JP2001199750A - Hydraulic calcium silicate-based raw material using ALC building waste and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new hydraulic calcium silicate-based raw material produced by reusing a waste ALC building material generated in the demolition site of a building, provide a method for producing the material and contribute to the reduction of industrial waste. SOLUTION: A demolition waste of ALC containing a part of tobermorite in carbonated state is reused as a hydraulic calcium silicate-based raw material usable as a substitution raw material for cement by heat-treating the waste at 600-1,500 deg.C. The hydraulic calcium silicate-based raw material contains calcium oxide and a calcium silicate mineral containing a part of tobermorite in decomposed state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology for effectively utilizing ALC building waste generated from a demolition site of a building, etc., and forming a hydraulic calcium silicate-based raw material which becomes a part of a raw material such as cement. is there.

[0002]

2. Description of the Related Art Generally, ALC (Lightweight Cellular Concrete) is mainly made of natural silica stone or silica sand as a siliceous raw material, and limestone or cement directly produced from a natural raw material as a calcareous raw material. It is obtained by foam curing and then steam curing.

[0003] In other words, in addition to gypsum as a secondary raw material, a repetitive raw material such as ALC cutting waste before autoclave is added to the above main raw material, and the resulting mixture is added to water to form a mixed slurry. Add a foaming agent
Inject into foam and foam. Further, when the plastic state is reached after a predetermined time, the piece is cut into a desired size with a piano wire, and then put into an autoclave and steam-cured at high temperature and high pressure.

[0004] The obtained ALC is cut into a predetermined size to be a building material such as a panel. ALC panels as building materials are widely used as materials for outer walls, partitions, roofs, floors and the like of steel structures and RC structures.

[0005] From the ALC manufacturing factory, ALC waste such as cutting chips and cutting chips generated due to dimensional adjustment or defective products due to breakage is generated. Almost all of the waste material generated in the ALC manufacturing factory (hereinafter referred to as factory waste material) is reused in the ALC manufacturing process.

[0006] As the method, it is common practice to repeatedly use the pulverized waste material in the factory as it is without particularly performing heat treatment or the like. In addition, JP-A-5
No. 319876 discloses that waste materials in a factory are 800 to 15 times.
It has been proposed to recycle the powder which has been baked at 00 ° C. and converted into a powder mainly composed of zonolite and wollastonite in an ALC production process.

[0007]

On the other hand, ALC building waste generated with the rebuilding and demolition of buildings is ALC.
Since the production has been started in Japan, more than 30 years have passed, and the number of such wastes has been particularly increasing. However, ALC building waste is
Some of them are crushed or crushed and used for roadbed materials and landfill works. However, most of ALC waste materials were treated as industrial waste without being reused.

The present invention has been made in view of such a conventional situation,
It is an object of the present invention to provide a new calcium silicate-based raw material and a method for producing the same, not only contributing to the reduction of industrial waste by recycling ALC building waste generated from the demolition site of a building.

[0009]

In order to achieve the above object, the present invention provides a hydraulic calcium silicate-based raw material using ALC building waste. That is, the method for producing a hydraulic calcium silicate-based raw material provided by the present invention comprises:
60 parts of ALC waste, which is partly carbonated with tobermorite,
The heat treatment is performed at 0 to 1500 ° C.

[0010] The hydraulic calcium silicate-based raw material provided by the present invention is obtained by heat-treating ALC building waste at 600 to 1500 ° C.
It is characterized in that a part of tobermorite contains a decomposed calcium silicate mineral.

[0011]

The main hydraulic components of the embodiment of the invention] ALC is tobermorite produced by performing the high-temperature high-pressure steam curing in an autoclave (5CaO _· 6SiO 2 · 5H
And crystalline calcium silicate hydrate called _{2 O),}
It consists of unreacted silica. This travolite reacts with carbon dioxide in the air in the presence of moisture to be carbonated, and is decomposed into calcium carbonate (CaCO ₃ ) and silica gel.

[0012] The rate of carbonation of tobermorite in ALC building waste depends not only on the concentration of carbon dioxide gas but also on the relative humidity, temperature, ALC water content, treatment condition of ALC surface (type of coating, thickness, repair), etc. Because they are affected, they vary within the same building and within the same ALC panel. However, since ALC after construction always has a surface in contact with air containing carbon dioxide gas, at least a part of tobermorite in ALC building waste is always carbonated.

Although the in-plant waste that has been reused in the ALC factory has come into contact with air, the time until the reuse is extremely short, about several hours, so that it has not substantially undergone carbonation. In Japanese Unexamined Patent Publication No. Hei 5-319876, it is shown that tobermorite that has not been subjected to carbonation changes into minerals called wollastonite and zonolite when heated to 800 ° C. or more. However, according to the study of the present inventors, it was found that zonolite was not formed in this case. This is supported by the literature, for example, “Hydrothermal Chemistry Handbook” published by Gihodo 2
On page 98, the zonolite decomposes into wollastonite (wollastonite) at 800 ° C, and on page 302, when the condensation form of silicate ions is a double chain (tobermorite is equivalent to this), it decomposes into wollastonite. It is described.

