JPH021105B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an auxiliary agent for spraying method,
In particular, the purpose is to significantly reduce "splashing of sprayed material" and "generation of dust" in dry spraying methods. The concrete or mortar spraying method is
It has been widely used in the architectural and civil engineering fields, and there are three types: dry spraying, semi-dry spraying, and wet spraying. Among these methods, the wet spraying method has disadvantages such as the large size of the spraying equipment and the need for large-capacity power, which makes on-site maintenance difficult, and it also has various problems such as difficulty in transporting the sprayed material over long distances. . The semi-dry spraying method also has the same problems as the wet spraying method described above, although there are varying degrees of severity. On the other hand, the dry spraying method does not have the disadvantages of the wet spraying method or the semi-dry spraying method, but on the other hand, it does have the disadvantages of a high rebound rate of the sprayed material during spraying and the generation of dust during spraying. The problem is that it's big. Wet and semi-dry spraying methods also have the same problems as the dry spraying method, such as the splashing of the sprayed material and the generation of dust, although there are differences in degree. In an attempt to improve these drawbacks of the spraying method, studies have been made on the aggregate particle size and its distribution, methods for adding water, etc. However, there has been no sufficient effect to improve the above-mentioned problems. This solution has been strongly desired. The present inventor completed the present invention as a result of intensive research in view of such technical issues, which consists of (a) 40 to 95 parts by weight of water-soluble cellulose ether;
(b) 1 to 30 parts by weight of water reducing agent, and (c) 0.1 to 30 parts by weight of antifoaming agent.
This relates to an auxiliary agent for spraying methods consisting of parts by weight. According to the present invention, by adding only a small amount of the above-mentioned auxiliary agent to the material to be sprayed in the spraying method, the rebound of the material to be sprayed during spraying is significantly reduced compared to when the auxiliary agent is not added. This has the remarkable effect of dramatically reducing dust generation by 1/3 to 1/10. The present invention will be explained in more detail below. The spraying method aid of the present invention is composed of the components (a), (b), and (c) described above, but the main component (a) water-soluble cellulose ether is a water-soluble cellulose ether. Of these, hydroxyalkylalkylcellulose and hydroxyalkylcellulose are preferred. The hydroxyalkyl group has 2 to 4 carbon atoms and the molar substitution degree (MS) per anhydroglucose unit is 0.01 to
0.5 (preferably 0.1 to 0.4), and the alkyl group has 1 to 2 carbon atoms and the degree of substitution (DS) per anhydroglucose unit is 0.5 to 2.5 (preferably 1.0 to 2.0), and The hydroxyalkyl group has 2 to 4 carbon atoms and the degree of molar substitution per anhydroglucose unit (MS)
Hydroxyalkylcellulose having a molecular weight of 1.0 to 3.5 (preferably 1.5 to 2.5) is preferred. Particularly desirable are mixtures of the above-mentioned hydroxyalkylalkylcelluloses and hydroxyalkylcelluloses. The ratio is preferably a mixture of 50 to 90 parts by weight of hydroxyalkylalkylcellulose and 10 to 50 parts by weight of hydroxyalkylcellulose. Examples of such hydroxyalkylalkyl cellulose include hydroxyethyl ethyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, hydroxybutyl methyl cellulose, and hydroxybutyl ethyl cellulose. Examples of hydroxyalkyl cellulose include hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxybutyl cellulose. The reason why the above-mentioned hydroxyalkylalkylcellulose and hydroxyalkylcellulose are preferred is as follows. That is, alkyl cellulose has a low thermal gelation point and is not completely dissolved when applied under high temperature conditions, resulting in a significant reduction in the effect of addition (see Table 4 of Example 2 below). On the contrary,
Hydroxyalkylalkylcellulose, hydroxyalkylcellulose has a high thermal gelation point, completely dissolves even under high temperature conditions, and has superior solubility compared to alkylcellulose, and shows a good addition effect. Due to its aqueous solution's unique viscosity and stringiness, it has the effect of improving the flow of the sprayed material in piping or nozzles, and the maximum effect is achieved when used in combination with hydroxyalkylalkylcellulose. do. Polyethylene oxide is a water-soluble polymer powder with similar properties, but in this case, the resin powder has poor solubility in water, making it difficult to use at construction sites, as well as being difficult to use in water piping or nozzles. This is not suitable for the present invention because there is a risk of causing problems such as blockage inside. The water-soluble cellulose ether used as component (a) used in the present invention preferably has a viscosity of 150,000 to 100,000 centipoise (particularly 500 centipoise or more) at 20°C in a 2% aqueous solution; If it is, the adhesion of the shotcrete (or mortar) to the wall is weak,
This is undesirable because the rebound rate is high and more dust is generated. (b) Water reducing agents include those whose main component is lignin sulfonate, those whose main component is polyoxyethylene alkylaryl ether, those whose main component is polyol complex, and sulfone of aromatic polycyclic condensates. Examples include those whose main component is an acid salt, and those whose main component is a sulfonate of water-soluble melamine-formalin resin (methylol melamine).
In particular, a lignin-based water reducing agent containing modified sodium ligninsulfonate as a main component is desirable. The use of these water reducing agents has the effect of improving the wetting of cement particles. The ratio of component (B) used is 1 to 30 parts by weight (preferably 10 parts by weight) of component (B) to 40 to 95 parts by weight of component (A).
~20 parts by weight). If it is too small, the above effects cannot be achieved, while if it is more than 30 parts by weight, it will cause a retarding effect on the setting of cement, reduce the initial strength of shotcrete, weaken the adhesion force, and increase the rebound rate. A problem arises. Examples of antifoaming agents (c) include polyoxyethylene-polyoxypropylene block copolymers resistant to alkalinity, special nonionic compounds, higher alcohols, tributyl phosphate, and silicones. Particularly desirable are those whose main component is a polyoxyethylene-polyoxypropylene block copolymer. By using these antifoaming agents, air entrainment into shotcrete is suppressed,
This has the effect of preventing concrete strength from decreasing. The proportion of component (c) used is 0.1 to 30 parts by weight (preferably 1 to 30 parts by weight) based on the amount of components (a) and (b) used.
5 parts by weight). If the amount added is less than this, no antifoaming effect can be expected, and if the amount added is more than this, the strength of the concrete will decrease, which is not preferable. When dry spraying concrete or mortar, the auxiliary agent of the present invention can be used either by dry blending it with cement, aggregate, etc. or by pre-dissolving it in added water, but the latter method is more uniform. Preferable in terms of mixing. It may also be added to the quick-setting agent used for shotcrete by mixing it in advance, and the quick-setting agent in this case may be either powder or liquid. Not only when dissolved and added to a liquid quick-setting agent, but also when premixed and added to a powdery quick-set agent, relatively uniform mixing can be expected. The amount of auxiliary agent used is 0.01 to 1% by weight (especially 0.05% by weight) based on the cement of concrete or mortar.
~0.5% by weight). If the amount used is too large, the viscosity of the concrete or mortar will increase, making spraying difficult, delaying the setting of the cement, weakening the adhesion, and increasing the bounce rate, so care must be taken. Next, specific examples will be given. However, the cellulose ethers listed in Table 1 below were used.

[Concrete mix]

The maximum coarse aggregate size is 15 mm, the water-cement ratio is 4.5%, and the fine aggregate ratio is 60%.The unit amount of each material is shown in the following table (Table 2).
It is as follows.

【table】

[Spraying test]

Using the Menadeier GM-90 model as a spray machine,
Spraying was carried out at a construction temperature of 20°C, the dust generation was measured using a digital dust meter, and after the spraying was completed, the weight of the rebound material was measured to determine the rebound rate. In addition, cores were taken from the shotcrete and the compressive strength of the concrete at 28 days old was measured. The results are shown in Table 3.

[Table] Example 2 The same water reducing agents and antifoaming agents as in Example 1 were used except that various cellulose ethers were used. How to add spraying aids, concrete mixing,
The spraying machine etc. were the same as in Example 1, and the construction temperature was 35
A spraying experiment was conducted at either ℃ or 20℃, and the dust generation, rebound rate, and concrete compressive strength were measured. The results are shown in Table 4.

【table】

[Table] Example 3 Hydroxyethyl methylcelluloses with different degrees of substitution were used as cellulose ethers and compared. A spraying experiment was conducted using the same method of adding the spraying aid, concrete formulation, spraying machine, etc. as in Example 1, and the dust generation, rebound rate, and compressive strength of the concrete were measured. The construction temperature was 20℃. The results are shown in Table 5.

[Table] Example 4 As the spraying method, an experiment was conducted using dry spraying and wet spraying. Wet spraying uses a lead gun in the spraying machine, unit cement amount is 350Kg/ ^m3 , W/C=55%,
The conditions were S/A = 70%, and the spraying aid was dissolved in kneading water before use. For dry spraying, the spraying machine and concrete mix were the same as in Example 1, and the experiment was conducted by adding the spraying aid directly to the cement/aggregate as a powder, or by mixing the powder with the powder quick-setting agent. I went. The dust generation, rebound rate, and concrete compressive strength were measured. The results are shown in Table 6.

【table】

【table】

Claims (1)

[Claims] 1 (a) 40 to 95 parts by weight of water-soluble cellulose ether,
(b) 1 to 30 parts by weight of water reducing agent, and (c) 0.1 to 30 parts by weight of antifoaming agent.
Auxiliary agent for spraying method consisting of parts by weight. 2. The spraying method aid according to claim 1, wherein the water-soluble cellulose ether is hydroxyalkylalkylcellulose and/or hydroxyalkylcellulose.