JPH0247469A - Method for continuous placing for layered concrete - Google Patents

Abstract

PURPOSE:To improve the continuity of surfaces of construction joints by forming a layer of steel fiber reinforced concrete cover an uppermost layer of a lower side concrete, and by placing an upper side concrete after exposing fibers by the application of roughing. CONSTITUTION:After the placing of concrete 1 for the lower side, fiber concrete 2 is placed over the outermost layer of the concrete 1, while the concrete 1 is still in hardening process. Then, roughing is applied with a chipping gun or the like to the surface of the fiber concrete 2, and thereby steel fibers 2a are made to be exposed to the surface. After this, an upper side concrete 4 is placed over the surface of the lower side concrete 1.

Description

[Detailed Description of the Invention] (Field of Industrial Application) This invention relates to laminated concrete in which the concrete on the upper side is successively poured in a layered state after the concrete on the lower side has solidified, and in particular in the pour joint area. This invention relates to a method for improving the strength of.

(Prior art) For example, when constructing a gravity dam or other large-scale concrete structure using unreinforced concrete, if a large amount of concrete is poured at one time, the heat of hydration released when the concrete hardens causes the concrete to become concrete. There is a risk that cracks may occur in itself.

Therefore, when constructing this type of large-scale unreinforced concrete structure, a predetermined amount of concrete is poured sequentially from the bottom, and when the bottom concrete has hardened, the top concrete is poured in a layered manner. A method is being used to suppress the generation of heat of hydration to a minimum level by setting silver.

However, when the concrete is cemented in a layered manner in this way, the integrity of the joint surfaces of the lower concrete and the upper concrete becomes a problem.

Conventionally, after curing the lower concrete, the surface layer is roughened by sandblasting or other physical roughening treatment, and the anchoring effect of the surface unevenness is used to improve the integrity of the pour joint. After spraying a surface setting retarder on the surface layer of the lower concrete and spraying high-pressure water with a hydrojet cleaner when the breathing has subsided to wash away the areas that have not solidified on the surface and roughen the surface, the upper concrete is A method was adopted in which the integrity of the joint was improved by pouring and joining the joint.

(Problem to be solved by the invention) However, any of these joining methods only aims to improve the physical strength by utilizing the anchoring effect of the surface unevenness, so it is difficult to improve the integrity of the joining part. I couldn't get any better than that.

This invention solves the above problems by exposing steel fibers on the surface of the lower concrete through surface roughening treatment, and using the bonding strength of these steel fibers to improve the integrity of the pour joint. The purpose of this invention is to provide a method for joining laminated concrete.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention places new concrete on top of the solidified concrete placed on the lower side, and integrates the concrete into a layered state. In the concrete pouring method as described above, a steel fiber-containing concrete layer is formed in advance on the top layer of the lower concrete, and then the surface of the concrete layer is roughened to expose the steel fibers contained in the concrete layer. Then, the upper concrete was poured in a layered manner on top of the lower concrete.

(Function) When the surface layer of the lower concrete is roughened, steel fibers are exposed along with the uneven rough surface, and when the upper concrete is poured in this condition, in addition to the anchoring effect due to the unevenness, the steel fibers are exposed. The interlocking effect of the fibers across both concrete layers makes it possible to obtain sufficient integrity at the pour joint.

(Example) Hereinafter, an example of the present invention will be described in detail using the drawings.

As shown in Fig. 1(a), after pouring the lower concrete 1 of a predetermined thickness and volume, fiber concrete 2 is placed on the surface layer of the concrete 1 before it hardens, and the two are integrated. Cultivate in the same state.

The fiber concrete 2 was originally developed to improve the strength of the building frame itself, and is a mixture of steel fibers in addition to the common concrete composition of mortar and aggregate.

In addition, a surface setting retarder may be mixed into the composition of fiber concrete 2 in preparation for later roughening treatment, or
Alternatively, as shown in FIG. 1(b), paper 3 impregnated with a setting retarder may be attached to the surface of the fiber concrete 2 during curing, or the setting retarder may be further spread.

After curing and solidification are completed, the surface of fiber concrete 2 is roughened using a physical roughening means such as a chipping gun or a hydro jet cleaner, and as shown in FIG. 1(c), fiber concrete 2 is roughened. The steel fibers 2a mixed inside are not removed and exposed on the surface.

When the upper concrete 4 is poured in this state, the pouring joint A shown by the chain line in Fig. 1(d) is partially enlarged as shown in Fig. 2, in addition to the anchoring effect of the unevenness caused by roughening. The steel fibers 28 are joined to connect the layers of the upper concrete 4 and the lower fiber concrete 2.

In addition, when concrete is to be placed on top of the upper concrete 4, the fiber concrete 2 is placed in the same manner as above before the surface layer is solidified, and then the same method as above is applied in the condition where the fiber concrete 2 is made into a lump. All you have to do is repeat the process of roughening the surface and pouring concrete.

For comparison, we used a test piece made of conventional laminated concrete without roughening treatment, a test piece with roughened surface treatment, and a test piece made of laminated concrete joined via the fiber concrete of the present invention. When an adhesion strength test was conducted, the test pieces of the present invention showed 3 to 7 times more adhesion than untreated specimens, and 2 to 4 times more adhesion than roughened specimens. It was confirmed that the integrity was significantly improved compared to the conventional method.

This also suggests that the exposed steel fibers not only have an anchoring effect due to the irregularities, but also function as a connecting material to increase the strength of the connection between the two concrete layers.

Note that the present invention may be implemented using not only concrete but also mortar instead.

(Effects of the Invention) As explained in detail using the examples above, in the method for pouring laminated concrete according to the present invention, when the surface layer of the lower concrete is roughened, the rough surface and the steel fibers are formed. Since the upper concrete is poured in this exposed state, in addition to the anchoring effect of the above-mentioned unevenness, the joining effect of the steel fibers across both concrete layers will
Sufficient integrity can be obtained at the joint part.

Furthermore, since the amount of fiber concrete used is only for the surface layer of the lower concrete that requires roughening, the amount used is small even in large-scale concrete structures, making it economical.

[Brief explanation of the drawing]

Figures 1 (a) to (d) are explanatory diagrams showing the working procedure of the method of pouring joints in laminated concrete according to the present invention, and Figure 2 is a
It is an enlarged view of the main part of figure (d). 1... Lower side concrete 2... Fiber concrete 2a... Steel fiber 4... Upper side concrete (d) Figure 1 (a) Pole 2 figure

Claims (1)

[Claims] (1) In a concrete pouring method in which concrete poured on the lower side is solidified and new concrete is poured on top of it to integrate it into a laminated state: The top layer of concrete on the lower side is placed in advance. A concrete layer mixed with steel fibers is formed in the upper part of the concrete layer, and then the surface of the concrete layer is roughened to expose the steel fibers contained in the concrete layer, and then the upper concrete is poured in a layered manner on the upper surface of the lower concrete. A method for pouring joints in laminated concrete, characterized by the following: