Water reducing agent applied to pipe pile and preparation process thereof

Abstract

This invention discloses a water-reducing agent for use in pipe piles and its preparation process. The water-reducing agent is composed of 65-75 parts of polycarboxylate mother liquor, 0.02-0.05 parts of defoamer, and 1-5 parts of ultrafine admixture. The polycarboxylate mother liquor is used to construct the initial high flow and rapid centrifugal setting rheological properties, which rapidly increases the yield stress of the slurry while meeting the material distribution requirements, eliminating residual slurry precipitation, and achieving clean production and raw material savings. Simultaneously, the micro-filling effect of the ultrafine admixture and the degassing effect of the defoamer further eliminate centrifugal bubbles and densify the microstructure, solving the problem of loose inner wall and uneven wall thickness of the pipe pile caused by residual slurry loss, significantly improving the physical quality and durability of the pipe pile.

Description

Technical Field

[0001] This invention relates to the field of water-reducing agent technology, specifically to a water-reducing agent for use in pipe piles and its preparation process. Background Technology

[0002] Prestressed concrete pipe piles are generally produced using high-speed centrifugal molding, which relies on high-efficiency water-reducing agents to achieve high strength and early strength at low water-cement ratios. Existing technologies often use polycarboxylate-based water-reducing agents combined with ordinary early-strength agents (such as sodium sulfate). The core drawback is the difficulty in balancing "material flowability" and "centrifugal slurry retention": to ensure uniform material distribution, existing formulations often have excessive slump retention, causing the concrete slurry to remain fluid during high-speed centrifugation. A large amount of cement slurry and fine particles are thrown out with the water, resulting in severe residual slurry precipitation.

[0003] This not only wastes raw materials and pollutes the environment, but also leads to quality problems such as loose inner walls, uneven wall thickness and insufficient protective layer of pipe piles; while simply increasing the setting-promoting components to suppress residual slurry can easily cause the concrete to set too early, resulting in difficulties in material placement or failure to form. Summary of the Invention

[0004] The present invention aims to provide a water-reducing agent for use in pipe piles and its preparation process, which solves the problems of loose inner wall and uneven wall thickness of pipe piles caused by residual slurry loss, and significantly improves the physical quality and durability of pipe piles.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a water-reducing agent for use in pipe piles, characterized in that the water-reducing agent comprises the following components in mass percentage: polycarboxylate water-reducing agent mother liquor: 65-75 parts; defoamer: 0.02-0.05 parts; ultrafine admixture: 1-5 parts; the balance being water.

[0006] Preferably, the defoamer is a modified polysiloxane defoamer.

[0007] Preferably, the solid content of the polycarboxylate superplasticizer mother liquor is 40 parts ± 1 part.

[0008] Preferably, the water-reducing agent has a pH value of 6.5 to 7.5.

[0009] On the other hand, this invention proposes a preparation process for a water-reducing agent applied to pipe piles, comprising the following steps: The polycarboxylic acid monomers were purified, the functional small monomers were metered and premixed, a composite initiator system was prepared, and the reaction medium water was purified and the temperature was pre-adjusted to obtain a pretreated monomer mixture, an initiator solution, and bottom water preheated to 55°C. A portion of the initiator solution was added to the bottom water to initiate the reaction. After generating initial free radicals, the monomer mixture was added dropwise to the reaction system at a constant rate. The reaction temperature was controlled at 60°C to 65°C to carry out the chain growth reaction. After the dropwise addition was completed, the temperature was raised to 68°C and kept for 2 hours to mature. Finally, the temperature was lowered to below 40°C to obtain the polycarboxylate superplasticizer mother liquor. An antifoaming emulsion is added, followed by an ultrafine admixture made from nano-silica, fluorogypsum, and mineral powder. Finally, the mixture is homogenized and conditioned to obtain the water-reducing agent used in pipe piles.

[0010] Preferably, the polycarboxylic acid monomer is methyl allyl polyoxyethylene ether or isobutylene polyoxyethylene ether.

