JP3560358B2 - Manufacturing method of lightweight cellular concrete - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a method for producing an autoclave-cured lightweight cellular concrete (hereinafter abbreviated as ALC) having excellent durability such as resistance to carbonation and drying shrinkage.
[0002]
[Prior art]
ALC is a method of adding an additive such as water and aluminum powder to calcareous raw material powders such as lime and cement and siliceous raw material powders such as silica sand and silica stone, foam molding, cutting this in a semi-cured state, and then cutting this. It is manufactured by subjecting a porous molded body to high-temperature and high-pressure steam curing in an autoclave. In the ALC thus produced, the calcareous raw material, the siliceous raw material, and water undergo a hydrothermal reaction in an autoclave to form calcium silicate hydrate, the main component of which is tobermorite crystals. The structural formula of tobermorite is generally represented by 5CaO · 6SiO ₂ · 5H ₂ O, and it is possible to form a solid solution of some aluminum components and alkali components.
[0003]
Since ALC is used as a building material, durability for maintaining the required performance for many years is important.
ALC contains more voids than ordinary concrete and has a low bulk specific gravity, so that it easily absorbs water. When water is absorbed, it slowly absorbs carbon dioxide in the atmosphere to cause carbonation. If this carbonation occurs continuously, the panel shrinks, and the progress may cause cracks or a decrease in strength.
[0004]
Therefore, in order to prevent this carbonation, an ALC comprising calcium silicate hydrate containing an organic phosphate or a strontium compound has been conventionally devised (JP-A-57-17909, JP-A-57-17909). No. 179011). As another method for preventing carbonation, there has been known a method for producing ALC which improves the crystallinity of tobermorite constituting ALC.
[0005]
[Problems to be solved by the invention]
However, ALC composed of these calcium silicate hydrates requires an expensive and special additive, or some additives have an adverse effect on foam molding such as increasing the mortar viscosity. Further, in order to obtain high crystallinity of tobermorite crystals, long-time high-temperature and high-pressure steam curing is required, and the productivity is lowered, which is not industrially satisfactory. Therefore, an object of the present invention is to provide an ALC having improved durability and dimensional stability without using a special additive and without reducing productivity.
[0006]
[Means for Solving the Problems]
In view of the above, the present inventor has found that in ALC containing calcium silicate hydrate as a main component, the crystal structure of tobermorite crystals constituting calcium silicate hydrate greatly affects carbonation resistance. It has been found that ALC having a tobermorite crystal structure in which the spacing between the (002) planes of the crystal has been increased greatly improves the resistance to carbonation.
[0007]
That is, the present invention uses silica stone containing 3.5 to 10.0 wt% alumite as a siliceous raw material, lime and cement as a calcareous raw material, and uses caustic soda as an alkali component in an amount of 0.2 to the raw material solids. １．０1.0 wt%, water and a foaming agent are added to these raw materials, and this slurry is poured into a mold and foamed to form a porous molded body, which is then subjected to autoclave curing. According to the present invention, in a method for producing concrete, according to the present invention, calcium silicate water is used in an autoclave-cured lightweight cellular concrete containing calcium silicate hydrate as a main component without using a special additive and without reducing productivity. An ALC in which the (002) plane spacing of the tobermorite crystals in the sum is 11.4 Å to 11.5 Å. . Increasing the interplanar spacing of the (002) plane of the tobermorite crystal from 11.4 angstroms to 11.5 angstroms is extremely effective in improving carbonation resistance and dimensional stability.
[0008]
If the (002) plane spacing of the tobermorite crystals in the calcium silicate hydrate constituting ALC is less than 11.4 angstroms, the effect of improving the durability of ALC is small, and when it exceeds 11.5 angstroms. However, no further effect can be obtained. The spacing between the (002) planes is preferably in the range of 11.42 to 11.48 angstroms.
[0009]
The spacing between the (002) planes of the tobermorite crystal can be measured by powder X-ray diffraction. For example, using a powder X-ray diffractometer equipped with a monochromator, it can be measured by a usual method of measuring a crystal lattice constant. At this time, the diffraction angle is geometrically corrected using Si as a standard sample.
[0010]
Further, a method for producing the above-described ALC of the present invention will be described. Silica containing 3.5 to 10.0 wt% of alumite is used as the siliceous raw material, lime and cement are used as the calcareous raw material, and caustic soda is used as the alkali component. 0.0 wt% is added. Further, the same admixture as the conventional ALC may be added. At this time, the silica stone containing alumite is used without calcining. These raw materials and water are mixed to form a slurry, a foaming agent is added to the slurry, and the mixture is poured into a mold in a conventional manner to form a foamed porous molded body, which is then autoclaved and manufactured.
