CN114671644B

CN114671644B - High-early-strength low-resilience high-performance sprayed concrete and preparation method thereof

Info

Publication number: CN114671644B
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: 2023-06-23
Anticipated expiration: 2042-03-24
Also published as: CN114671644A

Abstract

The invention discloses high-early-strength low-resilience high-performance sprayed concrete and a preparation method thereof, wherein the high-early-strength low-resilience high-performance sprayed concrete comprises the following components in parts by weight: 350-470 parts of cement, 22-90 parts of self-made admixture, 800-900 parts of sand, 800-900 parts of stone, 150-200 parts of water, 4-8 parts of water reducer and 27-40 parts of alkali-free accelerator; the method comprises the following steps: mixing and stirring cement, self-made admixture, sand, cobble, water and water reducing agent to obtain admixture, transporting the admixture to a construction position, mixing the admixture with alkali-free accelerator by a concrete wet spraying machine and spraying to obtain sprayed concrete; the concrete has excellent working performance, the spraying slurry can keep slump for two hours, after the alkali-free accelerator is added and sprayed, the concrete is quickly coagulated and hardened by the synergistic effect of the cement, the admixture and the accelerator, the wet spraying rebound rate of a 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 sprayed concrete and preparation method thereof

Technical Field

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

Background

The sprayed concrete is the concrete which is sprayed on the sprayed surface at high speed and is solidified and compacted instantaneously through an inflatable hose or a pipeline under the action of air pressure. The method is widely applied to the fields of initial 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 quickly coagulate and harden, and is an important constituent material of sprayed concrete. The early accelerator is mainly powder or alkali liquid accelerator, and has the advantages of small mixing amount, quick setting time and the like, but has larger corrosiveness, higher overall rebound rate, and excessively high alkali content is extremely easy to cause concrete strength collapse, shrinkage cracking and alkali aggregate reaction, thereby seriously affecting the durability of sprayed concrete. Along with the sequential implementation of the national standard GB/T35159-2017 'accelerator for sprayed concrete' and other standards, alkali-free liquid accelerators gradually gain market acceptance, but the alkali-free accelerators on the market at present have uneven quality, fluorine-containing substances such as hydrofluoric acid and fluosilicic acid system alkali-free accelerators are popular, the alkali content index of the accelerator is qualified, the setting time is faster, but the problems of toxic and harmful raw materials, strong corrosiveness, slow development of early strength and the like are also existed. The early strength of the sprayed concrete is too low, so that not only is the rebound rate increased, but also the primary support effect cannot be timely exerted, and surrounding rock deformation, sedimentation and even collapse accidents are easy to occur. Along with the construction of the projects such as new Sichuan-Tibetan railways of national strategic engineering, the traditional sprayed concrete can not meet the requirements of the construction period and the service period of railway tunnels. Therefore, it is imperative to develop a high-performance shotcrete with high early strength and low spray rebound.

The prior art has the publication number: CN110282936a discloses a high-performance sprayed concrete and a mixing method, wherein the ingredients comprise gel material, coarse aggregate, fine aggregate, water reducer, accelerator and water; the ultrafine silica powder is used as a cementing material like cement, so that the impermeability, chemical erosion resistance and early strength of the concrete are improved. But still exists: the early strength development is not rapid enough, the 3h compressive strength and the 8h compressive strength are not mentioned, the maximum 24h compressive strength is only 16MPa, and the index requirement of the early high-strength sprayed concrete of heavy-point engineering projects such as a Sichuan and Tibetan railway is difficult to meet.

Disclosure of Invention

1. The technical problems to be solved are as follows:

aiming at the technical problems, the invention provides the high-early-strength low-resilience high-performance sprayed concrete and the preparation method thereof, the high-early-strength low-resilience high-performance sprayed concrete has excellent working performance, the sprayed slurry can keep slump for two hours, after the alkali-free accelerator is added for spraying, the concrete is quickly coagulated and hardened by the synergistic effect of cement, admixture and accelerator, the wet-spraying rebound rate of a tunnel is greatly reduced, and the comprehensive rebound rate can be controlled within 10%. Meanwhile, the early-stage hour strength is rapidly improved, the 3-hour compressive strength can reach more than 5MPa, the 8-hour compressive strength can reach more than 15MPa, the 24-hour compressive strength can reach more than 25MPa, the later-stage strength is not inverted, and the design requirement of high-performance sprayed concrete can be met.

