High-specific-gravity self-compacting concrete and preparation method thereof

Abstract

The invention belongs to the technical field of concrete, and particularly relates to high-specific-gravity self-compacting concrete and a preparation method thereof. The high-specific-gravity self-compacting concrete is prepared from the following raw materials in parts by mass: 560 to 671 parts of natural coarse aggregate, 725 to 906 parts of iron ore, 300 parts of natural fine aggregate, 446 parts of steel slag sand, 383 parts of cement, 0 to 54 parts of steel slag powder, 107 parts of fly ash, 2.6 to 13.6 parts of water reducing agent and 150 to 182 parts of water. The performance of the concrete is greatly improved by improving the microcosmic performance of the concrete and grading of all the components, and the purposes of reducing the use amount of cement, reducing shrinkage and creep of the concrete, reducing CO2 emission, saving energy, protecting the environment and achieving green construction are achieved while high specific gravity, self-compaction and high strength of the concrete are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete, and in particular relates to a high specific gravity self-compacting concrete and a preparation method thereof. Background Art

[0002] In the field of architecture and engineering, concrete is one of the most important building materials and is widely used in various structures and foundation projects. With the development of science and technology and the diversification of engineering needs, higher requirements are placed on the performance of concrete. For example, some special projects, such as radiation protection, gravity-stabilized structures, explosion-proof and impact-resistant structures, require the use of high-density concrete (apparent density greater than 2.8g / cm 3 ). However, traditional high-density concrete has problems such as poor fluidity, poor self-compactness, difficulty in construction, and easy generation of bubbles and cracks, which limits its application in engineering.

[0003] In order to solve the above problems, in recent years, researchers have begun to explore the application of self-compacting concrete (SCC) in high-density concrete. Self-compacting concrete has good fluidity and self-compactness, and can fill the formwork by itself under the action of gravity without vibration, which reduces the generation of bubbles and cracks, improves construction efficiency and concrete quality. However, there are still some technical challenges in combining high-density materials with self-compacting concrete to prepare high-density self-compacting concrete, such as how to maintain the fluidity and self-compactness of concrete while improving its specific gravity and mechanical properties, and how to control the shrinkage and creep reduction of concrete.

[0004] In view of the above problems, the present invention provides a high specific gravity self-compacting concrete and a preparation method thereof to solve the fluidity and self-compacting problems of high specific gravity concrete. Summary of the invention

[0005] The purpose of the present invention is to overcome the problem that it is difficult to simultaneously achieve high specific gravity and self-compacting properties of concrete in the existing concrete technology, and to provide a high specific gravity self-compacting concrete and a preparation method thereof, wherein the high specific gravity self-compacting concrete is composed of the following raw materials in parts by mass:

[0006] 560-671 parts of natural coarse aggregate, 725-906 parts of iron ore, 300 parts of natural fine aggregate, 446 parts of steel slag sand, 383 parts of cement, 0-54 parts of steel slag powder, 107 parts of fly ash, 2.6-13.6 parts of water reducer, and 150-182 parts of water.

[0007] Furthermore, the high specific gravity self-compacting concrete is composed of the following raw materials in parts by mass:

[0008] 671 parts of natural coarse aggregate, 725 parts of iron ore, 300 parts of natural fine aggregate, 446 parts of steel slag sand, 383 parts of cement, 107 parts of fly ash, 2.6-9.8 parts of water reducer, 150-182 parts of water;

[0009] Or, the high specific gravity self-compacting concrete is composed of the following raw materials in parts by mass:

[0010] 560 parts of natural coarse aggregate, 906 parts of iron ore, 300 parts of natural fine aggregate, 446 parts of steel slag sand, 383 parts of cement, 54 parts of steel slag powder, 107 parts of fly ash, 13.6 parts of water reducer, and 182 parts of water.

