dosage or mix proportions. However, adjusting the admixture dosage can lead to poor concrete fluidity, or even segregation due to over-admixture, increasing project costs.

[0006] Currently, polycarboxylate superplasticizers, both domestically and internationally, do not effectively degrade residual flocculants in manufactured sand. Furthermore, the flocculants used in wastewater treatment are primarily anionic polyacrylamides with molecular weights of 12 million (X-2), 20 million (X-3), and 25 million (X-4); nonionic polyacrylamides with molecular weights of 10 million (X-6), 15 million (X-7), and 20 million (X-8); and cationic polyacrylamides with molecular weights of 10 million (X-10), 15 million (X-11), and 20 million (X-12). The molecular structure of polyether polycarboxylate superplasticizer is shown below:

[0007]

[0008] During the mixing process, it is impossible to effectively test and analyze the molecular weight of the residual flocculant in the manufactured sand. If traditional water-reducing agents are used, the state of each batch of concrete needs to be tested manually, resulting in inconsistent water-reducing agent dosages. This is especially true for projects with large concrete volumes, such as approximately 100,000 cubic meters, where the mixing state is difficult and the work quality of the concrete becomes hard to control.

[0009] In conclusion, it is essential to conduct analytical research on the degradation of residual flocculants in manufactured sand and even their conversion into underwater anti-dispersants. Summary of the Invention

[0010] According to one embodiment of the present invention, the objective is to provide a novel water-reducing agent, its preparation method, and its application. The novel water-reducing agent can improve the effect of residual flocculants in manufactured sand on concrete performance. This objective can be achieved through the following technical solutions:

[0011] According to one aspect of the present invention, a method for preparing a novel water-reducing agent is provided, comprising the following steps:

[0012] The unsaturated polyether macromonomer solution was poured into a reaction vessel, and an oxidant was added and stirred at 50℃~60℃. At the same time, an unsaturated carboxylic acid small monomer solution and a mixed solution of reducing agent and chain transfer agent were added dropwise to the reaction vessel and stirred. After keeping warm, the mixture was cooled to room temperature to obtain the mother liquor.

[0013] A lignin solution was added to the mother liquor, and the pH of the material in the reactor was adjusted to 11-12 to obtain the novel water-reducing agent.

[0014] Optionally, when preparing the mother liquor, the solid content of each solution is 25% to 35%.

[0015] Optionally, the lignin solution is incorporated at an amount of 8-12% of the total mother liquor and is obtained by extraction from sodium sulfite and forage.

[0016] Optionally, when preparing the mother liquor, the oxidant is added and then stirred for 3 to 7 minutes; when the unsaturated carboxylic acid monomer solution and the mixed solution of reducing agent and chain transfer agent are simultaneously added dropwise to the reaction vessel, the addition and stirring time is 100 to 140 minutes, and the holding time is 40 to 80 minutes.

[0017] Optionally, the preparation method further includes the step of preparing an unsaturated polyether macromonomer solution, wherein preparing the unsaturated polyether macromonomer solution includes: mixing the unsaturated polyether macromonomer with water and heating and stirring in a constant temperature water bath at 30℃~60℃ until the unsaturated polyether macromonomer is completely dissolved to obtain the unsaturated polyether macromonomer solution.

[0018] Optionally, the unsaturated polyether macromonomer is TPEG (i.e., methyl allyl polyoxyethylene ether) with an average molecular weight of 1000-16000; the unsaturated carboxylic acid micromonomer is one or more of acrylic acid, methacrylic acid, and fumaric acid.

[0019] Optionally, the ratio of the unsaturated polyether macromonomer to the unsaturated carboxylic acid micromonomer is (8-10):1.

[0020] Optionally, an anionic surfactant is added during the preparation of the unsaturated carboxylic acid monomer solution.

[0021] Optionally, the ratio of the oxidant to the reducing agent is 3 to 4.5:1.

[0022] Optionally, the reducing agent is VC and black sail in a ratio of 1.5 to 1.8:1.

[0023] According to another aspect of the present invention, a novel water-reducing agent is provided by the present invention and is prepared using the preparation method described herein.

[0024] According to another aspect of the present invention, the present invention provides an application of a novel water-reducing agent for preparing concrete, wherein the novel water-reducing agent improves the effect of residual flocculant in manufactured sand on concrete performance; wherein the amount of lignin incorporated is 0.15 to 0.3% of the amount of cement component in the concrete.

