JPS63103878A - Carbonation curing process for gamma type dilime silicate - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to the production of hardened concrete with a low alkali concentration useful as construction or civil engineering materials, and more specifically, to further improvement of γ-type dicalcium silicate. This relates to the carbonation curing method.

(Prior art) Cocrete products, which 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. This has the disadvantage that the glass fibers inevitably become solid during use, resulting in a significant decrease in the strength of the concrete.

γ-type dicalcium silicate (hereinafter referred to as “γ-C2S”) is γ-
It is a mineral represented by the chemical formula 2CaO.5i02, and when it is carbonated in the presence of water, it reacts and hardens according to the following formula.

7-2CaO・S i02 +2Ca02-7-2Ca
O-s 1c)2 +2CO2・・・・・・ (1
) This hardened γ-C2S has a significantly lower alkali concentration than conventional concrete, so it does not have the drawbacks of hardened Portland cement, and has long been attracting attention as an industrial material, but mass production technology for it has not been established until now. As a result, the reality is that there has been little research into applied technology using this technology.

However, the applicant had previously developed a mass production technology for inexpensively manufacturing γ-C2S powder from low-friction raw materials, and applied for this in a patent application filed in 1983.
It was proposed as No. 0-153154. Therefore, in the future, there will be a need to develop various applied technologies using γ-C2S, which can now be mass-produced in this way. Although the present applicant has already made several proposals related to this, there is a real need for further development of applied technology regarding γ-C2S.

(Problems to be Solved by the Invention) When kneading γ-C2S powder with water to obtain a molded product and carbonating and curing it to produce a cured product, it is necessary to take a sufficient amount of time at a high water saturation level. If carbonation curing is used, it is possible to obtain a fairly homogeneous cured product in the case of a thin molded product, but there is a problem in economical processing. Particularly in the case of a member having a certain degree of thickness, an uncured portion remains inside, making it impossible to obtain a uniform member. Further, even if carbonation curing is carried out at an appropriate water saturation level, it is extremely difficult to obtain a uniformly cured product with high strength, as corners and bonded areas become too dry and curing is insufficient. The present inventor has solved these problems by making it possible to carbonate the inside of the molded product uniformly as well as the outside surface, and to shorten the time required for carbonation, thereby achieving high strength and uniform hardening of the entire body. The purpose is to obtain a cured product.

(Means for Solving the Problems) This invention forms a molded article by adding water to a mixture of γ-type dicalcium silicate powder and sand, or a mixture of these with fibers as an admixture or reinforcing material. γ of this molded product
When producing a hardened body by carbonating mold dicalcium silicate, the moisture content of the molded product formed from the raw material mixture is adjusted to 0.4 to 0.8 at the moisture saturation defined by the following formula, and then carbonated. After curing, the surface of the cured material is treated with moisture absorption during curing.
This is a carbonation curing method for γ-type dicalcium silicate characterized by further carbonation curing. This invention will be further explained below.

γ-C2S used in the present invention reacts with CO2 and hardens according to the reaction shown in the following formula. In this case, water acts as a catalyst, and a predetermined amount of water must be present in order for this carbonation reaction to proceed smoothly.

CO2+H2O-4H2CO3...(2)2C
aO・S i02 +2H2CO3→2 Ca CO3
+ S i 02 + 2 H20 (3) As a result of various experiments on the carbonation reaction of γ-C2S, the present inventor found that even if the amount of water present here is too large, It has been confirmed that if the amount is too small, the carbonation reaction of the above formula (3) will not proceed smoothly and a cured product with high strength will not be obtained. Further experiments revealed that the carbonation reaction proceeded smoothly when the moisture content of the molded body was 0.25 to 0.95, preferably 0.4 to 0.8, as expressed by the above formula. It was discovered that high strength was developed in a short period of time.

