Method for improving rheological property of concrete

Abstract

The invention belongs to the technical field of building materials, and provides a method for improving the rheological property of concrete, which comprises the following steps: preparing the following raw materials in parts by weight: 500-1500 parts of cement and 1000-1500 parts of sand; 100 to 500 parts of water; 0.45 to 15 parts of a polycarboxylic acid type water reducing agent; 0.01 to 2.5 parts of isopentenol polyoxyethylene ether (IPEG); the preparation method comprises the following steps: pre-mixing a polycarboxylic acid water reducer and IPEG into water to obtain an admixture mixed solution, and the use amount of the water is 15-35% of the total use amount of the water; cement and sand are premixed, a premix is obtained, and the admixture mixed liquid and water are added into the premix together; all the components are mixed to be uniform. According to the method for improving the rheological property of the concrete, the workability, the coagulation characteristic and the strength development of the concrete are remarkably improved; the method is applied to tubular pile concrete, the early strength is increased, and the rheological property is improved; the water bleeding and segregation are reduced, the homogeneity of the concrete is improved, the setting time is shortened, and favorable conditions are provided for avoiding the steam curing step; the early strength development and the later strength can be simultaneously improved, and the concrete is suitable for concrete with early strength requirements.

Description

Technical Field

[0001] The invention belongs to the field of building materials, and specifically relates to the technical field of concrete admixtures. Background Art

[0002] PC (precast concrete) is a prestressed concrete that is used to compensate for the premature cracking of concrete. Before the component is used, a prestress is applied to the concrete. That is, the steel bars are artificially tensioned in the tensile zone of the concrete, and the shrinkage force of the steel bars is used to pre-stress the tensile zone of the concrete. When the component is subjected to the tensile force generated by external loads, the stored prestress first offsets the prestress in the concrete in the tensile zone, and then the concrete is tensile as the load increases. This limits the elongation of the concrete and delays or prevents the appearance of cracks.

[0003] Polycarboxylate water reducer (PCE) is an anionic surfactant used as a concrete admixture. It disperses cement particles after being added to concrete mixtures, reduces unit water consumption, and is beneficial to improving the fluidity of concrete. However, if the fluidity of concrete is too large or gradually increases, it may increase the risk of bleeding and segregation, which in turn affects the operation and molding of concrete, as well as its homogeneity, and ultimately affects the strength and durability of concrete. Moreover, admixtures may sometimes cause the setting time of concrete to be too long, which is not conducive to the development of early strength of concrete.

[0004] Therefore, it is necessary to further improve the concrete system with polycarboxylic acid-based water reducers to reduce the risk of increased initial fluidity of concrete, so as to adapt to the application range of prestressed concrete and pipe pile concrete with early strength requirements. Summary of the invention

[0005] In order to solve the above-mentioned problems of the prior art, the present invention provides a method for improving the rheological properties of concrete, adjusting the initial fluidity of concrete, reducing the risk of increased initial fluidity of concrete, and improving the homogeneity and durability of concrete and its early strength.

[0006] The object of the present invention is to provide a method for improving the rheological properties of concrete, comprising the following steps:

[0007] (1) Prepare raw materials containing the following parts by weight: cement: 500-1500 parts, sand: 1000-1500 parts; water: 100-500 parts; polycarboxylic acid water reducer: 0.45-15 parts; isopentanol polyoxyethylene ether IPEG: 0.01-2.5 parts;

[0008] (2) premixing a polycarboxylic acid water reducer and isopentanol polyoxyethylene ether (IPEG) into water to obtain an admixture mixture, wherein the amount of water is 15-35% of the total amount of water;

[0009] (3) Premixing cement and sand to obtain a premix, adding the admixture mixture from step (2) together with water to the premix, and mixing the components until uniform.

[0010] Furthermore, the molecular weight of isopentanol polyoxyethylene ether IPEG is 2000-3000.

[0011] Furthermore, the molecular weight of isopentanol polyoxyethylene ether IPEG is 2200-2600.

[0012] Furthermore, the dosage of isopentanol polyoxyethylene ether IPEG is 3%-15% of the weight of the polycarboxylic acid water reducer.

[0013] Preferably, the amount of isopentanol polyoxyethylene ether IPEG is 4%-6% by weight of the polycarboxylic acid water reducer.

[0014] The present invention also aims to apply the above method for improving the rheological properties of concrete to prestressed concrete.

[0015] The present invention also aims to apply the above method for improving the rheological properties of concrete to pipe pile concrete.