[0025] Optionally, the novel water-reducing agent is incorporated into the concrete at a dosage of 1.0–1.7%. Further, the novel water-reducing agent is incorporated into the concrete at a dosage of 1.2–1.6%.

[0026] Beneficial Effects: According to one embodiment of the present invention, using unsaturated polyether macromonomers, unsaturated carboxylic acid small monomers, oxidants, reducing agents, chain transfer agents, and lignin as main raw materials, and employing the preparation method described in this application, an oxidant is first added to a macromonomer solution at a specific temperature and stirred. Then, two solutions—a small monomer solution and a mixed solution formed by a reducing agent and a chain transfer agent—are simultaneously added dropwise. After stirring, the mixture is kept at a constant temperature and cooled to room temperature to obtain a mother liquor. Finally, a lignin solution is added to the mother liquor and the pH is adjusted, thereby obtaining a novel water-reducing agent. Using this novel water-reducing agent can reduce the dispersion and air-entraining effect of residual flocculants in manufactured sand by precipitating them, thereby improving the impact of residual flocculants in manufactured sand on concrete performance. Attached Figure Description

[0027] Figure 1 This is a comparative diagram of the flocculant addition test in one embodiment of the present invention;

[0028] Figure 2 This is a state diagram of the flocculant dissolved at 60°C in one embodiment of the present invention;

[0029] Figure 3 This is a comparison diagram of the effect of different flocculant dosages on strength in one embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram of a concrete mixture fresh out of the machine after adding a common water-reducing agent, according to one embodiment of the present invention.

[0031] Figure 5 This is a diagram showing the concrete output from the mixer as shown in one embodiment of the present invention, after being mixed with lignin water-reducing agent.

[0032] Figure 6 This is a schematic diagram showing the required water volume corresponding to different flocculant dosages in one embodiment of the present invention;

[0033] Figure 7 This is a comparative diagram showing the effects of different lignin admixture amounts on concrete strength and water demand in one embodiment of the present invention. Detailed Implementation

[0034] The technical solution of the present invention will be clearly and completely described below with reference to embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0035] The present invention will now be described in detail with reference to the research process of the present invention:

[0036] The purpose of employing the experimental certification method is to effectively address the impact of residual flocculants in manufactured sand on concrete performance through a novel water-reducing agent. This aims to adjust the state of the concrete mixture, increase its slump time and workability, enhance the pumpability of high-performance concrete, and improve its mechanical and durability properties. Currently, most evaluation methods for the application performance of admixtures and cement still rely primarily on cement paste testing. Cement paste refers to a slurry made of cement, water, and admixtures, and the cement paste test only reflects its fluidity.

[0037] 1.1 Raw materials and mix proportions required for the experiment

[0038] The cement used was PO 42.5 cement from the Pengzhou plant of Sichuan Yadong Cement Co., Ltd. The fly ash was Class F, Grade II, from Wenchuan Zhiyu Building Materials Co., Ltd. The aggregates were fine aggregate manufactured sand and crushed stone from Wenchuan Chuaneng Mining Investment and Development Co., Ltd. The water-reducing agent was polycarboxylate water-reducing agent from Xiamen Hongfa, with the following specific test indicators: water reduction rate 28%, bleeding rate 16%, chloride ion content 0.048%, and total alkali content (Na2O + 0.658K2O) 2.25%. The flocculant was 18 million polymer-based flocculant.

[0039] The aggregate gradation is shown in Tables 1 and 2 below. The benchmark mix design is shown in Table 3 below.

[0040] Table 1 Fine aggregate gradation

[0041]

[0042] Table 2 Coarse aggregate gradation

[0043]

[0044] Table 3. C30 Concrete Mix Proportion (Kg / m³) 3 )

[0045] Material cement fly ash sand pebbles water admixtures Dosage 330 58 817 1040 141 5.82

[0046] The admixtures in Table 3 mainly refer to water-reducing agents. However, they are not limited to this; for example, they may also include expanding agents, pumping agents, air-entraining agents, etc. Construction personnel in this field can add them according to the specific project. For example, high-performance expanding agents should be used for steel-concrete composites, pumping agents should be used for ultra-high-rise concrete pouring, and better anti-dispersing agents should be used for underwater concrete. In the embodiments of this invention, the mix proportions in Table 3 are used as the baseline mix proportions.

[0047] 1.2 Test Methods

[0048] Determination of flocculant dissolution temperature: First, the flocculant was dissolved at different temperatures (40℃, 50℃, 60℃, 70℃, 80℃) at a ratio of 1:100. The results showed that at 60℃, the more flocculent precipitates formed, the better the flocculant effect.

