JPH11228251A - Production of light-weight foamed concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide autoclaved lightweight concrete(ALC) of high productivity and economy that can suppress the formation of voids susceptible to occur around the reinforcing iron rods, and removes or reduces surface or small face depressions, when the cement slurry hardens in the frame work with increased commodity value. SOLUTION: A siliceous raw material as silica rock or the like, cement, a calcareous rock as gypsum and the power of recycled raw materials are used as a main material and the slurry containing the main material and a foaming agent is cast into the frame work in which reinforcing iron rods are arranged to produce the ALC. At this time, high early strength portland cement is used as a portland cement and the slurry temperature is set to 37-44 deg.C on the casting into the frame work.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing lightweight cellular concrete (ALC), and more particularly to a method for producing high-quality ALC by preventing cavities that are likely to be formed around reinforcing steel bars in the process of foaming a raw material slurry. How to do it.

[0002]

2. Description of the Related Art ALC is lightweight because it contains small air bubbles in its entirety, and has been conventionally used as a panel or the like for walls and floors of buildings. The production of such an ALC is carried out by a method described below using a siliceous raw material such as silica stone, ordinary Portland cement, a calcareous raw material such as gypsum, and a repeated raw material powder as a main raw material.

First, a suitable amount of a foaming agent such as aluminum powder and water are added to each of the above-mentioned main raw materials, and if necessary, additives such as a surfactant are further added and kneaded to form a slurry.
While maintaining the slurry at a temperature of 47 to 50 ° C., the slurry is poured into a mold in which a reinforcing steel bar is set inside. The slurry injected into the mold gradually hardens while the hydration reaction and foaming proceed simultaneously, and a semi-plastic body containing fine bubbles is formed. After a lapse of a desired time, the semi-plastic body cured to an appropriate hardness is removed from the mold.

[0004] Next, the outer shape of the semi-plastic body is adjusted to a shape having desired dimensions. For example, when manufacturing an ALC panel, a semi-plastic body is ground into a rectangular parallelepiped shape having a predetermined size or cut using a piano wire arranged in parallel at an interval corresponding to the thickness to obtain a desired panel shape. Thereafter, the semi-plastic body is charged into an autoclave and subjected to steam curing at high temperature and high pressure to obtain ALC. In addition, the obtained ALC is cut into various sizes or subjected to a groove processing on a long side small face, a chamfer processing of a green part, or the like based on its use. Furthermore, if necessary, cutting of design patterns, sticking of tiles,
Surface finish such as painting is applied.

[0005] The ALC thus produced has a uniform distribution of bubbles having a diameter of 2 to 3 mm, a bulk specific gravity of about 0.50 to 0.55 when dried, and a compressive strength of 42 to 45 kg.
/ Cm ² is desired. However, in the process of foaming and hardening of the slurry in the mold, giant air bubbles having a diameter exceeding 5 mm were apt to be generated, and these often became cavities and remained in the ALC product.

[0006]

In the conventional ALC, as described above, cavities derived from giant air bubbles are likely to remain in the product, and in particular, cavities are formed around reinforcing reinforcing bars set horizontally in a mold. Was easy to occur. The presence of such cavities reduces the compressive strength of ALC products,
Since the dents due to the cavities are exposed on the surface and the edge of the forehead, there is a problem that not only is it troublesome to repair, but also the appearance is deteriorated and the commercial value is reduced.

The causes of the above-mentioned huge bubbles or cavities are various, such as the quality and mixing ratio of each raw material, the viscosity and temperature of the slurry, the arrangement of reinforcing steel bars, the entrainment of air during the injection of the slurry, and the final stage of foaming of the slurry. Is considered to be related to the viscosity or expansion or contraction after the end of firing. Various methods have been studied for suppressing the generation of huge bubbles or cavities.

