Nanoscale admixture for wet shotcrete and its application method

Abstract

The invention discloses a nano-scale admixture for wet sprayed concrete, which comprises the following components in weight percentage: 92.44%-98.5% of nano-scale amorphous silica powder, 1.5%-6.5% of water reducing agent, thickening group 0.00% to 0.08%, retarding component 0% to 1%; the nano-scale amorphous silica powder in the natural dry state, loose bulk density ≤ 400kg / m 3 , when observed under a high-power electron microscope, the powder particles are in the state of dispersed single particles without obvious agglomerates; the water-reducing agent mentioned is a water-reducing rate ≥ 25% and an air content of ≤5.0% water reducing agent. The innovation of the comprehensive admixture and the use method of the present invention can effectively shorten the initial setting and final setting time of wet shotcrete, can effectively reduce the rebound rate and dust amount of wet shotcrete, improve the strength and durability of wet shotcrete, and pass The introduction of water reducing agent into concrete with low air content is beneficial to give full play to the strengthening effect of nano-scale admixtures on concrete.

Description

technical field [0001] The invention relates to the technical field of production and use of concrete, in particular to a nanoscale admixture for wet 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 mixture with a water-bi...

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Problems solved by technology

[0008] Invention patent application CN201510968974.3 "An early-strength shotcrete" contains silica fume characterized by "the specific surface area of ​​the silica fume of the present invention is 10,000-30,000 cm2 / g", but this silica fume is not mentioned The loose bulk density and particle dispersion, 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, the rebound rate of wet shotcrete using this cement (not specified is comprehensive rebound rate or the rebound rate of the side wall) the lowest 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 ultrafine silica fume is 1.5-10μm", but the loose bulk density and particle dispersibility of this silica fume are not mentioned, and the specific rebound rate of this admixture for wet shotcrete is not mentioned reduce the effect

[0024] Regarding the mixing sequence and the air content 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 wet shotcrete when using or not using nano-scale admixtures

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