Self-compacting concrete and preparation method thereof

Abstract

The invention discloses self-compacting concrete and a preparation method thereof, and belongs to the technical field of concrete.The self-compacting concrete is prepared from, by mass, 310-320 parts of cement, 75-85 parts of fly ash, 100-110 parts of mineral powder, 830-850 parts of machine-made sand, 770-790 parts of milling material coarse aggregate, 35-40 parts of steel fiber, 8-12 parts of rubber fiber, 25-30 parts of viscosity modifier, 175-180 parts of water and 7.5-8 parts of polycarboxylic acid type water reducer. According to the self-compacting concrete and the preparation method thereof, the coarse aggregate is prepared by virtue of the rubber fibers, the steel fibers, the viscosity modifier, the machine-made sand and the milling material, so that the problems that the existing self-compacting concrete is insufficient in impact resistance, the rubber component easily floats upwards, and greenization and high performance are difficult to consider at the same time are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete, in particular to a self-compacting concrete and a preparation method thereof. BACKGROUND

[0002] Under the trend of green and high-performance development of building materials, self-compacting concrete has become one of the important materials for modern engineering construction due to the advantages of no need for vibration, high construction efficiency, stable forming quality, etc. Although the existing self-compacting concrete technology can realize resource recycling and cost reduction by mixing solid waste, it does not solve the defects of toughness and impact resistance, and cannot meet the high mechanical performance engineering demand. The technology of mixing rubber powder and rubber particles can consider green and a certain degree of toughness improvement, but the toughening effect is limited, and the rubber is easy to float, which cannot adapt to the self-compacting concrete with high fluidity. Therefore, new targeted technology is needed to solve the problems of insufficient impact resistance of self-compacting concrete and easy floating of rubber components. SUMMARY

[0003] The purpose of the present application is to provide a self-compacting concrete and a preparation method thereof, which fully utilizes solid waste to realize the green of the whole component source of self-compacting concrete, and uses rubber fibers, steel fibers, viscosity modifiers, machine-made sand and milled material to make coarse aggregate, thereby solving the problems of insufficient impact resistance of existing self-compacting concrete, easy floating of rubber components and difficulty in considering green and high performance.

[0004] To achieve the above purpose, the present application provides a self-compacting concrete, which comprises cement 310-320 parts by mass, fly ash 75-85 parts by mass, mineral powder 100-110 parts by mass, machine-made sand 830-850 parts by mass, milled material coarse aggregate 770-790 parts by mass, steel fiber 35-40 parts by mass, rubber fiber 8-12 parts by mass, viscosity modifier 25-30 parts by mass, water 175-180 parts by mass and water reducing agent 7.5-8 parts by mass.

[0005] Preferably, the specific surface area of the fly ash is 420-450 m 2 / kg.

[0006] Preferably, the length of the steel fiber is 12-15 mm, and the diameter of the steel fiber is 0.3-0.5 mm.

[0007] Preferably, the length of the rubber fiber is 15-20 mm, and the width of the rubber fiber is 2-5 mm.

[0008] Preferably, the rubber fiber and the steel fiber are obtained by separating the rubber and the steel wire in the waste tire through a double-shaft shredder.

[0009] Preferably, the diameter of the milled material coarse aggregate is 5-20 mm.

[0010] Further, the milling material coarse aggregate is obtained by dust removal and screening of the pavement milling material.

[0011] Preferably, the viscosity modifier comprises silica ash, limestone powder, ultra-fine fly ash and hydroxyethyl methyl cellulose.

[0012] Further, the mass ratio of the silica ash, the limestone powder, the ultra-fine fly ash and the hydroxyethyl methyl cellulose is 13-15:5-6:5-6:0.10-0.12, and the specific surface area of the ultra-fine fly ash is 800-810 m 2 / kg.

[0013] Preferably, the water reducing agent comprises a polycarboxylic acid type water reducing agent.

[0014] The application further provides a preparation method of the self-compacting concrete, comprising the following steps: S1, mixing cement, fly ash, mineral powder, machine-made sand, milling material coarse aggregate, steel fiber, rubber fiber and viscosity modifier, and stirring to obtain a uniform dry mixture; S2, mixing a water reducing agent and water to obtain a mixed liquid, adding the mixed liquid into the dry mixture obtained in S1, and stirring to obtain the self-compacting concrete.