[0011] Furthermore, the natural coarse aggregate is 5-16 mm continuously graded natural crushed stone;

[0012] The iron ore is of continuous gradation of 5-16 mm;

[0013] The natural fine aggregate is river sand; the river sand fineness modulus is 2.9, medium sand in zone II;

[0014] The fineness modulus of the steel slag sand is 2.8, medium sand in zone II;

[0015] The cement is 42.5R ordinary Portland cement;

[0016] The steel slag powder density is 3210kg / m 3 , with a specific surface area of ​​380m 2 / kg;

[0017] The fly ash density is 2550kg / m 3 , with a specific surface area of ​​800m 2 / kg;

[0018] The water reducer is a polycarboxylic acid high efficiency water reducer.

[0019] The method for preparing the high specific gravity self-compacting concrete described above comprises the following steps:

[0020] S1. Add weighed cement, fly ash, steel slag powder and water reducing agent into a forced mixer, and dry mix to make the components evenly mixed;

[0021] S2. Add half of the total mixing water into the mixer and continue stirring to mix evenly to form a pure paste;

[0022] S3, keep the mixer stirring at medium speed for 30 seconds, and add the weighed natural coarse aggregate, iron ore, natural fine aggregate, and steel slag sand into the forced mixer at the same time within 30 seconds to fully mix the components;

[0023] S4. Stir rapidly for 30 seconds, and add the remaining half of the mixing water within 30 seconds to ensure that all components of the concrete are fully mixed;

[0024] S5, stop stirring for 90 seconds, scrape the clean slurry hanging on the wall during the stirring process into the mixer, so that the cementitious material is evenly wrapped on the surface of the coarse aggregate and the fine aggregate;

[0025] S6. Continue stirring for 1 minute without vibrating and put into mold to form.

[0026] S7. After molding, demoulding and curing are performed.

[0027] The beneficial effects of the present invention are:

[0028] The present invention adopts the above-mentioned optimized preparation process, adjusts the order of adding each component material, so that the cementitious material slurry can better adhere to the aggregate, strengthen the concrete interface transition zone, improve the microscopic properties of the concrete and the gradation between each component to greatly improve the macroscopic properties of the concrete. The use of fly ash and steel slag powder can improve the interface transition zone between the coarse aggregate and the cement paste in the concrete, and fill the ultrafine particles in the gaps of the cement particles, so that the cementitious material forms a good continuous micro-gradation and filling, and improves the macroscopic mechanical properties and durability of the concrete. The use of high-efficiency water reducer ensures the realization of high fluidity and homogeneity of the concrete.

[0029] The high specific gravity self-compacting concrete of the present invention can be regarded as composed of particles of various particle sizes. The particle grading optimization method is used to improve the particle stacking efficiency, maximize the use of aggregates, reduce the void ratio between aggregate particles, and reduce the amount of cementitious material paste (cement, fly ash, steel slag powder) used to fill the gaps between aggregates, save the amount of cement paste, and achieve the purpose of saving materials and environmental protection. Since the amount of paste in the concrete is reduced, the shrinkage and creep are reduced, the volume stability is improved, and the cost of concrete materials is reduced, making it more economical, making it a green building material that is both sustainable and can obtain greater economic benefits.

[0030] The high specific gravity self-compacting concrete of the present invention improves the construction efficiency and the quality of concrete, has the characteristics of high specific gravity, high fluidity, high self-compactness, high mechanical properties, etc., can meet the needs of special projects, and improve the quality and safety of projects. At the same time, the preparation method of the present invention is simple and easy, suitable for large-scale production and construction, and has good economic and social benefits. The high specific gravity self-compacting concrete of the present invention can not only meet the needs of special projects, but also reduce project costs, improve project quality and safety, and has broad application prospects. DETAILED DESCRIPTION

[0031] In order to better understand the present invention, the content of the present invention is further explained below in combination with tables and specific implementation cases, but the content of the present invention is not limited to the following embodiments.