When water is mixed into a compound containing γ-C2S powder, sand, and optionally other admixtures and/or reinforcing materials to form a molded body according to a conventional method, the water saturation of the molded body is 0.4 to 0.4.
A value of 0.8 is usually obtained when 5 to 10% by weight of water is added during molding, although it varies depending on the particle size distribution of the material used. However, from the perspective of molding technology, if the amount of water added during molding is small, such as 5 to 10% by weight, the kneaded material has almost no fluidity and normal pour molding is not possible, and the product cannot be manufactured without pressure molding. The problem is that it cannot be done. From the perspective of molding technology, in order to obtain a molded product with good moldability and a smooth surface, it is necessary to increase the fluidity of the kneaded product by adding excessive amounts of kneading water far exceeding the above water saturation level, and then perform pour molding. is preferred.

However, if cast molding is used, the molded product must be dried to adjust its moisture content to a moisture saturation of 0.4 to 0.8, and then subjected to carbonation curing. Otherwise, a good cured product cannot be obtained as described above. However, in this case, it is not easy to uniformly dry the interior and surface layer of the molded body containing excess water and adjust the moisture content of the entire molded body to the above range of water saturation, and often the surface layer of the molded body , corners, and edges were too dry. In particular, this tendency is unavoidable when the molded body is a thick plate. Therefore, if carbonation curing is carried out in this state, there is a problem that sufficient curing cannot be achieved in the surface layer of the molded article, where the degree of water saturation is extremely low.

In order to avoid this phenomenon, conventional methods have been to increase the moisture saturation of the compacts to be carbonated and cured slightly higher than the appropriate value, and to cure them over a long period of time. Productivity did not improve, which resulted in increased costs.

This will be further explained by showing an experimental example.

Experimental example γ-c2s powder shown in Table 1 1oogr-Toyoura standard sand 1
Add 60ml of water to a mixture of 4g of 00g and E glass fibers (13 pieces of chopped sulland) and knead.
This was poured into a formwork equipped with a suction device, and the lower part of the formwork was vacuum-suctioned to form a plate shape of 10×10XI (cm). This molded product was then placed in an airtight constant temperature box at 20° C. and cured for various times without flowing carbon dioxide gas at a concentration of 9996 or higher.

After that, a 4×9×1 (cm) specimen was prepared from the cured cured product, and after measuring the three-point bending strength (7 cm span) and bending strength, the carbonation rate of the sample was measured. Separately, when a molded article immediately after molding was molded in the same manner as above, the moisture saturation was 1.02.

Table 1 Three-point bending strength and carbonation rate of cured products
The J determination results are shown in the attached figure. As is clear from this figure, the carbonation rate exceeds 50% and the bending strength is 15%.
To exceed 0 kg/d, long-term curing of 15 hours or more is required. Furthermore, it can be seen that during the initial 5 hours of curing, the molded body contained too much moisture and was hardly cured.

In order to eliminate such gaps, in the present invention, the water saturation level of the molded product is adjusted in advance so that the start time of carbonation curing is brought forward, and the surface and corners of the molded product are In areas where moisture is likely to dissipate quickly, such as
During curing, water is sprayed on the surface of the cured product to absorb moisture, thereby avoiding insufficient carbonation and curing due to excessive drying of this portion.

The γ-C2S molded body to be carbonated and cured in the present invention can be produced by adding water to a mixture of γ-type dicalcium silicate powder and sand, or a mixture of these with an isolating agent or fibers as a reinforcing material. molded by.