[0015] Preferably, in S1, the stirring speed is 40-50 r / min, and the stirring time is 30-40 s.

[0016] Preferably, in S2, the stirring speed is 40-50 r / min, and the stirring time is 2-3 min.

[0017] Therefore, the application has the following beneficial effects by adopting the self-compacting concrete and the preparation method thereof: (1) The steel fiber and the rubber fiber in the self-compacting concrete of the application are obtained by processing recycled waste tires, the milling material coarse aggregate is obtained by pretreatment of pavement milling material, and the machine-made sand is made of ore or building solid waste, so that the solid waste materials are fully utilized, the resource utilization of the solid waste materials is maximized, the carbon emissions of the coarse and fine aggregates, the cementitious materials and the toughening components in the self-compacting concrete are greatly reduced, and the green preparation of all components of the self-compacting concrete is realized.

[0018] (2) The present invention achieves uniform dispersion of low-density rubber fibers in self-compacting concrete through two methods: one is to utilize the characteristics of the rubber fibers themselves being slender and having high friction, and the other is to add an organic-inorganic composite viscosity modifier to increase the viscosity of the concrete paste. The slenderness and high friction of the rubber fibers themselves generate greater "cohesive force" between the fibers and between the fibers and concrete particles, so as to counteract the upward tendency of the rubber fibers due to their low density and prevent agglomeration; the concrete after adding the viscosity modifier is more viscous, which can better wrap the low-density rubber fibers, restrict their movement, and make them uniformly suspended in the concrete paste.

[0019] (3) In this invention, the road milling material replaces ordinary gravel. The road milling material is attached with asphalt components and steel fiber-rubber fiber to achieve multi-scale toughening of self-compacting concrete, which significantly improves the impact resistance of self-compacting concrete.

[0020] (4) In this invention, manufactured sand replaces rounded river sand. The surface of manufactured sand particles is rougher and more angular, which can optimize the distribution environment of fibers in concrete, reduce the sliding friction between fibers and aggregates, and further enhance the impact toughness of concrete in conjunction with the dispersion effect of viscosity modifier on rubber fibers.

[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0022] Figure 1 These are impact stress-strain curves of self-compacting concrete in Embodiment 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0025] In this invention, unless otherwise specified, the test materials and instruments are all conventional test materials in the field and can be purchased through commercial channels.

[0026] Example 1 This invention provides a self-compacting concrete, comprising, by weight, 312 parts cement, 78 parts fly ash, 104 parts mineral powder, 840 parts manufactured sand, 780 parts milled coarse aggregate, 39.5 parts steel fiber, 10 parts rubber fiber, 25.1 parts viscosity modifier, 178 parts water, and 7.8 parts polycarboxylate superplasticizer. The specific surface area of ​​fly ash is 420 m². 2 / kg, the viscosity modifier includes 15 parts silica fume, 5 parts limestone powder, 5 parts ultrafine fly ash, and 0.10 parts hydroxyethyl methyl cellulose. The specific surface area of ​​the ultrafine fly ash is 800 m². 2 / kg.

[0027] This invention also provides a method for preparing self-compacting concrete, comprising the following steps: S1. Add cement, fly ash, mineral powder, manufactured sand, milled coarse aggregate, steel fiber, rubber fiber, and viscosity modifier to a concrete mixer and mix at a speed of 50 r / min for 30 s to obtain a uniform dry mixture. Among them, rubber fibers and steel fibers are obtained by separating and processing the rubber and steel wires in waste tires using a twin-shaft shredder. The rubber is processed into rubber fibers with a length of 15mm and a width of 3mm, and the steel wire is processed into steel fibers with a length of 12mm and a diameter of 0.3mm. The coarse aggregate made from milled material is obtained by removing dust and screening the milled material from the road surface. The diameter of the coarse aggregate made from milled material is 10mm.

[0028] S2. Mix the water-reducing agent and water evenly to obtain a mixture. Slowly add the mixture to the dry material mixture obtained in S1 and stir at 50 r / min for 3 minutes to obtain self-compacting concrete.