[0011]
As shown in the following examples, the number of days to reach 50% degree of carbonation in the severe accelerated carbonation test with severe carbon dioxide concentration is more than twice as long as that of the conventional product, and the carbonation resistance performance is greatly improved. I have. In building materials, the dimensional stability of members is an important product quality, and the drying shrinkage, which indicates dimensional stability, is also kept low. Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples.
[0012]
【Example】
To a commonly used calcareous material such as quicklime and Portland cement, add a predetermined amount of alumite containing a predetermined amount of alumite and sodium hydroxide, further add water and a foaming agent, and mold according to a conventional method, and perform autoclave curing. , ALC.
The interplanar spacing of the (002) plane of the thus-produced ALC tobermorite crystal was measured by a powder X-ray diffraction method and a step scanning method using an XRD with a monochromator (RAD-2C manufactured by Rigaku Corporation). The measurement conditions are a target Cu, a tube voltage of 40 kV, a tube current of 35 mA, a step sampling of 0.02 deg, and a fixed time of 1 second. At this time, the diffraction angle was corrected using Si as a standard sample. The carbonation test was performed under the conditions of a carbon dioxide concentration of 10%, a temperature of 20 ± 1 ° C., and a relative humidity of 70 ± 3%. The degree of carbonation was measured by the amount of CO ₂ at the time of HCl treatment, with the case where all the calcium content in the ALC was changed to calcium carbonate as 100%, and the number of days until the degree of carbonation reached 50% was measured. The drying shrinkage was tested according to JIS A5416. The crystallinity of tobermorite in ALC was measured with a powder X-ray diffractometer. The results are shown in Table 1 in comparison with Examples and Comparative Examples.
[0013]
[Table 1]
[0014]
Table * 1) For the determination of the content of alunite in silica stone, a calibration curve was prepared by adding the specified amount of alunite to silica stone and determining the intensity of the main peak (2θ = 29.9 °) by X-ray diffraction. Then, each sample was subjected to X-ray diffraction by the same operation, and the content was measured by converting this.
As is clear from Table 1, in Examples 1 to 4, the spacing between the (002) planes was as large as 1.40 to 11.46 angstroms, while in Comparative Examples 1 and 2, the spacing between the (002) planes was 11 0.34 to 11.36 angstroms. That is, the surface spacing of the (002) plane in the example is clearly larger than that in the comparative example.
[0015]
In the ALC of the example having a large (002) plane spacing, the number of days to reach the 50% degree of carbonation increases from 28 days to 52 days, and the carbonation resistance is improved by 2 to 4 times as compared with the comparative example. You can see that it is. Also, comparing Example 2 and Comparative Example 2 showing the same degree of X-ray diffraction intensity of tobermorite crystals, it was found that the ALC of the example composed of tobermorite having a (002) plane spacing of 11.42 angstroms showed 50% carbonation. The number of days to reach the degree is 37 days. On the other hand, in the ALC of the comparative example composed of tobermorite having a spacing of 11.36 angstroms of the (002) plane of the comparative example, the number of days required for the degree of 50% carbonation is 12 days. Therefore, it can be seen that the ALC composed of tobermorite crystals having a (002) plane spacing of 11.40 angstroms or more has improved resistance to carbonation. In comparison among the examples, the carbonation rate of Examples 2 to 4 is lower than that of Example 1, and the (002) plane spacing is 11.42 angstroms or more, which significantly improves the resistance to carbonation. This range is more preferable. You can see that.
[0016]
Further, in Examples 1 to 4, the drying shrinkage test showing the dimensional stability also showed that the drying shrinkage ratio was significantly smaller than that of Comparative Examples 1 and 2, indicating that the ALC was excellent in dimensional stability.
[0017]
【The invention's effect】
As described in detail above, according to the present invention, the carbonation resistance and drying shrinkage of ALC are significantly improved without using a special additive and without reducing the productivity, and the durability as a building material is improved. It is possible to provide an excellent ALC.

Claims (1)

Silica containing 3.5 to 10.0 wt% alumite as a siliceous raw material, lime and cement as calcareous raw materials, and caustic soda as an alkali component added at 0.2 to 1.0 wt% based on the raw material solids. A method for producing lightweight cellular concrete, comprising adding water and a foaming agent to these raw materials, injecting the slurry into a mold, foaming the resultant, and forming a porous molded body, followed by autoclaving.