Nano-scale admixture for dry-spray or tidal spray of concrete, and using method of nano-scale admixture

Abstract

The invention discloses a nano-scale admixture for dry-spray or tidal spray of concrete, and a using method of the nano-scale admixture. The admixture is prepared from the following components by weight percent: 94-99% of nano-scale amorphous silica powder, 1-4% of a water reducing agent, 0.00-0.08% of a thickening component and 0-2% of a retarding component; the nano-scale amorphous silica powderhas a loose bulk density of less than or equal to 400 kg / m<3>, preferably less than or equal to 300 kg / m<3> in a natural dry state, and the powder particles are dispersed in a single particle state without obvious agglomerates under a high power electron microscope. When in use, the admixture and coarse aggregate are firstly stirred to promote further dispersion of the amorphous silica powder under the action of rubbing and kneading of the coarse aggregate, and then other materials are added. The invention integrates the innovation of the admixture and the use method thereof, thus effectivelyshortening the initial setting time and final setting time of the concrete, effectively reducing the rebound rate and dust amount of the concrete, improving the strength and durability of the concrete, and helping to reduce the comprehensive construction cost of shotcreting.

Description

technical field [0001] The invention relates to the technical field of production and use of concrete, in particular to a nanoscale admixture for dry sprayed or tidal sprayed concrete and a use method thereof. Background technique [0002] Shotcrete is widely used in excavation and support of underground engineering, excavation and support of geotechnical engineering such as slopes and foundation pits, repair and reinforcement projects, etc. According to the commonly used spraying process, it is divided into dry spraying (abbreviation of dry or dry spraying), wet spraying (abbreviation of wet or wet spraying), tidal spraying (abbreviation of tidal spraying or semi-wet spraying) and cement-coated sand spraying concrete. Dry sprayed concrete is a dry bulk mixture made by mixing cement, sand and stone in a natural water state according to a certain ratio, and puts it into the sprayer. Send to the nozzle and spray with water pressure. Wet sprayed concrete is a concrete mixtur...

AI Technical Summary

Problems solved by technology

[0008] Invention patent application CN201510968974.3 "An early-strength sprayed concrete" is characterized by the silica fume contained in "the specific surface area of ​​the silica fume of the present invention is 10,000-30,000 cm 2 / g", but did not mention the loose bulk density and particle dispersion of this silica fume, and the rebound rate of concrete with this composition can only reach ≤15%, which is still high

[0009] Invention patent application CN201810036120.5 "A high-strength low-rebound shotcrete and its construction process" is characterized by the silica fume contained in the composition of "the silica fume that can be used for shotcrete purchased on the market, preferably with an average particle size of At 0.1μm~0.3μm, the specific surface area is 20m 2 / g~28m 2 / g of silica fume", but does not mention the loose bulk density and particle dispersion of this silica fume

And its dosage in the gelling material is as high as 12% to 19%, resulting in a large increase in the cost of the gelling material

[0010] Invention patent application CN201810189927.2 "A cement specially used for shotcrete mixed with an alkali-free liquid accelerator" is characterized by silica fume contained in the composition: "The silica fume described is ultrafine silica fume, and its average particle size is The diameter is 1.5μm-10μm", but the loose bulk density and particle dispersion of this silica fume are not mentioned, and according to its examples, even if this composition is used for the rebound rate is lower than that of dry sprayed or tidal sprayed concrete The wet sprayed concrete, its rebound rate (it is not specified whether it is the comprehensive rebound rate or the side wall rebound rate) can only reach ≤10.4%, which is still high

[0011] Invention patent application CN201710085030.0 "a high-strength ultra-fine shotcrete admixture" is characterized by the silica fume contained in the composition of "expanded superfine silica powder includes silicon dioxide, ferric oxide and alumina and the three substances The weight ratio of the three substances is 67.5-83.7:4.5-5.6:0.6-0.7", "expanded ultrafine silicon powder includes silicon dioxide, ferric oxide and alumina and the weight ratio of these three substances is 76.9:4.9:0.65" , "The particle size of expanded ultra-fine silica fume is 1.5-10 μm", but the loose bulk density and particle dispersibility of this silica fume are not mentioned, and the specific application of this admixture for dry spraying or tidal spraying concrete is not mentioned. Springback reduction effect

In the processing of such powdery materials, if liquid water-reducing components are used, due to their low dosage, it is easy to adhere to and form agglomerates with other powder components after feeding, and it is difficult to ensure the uniformity of powder mixing.

[0014] Moreover, the existing technology ignores the special requirements for the dissolution rate of the water-reducing agent when dry-sprayed or tidal-sprayed concrete, such as dry and hard concrete with low water consumption, is used in the powdery water-reducing agent——the mixture produced by the mixing plant is relatively dry or The wet mixture is mixed with water in the spray gun for less than 1 second. If the powdery water reducer cannot be dissolved quickly in such a short period of time, the sprayed mixture will not have enough workability and cannot be well attached to the surface. On the sprayed surface, the rebound is too large, and the concrete is not uniform enough, resulting in strength fluctuations, which forces the spray gun workers to increase the workability of the mixture by adding more water, which reduces the concrete strength.

[0020] With regard to the mixing sequence and the moisture control standard of the mixture, none of the prior art mentions the impact of these processes on the rebound rate, strength and dust content of dry sprayed or tidal shotcrete with or without nanoscale admixtures

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