2. The technical scheme is as follows:

a high-early-strength low-resilience high-performance sprayed concrete is characterized in that: the weight portion of the composition comprises:

350-470 parts of cement, 22-90 parts of self-made admixture, 800-900 parts of sand, 800-900 parts of stone, 150-200 parts of water, 4-8 parts of water reducer and 27-40 parts of alkali-free accelerator; the self-made admixture comprises the following components in percentage by mass: 30-60% of calcium sulfoaluminate, 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.

Further, the calcium oxide content of the calcium sulfoaluminate is more than or equal to 40%, and the aluminum oxide content is more than or equal to 20%.

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 m2/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%, the aluminum oxide content is more than or equal to 40%, and the activity index is more than or equal to 110%; the aluminum lactate is of industrial grade, and the purity is more than or equal to 99%; the lithium carbonate is of industrial grade, and the purity is more than or equal to 99 percent.

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%.

Further, 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 more than P.O and 42.5.

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

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

The preparation method of the high-early-strength low-resilience high-performance sprayed concrete is used for preparing the high-performance sprayed concrete, and cement, self-made admixture, sand, cobble, water and water reducer which are proportioned as above 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 to obtain the high-performance sprayed concrete.

3. The beneficial effects are that:

(1) In the self-made admixture adopted by the high-performance sprayed concrete, calcium sulfoaluminate occupies a relatively large amount, and the calcium sulfoaluminate firstly reacts with the dihydrate gypsum in a cement hydration system to generate a large amount of ettringite and aluminum glue, and the rapid formation of the ettringite can provide a framework structure for cement paste, promote the coagulation of the paste and improve the early strength, and simultaneously, the calcium sulfoaluminate and the accelerator are sprayed out by high-pressure air of a wet sprayer, so that the calcium sulfoaluminate and the accelerator can be rapidly coagulated and hardened after being contacted by a spray head to generate strength, and the spray rebound rate can be greatly reduced.

(2) Limestone powder in the self-made admixture is used as a main filler, and the compactness of the concrete can be improved through reasonable particle size distribution and proportion; the superfine silica fume and metakaolin are active admixture, and can be mixed into cement to generate secondary hydration reaction with cement hydration products to generate CSH gel, and the CSH gel has small granularity and large specific surface area, can be filled in the particle gaps of cement stones, so that the whole microstructure is more compact, and the high volcanic ash 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 condition, and provides effective aluminum ions in a cement hydration system, which plays a synergistic effect with an accelerator to effectively promote cement hydration; the lithium carbonate can be 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. Tartaric acid is properly doped, so that on one hand, the workability of sprayed concrete is ensured before the accelerator is added, the collapse damage is avoided to be too fast, and on the other hand, the setting and hardening effects of the sprayed concrete are not influenced after the accelerator is added.

Detailed Description

Example 1

The embodiment provides high-early-strength low-resilience high-performance sprayed concrete, 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 stone, 167 parts of water, 5 parts of water reducer and 36 parts of alkali-free accelerator;

wherein, the self-made admixture comprises the following components in percentage by mass: 50% of calcium sulfoaluminate, 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 807-2020 liquid alkali-free accelerator for tunnel injection concrete.

The embodiment of the invention also provides a preparation method of the high-early-strength low-resilience high-performance sprayed concrete, which comprises the following specific embodiments:

cement, self-made admixture, sand, cobble, water and water reducing agent are mixed and stirred uniformly to prepare admixture, the admixture is transported to a construction position, and the admixture and alkali-free accelerator are mixed and sprayed out through a concrete wet spraying machine to prepare the high-performance sprayed concrete.

Example 2

360 parts of cement, 90 parts of self-made admixture, 850 parts of sand, 850 parts of cobble, 171 parts of water, 5 parts of water reducer and 32 parts of alkali-free accelerator;

wherein, the self-made admixture comprises the following components in percentage by mass: 60% of calcium sulfoaluminate, 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 method is described in example 1.

Example 3

405 parts of cement, 45 parts of self-made admixture, 830 parts of sand, 870 parts of stone, 180 parts of water, 4 parts of water reducer and 38 parts of alkali-free accelerator;

wherein, the self-made admixture comprises the following components in percentage by mass: 40% of calcium sulfoaluminate, 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 method is described in example 1.