[0032] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form also includes the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this description, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0033] The methods for preparing the high specific gravity self-compacting concrete materials in the embodiment and the comparative example are the same, and the only difference is the raw materials and their proportions constituting the concrete. The raw materials and their masses constituting the concrete are shown in Table 1. The specific steps of the method for preparing the concrete materials in the embodiment and the comparative example are as follows:

[0034] S1. Add weighed cement, fly ash, steel slag powder and water reducing agent into a forced mixer and dry mix for 30 seconds to fully mix the components;

[0035] S2. Add half of the total mixing water into the mixer and continue stirring for 30 seconds to form a pure paste;

[0036] S3, keep the mixer stirring at medium speed for 30 seconds, add the weighed natural coarse aggregate, iron ore, natural fine aggregate, and steel slag sand into the forced mixer at the same time within 30 seconds, fully mix and disperse the coarse aggregate and fine aggregate, and fully mix the clean slurry paste with the coarse aggregate and fine aggregate;

[0037] S4. Stir rapidly for 30 seconds, and add the remaining half of the mixing water within 30 seconds to ensure that all components of the concrete are fully mixed;

[0038] S5, stop stirring for 90 seconds, scrape the clean slurry hanging on the wall during the stirring process into the mixer, so that the cementitious material is evenly wrapped on the surface of the coarse aggregate and the fine aggregate;

[0039] S6. Continue stirring for 1 minute without vibrating and put into mold to form.

[0040] S7. After molding, demoulding and curing are performed.

[0041] Wherein, the natural coarse aggregate is 5-16mm continuously graded natural crushed stone;

[0042] The iron ore coarse aggregate is 5-16 mm continuously graded;

[0043] The natural fine aggregate is river sand, the fineness modulus of the river sand is 2.9, and the sand is medium sand in zone II;

[0044] The fineness modulus of the steel slag sand is 2.8, medium sand in zone II;

[0045] The cement is 42.5R ordinary Portland cement;

[0046] The steel slag powder density is 3210kg / m 3 , with a specific surface area of ​​380m 2 / kg;

[0047] The fly ash density is 2550kg / m 3 , with a specific surface area of ​​800m 2 / kg;

[0048] The water reducer is a polycarboxylic acid high-efficiency water reducer (purchased from Shanghai Chenqi Chemical Technology Co., Ltd. Sika);

[0049] The present invention adopts the above-mentioned optimized preparation process to greatly improve the macroscopic properties of concrete by improving the microscopic properties of concrete.

[0050] The concrete raw material dosage and performance test results of the embodiments and comparative examples of the present invention are shown in Table 1. The slump expansion of fresh concrete is tested according to the national industry standard JGJ / T283-2012 "Technical Specification for Application of Self-compacting Concrete"; the compressive strength of hardened concrete is tested according to the national standard GB / T50081-2002.

[0051] Table 1 High specific gravity self-compacting concrete examples

[0052]

[0053] It can be seen from comparative examples 1-3 that, without changing the water reducing agent dosage, the fluidity of concrete increases with the increase of water reducing agent, but has little effect on the strength of concrete.

[0054] Combining Comparative Examples 1 and 4, it can be seen that when the water reducing agent dosage is low, iron ore replaces 40% of the volume of natural crushed stone, the expansion of concrete is reduced, but the apparent density of concrete is improved and the strength is slightly reduced, indicating that adding iron ore instead of natural crushed stone under low water reducing agent conditions will have an adverse effect on the strength. The reason is that due to the process of crushing, there are microcracks inside the iron ore, which leads to a slight decrease in the strength of the concrete.

[0055] Combining Example 1 with Comparative Example 4, it can be seen that by replacing 50% of the volume of river sand with steel slag sand, the expansion and apparent density of concrete are improved. Steel slag sand has a denser particle shape and a smoother surface, and can reduce the mechanical friction effect between coarse aggregates in concrete, thereby improving the density of concrete.

[0056] It can be seen from Examples 1-3 that after increasing the amount of water reducing agent, the apparent density and compressive strength are improved. This is because the increase in the amount of water reducing agent increases the setting time of the cementitious material, and the cementitious material slurry has more time to penetrate into the tiny weak cracks on the surface of the iron ore, repairing the microcracks, thereby improving the strength of the concrete.

[0057] Combining Example 4 with Example 3, it can be seen that by replacing 10% volume of cement with steel slag powder, and increasing the replacement rate of iron ore by 10% and the dosage of water reducer, the expansion and apparent density of concrete are increased, and the strength is almost unchanged. Due to its low hydration activity, steel slag powder plays the role of micro-aggregate in the early hydration process, filling pores and cracks. When the hydration reaction enters the later stage, the steel slag powder begins to hydrate, which provides material conditions for the later strength growth of concrete.

[0058] In summary, the present invention effectively overcomes various shortcomings of the prior art and has high industrial utilization value.

[0059] The apparent density of the concrete of the present invention is ≥2.8g / cm 3 , the slump expansion reaches more than 660mm, which meets the requirements of complex formwork on-site construction with large fluidity and dense reinforcement, and has high specific gravity and self-compacting performance; at the same time, on the basis of ensuring the requirements of slump expansion and apparent density, its 28-day compressive strength reaches more than 60MPa. The high specific gravity self-compacting concrete of the present invention fills the technical gap of compatibility between high performance and high fluidity and high specific gravity of concrete.

[0060] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs may also make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the scope of protection of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A high specific gravity self-compacting concrete, characterized in that: The high specific gravity self-compacting concrete is composed of the following raw materials in parts by mass: 560-671 parts of natural coarse aggregate, 725-906 parts of iron ore, 300 parts of natural fine aggregate, 446 parts of steel slag sand, 383-426 parts of cement, 0-54 parts of steel slag powder, 107 parts of fly ash, 2.6-13.6 parts of water reducer, and 150-182 parts of water.

2. The high specific gravity self-compacting concrete according to claim 1, characterized in that: The high specific gravity self-compacting concrete is composed of the following raw materials in parts by mass: 671 parts of natural coarse aggregate, 725 parts of iron ore, 300 parts of natural fine aggregate, 446 parts of steel slag sand, 383 parts of cement, 107 parts of fly ash, 2.6-9.8 parts of water reducer, and 150-182 parts of water.

3. The high specific gravity self-compacting concrete according to claim 1, characterized in that: The high specific gravity self-compacting concrete is composed of the following raw materials in parts by mass: 560 parts of natural coarse aggregate, 906 parts of iron ore, 300 parts of natural fine aggregate, 446 parts of steel slag sand, 383 parts of cement, 54 parts of steel slag powder, 107 parts of fly ash, 13.6 parts of water reducer, and 182 parts of water.

4. The high specific gravity self-compacting concrete according to claim 1, characterized in that: The natural coarse aggregate is natural crushed stone with continuous grading of 5-16 mm; The iron ore is of continuous gradation of 5-16 mm; The natural fine aggregate is river sand; the river sand fineness modulus is 2.9, medium sand in zone II; The fineness modulus of the steel slag sand is 2.8, which is medium sand in zone II.

5. The high specific gravity self-compacting concrete according to claim 1, characterized in that: The cement is 42.5R ordinary Portland cement; The density of the steel slag powder is 3210kg / m 3 , with a specific surface area of ​​380m 2 / kg; The fly ash density is 2550kg / m 3 , with a specific surface area of ​​800m 2 / kg; The water reducer is a polycarboxylic acid high efficiency water reducer.

6. A method for preparing the high specific gravity self-compacting concrete according to claim 1, characterized in that: The steps include: S1. Add weighed cement, fly ash, steel slag powder and water reducing agent into a forced mixer, and dry mix to make the components evenly mixed; S2. Add half of the total mixing water into the mixer and continue stirring for 30 seconds to form a pure paste; S3, keep the mixer stirring at medium speed for 30 seconds, and add the weighed natural coarse aggregate, iron ore, natural fine aggregate, and steel slag sand into the forced mixer at the same time within 30 seconds to fully mix the components; S4. Stir rapidly for 30 seconds, and add the remaining half of the mixing water within 30 seconds to ensure that all components of the concrete are fully mixed; S5, stop stirring for 90 seconds, scrape the clean slurry hanging on the wall during the stirring process into the mixer, so that the cementitious material is evenly wrapped on the surface of the coarse aggregate and the fine aggregate; S6. Continue stirring for 1 minute without vibrating, and then mold into a mold; S7. After molding, demoulding and curing are carried out.

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