JPS6355174A - Manufacture of cement set body - 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 (Industrial Field of Application) The present invention relates to a method for producing a hardened cement product, particularly a method for producing a hardened cement product that can be cured quickly and reliably without requiring large-scale equipment such as an autoclave. Regarding.

(Prior Art) Cement compositions are usually hardened by supplying water through underwater curing, moist curing, or the like. The supply of water advances the hydration reaction of the cement composition5, thereby achieving the desired hardening. However, with this method, it is difficult to obtain a hardened cement body with sufficient strength.

It is necessary to cure for a long period of about 10 to 30 days. Therefore, productivity is poor and it is unsuitable for continuous production on an industrial scale.

In order to solve such drawbacks, carbon dioxide is supplied to the cement composition, Ca(OH)2+CO2-CaC
A method has been proposed for producing a hardened cement body using heat generated by the reaction of O3+ HzO+ 19kcal. For example, British Patent No. 1460284 (Process for accelerating the hardening of cement molded bodies containing fibers) discloses a cement molded body reinforced with fibers, in which carbon dioxide is applied to the soft molded body immediately after molding. The manufacturing method is disclosed. U.S. Pat. No. 4,093,690 (method for producing concrete and similar products) describes a method in which a cement composition prepared by kneading cement with vinyl acetate-dibutyl maleate copolymer and water is pressure-molded and then reacted with carbon oxide. is disclosed. However, since these methods simply blow carbon dioxide into the cement, the carbon dioxide is not introduced into the cement molded body.

Therefore, the curing reaction does not proceed sufficiently. Therefore,
In order to accelerate the curing reaction, it is necessary to perform evacuation treatment before blowing in carbon dioxide, which requires a chamber, autoclave, etc. for evacuation treatment, making the apparatus complicated. Furthermore, even when such an apparatus is used, a certain amount of time is required for one reaction.

For these reasons, attempts have been made to obtain a hardened cement body without using a chamber or autoclave. U.S. Patent No. 4,362,679 (method for manufacturing cast concrete) involves filling a sealed container with a concrete product and then evacuating from one end while introducing carbon dioxide from the other end, which requires equipment such as a chamber or autoclave. Not needed.

However, in order to evacuate one end of a sealed container filled with concrete and introduce carbon dioxide from the other end,
It is necessary to keep the water/cement ratio sufficiently low.
This impairs the formability of the cement composition. Moreover, only one hardened cement product can be obtained from one sealed container, resulting in a lack of productivity. How to improve your productivity.

It is necessary to use a large number of sealed containers, which is expensive.

Moreover, there is a limit to the shapeability of the sealed container, and a hardened cement body with a complicated shape cannot be obtained.

(Problems to be Solved by the Invention) The present invention solves the above conventional problems, and its purpose is to cure cement quickly and reliably without the need for equipment such as an autoclave. The objective is to provide a method for manufacturing the body. Another object of the invention is to
It is an object of the present invention to provide a method for producing a hardened cement body that provides a hardened body with high strength. Still another object of the present invention is to provide a method for producing a hardened cement body that produces a hardened cement body with little efflorescence. A further object of the present invention is to provide a method for producing a hardened cement body, which allows a hardened body with a complicated shape to be easily obtained.

(Means for Solving the Problems) The method for producing a hardened cement body of the present invention includes a step of dehydrating and molding a cement composition, followed by heating and drying the cement composition, and heating and drying the resulting cement molded body with water vapor and carbon dioxide. The above object is thereby achieved.

Dehydration molding is performed by pressing and shaping the cement U product. As the shaping means, a conventional known shaping means can be used as is. Namely.

Examples include a papermaking method, an extrusion method, and a press method. The molded body obtained here is not sufficiently hardened, but is in a soft state and usually has a moisture content of 20 to 40% by weight.

The cement dehydrated molded body is then subjected to heat drying treatment. The moisture content of the obtained cement molded body is preferably adjusted to 10% by weight or less. The heating and drying treatment is carried out using a conventional heating and drying oven. As a result, a highly porous state in which the cement is hardly hydrated is maintained in the cement molded body.