[0049] Determining the amount of flocculant added: The effect of adding flocculant to manufactured sand, specifically observed in the following samples... Figure 1 As shown, Figure 1 The results are as follows: no flocculant added; 0.5% flocculant added; 1.0% flocculant added; 1.5% flocculant added. From... Figure 1 It can be seen that in this embodiment, the manufactured sand sample without flocculant was generally turbid, while after adding flocculant, the liquid gradually became clear and liquid again. Comparing the last three samples shows that the flocculation and sedimentation effect is better as the flocculant dosage gradually increases.

[0050] Concrete Experiment: The experiment ultimately determined that the optimal dissolution temperature for anionic 18 million molecular weight polyacrylamide was 60℃. At this temperature, the dissolution rate and sedimentation effect of the flocculant were better; therefore, 60℃ was determined as the optimal dissolution temperature. Figure 2 It is a flocculant that dissolves well at 60℃, such as Figure 2 The material is viscous. Based on the actual moisture content of the manufactured sand on site, it should be controlled to 4%–8% before use. Concrete tests should be conducted according to JTG 3420-2020 "Test Procedures for Cement and Cement Concrete in Highway Engineering". The degree of loss in slump and spread of the concrete mixture should be observed and measured to determine its impact on workability.

[0051] 1.3 Test Results

[0052] First, the dissolved flocculant was adjusted at 60℃. Then, the manufactured sand with a moisture content controlled at 5% was mixed with flocculant of different quantitative concentrations and washed. The overall condition of the mixed concrete mixture is shown in Table 4 below. The water-reducing agent used in this embodiment is ordinary polycarboxylate water-reducing agent, namely Xiamen Hongfa's polycarboxylate water-reducing agent.

[0053] Table 4. Slump and spread of concrete mixtures with different flocculant dosages.

[0054]

[0055] As can be seen from the experimental data in Table 4, the mixing state and slump retention time of both the manufactured sand without flocculant and the manufactured sand washed with flocculant were within the controllable range. This is because, under the action of the flocculant, the silt particles in the manufactured sand, due to the charge effect and the adsorption bridging effect of the long-chain molecular structure, cause the clay particles and hydration products in the manufactured sand to agglomerate, thus preventing the cement paste from flowing. Currently, the 18 million molecular weight anionic polyacrylamide organic polymer flocculant commonly used in existing technologies has a greater impact on the adsorption bridging effect of the water-reducing agent the larger its molecular weight. Based on the mechanism of action of flocculants, flocculants are a type of anionic "admixture." When flocculants are present in manufactured sand, the bidirectional positive and negative charge of the water-reducing agent molecules and ions causes them to aggregate due to attraction from the polymeric flocculant molecules and ions. This disrupts the original stable state, resulting in uneven distribution of polycarboxylate superplasticizer and affecting its effect on the cement paste in concrete. As the flocculant dosage increases, the unattracted flocculants react again with the disrupted molecular and ionic clusters, balancing the charges and gradually returning to the previous state. This gradually increases the fluidity of the cement paste to its limit. Afterward, excess flocculant affects the formation of hydrates, thus gradually reducing the fluidity of the cement paste. Adjusting the dosage of ordinary water-reducing agents makes their working state uncontrollable, leading to segregation due to over-dosing. This essentially fails to meet construction requirements. This is mainly because PAM flocculant, as a high-molecular-weight anionic product, has a strong thickening effect. Although increasing the dosage of water-reducing agent releases some free water and meets the initial performance requirements in a short time, the added water-reducing agent and the released free water will be gradually locked by the flocculant over time. The larger the dosage of this ordinary water-reducing agent, the greater the viscosity of the aggregate will be, resulting in a heavy and non-flowing material. For self-compacting concrete, this will manifest as non-flowing and excessively rapid slump, leading to an unstable state of the concrete and reducing its workability.

[0056] 2. The effect of residual flocculant in manufactured sand on strength

[0057] The basic standard for measuring the workability of concrete is its strength, and the main factor affecting concrete strength is the bonding performance of the concrete raw materials. Therefore, the effect of residual flocculants in manufactured sand on the precipitation of water-reducing agents and manufactured sand in concrete, and the bridging and adsorption effect of flocculants on the cement and fly ash slurry, are particularly important. In this embodiment, manufactured sand containing different amounts of flocculants was mixed into mixtures and made into standard test blocks. After curing under standard conditions, the strength of the test blocks was tested, and the test results are as follows: Figure 3 As shown.

