Hydraulic concrete based on composite coarse aggregate and preparation method thereof

Abstract

The invention provides hydraulic concrete based on composite coarse aggregate and a preparation method thereof, and belongs to the technical field of hydraulic concrete. The hydraulic concrete is prepared from the following raw materials in parts by weight: 258 to 290 parts of cement, 82 to 98 parts of fly ash, 1100 to 1150 parts of composite coarse aggregate, 680 to 720 parts of fine aggregate, 2 to 5 parts of additive and 140 to 160 parts of water. The method comprises the following steps: treating coarse aggregate by using a dilute acid solution; uniformly mixing the coarse aggregate treated by the dilute acid solution with a chitosan-bentonite compound and calcium sulfate whiskers to obtain modified coarse aggregate; and uniformly mixing the modified coarse aggregate, ceramsite and silica fume to obtain the composite coarse aggregate. Water slow release and deformation compensation are achieved in an internal regulation and control mode, so that the prepared hydraulic concrete based on the composite coarse aggregate has good mechanical performance and anti-permeability performance, and the core problems that the hydraulic concrete is large in dry shrinkage, high in cracking risk and the like are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of hydraulic concrete technology, specifically to a hydraulic concrete based on composite coarse aggregate and its preparation method. Background Technology

[0002] Hydraulic concrete, as a core structural material in water conservancy projects (such as pumping stations, dams, and canals), directly determines the service life and safety of the project due to its long-term deformation stability and crack resistance. According to Article 5.3.1 of the "Code for Construction of Hydraulic Concrete" (SL 677-2014), which states that "aggregate selection should follow the principles of high quality, economy, and local sourcing," a study on aggregate applicability for the Yangtze River-Huaihe River Water Diversion Project (Anhui section) revealed that the crushed stone market in Anhui Province mainly supplies 5~31.5 mm continuously graded coarse aggregate conforming to the "Construction Gravel and Crushed Stone" (GB / T14685-2022) standard. However, the commonly used 5~40 mm graded aggregate (conforming to DL / T 5144-2015) in traditional hydraulic concrete is difficult to obtain on a large scale due to material shortages. This practical contradiction compels the engineering community to urgently verify and optimize the application performance of 5~31.5 mm coarse aggregate in hydraulic concrete.

[0003] Existing research has confirmed that using 5-31.5 mm aggregate to prepare concrete increases its mechanical and deformation properties, meeting the required strength for concrete mix design. However, it is necessary to monitor concrete deformation to prevent cracking. Based on this, this invention provides a hydraulic concrete based on composite coarse aggregate, its preparation method, and its application, providing technical support for the local sourcing of materials in large-scale water conservancy projects. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a hydraulic concrete based on composite coarse aggregate and its preparation method. This invention optimizes the interfacial bonding performance and structure of the coarse aggregate through surface modification and compounding, and achieves slow moisture release and deformation compensation through internal regulation. While maintaining the durability and mechanical properties of hydraulic concrete, it effectively solves the core problems of high drying shrinkage and high cracking risk.

[0005] To achieve the above objectives, the specific technical solution of the present invention is as follows:

[0006] This invention provides a hydraulic concrete based on composite coarse aggregate. The raw materials, by weight, include: 258-290 parts cement, 82-98 parts fly ash, 1100-1150 parts composite coarse aggregate, 680-720 parts fine aggregate, 2-5 parts admixture, and 140-160 parts water. The preparation method of the composite coarse aggregate includes the following steps:

[0007] The coarse aggregate is treated with a dilute acid solution; the coarse aggregate treated with the dilute acid solution is mixed evenly with chitosan-bentonite composite and calcium sulfate whiskers to obtain modified coarse aggregate; the modified coarse aggregate, ceramsite and silica fume are mixed evenly at a weight ratio of 100:6~12:0.1~0.5 to obtain composite coarse aggregate.