[0011] Preferably, the chain growth reaction is added over a period of 3 hours, and the stirring speed is controlled at 80 revolutions per minute during the heat preservation and maturation period.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a water-reducing agent for use in pipe piles, comprising 65-75 parts of polycarboxylate mother liquor, 2.0-3.0 parts, 0.02-0.05 parts of defoamer, and 1-5 parts of ultrafine admixture. The polycarboxylate mother liquor is used to construct the initial high flow and rapid centrifugal setting rheological properties, which rapidly increases the yield stress of the slurry while meeting the material distribution requirements, eliminating residual slurry precipitation, and achieving clean production and raw material savings. Simultaneously, the micro-filling effect of the ultrafine admixture and the degassing effect of the defoamer further eliminate centrifugal bubbles and densify the microstructure, solving the problems of loose inner wall and uneven wall thickness of pipe piles caused by residual slurry loss, significantly improving the physical quality and durability of the pipe pile. Attached Figure Description

[0013] Figure 1 This is a process flow diagram of the water reduction preparation technology of the present invention applied to pipe piles. Detailed Implementation

[0014] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0015] This invention provides a water-reducing agent for use in pipe piles, the water-reducing agent comprising the following components by mass percentage: polycarboxylate superplasticizer mother liquor: 65-75 parts; defoamer: 0.02-0.05 parts; ultrafine admixture: 1-5 parts; the balance being water.

[0016] In the first embodiment, the water-reducing agent comprises the following components by mass percentage: polycarboxylate water-reducing agent mother liquor: 65 parts; defoamer: 0.02 parts; ultrafine admixture: 1 part; the balance being water.

[0017] The defoamer is a modified polysiloxane defoamer. The solid content of the polycarboxylate superplasticizer mother liquor is 40 parts. The pH value of the superplasticizer is 6.5.

[0018] In the second embodiment, the water-reducing agent comprises the following components by mass percentage: polycarboxylate water-reducing agent mother liquor: 70 parts; defoamer: 0.04 parts; ultrafine admixture: 3 parts; the balance being water.

[0019] The defoamer is a modified polysiloxane defoamer. The solid content of the polycarboxylate superplasticizer mother liquor is 40 parts to 1 part. The pH value of the superplasticizer is 7.

[0020] In the third embodiment, the water-reducing agent comprises the following components by mass percentage: polycarboxylate superplasticizer mother liquor: 75 parts; defoamer: 0.05 parts; ultrafine admixture: 5 parts; the balance being water. The defoamer is a modified polysiloxane defoamer. The solid content of the polycarboxylate superplasticizer mother liquor is 39 parts. The pH value of the water-reducing agent is 7.5.

[0021] like Figure 1 As shown, the preparation process of the water-reducing agent in Examples 1 to 3 above is as follows: Selection and pretreatment of basic raw materials: The polycarboxylic acid monomers are purified, the functional small monomers are metered and premixed, a composite initiator system is prepared, and the reaction medium water is purified and the temperature is pre-adjusted to obtain the pretreated monomer mixture, initiator solution and bottom water preheated to 55°C. Implementation of controlled free radical polymerization: A portion of the initiator solution is added to the bottom water for bottom water initiation. After the initial free radicals are generated, the monomer mixture is added dropwise to the reaction system at a constant rate. The reaction temperature is controlled at 60°C to 65°C for chain growth reaction. After the dropwise addition is completed, the temperature is raised to 68°C and kept for 2 hours for curing. Finally, the temperature is lowered to below 40°C to obtain polycarboxylate superplasticizer mother liquor. Directional compounding and early regulation of functional components: Add defoamer emulsion, then add ultrafine admixture made of nano silica, fluorogypsum and mineral powder, and finally homogenize and regulate to obtain the water-reducing agent applied to pipe piles.