[0008] As a result of various studies on methods for preventing the generation of such huge bubbles or cavities, it was found that it is effective to lower the viscosity of the slurry at the end of foaming in the mold.
As one of the methods, there is a method of increasing the water weight (water ratio) with respect to the solid weight of the raw material. However, in this method, the curing speed of the slurry becomes slow, and thus, the semi-plastic body has to be hardened until it reaches a hardness that can be cut. The longer the time, the lower the productivity. Another method is to improve the quality of raw lime,
There is also a method to reduce the amount of compounding and the repeated raw materials generated in the manufacturing process, but this method increases the raw material cost,
There was a drawback that the economy was reduced.

The present invention suppresses the generation of cavities in the ALC manufacturing process, particularly, the huge bubbles or cavities that are likely to be generated around the reinforcing steel bar when the raw material slurry is hardened in the mold.
An object of the present invention is to provide a method for manufacturing an ALC that eliminates or reduces the dents that appear on the surface or the edge and eliminates or reduces the need for repair, enhances commercial value, and is excellent in productivity and economy. I do.

[0010]

In order to achieve the above object, the present invention provides a method for producing ALC comprising a siliceous raw material such as silica stone, cement, and a calcareous raw material such as gypsum.
A method for producing a lightweight cellular concrete, comprising a step of injecting a slurry containing these main raw materials and a foaming agent into a mold set with reinforcing steel and foaming and hardening the same as a main raw material and a powder of a repetitive raw material, Is used, and the temperature of the slurry at the time of injection of the mold is set to 37 to 44 ° C.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the cement as a raw material for producing ALC is changed from conventional ordinary Portland cement to early-strength Portland cement,
By setting the slurry injection temperature to a temperature lower than the conventional temperature of 37 to 44 ° C., the viscosity of the slurry at the end of foaming in the mold can be reduced, and shrinkage during curing can be almost eliminated. As a result, during the curing of the slurry in the mold, the generation of giant air bubbles around the reinforcing steel bar and the generation of cavities resulting therefrom are prevented, and the dents on the surface of the product such as panels and small edges are eliminated. Repair is unnecessary or can be reduced, a product yield is high, and an ALC panel with high commercial value can be manufactured. In addition, early strength Portland cement
It is defined in JIS R 5210.

In the conventional method using ordinary Portland cement, it was necessary to adjust the slurry injection temperature usually in the range of 47 to 50 ° C. The reason is that if the slurry injection temperature is lower than this temperature range, the slurry viscosity at the end of foaming in the mold can be reduced, but the time for the semi-plastic body to harden to a cuttable hardness is remarkable. This is because, if it becomes longer, the productivity is greatly reduced.

However, in the method of the present invention, by using the early-strength Portland cement, the time required for the semi-plastic body to harden to a cuttable hardness is appropriate even if the slurry injection temperature is lowered compared to the prior art. This can be maintained for about 270 minutes, and the viscosity of the slurry at the end of foaming can be reduced to suppress the generation of huge bubbles or cavities.

The slurry injection temperature in the present invention is 37.
To 44 ° C, preferably 38 to 43 ° C. If the injection temperature is less than 37 ° C., the curing time becomes too long, and the productivity is significantly reduced. On the other hand, the injection temperature is 44 ° C
Exceeds, the viscosity of the slurry at the end of foaming increases, so the occurrence of cavities around the reinforcing steel bar increases rapidly,
In addition, since the curing time is too fast, when cutting is performed after a predetermined time, overcuring occurs, and the piano wire for cutting is disconnected.

Further, according to the present invention, it is possible to almost eliminate the shrinkage when the slurry injected into the mold is cured into a semi-plastic body. Therefore, the height at the end of foaming is stable,
The bulk specific gravity of the product during drying can be easily kept constant,
The quality can be made uniform.

[0016]

Example: Silica is used as a siliceous raw material, ordinary Portland cement or early-strength Portland cement is used as cement, and quicklime and gypsum are used as calcareous raw materials. They were blended so that the blending ratio was constant as shown in Table 1 below. Water was added to these main raw materials at a normal water ratio shown in Table 1 and kneaded to form respective slurries.