[0008] To address the issues of deformation and cracking risks in existing 5-31.5 mm coarse aggregate concrete, this invention modifies the coarse aggregate by first spraying a dilute acid solution onto its surface. This allows the acid to react with the mineral components (such as calcium carbonate) on the aggregate surface, creating a micron-level uneven surface structure. This surface structure facilitates the subsequent adhesion of chitosan-bentonite composites and calcium sulfate whiskers. Furthermore, this invention coats the coarse aggregate surface with an expansive material—a chitosan-bentonite composite. This chitosan-bentonite composite absorbs water and expands in a humid environment (e.g., during curing), forming a pre-forming layer at the coarse aggregate-slurry interface. The compressive stress counteracts early hydration shrinkage; in dry environments (e.g., during service life), it can slowly release internally adsorbed water, slowing down the humidity gradient inside the hydraulic concrete and reducing drying shrinkage deformation; furthermore, the embedded calcium sulfate whiskers can promote the hydration reaction of cement, increase the formation of hydration products, enhance the interfacial bond strength of coarse aggregate, inhibit crack propagation, and effectively reduce the risk of concrete cracking; simultaneously, this invention uses porous expanded clay aggregate to partially replace coarse aggregate. The micropores of the expanded clay aggregate store mixing water in the early stage of hardening and release it slowly in the later stage, forming "internal curing" and effectively reducing the autogenous shrinkage of hydraulic concrete. In addition, the silica fume in the formula combines with the modified coarse aggregate and expanded clay aggregate, filling the porous expanded clay aggregate and promoting secondary hydration at the coarse aggregate interface to form a denser structure, while generating micro-expansion to compensate for shrinkage, inhibiting the accumulation of shrinkage stress from the source, and further effectively reducing the risk of concrete cracking.

[0009] Furthermore, the dilute acid solution includes an acetic acid solution with a concentration of 0.5~2 mol / L.

[0010] Furthermore, the weight ratio of the coarse aggregate treated with dilute acid solution to chitosan-bentonite composite and calcium sulfate whiskers is 100:4~8:4~8.

[0011] Further, the preparation method of the chitosan-bentonite composite is as follows: using 0.1 mol / L acetic acid solution as solvent, prepare a chitosan solution with a mass concentration of 0.5%~2%, add bentonite to the chitosan solution and sonicate for 10~50 min to allow the chitosan to fully impregnate and insert into the bentonite layers, thereby obtaining the chitosan-bentonite composite.

[0012] Furthermore, the weight ratio of chitosan to bentonite is 1:5~10.

[0013] Furthermore, the power of the ultrasound is 300~600 W.

[0014] Furthermore, the coarse aggregate is crushed stone with a particle size of 3~31.5 mm, of which the proportion of particles with a particle size of 5~16 mm is 35%~45% and the proportion of particles with a particle size of 16~31.5 mm is 55%~65%.

[0015] Furthermore, the particle size of the ceramsite is 16~31.5 mm.

[0016] Furthermore, the fine aggregate is a mixture of natural sand and manufactured sand, with natural sand accounting for 60%~70% and manufactured sand accounting for 30%~40%; the stone powder (particle size <0.075 mm) content in the manufactured sand is 4%~5%. This invention uses a mixture of natural sand and manufactured sand as fine aggregate. The manufactured sand particles have many angular edges, forming a dense structure of "coarse aggregate skeleton + fine aggregate filling" with the modified coarse aggregate of this invention, reducing porosity. The stone powder in the manufactured sand can fill the pores of the adhesive material, synergistically improving the overall density of the concrete with the chitosan-bentonite composite and calcium sulfate whiskers on the surface of the modified coarse aggregate.

[0017] The present invention also provides a method for preparing the aforementioned hydraulic concrete based on composite coarse aggregate, comprising: weighing raw materials according to the weight parts, mixing cement, fly ash, composite coarse aggregate and fine aggregate evenly, then adding admixture and water and mixing evenly again to obtain hydraulic concrete based on composite coarse aggregate.

[0018] Compared with the prior art, the advantages of the present invention are:

[0019] (1) This invention treats coarse aggregate with a dilute acid solution to form a micron-level uneven surface structure, and then modifies the coarse aggregate with chitosan-bentonite composite and calcium sulfate whiskers to enhance the interfacial properties of the coarse aggregate, thereby reducing the hydration shrinkage of concrete and significantly improving the mechanical strength and impermeability of concrete; the modified coarse aggregate is compounded with ceramsite and silica fume, wherein the micropores of ceramsite store mixing water in the early stage of hardening and slowly release it in the later stage, forming "internal curing", which effectively reduces the autogenous shrinkage of hydraulic concrete; silica fume can fill the porous ceramsite and promote secondary hydration at the interface of coarse aggregate to form a denser structure, while generating micro-expansion to compensate for shrinkage, inhibiting the accumulation of shrinkage stress from the source, and further effectively reducing the risk of concrete cracking.

[0020] (2) The present invention adopts an internal regulation method to achieve moisture slow release and deformation compensation, so that the prepared hydraulic concrete based on composite coarse aggregate has good mechanical properties and impermeability, and effectively solves the core problems such as large drying shrinkage and high risk of cracking. Detailed Implementation

[0021] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This invention provides a hydraulic concrete based on composite coarse aggregate. The raw materials, by weight, include: 258-290 parts cement, 82-98 parts fly ash, 1100-1150 parts composite coarse aggregate, 680-720 parts fine aggregate, 2-5 parts admixture, and 140-160 parts water. The preparation method of the composite coarse aggregate includes the following steps: treating the coarse aggregate with a dilute acid solution; mixing the acid-treated coarse aggregate with a chitosan-bentonite composite and calcium sulfate whiskers to obtain modified coarse aggregate; and mixing the modified coarse aggregate, ceramsite, and silica fume at a weight ratio of 100:6-12:0.1-0.5 to obtain the composite coarse aggregate.

[0023] In some examples, the dilute acid solution is an acetic acid solution with a concentration of 0.5 to 2 mol / L.

[0024] In some examples, the weight ratio of the coarse aggregate treated with dilute acid solution to chitosan-bentonite composite and calcium sulfate whiskers is 100:4~8:4~8.

[0025] In some examples, the chitosan-bentonite composite is prepared as follows: a chitosan solution with a mass concentration of 0.5% to 2% is prepared using a 0.1 mol / L acetic acid solution as a solvent; bentonite is added to the chitosan solution and ultrasonically treated for 10 to 50 min to allow the chitosan to fully impregnate and insert into the bentonite layers, thereby obtaining the chitosan-bentonite composite; the weight ratio of chitosan to bentonite is 1:5 to 10; and the ultrasonic power is 300 to 600 W.

[0026] In some examples, the coarse aggregate is crushed stone with a particle size of 3 to 31.5 mm, of which 35% to 45% have a particle size of 5 to 16 mm and 55% to 65% have a particle size of 16 to 31.5 mm.

[0027] In some examples, the particle size of the ceramsite is 16~31.5 mm.

[0028] In some examples, the fine aggregate is a mixture of natural sand and manufactured sand, with natural sand accounting for 60% to 70% and manufactured sand accounting for 30% to 40%; the stone powder (particle size < 0.075 mm) content in the manufactured sand is 4% to 5%.

[0029] In the following specific embodiments, the chitosan-bentonite composite is prepared as follows: a chitosan solution with a mass concentration of 1% is prepared using a 0.1 mol / L acetic acid solution as a solvent. Bentonite is added to the chitosan solution at a weight ratio of 1:5 between chitosan and bentonite. The solution is then ultrasonically treated for 20 min at a power of 500 W to allow the chitosan to fully impregnate and insert into the bentonite layers, thereby obtaining the chitosan-bentonite composite.

[0030] In the following specific examples, the coarse aggregate contains 40% particles with a diameter of 5-16 mm and 60% particles with a diameter of 16-31.5 mm; the fine aggregate contains 62% natural sand (river sand, fineness modulus 2.43) and 38% manufactured sand (fineness modulus 2.8); the manufactured sand contains 4% stone powder (particle size <0.075 mm); the cement is P•O42.5 cement; the fly ash is Class II fly ash; and the admixture is polycarboxylate superplasticizer.

[0031] Example 1

[0032] A hydraulic concrete based on composite coarse aggregate, comprising, by weight, 270 parts cement, 90 parts fly ash, 1124 parts composite coarse aggregate, 689 parts fine aggregate, 3 parts admixture, and 151 parts water; wherein the composite coarse aggregate is prepared by the following method: a 1 mol / L acetic acid solution is uniformly sprayed onto the surface of the coarse aggregate to moisten it, and the mixture is allowed to stand for 6 hours to react; the coarse aggregate treated with dilute acid solution is mixed uniformly with chitosan-bentonite composite and calcium sulfate whiskers at a weight ratio of 100:6:6 to obtain modified coarse aggregate; the modified coarse aggregate, ceramsite, and silica fume are mixed uniformly at a weight ratio of 100:9:0.3 to obtain composite coarse aggregate.

[0033] Weigh the raw materials according to the weight proportions, mix the cement, fly ash, composite coarse aggregate, and fine aggregate evenly, then add the admixture and water and mix evenly again to obtain hydraulic concrete based on composite coarse aggregate.

[0034] Example 2

[0035] A hydraulic concrete based on composite coarse aggregate, comprising, by weight, 258 parts cement, 98 parts fly ash, 1100 parts composite coarse aggregate, 680 parts fine aggregate, 3 parts admixture, and 151 parts water; wherein the composite coarse aggregate is prepared by the following method: a 1 mol / L acetic acid solution is uniformly sprayed onto the surface of the coarse aggregate to moisten it, and the mixture is allowed to stand for 6 hours to react; the coarse aggregate treated with dilute acid solution is mixed uniformly with chitosan-bentonite composite and calcium sulfate whiskers at a weight ratio of 100:6:6 to obtain modified coarse aggregate; the modified coarse aggregate, ceramsite, and silica fume are mixed uniformly at a weight ratio of 100:6:0.1 to obtain composite coarse aggregate.

