JPH0481538B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to the production of concrete with a low alkali concentration useful as a construction or civil engineering material, and more specifically to a carbonation curing method for γ-type dicalcium silicate. (Prior art) Concrete products that have traditionally been used in large quantities are hydrates of Portland cement or mixed cement, so the alkali concentration in the hardened product is extremely high. However, it was inevitable that the glass fibers would deteriorate during service life, resulting in a significant decrease in the strength of the concrete. Further, even in the case of ordinary concrete, it has the disadvantage of being susceptible to efflorescence. γ-type dicalcium silicate (hereinafter referred to as γ-C ₂ S) is
It is a mineral with the chemical formula γ-2CaO・SiO ₂ , and when carbonated in the presence of water, it reacts and hardens according to the following formula. γ-2CaO・SiO ₂ +2CO ₂ +2H ₂ O →2CaCO ₃ +SiO ₂ +2H ₂ O ...(1) This hardened γ-C ₂ S has a significantly lower alkali concentration than conventional concrete, so it is It has no drawbacks and has long been attracting attention as an industrial material, but since mass production technology had not yet been established, almost no applied research had been conducted on it. However, the present applicant had previously established a technology for manufacturing γ-C ₂ S powder in large quantities and at low cost in a rotary kiln using inexpensive raw materials, and applied for this in a patent application filed in 1983.
It was proposed as No. 153154. Therefore, in the future, it is expected that a technology using γ-C ₂ S, which will be produced in large quantities by such a method, will be developed. (Problems to be Solved by the Invention) Having established the technology for industrially mass-producing γ-C ₂ S powder as described above, the inventor continued to research the application technology. One of the purposes is to provide a carbonation curing method for obtaining a cured product with even higher strength when carbonating and curing γ-C ₂ S powder to produce a cured product. (Means for solving the problem) In order to achieve the above object, the present invention
As a carbonation curing method for C ₂ S powder, a mixture of γ-type dicalcium silicate powder, sand, and other substances is kneaded with an aqueous solution and molded, and then the γ-type dicalcium silicate in this molded body is carbonated to form a hardened product. The method is characterized in that a 0.03 to 2.0% by weight aqueous solution of an anionic surfactant, a nonionic surfactant, or a mixture thereof is used as the aqueous solution. This invention will be further explained below. Conventionally, the method for manufacturing γ-C ₂ S hardened bodies has been to knead a mixture of γ-C ₂ S powder and sand with water, mold this, and then cure it with carbon dioxide gas. 0.03 of anionic surfactant or nonionic surfactant or a mixture thereof instead of kneading water
~2.0% by weight aqueous solution is used.
The concentration of the aqueous solution of the anionic surfactant or nonionic surfactant used in the present invention is preferably in the range of 0.03 to 2.0% by weight. Outside this range, if it is less than the lower limit, even if it exceeds the upper limit, the strength of the cured product will not improve much. The amount of anionic surfactant or nonionic surfactant aqueous solution added to the mixture of γ-C ₂ S powder and sand etc. is determined by the water saturation of the molded product as shown by the following formula.
It is preferable to add it so that it becomes 0.25-0.95. Moisture saturation = molded product moisture (%) / 100 - molded product moisture (%)
) × 100 − Apparent porosity of molded product (%) / Apparent porosity of molded product (%) × Apparent porosity of molded product (%) ……(4) When the water saturation is outside this range is not preferable because the strength of the cured product is low. Therefore, water saturation
When it is 0.95 or more, it is preferable to adjust the moisture content by drying so that it is between 0.25 and 0.95, and then carbonate and cure. In particular, when kneading and molding slurry, γ
-C ₂ S is well dispersed and a cured product with even higher strength can be obtained. The higher the concentration of carbon dioxide gas used in this invention, the more preferable it is, but combustion exhaust gas can also be used as long as the CO ₂ concentration is 10% or more. As in the past, a CO ₂ concentration of less than 10% is undesirable because the development of strength is slow and small. Note that the use of an aqueous solution of a cationic surfactant does not have the effect of increasing the strength of the cured product. This is thought to be because when the γ-C ₂ S powder is mixed with water, it becomes alkaline and loses its effectiveness as an activator. In the present invention, if an aqueous solution of an anionic surfactant or a nonionic surfactant is used instead of water, a cured product with high strength can be obtained, and the inventor believes that the reason for this is as follows. That is, when carbonating and curing γ-C ₂ S powder to harden it, water must be added as a catalyst.
Unless this water is added, carbonation of γ-C ₂ S will hardly proceed. When carbon dioxide gas dissolves in water, it becomes H ₂ CO ₃ according to the following formula. H ₂ O + C0 ₂ →H ₂ CO ₃ ...(2) Next, γ-C ₂ S is dissolved in H ₂ CO ₃ to precipitate CaCO ₃ crystals as shown in equation (3). 2CaO・SiO ₂ +2H ₂ CO ₃ →2CaCO ₃ +SiO ₂ +2H ₂ O ……(3) The more densely packed CaCO ₃ crystals, which are the reaction products of formula (3), are packed, the stronger the hardened body becomes. By the way, in the present invention, since the CaCO ₃ crystals are precipitated in an anionic surfactant or nonionic surfactant solution, the precipitated CaCO ₃ crystals are finely and densely packed, thereby obtaining a high-strength hardened product. It is considered that the Example 1 A 0.5% by weight aqueous solution of various surfactants shown in Table 2 was added to a mixture of 1 part by weight of γ-C ₂ S powder shown in Table 1 and 2 parts by weight of Toyoura standard sand to saturate the molded product with water. The mixture was added and mixed to a degree of 0.5, and then molded into a cylindrical body with a diameter of 25 mm and a height of 30 mm at a molding pressure of 50 kg/cm ² . This molded product was then placed in carbon dioxide gas at 20°C for 1
After curing for a period of time, the compressive strength was measured. The results are shown in Table 2. Note that the same table also shows a case where only water was added as a comparative example.