[0022] Furthermore, to more clearly explain the preparation process of the water-reducing agent, the following detailed explanation is provided in conjunction with specific methods: Step 1: Selection and Pre-treatment of Basic Raw Materials This step, as the starting point of the entire preparation process, has the core task of providing high-quality, high-purity basic raw materials for subsequent synthesis and compounding reactions.

[0023] Step 1.1: High-purity screening and impurity removal of polycarboxylate monomers First, it is necessary to strictly screen the polycarboxylate monomers that serve as the main skeleton of the water-reducing agent. In this embodiment, the polycarboxylate monomers selected are mainly methyl allyl polyoxyethylene ether (TPEG) or isobutylene polyoxyethylene ether (HPEG). These macromonomers have excellent side chain structures and can provide strong steric hindrance effects.

[0024] In practice, the macromonomer raw material needs to be filtered through multiple stages to remove any mechanical impurities and unreacted polymer gel particles. Subsequently, the macromonomer undergoes a slight heat treatment using a vacuum distillation apparatus to remove residual trace amounts of moisture and low-boiling-point impurities, ensuring a purity of at least 99.5 parts per million. After this step, the macromonomer exhibits significantly improved transparency and more uniform flowability.

[0025] Step 1.2: Metering and premixing of functional monomers Based on the requirements of rapid demolding and high early strength in pipe pile concrete, this embodiment selects acrylic acid (AA) as the main comonomer, while introducing a small amount of sodium methacrylate sulfonate (SMS) to introduce sulfonic acid groups and enhance the dispersion stability of the water-reducing agent under low water-cement ratio conditions. Operators need to weigh acrylic acid and sodium methacrylate sulfonate separately using an electronic scale according to the preset molar ratio. Then, the prepared macromonomer is slowly added to the mixing tank, and a low-speed agitator is started to allow the macromonomer and small monomer to undergo preliminary physical mixing at room temperature. The stirring speed during this process needs to be controlled between 60 and 80 revolutions per minute to ensure sufficient contact between the two monomers while avoiding the introduction of excessive air bubbles through vigorous stirring. Through this premixing step, a homogeneous monomer solution is formed, in which the long polyoxyethylene chains of the macromonomer and the active double bonds of the small monomer achieve preliminary interweaving at the microscopic level.

[0026] Step 1.3: Preparation and activation of the composite initiator system First, dissolve ammonium persulfate and sodium bisulfite separately in deionized water to prepare aqueous solutions of 10 parts each. During this process, the water temperature must be controlled below 25 degrees Celsius to prevent premature decomposition and inactivation of the initiator. Then, mix the two solutions in a specific ratio; however, a vigorous reaction does not occur immediately, but rather a latent initiation system is formed. The initiator solutions prepared in this step must be prepared fresh and used immediately, and stored under light-protected conditions to ensure they maintain maximum activity when added to the reaction vessel.

[0027] Step 1.4: Purification and temperature pre-regulation of the reaction medium, water. This embodiment uses deionized water with a resistivity greater than 18 megohm-cm as the reaction medium to eliminate the interference of metal ions in the water on the catalysis or inhibition of the polymerization reaction. During operation, a measured amount of deionized water is injected into the polymerization reactor equipped with a jacketed temperature control system. Then, the temperature control system is activated, gradually raising the water temperature inside the reactor to the preset initial reaction temperature, which is set at 55 degrees Celsius. This temperature selection is not arbitrary but determined based on the activation energy characteristics of the composite initiation system in step 1.3. 55 degrees Celsius ensures that the initiator begins to slowly decompose and release free radicals without causing the reaction to become too violent and out of control. During the process of reaching water temperature equilibrium, the bottom valve circulation pump of the reactor is also turned on to create weak convection in the water inside the reactor, ensuring a uniform temperature at all points and eliminating local hot spots. When the water temperature stabilizes at 55 degrees Celsius and the water quality test is qualified, it signifies that all the preparations in step one are complete, and a constant-temperature and pure reaction environment has been formed inside the reactor, awaiting the addition of monomers.