[0036] Weigh the raw materials according to the weight proportions, mix the cement, fly ash, composite coarse aggregate, and fine aggregate evenly, then add the admixture and water and mix evenly again to obtain hydraulic concrete based on composite coarse aggregate.

[0037] Example 3

[0038] A hydraulic concrete based on composite coarse aggregate, comprising, by weight, 290 parts cement, 82 parts fly ash, 1150 parts composite coarse aggregate, 720 parts fine aggregate, 3 parts admixture, and 151 parts water; wherein the composite coarse aggregate is prepared by the following method: a 1 mol / L acetic acid solution is uniformly sprayed onto the surface of the coarse aggregate to moisten it, and the mixture is allowed to stand for 6 hours to react; the coarse aggregate treated with dilute acid solution is mixed uniformly with chitosan-bentonite composite and calcium sulfate whiskers at a weight ratio of 100:6:6 to obtain modified coarse aggregate; the modified coarse aggregate, ceramsite, and silica fume are mixed uniformly at a weight ratio of 100:12:0.5 to obtain composite coarse aggregate.

[0039] Weigh the raw materials according to the weight proportions, mix the cement, fly ash, composite coarse aggregate, and fine aggregate evenly, then add the admixture and water and mix evenly again to obtain hydraulic concrete based on composite coarse aggregate.

[0040] Comparative Example 1

[0041] A type of hydraulic concrete based on composite coarse aggregate, comprising, by weight, 270 parts cement, 90 parts fly ash, 1124 parts composite coarse aggregate, 689 parts fine aggregate, 3 parts admixture, and 151 parts water; wherein the composite coarse aggregate is prepared by mixing coarse aggregate, ceramsite, and silica fume uniformly in a weight ratio of 100:9:0.3 to obtain the composite coarse aggregate. That is, no modification treatment is performed on the coarse aggregate in this comparative example.

[0042] Weigh the raw materials according to the weight proportions, mix the cement, fly ash, composite coarse aggregate, and fine aggregate evenly, then add the admixture and water and mix evenly again to obtain hydraulic concrete based on composite coarse aggregate.

[0043] Comparative Example 2

[0044] A hydraulic concrete based on composite coarse aggregate, comprising, by weight, 270 parts cement, 90 parts fly ash, 1124 parts composite coarse aggregate, 689 parts fine aggregate, 3 parts admixture, and 151 parts water; wherein the composite coarse aggregate is prepared by the following method: uniformly spraying a 1 mol / L acetic acid solution onto the surface of the coarse aggregate to moisten it, and allowing it to stand for 6 h to react; mixing the coarse aggregate treated with dilute acid solution with a chitosan-bentonite composite at a weight ratio of 100:6 to obtain modified coarse aggregate; and mixing the modified coarse aggregate, ceramsite, and silica fume at a weight ratio of 100:9:0.3 to obtain composite coarse aggregate.

[0045] Weigh the raw materials according to the weight proportions, mix the cement, fly ash, composite coarse aggregate, and fine aggregate evenly, then add the admixture and water and mix evenly again to obtain hydraulic concrete based on composite coarse aggregate.

[0046] Comparative Example 3

[0047] A hydraulic concrete based on composite coarse aggregate, comprising, by weight, 270 parts cement, 90 parts fly ash, 1124 parts composite coarse aggregate, 689 parts fine aggregate, 3 parts admixture, and 151 parts water; wherein the composite coarse aggregate is prepared by the following method: uniformly spraying a 1 mol / L acetic acid solution onto the surface of the coarse aggregate to moisten it, and allowing it to stand for 6 h to react; mixing the coarse aggregate treated with dilute acid solution with calcium sulfate whiskers at a weight ratio of 100:6 to obtain modified coarse aggregate; and mixing the modified coarse aggregate, ceramsite, and silica fume at a weight ratio of 100:9:0.3 to obtain composite coarse aggregate.

[0048] Weigh the raw materials according to the weight proportions, mix the cement, fly ash, composite coarse aggregate, and fine aggregate evenly, then add the admixture and water and mix evenly again to obtain hydraulic concrete based on composite coarse aggregate.