[0058] Figure 3The diagram showing the effect of different flocculant dosages (0–0.35%) on strength in this embodiment is illustrated. Figure 3 It can be seen that the residual flocculant in manufactured sand also has a certain impact on the strength of concrete. After excluding error factors, as the flocculant dosage gradually increases, the overall compressive strength of the concrete specimens gradually decreases. This is because the thickening effect of the flocculant reduces the fluidity and workability of the concrete, increases the water demand and water-reducing agent dosage, leading to an increase in the water-cement ratio, and thus reducing the strength of the concrete. Furthermore, increasing the dosage of water-reducing agent will lock up a large amount of pore water and free water, requiring more free water and admixtures to open up the concrete, thereby affecting the overall workability of the concrete. During the mixing process, it can be clearly observed that the higher the flocculant content, the lower the air content of the concrete, and the more viscous it becomes. Figure 4 This diagram illustrates the state of the concrete mixture immediately after leaving the machine in this example of adding a common water-reducing agent.

[0059] 3. Controllable water-reducing agent to improve the effect of residual flocculant in manufactured sand on concrete performance.

[0060] This project involves long-span bridges requiring retarded concrete with a long slump retention time. After being discharged from the mixer, the manufactured sand undergoes flocculant washing, inevitably leaving residual flocculant. Experiments have shown that ordinary polycarboxylate superplasticizers significantly impact the slump retention time of manufactured sand containing residual flocculant. Ordinary polycarboxylate superplasticizers cannot meet the concrete requirements of this project; therefore, a new superplasticizer formulation is needed. Compared to ordinary polycarboxylate superplasticizers, the novel superplasticizer in this invention is a controllable superplasticizer that can mitigate the impact of residual flocculant in manufactured sand on concrete performance.

[0061] For cast-in-place ultra-retarded concrete, slump retention is the primary requirement, followed by the concrete's condition upon exiting the mixer. The inventors discovered that the air content of concrete gradually exceeds its initial air content over time, sometimes reaching over 9%. This can easily cause pipe blockage and prevent flow during underwater concrete pouring. Extensive testing with manufactured sand revealed that only by replacing the flocculant with a smaller dosage could the air content of the concrete become gradually controllable. Therefore, the reason is that residual flocculant depletes the air-entraining components of the water-reducing agent during the concrete mixing process. Conventional production uses air-entraining agents, often sodium rosinate, modified rosinate salts, or soap-based air-entraining agents. Research has shown that polyacrylamide (a flocculant component) has a dispersing effect on air, which makes the air content of the concrete uncontrollable.

[0062] This invention, through continuous research on how to improve the effect of flocculants on concrete performance, has found that adding a certain amount of calcium lignosulfonate (lignin) to water-reducing agents can reduce the dispersing and air-entraining effects of flocculants, thus acting as an anti-dispersing agent and improving the performance of concrete.

[0063] The molecular structure of calcium lignosulfonate is shown below:

[0064]

[0065] Polyacrylamide (flocculator) has a high molecular structure. Lignin, specifically calcium lignosulfonate, can break down its molecular chains, causing the flocculant to precipitate. Lignin is a brownish-yellow powder that can be extracted from sodium sulfite and pasture. Extraction is possible when the pH is adjusted to 11-12. In this experiment, the inventors found that the addition of flocculant and lignin significantly improved the concrete's condition upon discharge. Research revealed that this is because the sulfite ions in lignin break down the high molecular chains of the flocculant. This improves the workability of concrete, enhances project quality, and, in southern summers, inhibits slump loss and delays setting time. It can also be used in conjunction with high-efficiency water-reducing agents.

[0066] Furthermore, extensive testing has verified that for concrete, the optimal lignin content is 0.15% to 0.3% of the cement content, such as 0.15%, 0.2%, 0.25%, and 0.3%, which achieves better results, superior concrete workability, excellent strength, and lower water requirements. In addition, the inventors conducted numerous comparative experiments, showing that mixing with cement paste can reduce water usage by at least 10 to 14 kg per kilogram of concrete, resulting in a significant reduction in water consumption. Simultaneously, the lignin utilization rate is high, and the concrete can still be used normally after hardening. Figure 5 This is the concrete discharge state after adding calcium lignosulfonate to the water-reducing agent in one embodiment. From Figure 5 It can be seen that the concrete mixed with a water-reducing agent containing lignin can meet the construction requirements in terms of both expansion and slump.

