CN114671644A

CN114671644A - High-early-strength low-resilience high-performance shotcrete and preparation method thereof

Info

Publication number: CN114671644A
Application number: CN202210294941.5A
Authority: CN
Inventors: 陈本稳; 甘杰忠; 王靖淳; 杜新康; 郑春扬
Original assignee: Chengdu Aolaite Times New Material Co ltd; Jiangsu China Railway ARIT New Materials Co Ltd
Current assignee: Chengdu Aolaite Times New Material Co ltd; Jiangsu China Railway ARIT New Materials Co Ltd
Priority date: 2022-03-24
Filing date: 2022-03-24
Publication date: 2022-06-28
Anticipated expiration: 2042-03-24
Also published as: CN114671644B

Abstract

The invention discloses a high-performance shotcrete with high early strength and low resilience and a preparation method thereof, wherein the ratio is as follows: 470 parts of cement 350-90 parts, 22-90 parts of self-made admixture, 900 parts of sand 800-900 parts, 900 parts of stone 800-900 parts, 200 parts of water 150-8 parts, 4-8 parts of water reducing agent and 27-40 parts of alkali-free accelerator; the method comprises the following steps: mixing and stirring cement, a self-made admixture, sand, pebbles, water and a water reducing agent to obtain a mixture, conveying the mixture to a construction position, mixing the mixture and an alkali-free accelerator through a concrete wet spraying machine, and spraying out to obtain sprayed concrete; the concrete has excellent working performance, the mortar material can resist slump for two hours, after the alkali-free setting accelerator is added and sprayed out, the concrete is quickly condensed and hardened under the synergistic action of the cement, the admixture and the setting accelerator, the wet-spraying rebound rate of the tunnel is greatly reduced, the comprehensive rebound rate can be controlled within 10 percent, and the design requirement of high-performance sprayed concrete is met.

Description

High-early-strength low-resilience high-performance shotcrete and preparation method thereof

Technical Field

The invention relates to the field of sprayed concrete, in particular to high-performance sprayed concrete with high early strength and low resilience and a preparation method thereof.

Background

The sprayed concrete is the concrete which is sprayed to a sprayed surface at a high speed through an inflation hose or a pipeline under the action of air pressure and is instantly solidified and compacted. The method is widely applied to the fields of primary or permanent support of tunnels and roadways, foundation pit slope support, structural reinforcement and maintenance and the like. The accelerator is an additive capable of promoting concrete to be rapidly set and hardened, and is an important component material of sprayed concrete. Early accelerators mostly take powder or alkaline liquid accelerators as the main materials, and the accelerators have the advantages of small mixing amount, short setting time and the like, but have high corrosivity and high integral resilience rate, and the excessive alkali content easily causes concrete strength shrinkage, shrinkage cracking and alkali-aggregate reaction, thereby seriously affecting the durability of sprayed concrete. With the successive implementation of standards such as national standard GB/T35159-2017 accelerator for sprayed concrete, and the like, alkali-free liquid accelerators are gradually accepted by the market, but the quality of the alkali-free accelerators on the market at present is uneven, fluorine-containing systems such as hydrofluoric acid and fluosilicic acid are superior to alkali-free accelerators, and although the alkali content indexes of the accelerators are qualified and the setting time is short, the accelerators also have the problems of toxic and harmful raw materials, strong corrosivity, slow development of early strength and the like. The early strength of the sprayed concrete is too low, so that the rebound rate is increased, the primary support effect cannot be exerted in time, and the accidents of deformation and settlement and even collapse of surrounding rocks are easy to occur. With the start-up construction of new Chuanheng railways and other projects of national strategic engineering, the traditional sprayed concrete can not meet the requirements of railway tunnels in construction period and service period. Therefore, it is imperative to develop a high-performance shotcrete having high early strength and low shotcrete resilience.

The prior art publication number is: CN110282936A discloses a high-performance shotcrete and a mixing method, wherein the ingredients comprise a gel material, coarse aggregates, fine aggregates, a water reducing agent, an accelerator and water; the ultrafine silicon powder is used as a cementing material like cement, so that the impermeability, the chemical erosion resistance and the early strength of the concrete are improved. But there are also: the early strength development is not rapid enough, the 3h compressive strength and the 8h compressive strength are not mentioned, the 24h compressive strength is only 16MPa at most, and the index requirements of the early high-strength shotcrete in the heavy-spot engineering projects such as Sichuan-Tibet railway are difficult to meet.