[0049] Comparative Example 4

[0050] A hydraulic concrete based on modified coarse aggregate, comprising, by weight, 270 parts cement, 90 parts fly ash, 1028 parts modified coarse aggregate, 93 parts ceramsite, 3 parts silica fume, 689 parts fine aggregate, 3 parts admixture, and 151 parts water; wherein the modified coarse aggregate is prepared by the following method: a 1 mol / L acetic acid solution is uniformly sprayed onto the surface of the coarse aggregate to moisten it, and the mixture is allowed to stand for 6 hours to react; the coarse aggregate treated with dilute acid solution is mixed uniformly with chitosan-bentonite composite and calcium sulfate whiskers at a weight ratio of 100:6:6 to obtain the modified coarse aggregate.

[0051] Weigh the raw materials according to the weight percentages, mix cement, fly ash, modified coarse aggregate, ceramsite, silica fume, and fine aggregate evenly, then add admixtures and water and mix evenly again to obtain hydraulic concrete based on modified coarse aggregate.

[0052] The performance of the composite coarse aggregate-based hydraulic concretes prepared in Examples 1-3 and Comparative Examples 1-4 was tested. The compressive strength and splitting tensile strength were tested in accordance with the Test Procedure for Hydraulic Concrete (SL / T 352-2020); the drying shrinkage, autogenous volume deformation and impermeability were tested in accordance with the Test Procedure for Hydraulic Concrete (DL / T5150-2017).

[0053]

[0054] As can be seen from the data in the table, compared with comparative examples 1-4, the hydraulic concrete based on composite coarse aggregate provided by the present invention has better mechanical properties and impermeability. Furthermore, by modifying the coarse aggregate and combining the modified coarse aggregate with ceramsite and silica fume in a specific ratio, the present invention can reduce the drying shrinkage rate and autogenous volume deformation of hydraulic concrete, effectively reducing the risk of concrete cracking.

[0055] The above detailed embodiments describe the implementation of the present invention; however, the present invention is not limited to the specific details described in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A type of hydraulic concrete based on composite coarse aggregate, characterized in that, The raw materials, by weight, include: 258-290 parts cement, 82-98 parts fly ash, 1100-1150 parts composite coarse aggregate, 680-720 parts fine aggregate, 2-5 parts admixture, and 140-160 parts water; wherein, the preparation method of the composite coarse aggregate includes the following steps: The coarse aggregate is treated with a dilute acid solution; the coarse aggregate treated with the dilute acid solution is mixed evenly with chitosan-bentonite composite and calcium sulfate whiskers to obtain modified coarse aggregate; the modified coarse aggregate, ceramsite and silica fume are mixed evenly at a weight ratio of 100:6~12:0.1~0.5 to obtain composite coarse aggregate.

2. The hydraulic concrete based on composite coarse aggregate according to claim 1, characterized in that, The weight ratio of the coarse aggregate treated with dilute acid solution to chitosan-bentonite composite and calcium sulfate whiskers is 100:4~8:4~8.

3. The hydraulic concrete based on composite coarse aggregate according to claim 1, characterized in that, The chitosan-bentonite composite is prepared as follows: a chitosan solution with a mass concentration of 0.5% to 2% is prepared using 0.1 mol / L acetic acid solution as solvent, and bentonite is added to the chitosan solution and mixed evenly to obtain the chitosan-bentonite composite.

4. The hydraulic concrete based on composite coarse aggregate according to claim 3, characterized in that, The weight ratio of chitosan to bentonite is 1:5~10.

5. The hydraulic concrete based on composite coarse aggregate according to claim 1, characterized in that, The dilute acid solution includes an acetic acid solution with a concentration of 0.5~2 mol / L.

6. The hydraulic concrete based on composite coarse aggregate according to claim 1, characterized in that, The coarse aggregate is crushed stone with a particle size of 3~31.5 mm, of which 35%~45% has a particle size of 5~16 mm and 55%~65% has a particle size of 16~31.5 mm.

7. The hydraulic concrete based on composite coarse aggregate according to claim 1, characterized in that, The particle size of the ceramsite is 16~31.5 mm.

8. The hydraulic concrete based on composite coarse aggregate according to claim 1, characterized in that, The fine aggregate is a mixture of natural sand and manufactured sand, with natural sand accounting for 60% to 70% and manufactured sand accounting for 30% to 40%.

9. The method for preparing hydraulic concrete based on composite coarse aggregate according to any one of claims 1-8, characterized in that, include: Weigh the raw materials according to the weight proportions, mix the cement, fly ash, composite coarse aggregate, and fine aggregate evenly, then add the admixture and water and mix evenly again to obtain hydraulic concrete based on composite coarse aggregate.

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