Admixture for shotcrete and preparation method and application thereof

Abstract

The invention relates to the technical field of shotcrete, in particular to an admixture for shotcrete and a preparation method and application thereof. Mineral composite powder is subjected to raw material component and a raw material ratio control, and the admixture is prepared from the mineral composite powder, a tackifier, a hydrophilic agent, an air entraining agent and a thickening agent. The admixture is added into shotcrete raw material preparation according to the mass ratio of 4-8% of the total amount of a cementing material, the comprehensive performance of shotcrete is improved, the hanging property, strength and durability of the shotcrete are improved, the setting time of the shotcrete is within 2 min, the plastic viscosity reaches 5.8 Pa.s or above, the spraying rebound rateis lower than 4%, the one-time spraying thickness reaches 30 cm or above, the compressive strength (28d) reaches 40-60 MPa, and the bonding strength (28d) reaches 2.4 MPa or above.

Description

technical field [0001] The invention relates to the technical field of shotcrete, in particular to an admixture for shotcrete and its preparation method and application. Background technique [0002] Shotcrete is the use of spraying machinery, using compressed air or other power, to transport the mixed concrete mixture through pipelines, and spray it to the sprayed surface at high speed, such as: rock walls, formwork, old buildings, etc., after condensation and hardening made concrete. At present, shotcrete is often used in thin-walled structures such as tunnel linings, walls, and ceilings, or as linings for other structures, and as protective layers for steel structures. Shotcrete has the advantages of timely support, high strength, strong compactness, simple operation, and great flexibility. [0003] With the continuous increase of investment in infrastructure construction in my country, shotcrete is widely used in tunnel engineering, underground engineering, slope engin...

AI Technical Summary

Problems solved by technology

However, when sprayed concrete is used in tunnel engineering, due to the poor cohesion and poor hanging performance of shotcrete, the rebound rate of shotcrete is generally above 30%, and the primary sprayed layer is thin, the construction rate is low, and the pollution is large. The dust is high and the loss is large, resulting in high cost of sprayed concrete and low economic benefits. At the same time, it is difficult to guarantee the strength and durability of the sprayed concrete layer

[0004] At present, researchers at home and abroad have made some progress in improving the cohesion, drape, strength, and durability of sprayed concrete. Use nano-silica and mineral admixtures to reduce the rebound rate of sprayed concrete, so that the rebound rate is ≤8%, the setting time is ≤2min, and the thickness of the one-time spray layer is ≥35cm; however, the quality of nano-silica is used in this document Accounting for 70-95%, while the raw material cost of nano-silica is high, and the effect of improving the cohesion of concrete is poor. High, which limits the promotion and application of admixtures

Another example: the preparation method of the low-alkali polymer high-efficiency liquid accelerator for shotcrete with the patent No. 201410053101.5 is added according to the proportion of 2-4% of the cement mass, so that the initial setting time of the shotcrete is within 2 minutes, and the final setting time is within 2 minutes. Within 5 minutes, the strength loss of the concrete in the later stage is within 10%, so as to reduce the dust amount and rebound rate in the shotcrete construction process and improve the strength of the shotcrete; Sodium carbonate is prepared from raw material components, which makes the cost of raw materials higher, and it is not suitable for widespread promotion, and the preparation process of the accelerator is complicated

Another example: the patent application number is 201711294401.2 low-resilience, anti-corrosion sprayed concrete special compound admixture and its application, using 4-30% of water reducer, 0.1-1% of thickener, 0-0.01% of air-entraining agent, eliminating Foaming agent 0-0.01%, retarder 0-0.8%, mineral admixture 70-90%, among which mineral admixture is fly ash, slag, silica fume, limestone powder, superfine calcium carbonate, zeolite powder, etc. , so that the rebound rate after being added to shotcrete is reduced to less than 5%, the corrosion resistance coefficient is increased to more than 90%, and the sulfate resistance level is increased to above KS150; Inappropriate, and the total content of mineral admixture components is low, and the comprehensive performance of concrete such as coagulation strength is still poor

Another example: the patent application number is 201811609906.8 shotcrete and its preparation method and application, using cement, limestone powder, crushed stone, sand, water reducing agent, quick-setting agent, tackifier, water, mixed and stirred evenly to form a sprayed concrete Concrete, it can be seen that limestone powder, water reducing agent, quick-setting agent, and tackifier are used as admixtures to add to shotcrete, so that the rebound rate of the resulting concrete is between 10.5-11.6%, so as to reduce the impact of shotcrete. application cost, however, the sprayed concrete obtained in this technical solution still has a relatively high spray rebound rate, which is difficult to meet the construction requirements of tunnel engineering, and the amount of dust is relatively large

Another example: the special admixture for high-performance sprayed concrete with the patent application number 201910371601.6 is formulated with cohesive components and early-strength components. Among them, the cohesive components are modified latex powder and superfine (d50<5μm ) a mixture of mineral admixtures (silica fume, ultra-fine slag powder), the early-strength component is high-activity tricalcium aluminate, and the early-strength component and the cohesive component act synergistically to reduce the rebound rate of shotcrete ( The rebound rate of the side wall is 1-3%, the rebound rate of the vault is 3-5%), and the compactness is improved, and through core sampling, the 1d compressive strength of shotcrete is 18.1-20.9MPa, and it is obtained with The increase in the amount of admixtures increases the cohesion of shotcrete, decreases the rebound rate, and increases the 1d compressive strength; however, in this technical literature, there is no change in the composition of mineral admixtures and the content of each component. Application research that leads to changes in the properties of the admixture, resulting in poor overall performance of the admixture

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