JPS62878B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention particularly relates to a method for producing autoclave-cured lightweight cellular concrete (hereinafter referred to as ALC), which has excellent freeze resistance. ALC (Autoclaved Lightweight Concrete) is generally a slurry whose main components are finely ground silicic acid and lime, mixed with a foaming agent such as metal aluminum powder, and injected into a formwork, and after reaching a semi-hardened state. It is a building material obtained by demolding, cutting into predetermined shapes, and curing it in an autoclave under high temperature and pressure.It is lightweight, heat-insulating and fire-resistant.
It has excellent workability and is widely used as exterior wall and roofing materials. However, as a general trend of concrete-based products, there is a problem with freeze resistance, and when used in cold regions, the performance is inferior in freeze-thaw tests compared to concrete containing air entraining agents.
There was an urgent need to resolve this issue. Conventionally, freezing resistance was considered to be closely related to open porosity, that is, water absorption rate, and from the viewpoint that reducing water absorption rate was the most effective way to improve freezing resistance, silicone oil etc. Various studies have been conducted to reduce water absorption and improve freeze resistance by mixing water repellents and waterproofing agents into raw material slurry, or by coating or impregnating products with polymeric substances after curing. However, as mentioned later, the effect is not as expected.
Economics was also a problem. As a result of intensive studies on the freeze-thaw properties of ALC, the inventors found that there is no relationship between the freeze resistance and water absorption properties of ALC products, and surprisingly, it was found that metal aluminum with an average particle size of substantially 15 μm or less It has been found that when ALC is produced by mixing silicic acid and lime as a foaming agent into a slurry whose main component is a silicic acid lime substance, a product with extremely good freeze resistance can be obtained. The average particle size of conventionally used metal aluminum is about 30 to 40 μm, and even if it is made into a finer powder, it has no effect at all, and has not been considered at all. However, when manufactured by adding metallic aluminum that has been pulverized to a size of 15 μm or less, the resulting product shows no significant difference compared to conventional products in the natural water absorption test, but in the boiling water absorption test, the amount of water absorbed is rather large. Freeze-thaw resistance is significantly improved, although performance deteriorates.
This fact is very clear in the comparative examples described below. The present invention can be applied to the production of ALC plates, plates, and other products of any shape.
The method specified in JIS-A-5416 can be applied as the most standard method for manufacturing ALC, and as long as metal aluminum under the conditions specified in the present invention is mixed into the slurry, the ALC manufacturing conditions It can also be applied under any variation of. The metal aluminum referred to in the present invention is a powder made of foil-like particles or a paste of powder, and has an average particle diameter of substantially 15 μm or less. Weight average particle size by wet sieving method is 15
A material of μm or less can be used. As long as metallic aluminum under these conditions is used as the main blowing agent component, metallic aluminum having a particle size exceeding 15 μm may be mixed. As to the amount of metal aluminum added, its form, conditions, and mixing conditions to the raw materials, known methods may be applied as they are, and it is also permissible to add appropriate auxiliaries. Examples of the present invention will be described below in comparison with comparative examples. Comparative Example Natural water absorption (vol.%) and boiling water absorption (vol.%) of each lightweight concrete sample prepared by the method described later.
%) and the volumetric residual rate by repeated freezing and thawing were determined by the following methods. Measurement of natural water absorption A 50 mm cubic specimen was placed under 30 mm of water and left for 24 hours, after which the weight increase rate was determined. Measurement of boiling water absorption A 50 mm cubic specimen was placed under the water surface, boiled for 1 hour, then left under the water for 24 hours, and the water absorption was measured using the same method used to measure natural water absorption. Freezing Resistance Evaluation Test A 50 mm cubic specimen was repeatedly thawed in air freezing water according to the method of ASTM-C-666 to determine the volumetric survival rate (%). Freezing was performed at an ambient temperature of -18°C and thawing was performed at an ambient temperature of +5°C, and freezing and thawing were repeated at a rate of 10 cycles/day. Each sample was made of lightweight aerated concrete with a specific gravity of approximately 0.5, which differed in particle size of metal aluminum used during preparation, consisting of 10 parts by weight of quicklime (all parts by weight below), 40 parts of cement, 50 parts of silica, and 0.07 parts of metal aluminum (however, It was manufactured using a method and conditions according to the method described in JIS-A-5416 using a slurry prepared with a raw material ratio of 70 parts of quicklime and cement) and 70 parts of water. Autoclave curing conditions were 180°C for 12 hours. Samples A, B, and C are comparison samples prepared using metallic aluminum having a weight average particle size of 32.4 μm as a blowing agent by a wet film method. Synthetic fatty acid waterproofing agent containing 1% by weight based on solid content
Sample C was prepared by adding IE (manufactured by Mitsubishi Oil Corporation), and sample C was prepared by adding a 5-fold dilution of water-soluble silicone water repellent TSW870 (manufactured by Toshiba Silicone Corporation) to the surface of sample A. It was made by applying 0.5Kg/ ^m2 of The natural water absorption test and boiling test results of each sample are
The results of the freezing resistance evaluation test are shown in the table in Figure 1.

[Table] * Weight average particle diameter (μm) by wet sieve method
As is clear from Table 1 and Figure 1, sample A
On the other hand, although the amount of water absorbed by Samples B and C was decreased and the water absorption capacity was decreased, the improvement in freezing resistance was slight. As shown in FIG. 1, the volume survival rates of Samples E, F, G, H, and I are 100% even after 90 freeze-thaw cycles. As described above, conventional products A, B, C, and J have a volume residual rate of approximately 50 after 50 to 60 cycles in the freeze-thaw test.
%, and as shown in Figure 1, this curve tends to collapse linearly (residual rate = 0), whereas the product according to the present invention has a higher water absorption amount than the conventional product, but it can be used for 100 cycles. However, there was no change in up to four of the five examples, and their excellent freeze resistance is noteworthy.

[Brief explanation of the drawing]

Figure 1 shows the results of the freezing resistance evaluation test of the samples. In the figure, the vertical axis shows the volume residual rate (%), and the horizontal axis shows the number of freeze-thaw cycles.

Claims (1)

[Claims] 1. Autoclave-cured lightweight cellular concrete with excellent freeze resistance, characterized by mixing aluminum metal with an average particle diameter of substantially 15 μm or less as a foaming agent into a raw material slurry whose main components are silicic acid and lime. manufacturing method.