Disclosure of Invention

1. The technical problem to be solved is as follows:

aiming at the technical problems, the invention provides high-performance shotcrete with high early strength and low resilience and a preparation method thereof, wherein the shotcrete has excellent working performance, the slump keeping capability can be realized for two hours, after an alkali-free setting accelerator is added and sprayed out, the concrete is rapidly solidified and hardened under the synergistic action of cement, an admixture and the setting accelerator, the wet-spraying resilience rate of a tunnel is greatly reduced, and the comprehensive resilience rate can be controlled within 10%. Meanwhile, the early hour strength is rapidly improved, the 3h compressive strength can reach more than 5MPa, the 8h compressive strength can reach more than 15MPa, the 24h compressive strength can reach more than 25MPa, and the later strength is not shrunk, so that the design requirement of high-performance sprayed concrete can be met.

2. The technical scheme is as follows:

the utility model provides a high performance shotcrete of low resilience of high early strength which characterized in that: comprises the following components in parts by weight:

470 parts of cement, 22-90 parts of self-made admixture, 900 parts of sand, 900 parts of stone, 150 parts of water, 4-8 parts of water reducing agent and 27-40 parts of alkali-free accelerator; the self-made admixture specifically comprises the following components in percentage by mass: 30-60% of calcium sulphoaluminate, 10-30% of limestone powder, 10-20% of superfine silica fume, 10-20% of metakaolin, 1-3% of aluminum lactate, 1-3% of lithium carbonate and 0.5-1% of tartaric acid.

Furthermore, the calcium sulphoaluminate has a calcium oxide content of more than or equal to 40 percent and an aluminum oxide content of more than or equal to 20 percent.

Further, the silicon dioxide content of the superfine silica fume is more than or equal to 95 percent, and the specific surface area is more than or equal to 20000 m 2/kg; the calcium carbonate content of the limestone powder is more than or equal to 95 percent, and the specific surface area is more than or equal to 1800 m 2/kg; the silicon dioxide content of the metakaolin is more than or equal to 50 percent, the alumina content is more than or equal to 40 percent, and the activity index is more than or equal to 110 percent; the aluminum lactate is in industrial grade, and the purity is more than or equal to 99 percent; the lithium carbonate is in industrial grade, and the purity is more than or equal to 99%.

Further, the tartaric acid is any one of DL-tartaric acid, D-tartaric acid or L-tartaric acid, and the purity is more than or equal to 99%.

Furthermore, the sand is medium coarse sand, the fineness modulus is 2.5-3.2, the grading area is more than 2 areas, and the mud content is less than 1%.

Further, the particle size of the crushed stone is 5-10 mm; the strength grade of the cement reaches above P.O 42.5.5.

Further, the water reducing agent is a polycarboxylic acid high-performance water reducing agent.

Further, the alkali-free setting accelerator is an accelerator with the initial setting time of less than or equal to 5min, the final setting time of less than or equal to 12min, the compressive strength of the mortar after 6h of more than or equal to 1.0MPa, and the compressive strength of the mortar after 1d of more than or equal to 10.0 MPa.

A preparation method of high-performance shotcrete with high early strength and low resilience is used for preparing the high-performance shotcrete, and cement, self-made admixture, sand, stones, water and water reducing agent in the proportion are mixed and stirred uniformly to prepare a mixture; and (3) transporting the mixture to a construction position, mixing the mixture with an alkali-free accelerator through a concrete wet spraying machine, and spraying out to obtain the high-performance sprayed concrete.

3. Has the advantages that:

(1) the self-made admixture adopted by the high-performance sprayed concrete provided by the invention has a large proportion of calcium sulfoaluminate, the calcium sulfoaluminate firstly and dihydrate gypsum quickly react in a cement hydration system to generate a large amount of ettringite and alumina gel, the rapid formation of the ettringite can provide a skeleton structure for cement slurry to promote the coagulation of the slurry and improve the early strength, and meanwhile, the calcium sulfoaluminate and the setting accelerator are sprayed out by high-pressure air of a wet sprayer by utilizing the synergistic action of the calcium sulfoaluminate and the setting accelerator, and can be quickly coagulated and hardened and generate strength after being contacted by a spray head, so that the spraying rebound rate can be greatly reduced.

(2) Limestone powder in the self-made admixture is used as a main filler, and the compactness of concrete can be improved through reasonable particle size distribution and proportion; the superfine silica fume and the metakaolin are active admixture, and can be mixed into cement to perform secondary hydration reaction with cement hydration products to generate CSH gel, and the superfine silica fume and the metakaolin have small granularity and large specific surface area and can be filled in particle gaps of the set cement to enable the integral microstructure to be more compact, so that the high pozzolanic activity and the micro-aggregate filling effect can effectively improve the early strength;

(3) the aluminum lactate in the self-made admixture has good coagulability under alkaline conditions, provides effective aluminum ions in a cement hydration system, and plays a synergistic effect with the accelerating agent to effectively promote cement hydration; lithium carbonate is used as an early strength agent, and can also improve the early strength of concrete. Tartaric acid is easy to combine with calcium in a cement hydration system to generate corresponding calcium salt, so that the concentration of calcium ions is reduced when cement is hydrated, hardening products are reduced, the hardening process is correspondingly delayed, and a certain retarding effect is achieved. The tartaric acid is added in a proper amount, so that the construction performance of the sprayed concrete is ensured before the accelerator is added, the collapse loss is prevented from being too fast, and the setting and hardening effects of the sprayed concrete are not influenced after the accelerator is added.