[0067] In summary, the addition of calcium lignosulfonate can significantly improve the workability of concrete. For concrete mixed with manufactured sand containing residual flocculants, calcium lignosulfonate can be added to the water-reducing agent to precipitate the high-molecular-weight polyacrylamide flocculant, thereby increasing the slump retention time and improving the quality of the project to a certain extent. Furthermore, besides the water-reducing agent studied in this invention, other admixtures can also be added to concrete depending on the specific circumstances. For example, high-performance expansive agents can be used for steel-concrete composites, pumping agents can be used for ultra-high-rise concrete pouring, and better anti-dispersing agents can be used for underwater concrete.

[0068] Furthermore, according to experimental results, both polyacrylamide flocculant and calcium lignosulfonate, when added in large quantities, will cause the water demand of the slurry to increase linearly. Figure 6 This example shows the required water volume for different flocculant dosages. Figure 6As shown, after the mixing process, the water demand gradually increases with the increase of flocculant dosage. When the flocculant dosage is 0.35%, the water demand increases to over 158 kg. Therefore, adding calcium lignosulfonate to concrete admixtures allows the wood fibers to disperse the flocculant components in the manufactured sand, thereby precipitating the residual flocculant in the manufactured sand. The water demand and concrete strength caused by the dosage of calcium lignosulfonate will be described in detail later.

[0069] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and various embodiments:

[0070] One embodiment of this application provides a method for preparing a novel water-reducing agent. The method involves first preparing a mother liquor and then adding a lignin solution to the mother liquor. Specifically, it includes the following steps:

[0071] Step 1): Mix the unsaturated polyether macromonomer with water and heat and stir in a constant temperature water bath at 30℃~60℃ until the unsaturated polyether macromonomer is completely dissolved and becomes transparent, obtaining an unsaturated polyether macromonomer solution. Pour the unsaturated polyether macromonomer solution into a reaction vessel, and add an oxidant at 50℃~60℃, for example, 60℃, and stir for 3min~7min, for example, 5min; simultaneously add the unsaturated carboxylic acid monomer solution, a mixed solution of reducing agent and chain transfer agent dropwise into the reaction vessel, stir, and then keep warm; wherein, the dropwise stirring time is 100min~140min, for example, 120min; the holding time is 40min~80min, for example, 60min, and cool to room temperature to obtain the mother liquor.

[0072] Step 2): Add lignin solution to the mother liquor and adjust the pH of the material in the reactor to 11-12 to obtain the novel water-reducing agent.

[0073] In this embodiment, during the synthesis of the novel water-reducing agent, as the conversion rate of the macromonomer increases under stirring conditions, the polymer backbone will become longer and the molecular weight will gradually increase. Based on the conversion state of the macromonomer, it can be deduced that the anion charge density increases with the increase of the proportion of A material added. The degree of lignin decomposition of polyacrylamide gradually increases, thus the residual polyacrylamide can be completely degraded, thereby giving full play to the main role of the macromonomer in the water-reducing agent.

[0074] In a preferred embodiment, the solid content of the mother liquor is designed to be 25%–35%. For example, the solid content of the unsaturated polyether macromonomer solution, the unsaturated carboxylic acid micromonomer solution, and the mixed solution formed by the reducing agent and the chain transfer agent is designed to be 30%. A lower water-cement ratio results in higher strength, which demonstrates the superior effect of water on water-reducing agents. Furthermore, the less water used and the lower the water-cement ratio, the higher the strength of the concrete produced.

[0075] In a preferred embodiment, the amount of lignin solution incorporated into the raw material of the novel water-reducing agent can be 8% to 12% of the mother liquor, for example, 8%, 9%, 10%, 11%, 12%, etc. Lignin is a brownish-yellow powder that can be extracted from sodium sulfite and pasture. Lignin can be extracted by adjusting the pH value to 11-12. This novel water-reducing agent can adjust the state of concrete mixtures, effectively reduce the amount of cementitious materials used in low water-cement ratio high-strength cement concrete, improve the poor workability of concrete due to residual flocculants, enhance the pumpability of high-performance concrete, increase the slump time and workability of concrete mixtures, and improve the mechanical and durability properties of concrete.