[0028] Step Two: Implementation of Controlled Free Radical Polymerization After the selection, pretreatment, and setup of all raw materials, the core chemical synthesis stage begins, namely the implementation of controlled free radical polymerization. This step is crucial for converting the previously physically mixed monomers into a polycarboxylate superplasticizer mother liquor with specific molecular structures and functional properties. The precision of the polymerization reaction directly determines the molecular weight, branching degree, and functional group distribution of the superplasticizer molecules, thus affecting its adsorption behavior and dispersion effect in pipe pile concrete.

[0029] Step 2.1: Bottom water initiation and generation of initial free radicals First, a bottom water initiation operation is performed to establish an initial free radical concentration in the reaction system before the monomer is added. The operator increases the stirring speed of the bottom water prepared in step 1.4 to 120 rpm to enhance heat and mass transfer efficiency. Then, five parts of the total amount of the composite initiator solution prepared in step 1.3 are added dropwise to the reactor as a bottom initiator. This small amount of initiator, upon entering the high-temperature bottom water, rapidly undergoes a redox reaction, releasing primary free radicals. These free radicals are evenly distributed in the water, forming an invisible but highly chemically active "initiation network." At this point, the temperature inside the reactor will rise slightly due to slight exothermic reaction, requiring immediate intervention from the control system. Fine-tuning is performed using the jacket cooling water to maintain the temperature within the range of 55 to 58 degrees Celsius.

[0030] Step 2.2: Constant-rate addition of monomer solution and chain growth control After establishing a stable initial free radical environment, the monomer solution is added dropwise. The premixed monomer solution from step 1.2 is poured into a high-level dropping tank, the dropping valve is opened, and the dropping time is set to 3 hours to ensure that the monomer flows into the reactor at a constant rate. During the dropping process, the principle of "slow and uniform" must be followed, and the dropping rate must match the rate of consumption of free radicals generated in step 2.1. As the monomer solution is continuously added, free radicals attack the monomer double bonds, initiating a chain reaction, and the polymer molecular chains begin to gradually extend in the solution. At this time, the temperature inside the reactor will show an upward trend due to the exothermic polymerization. The temperature control system needs to dynamically adjust the flow rate of the jacket cooling water to strictly lock the reaction temperature between 60 and 65 degrees Celsius. Temperature control is crucial; too high a temperature will lead to accelerated chain termination reaction and a decrease in molecular weight; too low a temperature will result in a slow reaction rate and low conversion rate. In the first hour of dropping, the main polymer backbone is formed; in the following two hours, the side chains gradually graft and improve, forming a three-dimensional comb-like structure. Throughout the dropwise addition process, samples must be taken every 15 minutes to test the viscosity and conversion rate to ensure that the reaction progresses as expected.

[0031] Step 2.3: Constant temperature curing and elimination of residual monomers After the monomer addition in step 2.2 is completed, the reaction does not terminate immediately, but enters the isothermal curing stage in step 2.3. The main purpose of this stage is to utilize the remaining initiator and heat energy in the system to encourage the unreacted residual monomers to continue participating in the polymerization reaction, thereby increasing the monomer conversion rate and making the polymer molecular chain structure more regular and stable.

[0032] Operationally, the reactor temperature is raised to 68 degrees Celsius and maintained at a constant temperature with stirring for 2 hours. During this process, the small amount of monomers that failed to react in step 2.2 and the shorter-active free radical segments gain sufficient energy under high temperature conditions to continue colliding and combining. During the heat preservation period, the stirring speed needs to be appropriately reduced to 80 revolutions per minute to reduce the damage of shear forces to the already formed long molecular chains.