On the other hand, since carbonated tobermorite in ALC building waste is decomposed into calcium carbonate and silica gel as described above, the calcium carbonate is decarbonated by heat treatment at 600 ° C. or more according to the present invention. To calcium oxide (CaO). When this calcium oxide comes in contact with water, it generates hydration heat and can be changed to slaked lime. At the same time, some non-carbonated tobermorite in ALC building waste is converted into unstable crystals from which a part of the crystallization water is removed at 600 ° C. or higher.

At 800 ° C. or higher, non-carbonated tobermorite turns into walathite, but unlike factory waste, when carbonized ALC building waste is fired at 800 ° C. or higher, the crystallinity of walathite is low. It has been found that an unstable substance whose crystal structure does not completely match is formed. This suggests that the structure of tobermorite, which has been partially carbonated, has also changed. Therefore, carbonated tobermorite has a temperature of 800 ° C.
It was found that the minerals generated by the above decomposition were unstable, in other words, those that easily reacted.

That is, in the present invention, by sintering at a temperature of 600 ° C. or more, ALC building waste partially carbonated with tobermorite, calcium oxide and a chemically unstable calcium silicate system in which tobermorite is partially decomposed are used. A novel calcium silicate-based raw material containing minerals and further containing unreacted silica stone can be obtained.

Accordingly, the calcium silicate-based raw material according to the present invention reacts with water, and at the same time as quicklime hydrates into slaked lime,
Calcium silicate-based minerals having low crystallinity and being chemically unstable hydrate to form calcium silicate-based hydrates, and thus have the property of hardening. That is, according to the present invention, a novel calcium silicate-based raw material having hydraulic properties is provided in the same manner as a commonly used cement.

The heating temperature is preferably from 600 ° C. to 1500 ° C. at which calcium carbonate is decomposed.
When the temperature exceeds 1500 ° C., not only does the energy cost for heating increase, but also the mineral particles in the ALC melt and the specific surface area decreases, and at the same time, the possibility that calcium silicate-based minerals with high crystallinity are generated by the solid-phase reaction is increased. This is because the hydration reactivity becomes poor. In addition, as a heat source for heating, waste heat of a garbage incineration plant can be used.

Since the calcium silicate-based raw material according to the present invention has hydraulic properties by itself, it is possible to reduce the amount of cement used by mixing it with ordinary Portland cement or the like. In addition, when used as a ground improvement material, it is expected that the ground strength will be increased due to its hydraulic property as compared with a case where the ALC waste material is simply buried and used.

[0020]

EXAMPLE A carbonized ALC building waste was collected from a building demolition site, placed in an electric furnace with the panel as it was, and fired at each temperature shown in Table 1 below for 2 hours. Although heat treatment was performed while leaving the coating material on the panel surface of the ALC waste material, the coating material was thermally decomposed and shrunk, and could be easily peeled off. Thereafter, the fired product was pulverized to a particle size of 150 μm or less to obtain a calcium silicate-based raw material. The presence or absence of carbonation of each ALC waste material was determined by X-ray diffraction using Cu _k α2θ = 36.9 °.
The measurement was performed based on the presence or absence of a peak of calcite in the vicinity or a calcite near Cu _k α2θ = 32.7 °.

Each of the obtained calcium silicate-based raw materials was replaced with 10% by weight or 50% by weight of ordinary Portland cement to prepare a normal mortar, and its 28-day compressive strength was measured according to JIS R5201. The mortar was mixed in all samples in a total of 520 g of ordinary Portland cement and calcium silicate-based raw materials, and standard sand 1040.
g of water and 338 g of water. For comparison, the compressive strength was similarly measured for Samples 1 and 2 obtained by calcining and adding non-carbonated in-plant waste generated in the ALC manufacturing plant and Sample 15 to which no ALC waste was added. . The results obtained are shown in Table 1 below.

[0022]

[Table 1] (Note) Samples marked with * in the table are comparative examples.

As can be seen from Table 1 above, in samples 1 and 2 in which the waste material in the ALC factory was calcined and added, AL
The compressive strength of the mortar is significantly lower than that of Sample 15 (normal mortar) without the addition of C waste material. Also, ALC
Also in Samples 3 and 14 in which the building waste was fired at a temperature outside the range of the present invention and added, the compressive strength of the mortar was much lower than that of Sample 15 without addition.

On the other hand, in the samples 4 to 13 of the present invention in which the calcium silicate-based raw material was replaced with a part of Portland cement and added to the mortar, the compressive strength of the mortar was slightly lower than that of the sample 15 without the ALC waste material. However, it can be seen that the strength is improved as compared with Samples 1 and 2 of the conventional example. That is, the calcium silicate-based raw material according to the present invention not only exhibits hydraulic property like Portland cement but also has an effect of improving the hardening performance of Portland cement.

[0025]

According to the present invention, it is possible to provide a calcium silicate hydraulic raw material that can be used as a substitute material for cement by recycling ALC building waste generated from a building demolition site, and to provide industrial waste. Not only does it contribute to the reduction of natural resources, but it is also effective in saving resources of depleting natural raw materials.

Claims (2)

[Claims] 1. An ALC building waste obtained by heat treatment at 600 to 1500 ° C., comprising calcium oxide,
A hydraulic calcium silicate-based raw material comprising a part of tobermorite decomposed with a calcium silicate-based mineral. 2. AL in which a part of tobermorite is carbonated
C. A method for producing a hydraulic calcium silicate-based raw material, wherein a waste construction material is heat-treated at 600 to 1500 ° C.