A nano rebound inhibitor for shotcrete and preparation method thereof

Abstract

The invention relates to the technical field of concrete admixtures, and discloses a nano rebound inhibitor for shotcrete and a preparation method thereof. The components, measured by weight, include 400-600 parts of nano microspheres, 400-550 parts of nano calcium carbonate, 10-30 parts of sodium carbonate, 1-10 parts of sodium aluminate, 10-30 parts of alum, 18-40 parts of polycarboxylic acid water reducer, and 0-0.5 parts of triterpenoid saponin; the nano microspheres are hydrated calcium silicate with silicon dioxide as the core material and colloid as the shell material, and the colloid is doped with a lithium source. The nano rebound inhibitor of the present application can significantly improve the state of shotcrete and greatly reduce the rebound amount of concrete, thereby further saving construction costs and accelerating construction accuracy. By utilizing the characteristics of the mineral admixture in the nano rebound inhibitor, the compactness of the concrete can be improved, and the durability of the shotcrete can be further improved.

Description

Technical Field

[0001] The invention relates to the technical field of concrete admixtures, in particular to a nano rebound inhibitor for shotcrete and a preparation method thereof. Background Art

[0002] Nano rebound inhibitor for shotcrete is a new product developed according to the construction characteristics and development direction of the new Austrian Tunneling Method. This product has the advantages of reducing cement dosage, replacing water reducer, preservative, airtight agent (if involved) in shotcrete to reduce the rebound rate of shotcrete (the rebound rate after addition is generally controlled at about 5.0% to 20.0%), shortening the initial setting time of shotcrete, and improving the strength of shotcrete. It increases the compactness of concrete by adding water reduction, anti-corrosion, waterproof, air entrainment, airtightness and enhanced viscosity-enhancing components, and improves the concrete's resistance to the invasion of poor water quality. By adding high-performance air entraining agents, the freeze-thaw resistance and durability of concrete are improved; by using composite rust-proof and anti-corrosion agents, the steel bars and concrete are protected after the invasion of poor water quality, and the concrete's resistance to sulfate erosion is improved, so that the concrete has better working performance, higher strength, and faster construction speed, and the surrounding rock is protected and reinforced in a closed manner in a timely and effective manner, thereby improving the strength and bearing capacity of the surrounding rock.

[0003] The current nano-rebound inhibitors, due to the addition of nano-materials, reduce rebound by increasing the cohesion and adhesion of concrete mixtures, further increasing the density of hardened concrete to improve strength. However, due to the small particle size of nano-materials, direct addition leads to agglomeration problems, which in turn makes the viscosity of concrete too high, affecting the pumpability of concrete. Summary of the invention

[0004] <Technical Problems Solved by the Invention>

[0005] The invention is used to solve the problem in the prior art that the pumpability of shotcrete is affected due to the use of nano materials, which leads to poor setting time and early strength at the construction site.

[0006] <Technical solution adopted by the present invention>

[0007] In view of the above technical problems, the object of the present invention is to provide a nano rebound inhibitor for shotcrete and a preparation method thereof.

[0008] The specific contents are as follows:

[0009] First, the present invention provides a nano rebound inhibitor for shotcrete, wherein the components, by weight, include 400-600 parts of nano microspheres, 400-550 parts of nano calcium carbonate, 10-30 parts of sodium carbonate, 1-10 parts of sodium aluminate, 10-30 parts of alum, 18-40 parts of polycarboxylate water reducer, and 0-0.5 parts of triterpenoid saponin;

[0010] The nano-microspheres are made of silicon dioxide as the core material and colloid as the shell material, and the colloid is doped with calcium silicate hydrate with lithium source.

[0011] <Technical mechanism and beneficial effects of the present invention>

[0012] The nano-rebound inhibitor of the present application can significantly improve the state of shotcrete and significantly reduce the rebound of concrete, thereby further saving construction costs and accelerating construction accuracy. The characteristics of the mineral admixture in the nano-rebound inhibitor can not only improve the compactness of concrete, but also further enhance the durability of shotcrete.