【table】

【table】

[Table] Increase rate
When no surfactant is added
(%)
Compressive strength (Kg/cm ² )
As is clear from Table 2, when producing a cured product by carbonating and curing γ-C ₂ S powder, using an aqueous solution of an anionic surfactant or a nonionic surfactant results in a high-strength cured product. You can see what you can get. _Example 2 A polyalkyl sulfonate ( 1 part by weight of tridecyl alcohol ethylene oxide (5 mole adduct) and polyalkyl sulfonate (trade name IPC-TS, manufactured by Idemitsu Petrochemical Co., Ltd.) and tridecyl alcohol ethylene oxide ( 5 molar adduct)
1 part by weight of an aqueous solution of the mixture was added and mixed, and then molded and cured with carbon dioxide gas in the same manner as in Example 1. The compressive strength of the cured product was measured, and the results shown in the attached diagram were obtained. As is clear from the figure, the concentration of the aqueous solution of the surfactant to be added is preferably in the range of 0.03 to 2.0% by weight. Example 3 A sample with a surfactant concentration of 0.5% by weight, which was used for the test measurement in Example 2, was then
It was ground to 0.5 mm diameter, 20 g of it was stirred in 30 ml of distilled water, and after 24 hours, the pH value of the supernatant liquid was measured and found to be 10.2 to 10.3. Since the PH value of conventional hardened concrete is approximately 13.0, the present invention's PH value is approximately 13.0.
It can be said that the PH value is extremely low. (Effects of the Invention) When the curing method of the present invention is employed, the strength of the hardened low-alkali γ-type dicalcium silicate powder can be improved. This also means that the cured product can have high strength in a short time.

[Brief explanation of the drawing]

The figure is a diagram showing the relationship between the concentration of surfactant in an aqueous solution and the compressive strength of the obtained cured product.

Claims (1)

[Claims] 1 A mixture of γ-type dicalcium silicate powder, sand, and other substances is kneaded with an aqueous solution and then molded, and then the γ-type dicalcium silicate in this molded body is carbonated to produce a hardened body. 0.03 of a nonionic surfactant or a mixture thereof
A carbonation curing method for γ-type dicalcium silicate powder, characterized by using an aqueous solution of ~2.0% by weight.