Detailed Description

Example 1

The embodiment provides a high-performance shotcrete with high early strength and low resilience, which comprises the following components in parts by weight:

390 parts of cement, 60 parts of self-made admixture, 870 parts of sand, 830 parts of stones, 167 parts of water, 5 parts of water reducing agent and 36 parts of alkali-free setting accelerator;

wherein, the self-made admixture comprises the following components in percentage by mass: 50% of calcium sulphoaluminate, 20% of limestone powder, 15% of superfine silica fume, 10% of metakaolin, 3% of aluminum lactate, 1.5% of lithium carbonate and 0.5% of tartaric acid; the alkali-free accelerator is an accelerator which accords with national iron QCR 807 and 2020 liquid alkali-free accelerator for tunnel shotcrete.

The embodiment of the invention also provides a preparation method of the high-performance shotcrete with high early strength and low resilience, and the specific implementation mode is as follows:

the high-performance shotcrete is prepared by uniformly mixing and stirring cement, a self-made admixture, sand, stones, water and a water reducing agent to prepare a mixture, transporting the mixture to a construction position, mixing the mixture with an alkali-free accelerator through a concrete wet spraying machine, and spraying the mixture out.

Example 2

360 parts of cement, 90 parts of self-made admixture, 850 parts of sand, 850 parts of pebbles, 171 parts of water, 5 parts of water reducing agent and 32 parts of alkali-free setting accelerator;

wherein, the self-made admixture comprises the following components in percentage by mass: 60% of calcium sulphoaluminate, 15% of limestone powder, 12% of superfine silica fume, 10% of metakaolin, 2% of aluminum lactate, 0.5% of lithium carbonate and 0.5% of tartaric acid.

The preparation process is referred to example 1.

Example 3

405 parts of cement, 45 parts of self-made admixture, 830 parts of sand, 870 parts of stones, 180 parts of water, 4 parts of water reducing agent and 38 parts of alkali-free setting accelerator;

wherein, the self-made admixture comprises the following components in percentage by mass: 40% of calcium sulphoaluminate, 25% of limestone powder, 18% of superfine silica fume, 14% of metakaolin, 1% of aluminum lactate, 1% of lithium carbonate and 1% of tartaric acid.

The preparation process is referred to example 1.

Example 4

427 parts of cement, 23 parts of self-made admixture, 860 parts of sand, 840 parts of stones, 190 parts of water, 6 parts of water reducing agent and 30 parts of alkali-free setting accelerator;

wherein, the self-made admixture comprises the following components in percentage by mass: 30% of calcium sulphoaluminate, 30% of limestone powder, 16% of superfine silica fume, 20% of metakaolin, 2% of aluminum lactate, 1% of lithium carbonate and 1% of tartaric acid.

The preparation process is referred to example 1.

Comparative example 1

The comparative example was substantially identical to example 1 in the composition of the raw materials except that cement was used instead of the home-made admixture.

The preparation process is referred to example 1.

Comparative example 2

The comparative example is substantially the same as example 2 in the raw material components, except that the self-made alkali-free accelerator is replaced by the commercially available fluorine-containing alkali-free accelerator.

The preparation process is referred to example 1.

Comparative example 3

The raw material components of the comparative example are basically the same as those of the example 3, and the difference is that the water consumption of the concrete mixing ratio is adjusted to 240 parts, and a water reducing agent is not used.

The preparation process is referred to example 1.

Application example:

the shotcrete prepared according to the above examples 1-4 and comparative examples 1-3 was sprayed on the tunnel site, the rebound material was collected to test the rebound rate, the large panel was formed and the compression strength of the concrete was tested for 3h, 8h and 1d, and the test results are shown in the following table.

From the test data in the table above, it can be seen that the high performance shotcrete prepared by the examples 1-4 of the present invention is significantly better than the comparative examples 1-3 in terms of both the shotcrete resilience and the concrete compressive strength data. In the aspect of the compressive strength of the concrete, the compressive strength of 3h in examples 1 to 4 is more than 4MPa, the compressive strength of 8h in examples 1 to 4 is more than 10MPa, the compressive strength of 1d in examples 1 to 3 is more than 20MPa, the compressive strength of 3h in comparative examples 1 to 3 is not more than 3MPa, the lowest compressive strength is only 1.8MPa, the compressive strength of 8h in examples is not more than 10MPa, the lowest compressive strength is only 2.5MPa, the compressive strength of 1d in examples is not more than 15MPa, and the lowest compressive strength is only 6.3 MPa. In the aspect of the rebound rate of the on-site injection, the rebound rates of the side walls of the examples 1 to 4 are controlled within 5 percent, the rebound rate of the arch crown is controlled within 12 percent and is far lower than the control indexes in the industry: the rebound rate of the side wall is not more than 15 percent, and the rebound rate of the arch crown is not more than 25 percent.

