WO1988006083A1

WO1988006083A1 - Process for forming cement moldings

Info

Publication number: WO1988006083A1
Application number: PCT/JP1988/000154
Authority: WO
Inventors: Toshiro Suzuki
Original assignee: Toshiro Suzuki
Priority date: 1987-02-20
Filing date: 1988-02-16
Publication date: 1988-08-25

Abstract

A process for forming cement moldings, which comprises adding water to cement in an amount less than that necessary for forming cement moldings, compacting the cement composition thus prepared by, for example, pressing, and continuing curing of the composition by, for example, water or steam curing while supplying water, when shape retention of the compacted composition has become possible or when curing has proceeded to some extent. This process enables to supply water necessary for hydration reaction of cement in a suitable amount and obtain moldings with dense structure, high strength, and less scatter in quality.

Description

Specification

Manufacturing method of cement-based products

Technical field -

This invention is based on cement paste, cement mortar, cement concrete and other cement-based materials for civil engineering construction, or on-site construction. The present invention relates to a method for producing cement-based molded products such as structures.

Background technology

In order to produce high-quality, high-strength cement-based moldings, cement compositions with a low water-cement ratio to which the minimum amount of water required for cement hydration is added are used. It is preferred to use and manufacture. However, it is difficult to accurately control the water content of the cement-based molded product formed by fluctuations in the amount of aggregate water and drying during molding curing, etc., especially at low water cement ratios. When the composition was used, there was a tendency that the quality of the obtained molded product had a large variation.

The present invention has been made in view of the above problems. The purpose is to propose a method for producing cement-based molded products with high strength and low quality variation.

Disclosure of the invention

This method for producing a cement-based molded product is a method for producing a cement-based molded product by molding a cement-based composition and subjecting it to a hydration reaction. The water content required for the molded article is added or less, and the cement composition is mixed, This composition is compacted]. The molded product is first cured at least to the extent that shape retention can be maintained, and then the compacted product is cured while receiving water and then secondary cured. I do.

The water content of the cement composition used in this production method is considerably smaller than the amount required for the cement molding to be produced. For example, in the case of a cement paste in which the composition is generally used, a water cement ratio of 15% or less, and in a cement mortar having a cement cement fine aggregate ratio of about 1: 2, water is used. Cement ratio 25% or less, Cement / fine aggregate Z About 30% of water cement ratio for concrete with a coarse aggregate ratio of about 1: 2: 2 It is.

To prepare a cement-based composition with a small amount of water, that is, a low water-cement ratio, by adding the prepared water as small ice blocks, a composition with high homogeneity and excellent quality can be obtained. It can be easily made. That is, when mixed water is added to cement aggregate, etc. in the form of small ice blocks, cement particles and fine fine aggregates adhere to the surface of the small ice blocks whose surface is wet, and the small ice blocks are used as nuclei. It disperses in surrounding solid particles such as cement and aggregates, and becomes a macroscopic homogeneous system in which the aggregates and the like are easily and uniformly dispersed. Subsequently, at ambient temperature, the small ice blocks gradually melt and wet the surrounding solids, resulting in a homogeneous composition. Since this composition is formed in a low-temperature condition in which small ice blocks coexist, the hydrated reaction is slow for a while even after blending, and it can be used in the manufacturing process before causing a decrease in plasticity. . Other low water .

Three

The composition having a cement ratio can also be prepared by adding the prepared water by spraying or wet impregnating the aggregate.

Since the composition having a low water cement ratio used in the present invention shows almost no fluidity, it is compacted by a method such as pressure molding, vibration compaction, pressing, rolling, vacuum matting, or mouth-roller compaction. It must not be molded. This manufacturing method can be applied to the production of concrete products, etc. in factory production, or to the construction of mass concrete structures, etc. by casting in place. For example, when producing concrete products in factory production, press molding, or when constructing a slab at the construction site, press-molding by pressing, compacting, etc. It is transferred to the curing process.

General cement-based compositions have a high water-cement ratio and are in a liquid phase, so that the compacting effect is easily saturated, and the compacting effect is poor. Therefore, there is a defect that a defective portion is generated, and thickness unevenness is easily generated due to slight inclination of the pressing plate when pressing with a pressing plate or the like. However, since the cement composition used in this production method has a low water cement ratio that does not show fluidity as a liquid phase, it can be compacted even at high pressure where the compaction effect is close to saturation. There is virtually no drainage, and there is no danger of a change in the composition of the composition or the occurrence of defects.

The solidified composition, after casting, undergoes solidification, begins to develop strength, and cures at least to the extent that it retains its shape even after demolding, for example, after 4 hours, or slightly hardens. After the water reaches 50 to 80% of the final attained intensity, for example, 24 hours later, it is cured while collecting water and is secondarily hardened. Means for capturing water include a method of moistening the surface of the molded product by covering it with water, steam, spray water, a wet cloth, a method of immersing the molded product in water, or a method of curing in an autoclave. There is a method of exposing to high-pressure water vapor, condensed water, etc. The compacted, hardened, primary-hardened molded product does not absorb excessive moisture during the curing process, but only absorbs the insufficient water required for the hydration reaction and moves to a cured product. .

The molded product at the early stage of the secondary curing stage, which has been replenished with the insufficient water, is pressurized again, and the air enclosed at the time of the initial molding is exhausted with water, so that a more dense structure can be obtained.

