JPH0254312B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Concrete washout finishing is a finishing method that has been used conventionally, and is applied to decorating concrete surfaces and roughening concrete joints. The principle is to wash away the cement paste on the concrete surface by some means to expose the aggregate.

Specifically, there is a physical method of forcibly washing the uncured concrete surface with water;
Chemical methods include dissolving the cement paste on the concrete surface with hydrochloric acid, using a cement retardant called a retarder to delay the hardening of the cement on the concrete surface, and washing the concrete with water after it hardens.

There are two methods of cleaning using a cement retarder:

(i) Apply retarder to the inside of the formwork with a brush, and after drying, pour concrete. After the concrete has hardened, it is removed from the mold and washed with water using a brush to expose the aggregate (form surface application method).

(ii) Spread retarder on the unhardened concrete pouring surface, and after the concrete hardens, wash it with water using a brush to expose the aggregate (concrete surface application method).

The present invention relates to the improvement of the wash-out finishing method according to (ii) above.

Conventionally, the concrete surface application method generally used sprays a low-viscosity retarder of 100 cp (centipoise) or less onto the concrete surface, but due to fluctuations in the amount of retarder applied, the washing depth may vary. In areas where there are many voids on the concrete surface, there were problems in that the retarder penetrated deeply, resulting in excessive washout depth and peeling of the decorative aggregate.

The present inventors obtained the following findings as a result of various experimental studies. That is, FIG. 1 is a diagram illustrating how the decorative aggregate 1 peels off, and a shows the initial state after the retarder 2 has been sprayed, and b shows the state just before washing out.

In this case, depending on the mix of concrete and other conditions, the retarder 2 may penetrate under the decorative aggregate 1 due to capillary action.

It was found that due to the curing retardation effect of the retarder, when washed with water, it was washed away along with the uncured concrete, resulting in an unsightly condition, as shown in Figure c.

Based on this knowledge and as a result of further experimental research, the present invention solves this problem by setting the viscosity of the cement retarder to 200 to 2000 cp.

By using a retarder with a high viscosity of 200 cp or more, the depth of washing remains almost constant even if the applied amount varies in the range of 100 to 500 g/ ^m2 , and even if there are some voids on the concrete surface. The washing depth is almost constant.

Therefore, this method is suitable as a cleaning finishing method when mass producing molded products by immediate demolding.

Furthermore, it is possible to apply retarder by placing a paper pattern on the concrete and partially washing it out, which is a useful invention in eliminating the occurrence of defective products and increasing the variety of concrete finishes.

In addition, when the viscosity of the retarder exceeds 2000 cp,
It is unsuitable from an engineering perspective because it makes spraying work difficult.

As the retarder, soda salts of hydroxycarboxylic acids such as gluconic acid, tartaric acid, citric acid, and malic acid, sugars, and the like are used.

Example As shown in Figure 2, a 500 cp retarder 4 consisting of 5 parts of sodium gluconate, 2 parts of sodium sulfate, 2 parts of methyl cellulose, and 91 parts of water was sprayed onto 5 surfaces of a concrete block that had not hardened yet and was ready for immediate demolding.
After the concrete hardens, it is washed with water and used as decorative aggregate 6.
exposed.

As a result of numerous experiments, it has been found that the finish is good, and most importantly, there are no defective products, and the work can be mechanized, which will greatly contribute to the mass production of concrete products with a decorative finish.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing conventional problems, and FIG. 2 is an explanatory diagram of an embodiment of the present invention. 4...Retarder, 5...Concrete, 6...
...Cosmetic aggregate.

Claims (1)

[Claims] 1 200~ on the concrete surface immediately after pouring
Apply 2000cp high viscosity cement retarder,
A concrete washing and finishing method characterized by washing with water after the concrete has hardened.