[0016] The method for improving the rheological properties of concrete of the present invention has the following advantages:

[0017] (1) Enhanced particle dispersion: ① Steric hindrance: When IPEG monomers are integrated into polycarboxylic acid superplasticizers, they provide significant steric hindrance. This means that the polymer chains extend outward from the cement particles, preventing them from agglomerating together. This continuous separation can maintain the fluidity of the mixture for a long time; ② Electrostatic repulsion: IPEG enhances the electrostatic repulsion between cement particles. The negatively charged carboxylic acid groups in the superplasticizer repel each other, further separating the particles and preventing early agglomeration, which is a key factor in maintaining processability.

[0018] (2) Molecular weight effect: Molecular weight: The specific molecular weight range of IPEG (e.g., Mw = 2400) plays a crucial role. The higher the molecular weight, the more effective adsorption and better dispersibility it can provide. This specific molecular weight and molecular configuration will make the slump more stable over time. Other admixtures without this specific molecular configuration may not provide the same level of performance, resulting in a higher slump increase, because they may not be able to effectively maintain dispersibility.

[0019] (3) Chemical structure and interaction: IPEG itself does not undergo obvious chemical reaction in the system, but its presence in the high-efficiency water reducer formula improves the overall performance by improving the interaction between the high-efficiency water reducer and cement particles. With the help of IPEG, the polycarboxylic acid chains in the high-efficiency water reducer are anchored on the cement particles and extend into the water phase, forming a network that keeps the particles separated and evenly dispersed.

[0020] (4) Thom Effect - Unreacted IPEG macromer contributes to various properties such as rheology (handling properties). Dr. Ohta (Pozzol ith Japan) and Professor Sakai (Tokyo Institute of Technology) state that unreacted macromer produces a "Thom effect". "In 1948, Thoms experimentally discovered that adding a small amount of polymer (parts per million by weight) to a turbulent Newtonian solvent, thereby producing a non-Newtonian fluid solution, can reduce the friction of the surface against the stationary surface by up to 80%. Unreacted IPEG macromer controls the adsorption rate of PCE (the rate at which cement particles are adsorbed), which may lead to the inhibition of slump gain. As mentioned above, the strength tends to increase with the enhancement of particle dispersion and molecular weight effects, especially with the increase in the amount of surfactant (such as EO). IPEG-2400 has no retarding effect, so it is believed that the strength may become higher due to surfactant (such as EO).

[0021] Compared with the prior art, the method for improving the rheological properties of concrete in the present invention is as follows:

[0022] (1) By adding IPEG to the concrete system, IPEG is unreacted in the system, which adjusts the initial fluidity of the concrete system containing polycarboxylate water reducer, reduces the increase in concrete fluidity, and significantly improves the workability, homogeneity, setting characteristics, strength development and durability of the concrete;

[0023] (2) This method is applied to prestressed concrete and pipe pile concrete, which significantly improves their rheological properties and makes them more stable;

[0024] (3) The method of the present invention reduces the bleeding and segregation of concrete, improves the homogeneity of concrete, shortens the setting time, and can simultaneously improve the early strength development and late strength. It is suitable for concrete with early strength requirements and provides favorable conditions for eliminating the steam curing step. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a comparison chart of mortar fluidity between the experimental group and the control group of Example 1;

[0026] Figure 2 This is a comparison chart of the coagulation time of the experimental group and the control group in Example 1;

[0027] Figure 3 This is a comparison chart of the compressive strength of the experimental group and the control group of Example 1;

[0028] Figure 4 This is a comparison chart of mortar fluidity between the experimental group and the control group of Example 2;

[0029] Figure 5 This is a comparison chart of the coagulation time of the experimental group and the control group in Example 2;

[0030] Figure 6 This is a comparison chart of the compressive strength of the experimental group and the control group in Example 2. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Method used in the embodiment of the present invention

[0033] 1. Preparation of Mixtures: Each mix is ​​prepared using standardized procedures to ensure consistency across all batches. Cement, sand and additives are accurately weighed, and water is measured to keep the dosage of all mixes accurate.

[0034] First, cement and sand were added to the mixing bowl, and then the admixtures were added to the mix along with 25% of IPEG and water, and the unadded water was added gradually. Cement and sand were premixed for 5 seconds before adding water and admixtures. The components were mixed using a mechanical mixer at a controlled speed of 281 rpm and a duration of 3 minutes to achieve a uniform consistency.