Note that carbon fiber, glass fiber, synthetic inorganic U&fiber, and organic fiber can be used as the reinforcing fiber used here. Further, as the molding method, any of the premix method, spray suction method, and direct spray method can be adopted. Next, the moisture content of this molded body is adjusted to a moisture saturation level of 0.4 to 0.8 using known means such as drying and vacuum suction. If the water saturation degree is less than 0.4, the strength of the cured product after carbonation curing will not be sufficient, and if it exceeds 0.8, the carbonation curing time will become long, which is not preferable. The molded body whose moisture content has been adjusted as described above is then carbonated and cured in a carbon dioxide atmosphere. At this time, C02i of the C02-containing gas
The a degree is preferably 3Qvo196 or higher. As this carbon dioxide curing continues, the surface layer of the molded product, such as the surface and corners, will dry faster than the inside.
Water is sprayed onto the surface layer of the dried molded body to moisten the molded body. The amount of water sprayed here is generally preferably 0.25 to 3.0% by weight of the molded body. If it is less than 0.25% by weight, the moisture absorption effect will be small, and if it exceeds 3.0%, it will absorb too much moisture and the next carbonation curing will take a long time, which is not preferable. The molded body subjected to the moisture absorption treatment described above is then carbonated and cured to form a final hardened body.

By doing so, it is possible to maintain the inside and surface portions of the molded body at a substantially even moisture saturation level throughout the entire period of carbonation and curing.

The present invention will be further explained below with reference to Examples.

Example 1゜50g of γ-C2S powder shown in Table 1, Toyoura standard sand 50
gr and E glass fiber (ILmm chopped strand)
2gr mixture and 30ml water! was added and kneaded, and then molded into a plate shape of 10 x 5 x 1 (cm) at a molding pressure of 100 kg/cJ. This molded body was then heated at 20°C and relative humidity 5.
The moisture content was adjusted by leaving the samples in a 0% chamber for various times. As a result, molded bodies with various water contents were obtained.

Separately, the water content, apparent porosity, and apparent specific gravity of the molded body molded in the same manner as above were measured, and the water saturation degree of the molded body was determined from this.

In addition, the moisture saturation of various molded bodies with different moisture contents was calculated from the dried raw materials.

The various molded bodies whose moisture content had been adjusted as described above were placed in an airtight constant temperature box at 20°C, and carbonated and cured for various times while flowing carbon dioxide gas with a concentration of 99% or more into the box. After 2 and 4 hours of curing, water was added to the surface of the molded product.
It was sprayed in a weight percent manner to absorb moisture, and then continued to be cured with carbon dioxide gas for 2 hours.

After curing, each cured product was cut out from the edge of the cured product at a size of 10XIX0.3 (cm).

The carbon content of this cut piece was analyzed, and the carbonation rate of the edge of the γ-C2S powder compact was measured. In addition, each cured product has a three-point bending strength of 7 cm.
Span) was measured. These are shown in Table 2. In addition, in the table, samples that were not subjected to intermediate moisture absorption treatment and samples whose moisture saturation was outside the range defined by the present invention are also shown as comparative examples.

As is clear from the results in Table 2, it is preferable to adjust the moisture content of the molded product so that the moisture saturation level is 0.4 to 0.8. If the water saturation is less than 0.4, the strength of the cured product after carbonation curing will be low, and even if moisture absorption treatment is performed during curing, there will be little effect on improving the strength. In addition, the water saturation level is 0.
If it exceeds 8, the curing time becomes longer, which is not preferable. Table N
The cured products of α6.7.9 and 11 (both comparative examples) had brittle parts on the surface, corners, and ridges where the carbonation reaction was thought to be insufficient. No
, 4.5.8 and 10), such brittle portions were not observed.

Example 2 In the same manner as in Example 1, a molded article having a moisture saturation of 0.45 and the same shape as in Example 1 was obtained. This was carbonated and cured for 4 hours in the same manner as in Example 1, and then water was sprayed onto the surface of the cured product as described in Table 3. Subsequently, this was further carbonated and cured for 2 hours. A three-point bending strength test was conducted on the obtained product in the same manner as in Example 1, and the carbonation rate of the ridge was measured. The results are shown in Table 3.

As is clear from Table 3, it is found that the amount of moisture absorbed by the cured product in the present invention is preferably 0.25 to 3.0%. If the amount of water absorbed is less than 0.25% by weight, the effect of improving the properties of the cured product due to moisture absorption is small, and if it exceeds 3% by weight, curing cannot be completed in a short time and a good cured product cannot be obtained. do not have.