[0013] The present application adopts nano-microspheres, which are coated with silica to avoid the agglomeration problem caused by silica. The colloid is used as the shell material. As a storage material, it can well improve the pumpability of the slurry. Under the force of the injection, the shell material breaks. Since the shell material is doped with lithium-sourced calcium silicate hydrate, it can promote the rupture of the metastable hydration film produced by cement in the early hydration process, thereby further promoting the improvement of the early strength of cement. In this process, nano-silica, as a micron-sized material, can exist as a nucleation substance in the process of promoting hydration, so that the hydration product is polymerized on the surface of the nucleation substance, thereby achieving the purpose of improving the setting time and early strength. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0015] <Technical solution>

[0016] Specifically, the present invention provides a nano rebound inhibitor for shotcrete, wherein the components, measured by weight, include 400-600 parts of nano microspheres, 400-550 parts of nano calcium carbonate, 10-30 parts of sodium carbonate, 1-10 parts of sodium aluminate, 10-30 parts of alum, 18-40 parts of polycarboxylate water reducer, and 0-0.5 parts of triterpenoid saponin;

[0017] The nano-microspheres are made of silicon dioxide as the core material and colloid as the shell material, and the colloid is doped with calcium silicate hydrate with lithium source.

[0018] Furthermore, the components, by weight, include 450-550 parts of nano-microspheres, 400-500 parts of nano-calcium carbonate, 10-25 parts of sodium carbonate, 1-8 parts of sodium aluminate, 10-25 parts of alum, 18-30 parts of polycarboxylic acid water reducer, and 0-0.4 parts of triterpenoid saponin.

[0019] In the present invention, the mass ratio of silicon dioxide, colloid, lithium source and hydrated calcium silicate in the nano-microspheres is 1:0.1-0.5:0.01-0.08:0.1-0.3.

[0020] In the present invention, the method for preparing nanospheres comprises the following steps:

[0021] Under a nitrogen atmosphere, the colloid is dissolved to form a colloidal liquid, into which a silicon dioxide dispersion is added, and after ultrasonic dispersion, a pretreatment liquid is obtained; a soluble lithium salt aqueous solution and a silicate aqueous solution are added dropwise to the pretreatment liquid, and after the addition is completed, an activator is added, and then the nano-microspheres are obtained through filtration, washing, precipitation and drying.

[0022] Specifically, the lithium salt is lithium sulfate.

[0023] Specifically, the silicate is sodium silicate or potassium silicate.

[0024] Specifically, the activator is diethanolamine.

[0025] Specifically, the colloid is hydroxyethyl cellulose ether.

[0026] The preparation method of the aforementioned nano rebound inhibitor for shotcrete is to weigh each component in proportion, add the components into a mixer for stirring, and automatically measure and package them into finished products.

[0027] The nano rebound inhibitor provided by the present invention has the following performance characteristics:

[0028] (1) High cohesion: Ensure the suspension stability of coarse aggregate in cement paste, so that there will be no problems such as aggregate sinking, segregation and bubble floating during the shotcrete construction process, and ensure that there will be no water seepage on the surface of the hardened concrete.

[0029] (2) Low shrinkage: It has micro-expansion properties, which can effectively reduce the shrinkage deformation of the hardened body of self-compacting concrete and reduce the cracking of concrete.

[0030] (3) High adhesion: It has high bonding strength with the sprayed surface.

[0031] <Example>

[0032] Example 1

[0033] The preparation of nano-microspheres comprises the following steps: preparing a solution of 2 wt% of hydroxyethyl cellulose ether, adding an aqueous dispersion of nano-silicon dioxide to the liquid, performing conventional ultrasonic dispersion to obtain a pre-treated liquid, dripping an aqueous lithium sulfate solution and an aqueous sodium silicate solution therein, adding diethanolamine after the dripping, uniformly blending, filtering, washing, precipitating and drying in a conventional manner to obtain nano-microspheres. In the aforementioned preparation process, the ratio of nano-silicon dioxide, hydroxyethyl cellulose ether, lithium sulfate and hydrated calcium silicate is 1:0.5:0.08:0.2.