[0033] Step 2.4: Determining the reaction endpoint and initial cooling treatment After sufficient heat preservation and maturation in step 2.3, step 2.4 is responsible for confirming the reaction endpoint and performing preliminary cooling treatment, marking the successful completion of the polymerization synthesis stage. Operators take samples again for comprehensive performance testing, focusing on solid content, pH value, and residual monomer content. When the test data shows that the solid content reaches the design standard (usually 40 parts ± 1 part), the pH value is stable between 6.5 and 7.5, and the residual monomer content is less than 0.05 parts, the polymerization reaction can be determined to have reached its endpoint. At this point, the heating system is immediately shut off, and the maximum flow rate of cooling water circulation is started to rapidly reduce the material temperature in the reactor from 68 degrees Celsius to below 40 degrees Celsius. The purpose of rapid cooling is to "freeze" the conformation of the polymer molecules, preventing molecular chain degradation or cross-linking side reactions caused by prolonged exposure to high temperatures. During the cooling process, stirring must not be stopped to prevent localized overheating or material stratification. When the material temperature drops to near room temperature, the originally transparent and viscous liquid becomes clearer, and its fluidity stabilizes, indicating that the polycarboxylate superplasticizer mother liquor with the predetermined molecular structure has been successfully synthesized.

[0034] Step 3: Targeted compounding and early regulation of functional components The core task of this step is to introduce specific early-strength components and auxiliary functional materials into the mother liquor, and through physical compounding and chemical synergy, endow the water-reducing agent with special properties that promote early cement hydration and inhibit the precipitation of excess slurry.

[0035] In this embodiment, a modified polysiloxane defoamer is used in extremely small amounts, only 0.02 to 0.05 parts by total mass. Since defoamers are generally insoluble in water, direct addition would cause floating or agglomeration. Therefore, it is necessary to pre-emulsify it with a small amount of nonionic surfactant to form a stable emulsion. Then, the defoamer emulsion is slowly added in a thin stream under low-speed stirring. The stirring speed should be controlled at approximately 50 revolutions per minute; excessively rapid stirring will re-enter air into the liquid, negating the effect of the defoamer.

[0036] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A water-reducing agent for use in pipe piles, characterized in that, The water-reducing agent comprises the following components by mass percentage: Polycarboxylate superplasticizer mother liquor: 65-75 parts; Defoamer: 0.02-0.05 parts; Ultrafine admixture: 1-5 parts; The remainder is water.

2. The water-reducing agent for use in pipe piles according to claim 1, characterized in that, The defoamer is a modified polysiloxane defoamer.

3. The water-reducing agent for use in pipe piles according to claim 1, characterized in that, The solid content of the polycarboxylate superplasticizer mother liquor is 40 parts ± 1 part.

4. The water-reducing agent for use in pipe piles according to claim 1, characterized in that, The water-reducing agent has a pH value of 6.5 to 7.

5.

5. A process for preparing the water-reducing agent as described in any one of claims 1-4, characterized in that, Includes the following steps: The polycarboxylic acid monomers were purified, the functional small monomers were metered and premixed, a composite initiator system was prepared, and the reaction medium water was purified and the temperature was pre-adjusted to obtain a pretreated monomer mixture, an initiator solution, and bottom water preheated to 55°C. A portion of the initiator solution was added to the bottom water to initiate the reaction. After generating initial free radicals, the monomer mixture was added dropwise to the reaction system at a constant rate. The reaction temperature was controlled at 60°C to 65°C to carry out the chain growth reaction. After the dropwise addition was completed, the temperature was raised to 68°C and kept for 2 hours to mature. Finally, the temperature was lowered to below 40°C to obtain the polycarboxylate superplasticizer mother liquor. Add defoamer emulsion and ultrafine admixture, and finally homogenize and regulate to obtain the water-reducing agent applied to pipe piles.

6. The process according to claim 5, characterized in that, The polycarboxylic acid monomer is methyl allyl polyoxyethylene ether or isobutylene polyoxyethylene ether.

7. The process according to claim 5, characterized in that, The chain growth reaction was added over a period of 3 hours, and the stirring speed was controlled at 80 revolutions per minute during the heat preservation and maturation period.

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