[0076] Furthermore, the raw materials of the novel water-reducing agent mainly include unsaturated polyether macromonomers, unsaturated carboxylic acid monomers, reducing agents, chain transfer agents, oxidizing agents, lignin, and pH adjusters. The unsaturated polyether macromonomer is TPEG (methyl allyl polyoxyethylene ether), with an average molecular weight of 1000–16000. The unsaturated carboxylic acid monomer is one or more of acrylic acid, methacrylic acid, and fumaric acid, for example, acrylic acid and methacrylic acid. The chain transfer agent can be thiol acetic acid. Further, the ratio of unsaturated polyether macromonomer to unsaturated carboxylic acid monomer can be controlled at (8–10):1, for example, 9:1. The oxidizing agent is a conventional oxidizing agent, such as hydrogen peroxide or sodium peroxide, with no specific limitation. The reducing agent can be one or two of VC and black shale, preferably VC and black shale, with their ratio controlled at 1.5–1.8:1. This allows the novel water-reducing agent to better improve the impact of residual flocculant in manufactured sand on concrete performance while controlling raw material costs.

[0077] In addition, in optional embodiments, the amount of oxidant can typically be 3 to 4.5 times the amount of reducing agent, without specific limitation. Furthermore, the oxidant can also be 1.0% to 2.0% of the amount of unsaturated polyether macromonomer, for example, 1.56%; the amount of reducing agent can be 0.2% to 0.7% of the amount of unsaturated polyether macromonomer, for example, 0.52%. The amount of chain transfer agent can be adjusted according to specific circumstances, for example, it can be 0.1% to 1.0% of the total amount of the new water-reducing agent raw material, specifically, 0.5%. By controlling the amount of each component in the new water-reducing agent raw material to meet the performance requirements of the water-reducing agent, the influence of residual flocculant in manufactured sand on concrete performance can be improved.

[0078] In addition, in optional embodiments, a surfactant may be added when preparing the unsaturated carboxylic acid monomer solution. Further, an anionic surfactant may be added as a macromonomer stock solution. The anionic surfactant is primarily an epoxy propylene-epoxy ethylene block copolymer, such as a polyoxyethylene-polyoxypropylene block copolymer, an epoxy propylene-epoxy ethylene block copolymer, etc. Further, for example, the amount of anionic surfactant added may be 0.25% to 0.50% of the amount of the unsaturated carboxylic acid monomer; more specifically, if the amount of the unsaturated carboxylic acid monomer is 35g to 55g, the anionic surfactant may be 10g to 25g.

[0079] The present invention will now be described in more detail with reference to two specific embodiments. It should be noted that any content not mentioned in the specific embodiments can be implemented according to the embodiments of this application, and other content not involved are conventional in the art and are not specifically limited.

[0080] In one specific embodiment, the preparation method of the novel water-reducing agent includes the following steps.

[0081] Step 1) Prepare ingredients and prepare mother liquor:

[0082] Ingredients: Base material: TPEG macromonomer and appropriate amount of deionized water. Component A: Acrylic acid and methacrylic acid, and appropriate amount of deionized water; wherein, the ratio of acrylic acid to methacrylic acid is 3:2; (acrylic acid + methacrylic acid): TPEG macromonomer is 9:1. Component B: Vitamin C, vanadium black, chain transfer agent and appropriate amount of deionized water; wherein, the reducing agent is composed of VC and vanadium black in a mass ratio of 1.9:0.8, and the amount of reducing agent can be 0.52% of the mass of TPEG macromonomer.

[0083] Preparation: The base material is heated and stirred in a constant temperature water bath at 50°C until the unsaturated polyether macromonomer is completely dissolved and becomes transparent, thus obtaining a TPEG macromonomer solution; the TPEG macromonomer solution is poured into a reaction vessel, and an oxidant (usually hydrogen peroxide, the amount added is 3 times that of the reducing agent, 1.56%) is added at 60°C and stirred for 5 min; components A and B are simultaneously added dropwise to the reaction vessel and stirred for 120 min, and then kept warm for 60 min; the mother liquor is obtained.

[0084] Step 2) Add lignin solution to prepare a novel water-reducing agent:

[0085] A lignin solution was added to the mother liquor cooled to room temperature, with the addition amount being 10% of the mother liquor. Then, a pH adjuster was added to adjust the pH of the material in the reactor to 11-12, resulting in a novel water-reducing agent.

[0086] In one specific embodiment, the preparation method of the novel water-reducing agent includes the following steps:

[0087] Step 1) Prepare ingredients and prepare mother liquor:

[0088] Ingredients: Base material: TPEG macromonomer and appropriate amount of deionized water. Component A: Acrylic acid, methacrylic acid and appropriate amount of deionized water. Component B: Vitamin C, alum, thioglycolic acid and appropriate amount of deionized water, wherein Vitamin C and alum are used as reducing agents, with a ratio of 1.7:1.