Example 3 Water was added to a mixture of 1 part by weight of the γ-C2S powder used in Example 1 and 1 part by weight of river sand from two companies or less to prepare a mortar. Along with this mortar, E-glass roving prepared separately was cut into 25 mm chopped strands and then sprayed into 900 x 450 x 1 pieces using the spray suction method.
It was molded into a thin plate of 0 mm. The amount of fiber added was 5%.

Thereafter, this molded body was dried in a dryer at 60° C. until the moisture saturation of the molded body became 0.50. Next, this was placed in an airtight thermostatic box and carbonated and cured at room temperature for 4 hours without flowing carbon dioxide gas with a concentration of 99% or higher. Thereafter, water was sprayed onto the surface, edges, etc. of the molded body, and then the molded body was further cured with carbon dioxide gas for 2 hours. Note that the amount of water sprayed was 1.5% by weight. A specimen of 250 x 50 x 10 mz was prepared from the cured product obtained after curing, and the three-point bending strength (200 mm span) was measured.

The value was 275 kg/c-.

The sample measured above was crushed into pieces of 1 piece or less, and 5
0 kg was placed in 70 ml of distilled water and stirred, and the pH value of the supernatant liquid after 24 hours was measured and found to be 10.3.

Example 4゜100g of 7-C2S powder shown in Table 1, Toyoura standard sand 1
60ml of water is added to a mixture of 4g of 00g and E glass fibers (13M chopped strands) and kneaded.Then, this is poured into a formwork equipped with a suction device, and the lower part of the formwork is suctioned under reduced pressure to produce ICXIO (cm ) to form plate-shaped molded products of various thicknesses. This molded product was dried in a dryer at 50° C. until the molded product Q moisture saturation level became 0155. After that, put it in an airtight thermostatic box at 30℃ to a concentration of 999.
It was cured for 5 hours without flowing carbon dioxide gas. After step 1, this was taken out from the thermostatic box, 1.5 wt % of water was sprayed onto its surface to moisten it, and it was further cured with carbon dioxide gas for 2 hours. After curing, a 4×9×3 (cm) specimen was prepared, and a 3-point bending test (7 cm span) and carbonation rate were measured. The results showed that the bending strength was 143 kg/cm and the carbonation rate was 54%. Furthermore, there was no uncured portion in the center of this cured product.

As a comparative example, a molded body similar to that described above was molded, placed in a similar airtight box, and cured with carbon dioxide gas for 20 hours. After that, a specimen of the same size was created and 3
Point bending test and carbonation rate were measured. The results are shown in Table 4.

Table 4 (Effects of the Invention) As described above, according to the present invention, all parts of the hardened material can be uniformly cured in a short time, and concrete with high strength and low alkalinity can be obtained. It is believed that its use will be of wide interest to those skilled in the art.

[Brief explanation of the drawing]

The figure shows the curing time, carbonation rate, and bending strength of the compact (kg)
/cd) is a diagram showing the relationship between Applicant's representative Patent attorney Takehiko Suzue for 1 hour (IγS)

Claims (1)

[Claims] Water is added to a mixture of γ-type dicalcium silicate powder and sand, or a mixture in which fibers as an admixture or reinforcing material are added to form a molded product, and the γ-type of this molded product is When producing a hardened product by carbonating dicalcium silicate, the moisture content of the molded product formed from the raw material mixture is adjusted to 0.4 to 0.8 at the water saturation level defined by the following formula, and then carbonated. Take care of yourself,
A method for carbonation curing of γ-type dicalcium silicate, which comprises subjecting the surface of the molded product to moisture absorption treatment during curing and further carbonation curing. Moisture saturation = (Moisture content of molded product (%) / 100 - Moisture content of molded product (%)) x (100 - Apparent porosity of molded product (%) / Apparent porosity of molded product (%)) x Molded product apparent specific gravity of