[0034] The nano-microspheres prepared as above are used as nano-materials and added into the nano-rebound inhibitor of shotcrete. Specifically, the components are calculated by weight as follows: 500 parts of nano-microspheres, 480 parts of nano-calcium carbonate, 20 parts of sodium carbonate, 5 parts of sodium aluminate, 20 parts of alum, 30 parts of polycarboxylate water reducer, and 0.3 parts of triterpenoid saponin.

[0035] Example 2

[0036] The nano rebound inhibitor for shotcrete comprises, specifically, 420 parts of nano microspheres, 400 parts of nano calcium carbonate, 15 parts of sodium carbonate, 3 parts of sodium aluminate, 15 parts of alum, 20 parts of polycarboxylate water reducer and 0.1 parts of triterpenoid saponin in parts by weight.

[0037] Example 3

[0038] The nano rebound inhibitor for shotcrete comprises, specifically, 580 parts of nano microspheres, 520 parts of nano calcium carbonate, 25 parts of sodium carbonate, 8 parts of sodium aluminate, 28 parts of alum, 35 parts of polycarboxylate water reducer and 0.5 parts of triterpenoid saponin in parts by weight.

[0039] <Comparative Example>

[0040] Comparative Example 1

[0041] The difference between this comparative example and Example 1 is that the nano-microspheres are replaced by nano-silicon dioxide.

[0042] <Test example>

[0043] The nano rebound inhibitors obtained in Example 1 and Comparative Example 1 were used as samples for testing.

[0044] Specifically, they are: standard shotcrete C0 (wet shotcrete method), shotcrete C1 (with commercial rebound inhibitor added), shotcrete C2 (with comparative example 1 sample added), and shotcrete E1 (with example 1 added).

[0045] The distribution ratio of each group of the commercial rebound inhibitor is: anionic polyacrylamide: maltodextrin: fly ash = 1:30:969.

[0046] The mix ratio of the aforementioned shotcrete is shown in Table 1.

[0047] Table 1 Specific proportion of shotcrete

[0048]

[0049] 1. Comparative analysis of the rebound of shotcrete. The results are shown in Table 2.

[0050] Table 2 Comparison of shotcrete rebound

[0051]

[0052] 2. Compressive strength analysis of shotcrete. The results are shown in Table 3.

[0053] Table 3 Indoor strength comparison table (without adding accelerator)

[0054]

[0055] 3. Performance indicators of nano rebound inhibitor (E1) for shotcrete

[0056] Its technical indicators comply with the requirements of (Q / CR596-2017), and the specific technical indicators are shown in Table 4.

[0057] Table 4 Performance indexes of nano rebound inhibitor

[0058]

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A nano rebound inhibitor for shotcrete, characterized in that: The components are calculated by weight, including 400-600 parts of nano-microspheres, 400-550 parts of nano-calcium carbonate, 10-30 parts of sodium carbonate, 1-10 parts of sodium aluminate, 10-30 parts of alum, 18-40 parts of polycarboxylate water reducer, and 0-0.5 parts of triterpenoid saponin; The nano-microspheres are made of silicon dioxide as a core material and colloid as a shell material, wherein the colloid is doped with calcium silicate hydrate with a lithium source; the mass ratio of silicon dioxide, colloid, lithium source and calcium silicate hydrate in the nano-microspheres is 1:0.1~0.5:0.01~0.08:0.1~0.3; and the colloid is hydroxyethyl cellulose ether.

2. The nano rebound inhibitor for shotcrete according to claim 1, characterized in that: The components are calculated by weight and include 450-550 parts of nano-microspheres, 400-500 parts of nano-calcium carbonate, 10-25 parts of sodium carbonate, 1-8 parts of sodium aluminate, 10-25 parts of alum, 18-30 parts of polycarboxylic acid water reducer, and 0-0.4 parts of triterpenoid saponin.

3. The method for preparing a nano rebound inhibitor for shotcrete according to any one of claims 1 to 2, characterized in that: Weigh each component in proportion and blend them evenly.

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