JPH02125070A - Repair method for surface of concrete left placed - Google Patents

Abstract

PURPOSE:To perform rendering of the appearance like unifinished concrete by a method wherein the deterioration part of unifinished concrete is filled with polymer cement mortar, and a plastic sheet is pressed in a flat manner against thereon without discharging air bubbles. CONSTITUTION:The surface of deteriorated unifinished concrete is washed by a high pressure to removed a deteriorated part. A polyacrylic ester series cement additive is blended in cement in a solid ratio of 10%, and mortar is coated approximate 8mm thick in a cement sand ratio of 1 to two. A polyethylene sheet is pressed in an adhered state against a mortar surface. The mortar is left standing in a state that the pores produced in this case are present therebetween until it is cured, and after curing, the polyethylene sheet is removed. This method causes the slight number of pores to be scattered to perform rendering of the appearance like unifinished concrete, and enables improvement of neutralization resistance performance.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for repairing an exposed concrete surface, in which the repaired surface seamlessly integrates the appearance with the surrounding surface.

Conventional technology The surface of exposed concrete is a type of architectural wall finish designed to reflect the natural phenomenon that occurs at the interface between a concrete panel and concrete. In recent years, due to the deterioration of the atmospheric environment, the neutralization of concrete due to nitrogen oxides, carbon dioxide, etc. is progressing. Walls protected by tiles, organic exterior materials, etc. have relatively little damage, but exposed concrete walls with exposed cementitious material may become neutralized due to carbon dioxide, acid rain, and other factors. As a result, the bonding strength is reduced, and the surface often shows a deteriorated state in which the aggregate flakes off.

When it comes to repairing such exposed concrete surfaces, there are two ways to repair the entire surface: using a different finishing method or exterior material, and continuing the design as an exposed concrete surface. There are cases where only partial repairs are required. There is no problem if a different type of exterior is used, but it is extremely difficult to reproduce the exposed design. The reason for this is that during new construction, concrete is poured into a framework of concrete panels, and the rheological properties such as flow and pressure of the concrete, combined with the panel surface condition and natural distribution of pores, create a design unique to exposed concrete surfaces. On the other hand, when renovating or repairing, it is necessary to apply a thin layer of mortar to the surface of the concrete and perform some kind of artificial processing to make it resemble the appearance of exposed concrete.

Problems to be Solved by the Invention Conventionally, there has been a method for repairing exposed concrete by using ordinary mortar or polymer cement mortar with a metal trowel. In order to create a sense of unnaturalness, the mortar surface that has been pressed down with a metal trowel with a polystyrene or other foamed plastic plate is flattened, or a panel-like design is imitated using a brush or brush to make it look like a craft. Methods such as these are being used. However, there is a clear visual incongruity between the exposed surface, which is a type of "mold-cut" design, and the above-mentioned hand-worked plastering design, and especially in the case of partial repairs, it is difficult to compare the exposed surface with the surrounding exposed concrete surface. Therefore, the difference is particularly clear. The points of difference are: firstly, the time it takes for mortar to harden is that, like concrete panels, it is in close contact with some surface, and secondly, there are natural phenomena such as small pores caused by air bubbles that occur during concrete pouring. However, the overall appearance of exposed concrete is difficult to express using the above-mentioned plastering method, and is extremely time-consuming work.

Means to Solve the Problems As already mentioned, the key to achieving a repair method using mortar that has the "likeness" of exposed concrete is how to apply a thin coat of mortar to the surface in a manner similar to that used with concrete panels. It all depends on whether you want to create a molded surface and whether you want to create naturally occurring external air holes. The inventors of the present invention focused their research on this problem, and as a result, they obtained the following solution.

In other words, mortar is applied to deteriorated areas of exposed concrete.
Preferably, polymer cement mortar is filled to the level of the concrete surface, a plastic sheet such as a polyethylene sheet is pressed flat onto the mortar surface, and the mortar is left until it hardens. What should be noted here is that when the sheet is pressed against the mortar surface, some air bubbles are interposed between the mortar and the sheet, but these air bubbles are not expelled and these air bubbles form natural small pores on the mortar surface after hardening. By interspersing them, this treatment vividly reproduces the ``likeness'' of fair-faced concrete, which was lacking in conventional methods.

Function Concrete and mortar contain some air when they are mixed with cement, aggregate, water, and admixtures in a mixer. Furthermore, when concrete is placed within a frame surrounded by concrete panels, or when a watertight sheet is pressed onto a mortar-coated surface, air becomes trapped between the panel or sheet and the concrete or mortar. Generally, when concrete is poured, this air is exhausted using a pipe resonator, but the remaining air is present near the panel surface and forms small pores in the hardened concrete surface.

In the present invention, this phenomenon is solved by placing a plastic sheet on the thin layer of mortar used for repair work, which acts as a concrete panel, and intentionally creating pores due to residual air, so that the mortar hardens while being in close contact with the plastic sheet. In combination with the surface pattern design, it is possible to obtain a similar effect that harmonizes with the exposed concrete surface.

Example 1 The exposed concrete surface deteriorated due to carbonation was removed by high-pressure washing, and a PAE (polyacrylic acid ester) cement admixture [trade name AD-51, manufactured by Nippon Shokubai Kagaku Kogyo ■] was added to the cement. Mixed with a solid content ratio of 10%, □Cement and sand mortar with a ratio of 1:2 to an average thickness of g.
It was applied to gm. Immediately after application, a 1 m wide polyethylene sheet was brought into close contact with the mortar surface and pressed down with a flat plate. When polyethylene sheets are brought into close contact, usually in such cases, the intervening air is expelled, or in this case, the air is intentionally removed (ζ
I allowed some air to intervene. The next day, after the mortar had hardened, we removed the polyethylene sheet and observed the surface. We found that there were a few pores scattered here and there, making it look like concrete had been re-cast. In particular, since Repair 41 is made of polymer cement mortar, it has much better carbonation resistance than conventional exposed surfaces:
The improvement in ζ was also a noteworthy effect.

Example 2 Seven parts of a partially neutralized exposed concrete exterior wall were removed with vinegar, washed with water, and filled with mortar with a cement-to-sand ratio of 1:2 as described in Example 1 to the level of the concrete surface.

A polyethylene sheet was brought into close contact with the mortar surface with some air bubbles interposed between it, and after the mortar had hardened, the sheet was removed. As in Example 1, the surface resembled the adjacent exposed concrete surface due to the natural scattering of pores. By integrating the parts, we were able to obtain a satisfactory partial repair finish.

Effects of the Invention The design of the exposed concrete surface is an architectural finishing style that suits the Japanese sense of using unpainted wood, but unfortunately there is no appropriate repair method, and when it comes to maintenance, it is necessary to change to other finishing methods. There are many people who tend to do 4. Since the present invention can be repaired without impairing the elegance of exposed surfaces, it can provide the effect of securing a category of architectural finishing methods such as exposed surfaces and concrete finishing, which are decreasing due to the difficulty of repair.

Patent license issued by Chugai Shoko Co., Ltd. II) 1.

Claims (1)

[Claims] When repairing an exposed concrete surface, mortar is applied to the surface to be repaired, and a watertight sheet is adhered to the applied surface with a suitable amount of air bubbles.
Pores similar to the pores scattered on the exposed concrete surface appear on the surface repaired with mortar as described above, and in the case of a full-scale repair, the appearance of the exposed finish is reproduced, and in the case of a partial repair, the appearance of the repaired area and the surrounding concrete surface is harmonized and integrated. A method of repairing exposed concrete surfaces that achieves a leveling effect.