The rebound rate of the side wall of the comparative examples 1 and 2 is increased, and the rebound rate of the vault is increased by more than 50%, the main reason is that the self-made admixture is not added in the comparative example 1, the setting time is prolonged, the early strength development is slow, the comparative example 2 replaces the fluorine-containing alkali-free setting accelerator, the rebound rate is lower than that of the comparative example 1 because the setting time is fast, but the early strength development is almost stopped, the sprayed material cannot form a stable structure in time, the sprayed material is easy to fall off under self weight, and the phenomenon of block falling is generated, so that the integral rebound rate is obviously increased compared with that of the embodiment. In the comparative example 3, because no water reducing agent is used, the proper slump can be obtained only by the test of a larger water-cement ratio, and the excessively high water-cement ratio is unfavorable for the coagulation effect of the accelerating agent and the strength development of concrete, so that the rebound rate of the side wall and the vault is greatly increased.

In conclusion, the invention discloses high-performance shotcrete with high early strength and low resilience and a preparation method thereof, the high-performance shotcrete has excellent working performance, the shotcrete can resist slump for two hours, after an alkali-free accelerating agent is added for ejection, the concrete is rapidly solidified and hardened under the synergistic action of cement, an admixture and the accelerating agent, the wet-spraying resilience rate of a tunnel is greatly reduced, and the comprehensive resilience rate can be controlled within 10%. Meanwhile, the early hour strength is rapidly improved, the 3h compressive strength can reach more than 5MPa, the 8h compressive strength can reach more than 15MPa, the 24h compressive strength can reach more than 25MPa, and the later strength is not shrunk, so that the design requirement of high-performance sprayed concrete can be met.

Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. The utility model provides a high performance shotcrete of low resilience of high early strength which characterized in that: comprises the following components in parts by weight:

2. The high-performance shotcrete with high early strength and low resilience of claim 1, wherein: the calcium sulphoaluminate has a calcium oxide content of more than or equal to 40 percent and an aluminum oxide content of more than or equal to 20 percent.

3. The high-performance shotcrete with high early strength and low resilience of claim 1, wherein: the silicon dioxide content of the superfine silica fume is more than or equal to 95 percent, and the specific surface area is more than or equal to 20000 m²Per kg; the calcium carbonate content of the limestone powder is more than or equal to 95 percent, and the specific surface area is more than or equal to 1800 m²Per kg; the silicon dioxide content of the metakaolin is more than or equal to 50 percent, the alumina content is more than or equal to 40 percent, and the activity index is more than or equal to 110 percent; the aluminum lactate is of industrial grade, and the purity is more than or equal to 99 percent; the lithium carbonate is in industrial grade, and the purity is more than or equal to 99%.

4. The high-performance shotcrete with high early strength and low resilience of claim 1, wherein: the tartaric acid is any one of DL-tartaric acid, D-tartaric acid or L-tartaric acid, and the purity is more than or equal to 99%.

5. The high-performance shotcrete with high early strength and low resilience of claim 1, wherein: the sand is medium coarse sand, the fineness modulus is 2.5-3.2, the grading zone is more than 2 zones, and the mud content is less than 1%.

6. The high-performance shotcrete with high early strength and low resilience as claimed in claim 1, wherein: the particle size of the crushed stone is 5-10 mm; the strength grade of the cement reaches above P.O 42.5.5.

7. The high-performance shotcrete with high early strength and low resilience of claim 1, wherein: the water reducing agent is a polycarboxylic acid high-performance water reducing agent.

8. The high-performance shotcrete with high early strength and low resilience of claim 1, wherein: the alkali-free setting accelerator is an accelerator with the initial setting time of less than or equal to 5min, the final setting time of less than or equal to 12min, the compressive strength of the mortar after 6h of the mortar is more than or equal to 1.0MPa, and the compressive strength of the mortar after 1d of the mortar is more than or equal to 10.0 MPa.

9. A method for preparing a high early strength low resilience high performance shotcrete for use in preparing a concrete according to any one of claims 1 to 8, wherein: mixing and stirring cement, self-made admixture, sand, gravel, water and water reducing agent according to the proportion of any one of claims 1 to 8 uniformly to prepare a mixture; and (4) conveying the mixture to a construction position, and passing through a concrete wet spraying machine.