Example 4

427 parts of cement, 23 parts of self-made admixture, 860 parts of sand, 840 parts of stone, 190 parts of water, 6 parts of water reducer and 30 parts of alkali-free accelerator;

wherein, the self-made admixture comprises the following components in percentage by mass: 30% of calcium sulfoaluminate, 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 method is described in example 1.

Comparative example 1

This comparative example is essentially identical to the raw material components of example 1, except that cement is used instead of the self-made admixture.

The preparation method is described in example 1.

Comparative example 2

The comparative example is substantially identical to the raw material components of example 2, except that a commercially available fluorine-containing alkali-free accelerator is used instead of a self-made alkali-free accelerator.

The preparation method is described in example 1.

Comparative example 3

The comparative example was substantially identical to each of the raw material components of example 3 except that the concrete mix ratio was adjusted to 240 parts of water consumption without using a water reducing agent.

The preparation method is described in example 1.

Application example:

the sprayed concrete prepared according to the above examples 1 to 4 and comparative examples 1 to 3 was subjected to test spraying on the tunnel site, and the rebound materials were collected to test the rebound rate, and the large plate was molded and the compressive strength of the concrete was tested for 3h, 8h and 1d, with the test results shown in the following table.

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

The rebound rate of the side walls of the comparative examples 1 and 2 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 and the early strength development is slower, the fluorine-containing alkali-free accelerator is replaced in the comparative example 2, the rebound rate is lower than that in the comparative example 1 due to the quicker setting time, but the early strength development is almost stagnant, the ejected material cannot form a stable structure in time, and is easy to fall off under self weight, and a phenomenon of falling of a block occurs, so that the overall rebound is obviously increased compared with the embodiment. In comparative example 3, the proper slump can be tried out only by means of a larger water-gel ratio without using the water reducer, and the too high water-gel ratio is unfavorable for the setting effect of the accelerator and the strength development of the concrete, so that the rebound rate of the side wall and the vault is greatly increased.

In summary, the invention discloses high-early-strength low-resilience high-performance sprayed concrete and a preparation method thereof, the high-early-strength low-resilience high-performance sprayed concrete has excellent working performance, the sprayed concrete can keep slump for two hours, after being sprayed by adding an alkali-free accelerator, the concrete is quickly coagulated and hardened by the synergistic effect of cement, an admixture and the accelerator, the wet-spraying rebound rate of a tunnel is greatly reduced, and the comprehensive rebound rate can be controlled within 10%. Meanwhile, the early-stage hour strength is rapidly improved, the 3-hour compressive strength can reach more than 5MPa, the 8-hour compressive strength can reach more than 15MPa, the 24-hour compressive strength can reach more than 25MPa, the later-stage strength is not inverted, and the design requirement of high-performance sprayed concrete can be met.

While the invention has been described with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended that the scope of the invention shall be limited only by the claims appended hereto.

Claims

1. A preparation method of high-early-strength low-resilience high-performance sprayed concrete is characterized by comprising the following steps of: the high-early-strength low-resilience high-performance sprayed concrete comprises the following components in parts by weight:

350-470 parts of cement, 22-90 parts of self-made admixture, 800-900 parts of sand, 800-900 parts of stone, 150-200 parts of water, 4-8 parts of water reducer and 27-40 parts of alkali-free accelerator; the self-made admixture comprises the following components in percentage by mass: 30-60% of calcium sulfoaluminate, 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;

the calcium oxide content of the calcium sulfoaluminate is more than or equal to 40 percent, and the aluminum oxide content is more than or equal to 20 percent;

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 and 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 and 1800 m ² /kg; the silicon dioxide content of the metakaolin is more than or equal to 50%, the aluminum oxide content is more than or equal to 40%, and the activity index is more than or equal to 110%; the aluminum lactate is of industrial grade, and the purity is more than or equal to 99%; the lithium carbonate is of industrial grade, and the purity is more than or equal to 99%;

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 percent;

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%;

the particle size of the stones is 5-10 mm; the strength grade of the cement reaches more than P.O and 42.5;

the water reducer is a polycarboxylic acid high-performance water reducer;

the alkali-free accelerator is an accelerator with initial setting time less than or equal to 5min, final setting time less than or equal to 12min, gel sand compression strength of more than or equal to 1.0MPa for 6h, and gel sand compression strength of more than or equal to 10.0MPa for 1 d;

mixing and stirring the cement, the self-made admixture, the sand, the cobble, the water and the water reducing agent uniformly to obtain 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 to obtain the high-performance sprayed concrete.