[0035] 2. Construction performance testing: Use a flow cone to test fluidity immediately after mixing, and evaluate the workability of each mixture every 1 hour, 2 hours and 3 hours to determine the effect of IPEG on workability over time. The initial workability of the first group of mixtures (control mixtures) was fine-tuned by changing the water content to achieve a flow diameter of 270 mm. Subsequent mixes will maintain a consistent water-cement ratio with the first group of mixtures.

[0036] 3. Setting time: Use ASTM C191 (Standard Test Method for Setting Time of Hydraulic Cement by Vicat Needle) to determine the initial and final setting times and compare how IPEG affects the setting of concrete.

[0037] 4. Compressive strength test: Compressive strength tests were performed at specified time intervals (1, 3, and 28 days) to evaluate the effects of different IPEG 2400 doses on the rate and extent of strength development.

[0038] 5. Polymer molecular weight determination: Use GPC equipment, such as Viscoteck GPCmax (VE2001 GPC solvent / sample module), a complete injection system. It includes a degasser, a pump, an autosampler, and an automatic injection loop (with a three-way valve) in sequence. After the sample is injected, it passes through a set of 3 columns with a guard column in front (see the table below for details on the columns used). Place the column and detector in an oven and adjust the temperature to 30°C. There is a triple detection system at the outlet of the column, consisting of 3 detectors: multi-angle light scattering (MALS), refractive index (RI) and viscometer.

[0039] The test conditions for GPC are shown in the following table:

[0040]

[0041] Materials used in the embodiments of the present invention

[0042] Cement: The cement to be tested should be exposed to ambient air for the shortest possible time. If cement needs to be stored for more than 24 hours between sampling and testing, store it in sealed containers that are completely filled and made of a material that does not react with cement. Prior to testing, use a machine to homogenize laboratory samples to ensure consistency before resampling.

[0043] Water: Use distilled or deionized water.

[0044] Sand: EN 196 sand, pre-filled in bags opened only before testing.

[0045] Polycarboxylate water reducer (PCE): solid content 45%.

[0046] IPEG: isopentanol polyoxyethylene ether, molecular weight 2400, solid content 50%.

[0047] Example 1

[0048] The cement used is YTL OPC (42.5N ordinary Portland cement, YTL Singapore, the Singapore agent of bagged cement) with the formula shown in the following table:

[0049]

[0050] The test data of Example 1 are shown in the following table:

[0051]

[0052] By comparing the test results of Group 1, Group 2, and Group 3, we can see that:

[0053] 1. Flow characteristics: such as Figure 1 As shown, the control group 1 without adding IPEG had the problem of increased fluidity after concrete mixing for 30 minutes, and the experimental groups 2 and 3 with adding IPEG had no increased fluidity within 1 hour and 3 hours respectively. The method for improving the rheological properties of concrete of the present invention was used to adjust the initial fluidity of concrete, and as the amount of IPEG increased, the fluidity became more stable;

[0054] 2. Setting time: Figure 2 As shown, by using the method of the present invention for improving the rheological properties of concrete, the experimental groups 2 and 3 to which IPEG is added shorten the setting time compared with the control group 1 to which IPEG is not added, and as the amount of IPEG increases, the setting time is still shortened;

[0055] 3. Compressive strength: Figure 3 As shown, by using the method of improving the rheological properties of concrete of the present invention, the strength of the experimental groups 2 and 3 with the addition of IPEG was generally improved within 1 day, 3 days and 28 days compared with the control group 1. The compressive strength at 1 day: the improvement of group 2 was larger, and the compressive strength at 28 days: the improvement of group 3 was larger. The method of improving the rheological properties of concrete of the present invention can enhance the early and late strength of concrete.

[0056] Example 2

[0057] The cement used is ASIA OPC (52.5N ordinary Portland cement, Asia Cement Singapore, the Singapore agent of bagged cement), and the formula is shown in the following table:

[0058]

[0059] The test data of Example 2 are shown in the following table:

[0060]

[0061] By comparing the test results of Group 1, Group 2, and Group 3, we can see that:

[0062] 1. Flow characteristics: such as Figure 4 As shown, compared with the control group 1, the method of improving the rheological properties of concrete of the present invention is used to adjust the fluidity of concrete. The fluidity increase of the experimental groups 2 and 3 is relatively low. Compared with the control group 1 with a fluidity increase of 49% in one hour, the fluidity of the experimental groups 2 and 3 with the addition of IPEG increases by 36% and 37% respectively.