[0017]

TABLE 1 raw material blending ratio (wt%) silicofluoride stone quicklime stone plaster cement repeated raw aluminum powder water ratio 40 4 6 28 22 0.06 0.65

Each of the slurries adjusted as described above was poured into a mold in which reinforcing steel was set in a fixed state. At that time, as shown in Table 2 below, the slurry injection temperature was changed for each sample, and the curing time until a semi-plastic body was obtained was measured. Further, with respect to each of the obtained semi-plastics, an ALC panel was further manufactured through a normal cutting and cutting step and a steam curing step, and the occurrence rate of a dent that appeared on the small face of each ALC panel was examined. The results of these investigations are shown in Table 2 below.

The hardening time is such that an iron ball having a diameter of 45 mm is dropped on the surface of the semi-plastic body from a position of 50 mm in height, and the diameter of the depression on the surface of the semi-plastic body at that time is 25 mm.
The appropriate time is generally about 210 to 270 minutes. In addition, the incidence of pits on the ALC panel's small face was determined by examining 1200 panels for each sample and calculating the ratio of panels having a pit with a diameter of 5 mm or more on the small face.

[0020]

[Table 2] (Note) Samples marked with * in the table are comparative examples.

Sample 1 in Table 2 above was obtained by a conventional method using ordinary Portland cement at a slurry injection temperature of 48 ° C., which is generally used. Is very high at 7.3%. On the other hand, Examples of the present invention of Samples 2 to 5 use the early-strength Portland cement and vary the slurry injection temperature at 37 to 43 ° C. The occurrence rate of cavities could be reduced to the range of 0.06 to 0.4%.

On the other hand, in Comparative Examples of Samples 6 and 7, Portland cement of early strength was used, but the injection temperature of the slurry was 35 ° C. and 45 ° C., respectively. For this reason, the sample 6 with a low injection temperature has a low cavitation rate of 0.20%, but the curing time is too long at 300 minutes, and the sample 7 with a high injection temperature has an extremely short curing time of 165 minutes. ,
The void generation rate is also rapidly increasing to 7.6%.

Further, in Comparative Examples of Samples 8 and 9, ordinary Portland cement was used, and the injection temperature of the slurry was 38 ° C. and 43 ° C., respectively, which were the same as Samples 4 and 2 of the Examples. However, since Portland cement is usually used, the sample 8 with a low injection temperature has a low cavitation rate of 0.50%, but has an extremely long hardening time of 315 minutes. In the case of Sample 9 in which the injection temperature was close to that of the conventional example, the curing time was 270 minutes, but the void generation rate was 5.6.
%, Which is very high.

[0024]

According to the method for producing ALC of the present invention, an early-strength Portland cement is used as the main raw material cement instead of the conventional Portland cement,
The injection temperature of the slurry at the time of injection into the mold is 37 to 44.
By lowering the temperature to less than the conventional temperature, the viscosity of the slurry at the end of foaming in the mold can be reduced while maintaining an appropriate curing time, and at the same time, shrinkage during curing can be almost eliminated.

Therefore, it is possible to prevent the cavity from being formed around the reinforcing steel bar when the slurry is hardened in the mold, and to reduce the AL.
The dents appearing on the surface and the edge of the C product can be eliminated. For this reason, the repair of the dent can be made unnecessary or reduced, the product yield is improved, and the AL with high commercial value is improved.
C products can be manufactured.

Further, since the temperature at which the slurry is injected into the mold can be made lower than before, the energy is saved, and the curing time is appropriate, so that the productivity is not reduced. Furthermore,
There is no need to use high quality lime as a calcareous material,
Since there is no need to repeatedly reduce the amount of raw materials, the cost of raw materials can be kept low and the economy is excellent.

Claims (1)

[Claims] Claims: 1. A siliceous material such as silica stone, cement,
Light-weight cellular concrete comprising a process in which a calcareous material such as gypsum and a powder of a repeated material are used as main materials, and a slurry containing these main materials and a foaming agent is poured into a formwork in which reinforcing steel bars are set to foam and harden. In the method of manufacturing, using early strength Portland cement as the cement,
The method for producing lightweight cellular concrete, wherein the temperature of the slurry at the time of casting the mold is set to 37 to 44 ° C.