JPS60144466A - Dry spraying construction method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION The present invention relates to a dry spraying method for mortar and concrete. More specifically, dry spraying relates to a method for reducing rebound in construction methods.

[Prior art]

Dry spraying is a construction method in which cement and aggregate are transported floating by a machine, and pressurized water is added before the nozzle to spray the mixed slurry from the nozzle onto the surface to be painted, such as ceilings, walls, etc. This is a construction method for forming floors, etc.

On the other hand, wet spraying is a construction method in which a slurry made by kneading cement, aggregate, and water is sprayed using a spraying machine.

Compared to the wet method 1, the dry method 1 only needs to supply the dry kneaded material, so there are fewer restrictions on supply operations such as transportation time, but the wet method 1 has limitations because it supplies hydraulic slurry. For this reason, the wet method is unsuitable for long-distance pressure feeding, but the dry method has the advantage of being possible, but it also has disadvantages such as more rebound and more dust than the wet method. Improvements to this were requested.

In order to prevent such rebound and dust generation, attempts have been made to bind cement and aggregate together by adding, for example, polyethylene oxide or polyacrylic acid resin. However, in this method, the cement and aggregate must be sufficiently immersed in polyethylene oxide or polyacrylic acid resin, and even if the content of polyethylene oxide or polyacrylic acid resin is increased considerably, rebound and dust cannot be completely eliminated. It is not possible to prevent the occurrence of Furthermore, when a large amount of polyethylene oxide or polyacrylic acid resin is added, the performance of mortar or concrete after hardening is significantly reduced.

[Structure of the Invention] The present invention has been made to solve the above-mentioned problems, and provides an efficient dry spraying method that uses a dry spraying device and is free of dust and has little rebound. It is something.

That is, the present invention involves transporting (a) a powder mixture consisting of cement and aggregate and fb) a liquid mixture consisting of a synthetic resin emulsion and water separately, and mixing them before the spray nozzle. However, dry spraying is a construction method characterized by spraying a slurry of both onto the surface to be painted.

The synthetic resin emulsions used in the present invention include α, β
- Emulsion polymerization of monoethylenically unsaturated monomers is used, but particularly preferred are those using a polymeric protected cotetraide such as polyvinyl alcohol or human tetraxyethyl cellulose as an emulsifier. good. Of course, a surfactant-based emulsifier may also be used. However, emulsions using only surfactant-based emulsifiers tend to rebound more easily than colloid-based emulsions with polymer retention.
The sprayed slurry tends to drip down easily.

Moreover, it is preferable that the synthetic resin emulsion is a polyvinyl acetate thread emulsion. Emulsions other than those based on polyvinyl acetate tend to have poor miscibility with cement.

Moreover, it is preferable that the synthetic resin emulsion is an ethylene-vinyl acetate copolymer emulsion. Polyvinyl acetate polymers are easily saponified by the alkali in cement and become water-soluble resins, which tends to reduce their strength, but ethylene-vinyl acetate copolymer emulsions are water-insoluble even when saponified, so , strength is less likely to decrease.

Also, the synthetic resin emulsion is ethylene-vinyl acetate-
Preferably, it is a vinyl chloride copolymer emulsion. This emulsion is thought to have the characteristics of low air bubble entrainment and high water reduction properties when mixed together with cement, aggregate, and water, but it also has low rebound properties and generates little dust.

Emulsions with low bubble entrainment and high water reduction properties are
It is believed that this method is extremely effective in achieving the object of the present invention. Specifically, cement: fine aggregate; water; emulsion (solid content) = 100 + 1 SOO: 50! 20
'? 'preparation, tar 1 - tartar c7) unit volume mass (
kg/l) of 2.0 to 2.2 is preferred.

The amount of emulsion used is preferably 1 to 10% by weight, in particular 2 to 5% by weight, based on the cement.

The synthetic resin emulsion used in the present invention has good miscibility with cement, and even when mixed in a large amount, it has the effect of improving the performance of concrete or mortar.

The cements used in the present invention include various Portland cements such as ordinary Boltland cement, early strength Rutland cement, and moderate heat Portland cement; mixed cements such as blast furnace cement and fly ash cement; and special cements such as alumina cement. Appropriate.

As the aggregate, fine aggregates such as river sand, silica sand, sea sand, and mountain sand, and coarse aggregates such as river gravel and crushed stones are used, and river sand and river gravel are particularly suitable.

〔Effect of the invention〕

According to the dry spraying method of the present invention, the sprayed slurry produces very little rebound and dust generation, and can be sprayed to a thickness of about 5 cm at a time.

Next, the present invention will be explained with reference to Examples and Comparative Examples.

Examples and Comparative Examples A powder mixture of ordinary Portland cement and aggregate having the composition shown in Table 1 was supplied to a cement gun, and then floated to a nozzle by air pressure using a hose. A water ring or rubber provided in front of the nozzle sprays water, an aqueous dispersion of a predetermined amount of synthetic resin emulsion diluted with water, or an aqueous solution of a predetermined amount of polyacrylic soda or gel ethylene oxide dissolved in water. The slurry was instantly mixed with the above powder mixture in the nozzle, and the slurry was sprayed to a thickness of 5 cm from the nozzle onto the surface to be coated. Table 1 shows the bet data measured at this time.

These results show that when a synthetic resin emulsion containing a polymeric protective colloid such as polyvinyl alcohol or hydroxyethyl cellulose as an emulsifier is used, the rebound rate is significantly reduced and the dust concentration during construction is also significantly reduced. Ta. Furthermore, because the water/seven ment ratio was lowered by mixing the synthetic resin emulsion, it was also recognized as a positive effect that the compressive strength of mortar or concrete with hardening spraying was higher than that without mixing.

Claims (1)

[Claims] 1(a) A powder mixture consisting of cement and aggregate; and (b)
Dry spraying is characterized in that a liquid mixture consisting of a synthetic resin emulsion and water is conveyed separately, the two are mixed before the spray nozzle, and a slurry of both is sprayed onto the surface to be painted. is a construction method. 2. Claim 1, wherein the synthetic resin emulsion is an emulsion using a polymeric protective coside as an emulsifier.
The dry spraying described in the section is a construction method. 6. The dry spraying method according to claim 1 or 2, wherein the synthetic resin emulsion is a polyvinyl acetate emulsion. 4 The synthetic resin emulsion is an ethylene-vinyl acetate copolymer emulsion. Dry spraying according to claim 1 or 2 is a construction method 0. 5 The synthetic resin emulsion is an ethylene-vinyl acetate-vinyl chloride copolymer emulsion. Dry spraying according to claim 1 or 2, which is a combined emulsion, is a construction method.