Because of this porous state, when the cement molded body is moved to the first step, that is, the step of holding the cement molded body in a mixed gas of water vapor and carbon dioxide, the introduction of carbon dioxide into the interior of the cement molded body, particularly deep part, is promoted. Along with carbon dioxide, water vapor also enters the cement molded body, where a hydration reaction proceeds. Carbon dioxide dissolves in water in steam and becomes carbonate ions through the reaction of equation 1(1).

CO, +l120 →CO,,"-+211"+aq,
-・-(11 Water and carbonate ions taken into the MI weave inside the cement molded body significantly promote the hydration reaction between the cement mineral and water. Ca (Oil) 2 generated by this hydration reaction is Furthermore, carbonate ion CO32−
A neutralization reaction occurs as shown in equation (2).

Ca(Oil)z+CO:l"-+211"+aq.

→CaC01+ 1120 + aq, -
(21 Calcium carbonate is produced by this neutralization reaction.

(3) 2 is derived from equations (1) and (2).

Ca(Off)z+cO□−CaCO,,+H20+1
9kcal (31) This reaction is an exothermic reaction. The heat generated by the reaction accelerates the hardening of the cement molded body.Moreover, since the above-mentioned neutralization reaction proceeds quickly, the resulting cement 1-hardened The body has few defects such as efflorescence because dehydration molding gives it a good shape.

Hardened cement bodies with complex shapes can also be easily obtained.

Examples of the cement composition in the present invention include portland cement, blast furnace cement, alumina cement, and mixtures with other hydraulic cements. , organic or inorganic reinforcing fibers such as nylon and vinylon, calcium carbonate, river sand, other inorganic fillers, and organic binders for improving plasticity.

Such a cement composition may contain, for example, 100 parts by weight of Portland cement, 2 synthetic fibers, 0.3 to 7 parts by weight, and 200 parts by weight or less of inorganic filler.

It is obtained by kneading 30 parts by weight or more of water and 0.1 part by weight or more of a water-soluble polymer substance.

(Example) The present invention will be described below with reference to examples.

Ordinary Portland cement on castration spots 100 parts by weight Silica sand No. 7 50 parts by weight Vinylon
2.5 parts by weight methylcellulose 1.5 parts by weight water
35 parts by weight of the above formulation was mixed in an omnimixer for 10 minutes.

This mixture was pressed at a pressure of 65 kg/crA,
Dehydration molding was performed at a press speed of 31/sec. The obtained cement molded body was heat-dried at 200°C for 10 minutes in a heat-drying oven. Next, this was mixed with a gas mixture of 1 atmosphere of water and carbon dioxide (carbon dioxide was 40% of carbon dioxide, R11 was 95%
%) for 30 minutes to obtain a hardened cement body.

When the bending strength of the obtained cement hardened body was measured,
It was 65 kg/cot. These results are shown in FIG.

A hardened cement body was obtained in the same manner as in Example I, except that the retention time in the mixed gas was 1 hour.

When the bending strength of the obtained cement hardened body was measured,
It was 106 kg/cJ. These results are the first
As shown in the figure.

Except that the retention time in the general mixed gas was 1.5 hours,
A hardened cement body was obtained in the same manner as in Example 1.

When the bending strength of the obtained cement hardened body was measured,
It was 120 kg/cnf. These results are the first
As shown in the figure.

A hardened cement body was obtained in the same manner as in Example 1, except that the retention time in the mixed gas was 2 hours.

When the bending strength of the obtained cement hardened body was measured,
It was 125 kg/cJ. These results are shown in FIG.

Tin plate craftsmanship Except that the temperature of the heat drying treatment was 150°C.

A hardened cement body was obtained in the same manner as in Example 1.

When the bending strength of the obtained cement hardened body was measured,
It was 52 kg/cJ. These results are shown in FIG.

A hardened cement body was obtained in the same manner as in Example I, except that the temperature of the heat drying treatment was 150° C. and the holding time in the mixed gas was 1 hour.

When the bending strength of the obtained cement hardened body was measured,
It was 100 kg/cnl. These results are the first
As shown in the figure.