[0089] Preparation: Heat and stir the base material in a water bath at about 50°C until the unsaturated polyether macromonomer TPEG is completely dissolved and becomes transparent. Then pour it into a reaction vessel. Under the condition of 60°C, add the oxidant (sodium peroxide, the amount of which is 3.5 times that of the reducing agent), stir evenly, and add material A + material B at the same time. The addition time is 120 min, and then keep warm for 60 min to obtain the mother liquor.

[0090] Step 2) Add lignin solution to prepare a novel water-reducing agent:

[0091] A lignin solution was added to the mother liquor cooled to room temperature, with the amount added being 10% of the mother liquor. The pH was adjusted to 11-12 to obtain a new type of water-reducing agent.

[0092] One embodiment of this application also provides a method for preparing concrete using the novel water-reducing agent described in this embodiment of the invention. This method aims to reduce the dispersion and air-entraining effect of residual flocculants in manufactured sand by precipitating them with the novel water-reducing agent, thereby improving the impact of residual flocculants in the manufactured sand on concrete performance. The raw materials of the concrete mainly include: cement, fly ash, manufactured sand, aggregate, water, and the novel water-reducing agent of this invention. The manufactured sand can be manufactured sand treated with a flocculant. Of course, the raw materials for concrete are not limited to this and may also include other admixtures.

[0093] In a preferred embodiment, for concrete, the amount of lignin (calcium lignosulfonate) is 0.15-0.3% of the cementitious components in the concrete. Here, lignin refers to the original component content, not the amount added in the solution. The inventors of this application conducted experiments on the amount of lignin in concrete, with the concrete mix proportions based on Table 3. Figure 7 The diagram shows the relationship between the dosage of calcium lignosulfonate, the water requirement of concrete, and the concrete strength in this embodiment. The dosage of calcium lignosulfonate in the diagram represents the proportion of lignin in the cementitious components of the concrete. From... Figure 7 It can be seen that when the calcium lignosulfonate content is 0.15 to 0.3% of the cement component in the concrete, the water requirement is 120 to 130 kg, the 7-day strength of the concrete is greater than 50 MPa, the 28-day strength is greater than 59 MPa, and the workability of the concrete is also greatly improved, with good fluidity.

[0094] Furthermore, the inventors also studied the low water-cement ratio and high strength performance exhibited by the novel water-reducing agent of this invention under different water-cement ratios. No flocculant was added in the experiment; the mix proportions in Table 3 were used as the baseline mix proportions, the difference being the preparation of concrete with different water-cement ratios. The workability and mechanical properties of four groups of cement concrete with different water-cement ratios were tested, and the test results are shown in Table 5 below:

[0095] Table 5 Performance test results of cement concrete with different water-cement ratios prepared with the new polycarboxylate superplasticizer

[0096]

[0097] As shown in Table 5, the novel water-reducing agent can improve the strength of concrete mixes with low water-cement ratios (0.34–0.40). Using the novel water-reducing agent of this invention to prepare cement concrete effectively makes it possible to reduce the amount of cementitious materials used in high-strength cement concrete with low water-cement ratios. This improves the poor workability of concrete caused by residual flocculant, achieving the goal of both reducing the amount of cementitious materials used and meeting the workability requirements of cement concrete.

[0098] In an optional embodiment, experiments were conducted using manufactured sand treated with a flocculant and the novel water-reducing agent of this invention to prepare cement concrete, with the mix proportions also based on Table 3. The dosage of the novel water-reducing agent in the cement concrete was determined to be 1.0–1.7%, with a more preferred dosage of 1.2–1.6%. The performance test results of the cement concrete prepared with the novel water-reducing agent are shown in Table 6.

[0099] Table 6 Performance test results of cement concrete prepared with the addition of the new water-reducing agent

[0100]

[0101] As can be seen from Table 6, when the dosage of the new water-reducing agent in concrete is in the range of 1.2% to 1.6%, it effectively improves the poor workability of concrete caused by residual flocculant. The spread and slump can both meet the construction requirements of concrete, the fluidity is good, the pumpability of high-performance concrete is enhanced, the water demand is reduced, and the mechanical properties of concrete are improved compared with ordinary water-reducing agents, especially the 28-day strength.