The present invention has the above configuration. In this production method, a cement-based composition is prepared by adding a compounding water having a water amount not more than that required for the cement-based molded product to be produced, and the composition is compacted and formed. Primary curing is performed to the extent that shape retention is maintained, and a solid compact of the low-water cement composition is formed. The molded body is cured while capturing water, and then secondary cured. The compact molded product absorbs the water shortage required for the hydration reaction and hardens without absorbing excessive ice, so it has high strength. In addition, the shortage of water is collected while maintaining the balance with the hydration reaction during the curing process, so that there is no variation in quality.

Therefore, the molded product by this manufacturing method has a low water cement ratio, The weave is dense, high in strength and low in quality. Brief explanation of drawings

FIGS. 1 and 2 are graphs showing the correlation between the water cement ratio and the compressive and bending tensile strengths of the test specimens of Example No. 4 and Comparative Example α2, respectively, and FIGS. 3 and 4 are, respectively. Correlation between water cement ratio and compressive strength and flexural tensile strength of the specimens of Example α5 and Comparative Example No. 3Drafts, FIGS. 5 and 6 are comparisons with Example o.6 respectively Example This is a graph showing the water cement ratio, compressive strength, and flexural tensile strength of the specimen of No. 4.

Explanation of the embodiment

Example 1

Formulation of cement composition:

0.6 Small ice blocks passed through a dragon sieve were used as preparation water. The small ice blocks are frozen before mixing, kept at a low temperature of -20, mixed at a water-cement ratio of 4% and 10%, and stirred with a mortar mixer at a room temperature of 20. And two cement pastes.

Pressure molding conditions:

Each of the two cement pastes, in which the small ice blocks are completely melted, is filled in a forming mold, and the pressure is 1000 kg oi for a short time (from pressurization to unloading for about 5 minutes). ) Pressure molding was carried out, and a test specimen of (height 4 on) X (width 4 cm) X (length 16 cm) was made.

Curing conditions:

Example No. 1 Demold 24 hours after casting, then cured in water. Example o. 2 Demold 4 hours after casting, then cured in water. Example 3 The mold was released 24 hours after casting, moistened in water for 2 hours, and then sealed and cured. Comparative Example 脱 Demolded 24 hours after casting, then sealed and cured. The strength of these specimens was as shown in the table below.

[Table] Grain kg / cm cement paste 4% 10% water cement ratio α1 Flexural strength 195 301

Compressive strength 1266 1328

No. 2 Flexural strength 260

Compressive strength 1217 examples

Ν 3 Flexural strength 103

Compressive strength 1122 Comparative example Bending strength 84 174

No. 1 Compressive strength 669 1150

Example 2 Preparation of cement composition: The materials used are usually Portland cement, sand (through a 2.5 M sieve), and small ice blocks (through a 0.6 sieve). Each of them was cooled to -10. Mixing the cement and small ice blocks, and the cement sand (1: 2) mixture and small ice blocks (緣 650 g) each in a water mortar mixture, in a two-room mortar mixer Mix for 3 minutes and after kneading The small ice block completely melted in about 5 minutes. About 4. Several cements with different ice-cement ratios of c were obtained.

Pressure molding conditions:

4 cm x 4 cm x 16 cm specimens are pressed at 250 kg / crf and 1 000 kg / αί (pressing in parallel to the 4 x 4 n cross section, approx. Min) and molded.

Curing conditions:

20 in the press forming mold. After leaving C for 24 hours, it was demolded, immersed in water at 20 ° C for 28 days, and cured in water (Example). At the same time, the sealed curing was performed for 20 days for 20 days (comparative example).

Specimens and manufacturing conditions:

Specimens and manufacturing conditions are as shown in the table below. Specimen composition Press molding condition Curing condition Example Να4 cement 250 kg / cm Curing in water α5 cement ぺ 1000 kgr / ci Curing in water

Να6 concrete 1000 kg / ci Cured in water Comparative example Να2 cement 250250 kg / ci Sealed curing α3 cement ぺ -Slot 1000 kg / ci Sealed curing i

Να4 concrete 1 000 kg / cifi Sealed curing i

1 Test specimen ffi results:

The relationship between the water cement ratio, the compressive strength, and the bending tensile strength of the test pieces of the examples and comparative examples was as shown in the graphs of FIGS.

Industrial applicability

This method for producing cement-based moldings can be used for the production of cement-based moldings such as precast members or on-site constructions, and is effective in improving the strength and reducing variations in quality.攆

Claims

The scope of the claims

In the method for producing a cement-based molded product by molding a cement-based composition and allowing it to undergo a hydration reaction, add water that is less than the amount of water required for the cement-based molded product to be produced. The cement-based composition is prepared in this manner, and the composition is hoof-molded and primarily cured to at least the extent that the shape-retaining property is maintained, and then cured while supplying water to the compacted molded product. A method for producing a cement-based molded product, which is subjected to secondary curing.

2. The cement-based molding according to claim 1, wherein the cement-based composition is prepared by adding and mixing small ice blocks in place of the preparation water and melting the small ice blocks. Manufacturing method. 2. The method for producing a cement-based molded product according to claim 1, wherein the cement-based composition is prepared by adding, mixing, and preparing the prepared water in the form of a spray.

The method for producing a cement-based molded product according to claim 1, wherein the composition is cured in water and replenished with water.

2. The method for producing a cement-based molded product according to claim 1, wherein steam curing is performed and water is supplied.

2. The method for producing a cement-based molded product according to claim 1, wherein high-pressure steam curing is performed and water is supplied.