[0063] 2. Setting time: Figure 5 As shown, experimental groups 2 and 3 shortened the coagulation time compared with control group 1. As the amount of IPEG added increased, it was beneficial to shorten the coagulation time;

[0064] 3. Compressive strength: Figure 6 As shown, by using the method of the present invention to improve the rheological properties of concrete, the strength of the experimental groups 2 and 3 is generally improved compared with the control group 1 within 1 day, 3 days and 28 days, and the concrete adding IPEG is beneficial to improve its compressive strength.

[0065] Example 3

[0066] The method for improving the rheological properties of concrete of the present invention is applied to prestressed concrete:

[0067] Cement uses OPC from CCCC Indonesia Industrial Co., Ltd. (OPC I cement produced by CONCH)

[0068] The formula is shown in the following table:

[0069]

[0070] The fluidity test data of Example 3 is shown in the following table:

[0071]

[0072] The test results confirm that the experimental group 1 adopts the method of improving the rheological properties of concrete of the present invention, and the PC component contains polycarboxylate water reducer and IPEG2400 component. Compared with the control group 2 using traditional admixture products, the fluidity increase can be reduced, the fluidity increase can be minimized, and the fluidity is more stable.

[0073] Example 4

[0074] The method for improving the rheological properties of concrete of the present invention is applied to prestressed concrete:

[0075] The cement adopts the above-mentioned ASIA OPC, and the formula is shown in the following table:

[0076]

[0077] The fluidity test data of Example 4 is shown in the following table:

[0078]

[0079] The test results confirm that the experimental group 1 adopts the method of improving the rheological properties of concrete according to the present invention, and the PC component contains polycarboxylate water reducer and IPEG2400 component. Compared with the control group 2 using traditional admixture products, the experimental group 1 has more stable flow characteristics, controllable initial fluidity, and can minimize the increase in fluidity.

[0080] Therefore, it can be concluded from the above embodiments that, compared with the existing concrete, the concrete obtained by the method for improving the rheological properties of concrete of the present invention has the advantages that IPEG is added to the concrete system, and IPEG is not reacted in the system, the initial fluidity of the concrete system containing the polycarboxylate water-reducing agent is adjusted, the increase in the fluidity of the concrete is reduced, and the concrete has more stable flow characteristics, and the workability, homogeneity, coagulation characteristics, strength development and durability of the concrete are significantly improved, the early compressive strength and late compressive strength of the concrete are improved, and the setting time is shortened. The concrete is suitable for concrete with early strength requirements and is conducive to steam-free curing. The method is applied to prestressed concrete and pipe pile concrete, and its rheological properties are significantly improved.

[0081] The above embodiments are only used to illustrate the present invention, rather than to limit the present invention. Those skilled in the relevant technical field may make various changes or modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should also belong to the scope of the present invention and should be defined by the claims.

Claims

1. A method for improving the rheological properties of concrete, characterized in that: The following steps are included: (1) Prepare raw materials containing the following parts by weight: cement: 500-1500 parts, sand: 1000-1500 parts; Water: 100-500 parts; Polycarboxylic acid water reducer: 0.45-15 parts; IPEG: 0.01-2.5 parts; (2) premixing the polycarboxylic acid water reducer and isopentanol polyoxyethylene ether (IPEG) into water to obtain an admixture mixture, wherein the amount of water is 15-35% of the total amount of water; (3) Premixing the cement and sand to obtain a premix, adding the admixture mixture and water in step (2) to the premix, and mixing the components until they are uniform.

2. A method for improving the rheological properties of concrete according to claim 1, characterized in that: The molecular weight of the isopentenol polyoxyethylene ether IPEG is 2000-3000.

3. A method for improving the rheological properties of concrete according to claim 2, characterized in that: The molecular weight of the isopentanol polyoxyethylene ether IPEG is 2200-2600.

4. A method for improving the rheological properties of concrete according to claim 3, characterized in that: The dosage of the isopentanol polyoxyethylene ether IPEG is 3%-15% of the weight of the polycarboxylic acid water reducer.

5. A method for improving the rheological properties of concrete according to claim 4, characterized in that: The dosage of the isopentanol polyoxyethylene ether IPEG is 4%-6% of the weight of the polycarboxylic acid water reducer.

6. The method for improving the rheological properties of concrete according to any one of claims 1 to 5 is applied to prestressed concrete.

7. The method for improving the rheological properties of concrete according to any one of claims 1 to 5 is applied to pipe pile concrete.

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