Example I A hardened cement body was obtained in the same manner as in Example 1, except that the temperature of the heating and drying treatment was 150° C. and the holding time in the mixed gas was 1.5 hours.

When the bending strength of the obtained cement hardened body was measured,
It was +r/cut at 111. These results are shown in FIG.

A hardened cement body was obtained in the same manner as in Example 1, except that the temperature of the main heating and drying treatment was 150° C., and the holding time in the mixed gas was 2 hours.

When the bending strength of the obtained cement hardened body was measured,
It was 120 kg/cut. These results are shown in FIG.

A cement molded body mixed and dehydrated using the same formulation as in Example 1 and molded by the same method was steam-cured for 1 hour (R1 (
(95%) to obtain a hardened cement body.

When the bending strength of the obtained cement hardened body was measured,
It was 26 kg/c++I. These results are shown in FIG.

A cement molded body mixed and dehydrated in the same manner as in Example 1 was steam-cured for 2 hours (R11
(95%) to obtain a hardened cement body.

When the bending strength of the obtained cement hardened body was measured,
It was 30 kg/cat. These results are shown in FIG.

Comparison ±1 A cement molded body mixed and dehydrated in the same manner as in Example 1 was steam-cured for 3 hours (R11
(95%) to obtain a hardened cement body.

When the bending strength of the obtained cement hardened body was measured,
50kg/cn! Met. These results are shown in FIG.

Comparison↓ A cement molded body mixed and dehydrated in the same manner as in Example 1 was cured in steam for 4 hours (RH: 95%) to obtain a hardened cement body.

When the bending strength of the obtained cement hardened body was measured,
It was 76 kg/cnl. These results are shown in FIG.

A cement molded body mixed and dehydrated using the same formulation as in Example 1 and molded by dehydration was naturally cured to obtain a hardened cement body.

When the bending strength of the obtained cement hardened body was measured,
10kg/co! Met. These results are shown in FIG.

As is clear from the Examples and Comparative Examples, according to the method for producing a hardened cement body of the present invention, a hardened cement body with high strength can be obtained through a simple process. If the treatment time with a mixed gas of water vapor and carbon dioxide is increased, the bending strength of the hardened cement will increase. A hardened cement body obtained by conventional steam curing has a lower bending strength than a hardened body obtained by the method of the present invention.

(Effects of the Invention) According to the present invention, since a mixed gas of water vapor and carbon dioxide is introduced into the cement molded body which has been subjected to a heat drying process in advance, a device such as an autoclave is not required. A hardened cement body can be obtained quickly and reliably through a simple process.

The obtained cement hardened body has high strength and has few defects such as efflorescence. Hardened cement bodies with complex shapes can also be easily obtained. Therefore, the method for producing a hardened cement body of the present invention can be effectively used for hardening cement.

Figure 1 shows the retention time in a mixed gas of water vapor and carbon dioxide and the retention time of the obtained hardened cement body in the method for producing a hardened cement body of the present invention in an example. It is a graph showing the relationship with bending strength. FIG. 2 shows the steam curing time in a comparative example of a conventional method for producing a hardened cement body using steam curing.

It is a graph which shows the relationship with the bending strength of the obtained cement hardened body.

that's all

Claims (1)

[Claims] 1. A cement comprising the following steps: 1. After dehydrating and molding a cement composition, heating and drying the cement composition; and holding the obtained cement molded body in a mixed gas of water vapor and carbon dioxide. Method for producing cured product. 2. The method for producing a hardened cement body according to claim 1, wherein the cement molded body has a moisture content of 10% by weight or less. 3. The relative humidity of the water vapor in the mixed gas is 9
The method for producing a hardened cement body according to claim 1, wherein the content is 0% or more. 4. The cement composition contains 0.3 to 7 parts by weight of synthetic fibers, 200 parts by weight or less of an inorganic filler, 30 parts by weight or more of water, and 0.1 parts by weight of a water-soluble polymer substance, based on 100 parts by weight of ordinary Portland cement. The method for producing a hardened cement body according to claim 1, which is obtained by kneading at least 10 parts.