[0029] Comparative Example 1 A self-compacting concrete, by weight, comprises 312 parts cement, 78 parts fly ash, 104 parts mineral powder, 840 parts ordinary river sand, 780 parts coarse aggregate made from ordinary gravel, 25.1 parts viscosity modifier, 178 parts water, and 7.8 parts polycarboxylate superplasticizer. The specific surface area of ​​fly ash is 420 m². 2 / kg, the viscosity modifier includes 15 parts silica fume, 5 parts limestone powder, 5 parts ultrafine fly ash, and 0.10 parts hydroxyethyl methyl cellulose. The specific surface area of ​​the ultrafine fly ash is 800 m². 2 / kg.

[0030] A method for preparing self-compacting concrete includes the following steps: S1. Add cement, fly ash, mineral powder, ordinary river sand, ordinary gravel coarse aggregate, and viscosity modifier to a concrete mixer and mix at a speed of 50 r / min for 30 s to obtain a uniform dry mixture. S2. Mix the water-reducing agent and water evenly to obtain a mixture. Slowly add the mixture to the dry material mixture obtained in S1 and stir at 50 r / min for 3 minutes to obtain self-compacting concrete.

[0031] The stress-strain curves of the self-compacting concrete prepared in Example 1 and Comparative Example 1 under different impact strain rates are shown below. Figure 1As shown, 0 represents the peak strain of concrete, and the impact toughness is expressed as 0-2. An area gauge covering the stress-strain curve within the 0 range. From Figure 1 From this, it can be concluded that at low (30s) -1 ), Middle (60s) -1 ), high (90s -1 The strain rate was measured at different speeds during the experiment, and the strain rate was then calculated based on the speed. Therefore, a perfect match could not be achieved. Figure 1 For 30 seconds -1 60s -1 90s -1 (Based on nearby data), the impact toughness of the self-compacting concrete in Example 1 was increased by 55.3%, 71.4%, and 68.1% compared to the self-compacting concrete in Comparative Example 1, respectively.

[0032] Therefore, the present invention adopts the above-mentioned self-compacting concrete and its preparation method, making full use of solid waste to achieve greening of all components of self-compacting concrete. By using rubber fiber, steel fiber, viscosity modifier, manufactured sand and milling material to make coarse aggregate, it specifically solves the problems of insufficient impact resistance, easy floating of rubber components and difficulty in balancing greening and high performance in existing self-compacting concrete.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A self-compacting concrete, characterized in that: By weight, it includes 310-320 parts cement, 75-85 parts fly ash, 100-110 parts mineral powder, 830-850 parts manufactured sand, 770-790 parts milled coarse aggregate, 35-40 parts steel fiber, 8-12 parts rubber fiber, 25-30 parts viscosity modifier, 175-180 parts water, and 7.5-8 parts water-reducing agent.

2. The self-compacting concrete according to claim 1, characterized in that: The steel fibers are 12-15mm long and 0.3-0.5mm in diameter.

3. The self-compacting concrete according to claim 1, characterized in that: The length of the rubber fiber is 15-20mm, and the width of the rubber fiber is 2-5mm.

4. The self-compacting concrete according to claim 1, characterized in that: The diameter of coarse aggregate produced by milling is 5-20mm.

5. The self-compacting concrete according to claim 1, characterized in that: Viscosity modifiers include silica fume, limestone powder, ultrafine fly ash, and hydroxyethyl methyl cellulose.

6. The self-compacting concrete according to claim 5, characterized in that: The mass ratio of silica fume, limestone powder, ultrafine fly ash, and hydroxyethyl methyl cellulose is 13-15:5-6:5-6:0.10-0.12, and the specific surface area of ​​the ultrafine fly ash is 800-810 m². 2 / kg.

7. The self-compacting concrete according to claim 1, characterized in that: Water-reducing agents include polycarboxylate-based water-reducing agents.

8. A method for preparing self-compacting concrete according to any one of claims 1-7, characterized in that: Includes the following steps: S1. Mix cement, fly ash, mineral powder, manufactured sand, milling material coarse aggregate, steel fiber, rubber fiber, and viscosity modifier to obtain a uniform dry mixture. S2. Mix the water-reducing agent and water to obtain a mixture. Add the mixture to the dry material mixture obtained in S1 and stir to obtain self-compacting concrete.

9. The method for preparing self-compacting concrete according to claim 8, characterized in that: In S1, the stirring speed is 40-50 r / min and the stirring time is 30-40 s.

10. A method for preparing self-compacting concrete according to claim 8, characterized in that: In S2, the stirring speed is 40-50 r / min, and the stirring time is 2-3 min.

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