[0102] Based on the above research, according to some embodiments of the present invention, a novel water-reducing agent was prepared using unsaturated polyether macromonomers, unsaturated carboxylic acid micromonomers, oxidants, reducing agents, chain transfer agents, and lignin as main raw materials, and employing the specific preparation method described above. When this novel water-reducing agent is used to prepare cement concrete, it can reduce the dispersion and air-entraining effect of residual flocculants in the manufactured sand by precipitating them, thereby improving the impact of residual flocculants in the manufactured sand on concrete performance. Specifically, during the synthesis of the novel water-reducing agent, as the conversion rate of the macromonomer continuously increases under stirring conditions, the polymer backbone continuously lengthens, and the molecular weight gradually increases. Based on the conversion state of the macromonomer, it can be deduced that the anionic charge density continuously increases with the increase of component A, and the degree of lignin decomposition of polyacrylamide gradually enhances, thus completely degrading the residual polyacrylamide. For example, it can adjust the state of concrete mixtures, effectively reducing the amount of cementitious materials used in low water-cement ratio high-strength cement concrete; improve the poor workability of concrete due to residual flocculants, enhancing the pumpability of high-performance concrete; increase the slump time and workability of concrete mixtures, enhancing the pumpability of high-performance concrete, and improving its mechanical and durability properties. Furthermore, the novel water-reducing agent provided in this invention is particularly preferred for bridge piers, cap beams, and other projects constructed using "long-distance concrete delivery" technology.

[0103] The description of this invention is given for illustrative and descriptive purposes only and is not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A method for preparing a novel water-reducing agent that improves the effect of residual flocculant in manufactured sand on concrete performance, characterized in that, The preparation method includes: The unsaturated polyether macromonomer solution was poured into a reaction vessel, and an oxidant was added and stirred at 50℃~60℃. At the same time, an unsaturated carboxylic acid small monomer solution and a mixed solution of reducing agent and chain transfer agent were added dropwise to the reaction vessel and stirred. After keeping warm, the mixture was cooled to room temperature to obtain the mother liquor. A lignin solution was added to the mother liquor, and the pH of the material in the reactor was adjusted to 11-12 to obtain the novel water-reducing agent. The lignin solution was obtained by extraction with sodium sulfite and forage.

2. The preparation method of the novel water-reducing agent according to claim 1, characterized in that, When preparing the mother liquor, the solid content of each solution is 25% to 35%.

3. The preparation method of the novel water-reducing agent according to claim 1, characterized in that, The amount of lignin solution incorporated is 8-12% of the total amount of mother liquor.

4. The method for preparing the novel water-reducing agent according to any one of claims 1-3, characterized in that, When preparing the mother liquor, stir for 3 min to 7 min after adding the oxidant; when simultaneously adding the unsaturated carboxylic acid monomer solution and the mixed solution of reducing agent and chain transfer agent dropwise into the reaction vessel, the addition and stirring time is 100 min to 140 min, and the holding time is 40 min to 80 min. And / or, the preparation method further includes the step of preparing an unsaturated polyether macromonomer solution, wherein preparing the unsaturated polyether macromonomer solution includes: mixing the unsaturated polyether macromonomer with water and heating and stirring in a constant temperature water bath at 30℃~60℃ until the unsaturated polyether macromonomer is completely dissolved to obtain the unsaturated polyether macromonomer solution.

5. The method for preparing the novel water-reducing agent according to any one of claims 1-3, characterized in that, The unsaturated polyether macromonomer is TPEG with an average molecular weight of 1000-16000; the unsaturated carboxylic acid micromonomer is one or more of acrylic acid, methacrylic acid, and fumaric acid. And / or, the ratio of the unsaturated polyether macromonomer to the unsaturated carboxylic acid micromonomer is (8-10):

1.

6. The method for preparing the novel water-reducing agent according to any one of claims 1-3, characterized in that, Anionic surfactants are also added during the preparation of the unsaturated carboxylic acid monomer solution.

7. The method for preparing the novel water-reducing agent according to any one of claims 1-3, characterized in that, The ratio of the oxidant to the reducing agent is 3-4.5:1; The reducing agent is VC and ferrous sulfate in a ratio of 1.5 to 1.8:

1.

8. A novel water-reducing agent prepared by the method according to any one of claims 1-7.

9. The application of the novel water-reducing agent according to claim 8, characterized in that, Used in the preparation of concrete, the novel water-reducing agent improves the effect of residual flocculant in manufactured sand on concrete performance; The amount of lignin incorporated is 0.15 to 0.3% of the amount of cement components in the concrete.

10. The application of the novel water-reducing agent according to claim 9, characterized in that, The novel water-reducing agent is incorporated into the concrete at a dosage of 1.0–1.7%.

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