JP2530637B2 - Method for producing cement molded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a method for producing a cement molded product by rapid high temperature curing in an extremely short time (1 to 4 hours). As cement molding, asbestos cement board, pulp cement board, wood wool cement board, wood chip cement board, GR
C, cement roof tiles, mortar boards, terrazzo blocks, concrete boards, concrete piles, Hume tubes, U-shaped grooves, concrete blocks, tetrapots, concrete sleepers, civil engineering such as ALC, cement for construction, mortar,
Concrete products are included.

[Conventional technology]

Although it varies depending on the product, conventionally, in order to manufacture a cement molded product, portland cement, water and aggregate are mixed and kneaded, and after filling the mold, the temperature is 2 to 4 at room temperature (normal temperature).
Recover for hours. Then, using steam, the temperature is raised to 60 to 70 ° C. at a rate of 11 to 33 ° C./hour, and the curing temperature is set to 4 to 8
After holding for a while, the steam is stopped, and the mold is removed by natural cooling for 6 to 12 hours [Japanese Patent Publication No. 57-17871, Nippon Master Builders Co., Ltd. Technical Material No. L-001 "steam curing". -OF1517 Committee Report August 1963].

According to the conventional method, the production cycle of cement molding is 1
~ 3 cycles / day. Concrete cannot be sufficiently hardened by simply reducing the production time. Further, when the pre-curing time is shortened and the heating rate and the curing temperature are increased as compared with the conventional curing conditions, expansion, foaming and cracks occur in the cement molded product, and a sound product cannot be obtained.

The present inventors previously studied various cement admixtures,
After examining the necessity of pre-curing and the necessity of cooling after steam-curing, when a specific sulfate is used as a cement admixture, even an open mold does not require pre-curing and molding Immediately after that, rapid high temperature curing with a heating rate of 40 ° C./hour or more and a curing temperature of 80 ° C. or more can be performed, whereby a healthy cement molded body without a defect can be obtained in a curing time of 1 to 3 hours. It was found that the production cycle is possible to be 10 cycles / day or more, and first, for hydraulic cement, one of the sulfates of lithium, aluminum, potassium, thallium and sulfate double salts containing these metals or A method for producing a cement molded body has been proposed, which is characterized in that a hydraulic cement mixture containing two or more kinds added in a proportion of 0.1 to 20% by weight is molded and then cured at a high temperature (JP-A-60-21839).
Issue).

This method has the advantage that a high-strength cement molded product can be produced in 1 to 3 hours, but since a specific sulfate salt is used, the setting of the hydraulic cement mixture is rapid and the fluidity decreases in a short time. Since workability is poor, a large amount of expensive oxycarboxylic acids such as citric acid, tartaric acid, etc. or their sodium salts, potassium salts, naphthalene sulfonate formalin condensates, melamine resin sulfonates, etc. It is necessary to add [JP-A-60-42263, JP-A-61-122146 [Specific means for solving the problem] in the present invention, by using an inexpensive calcium aluminate-based mineral, Produces a high-strength cement molded body in 1 to 3 hours by adding a sufficient amount of time to keep the fluidity of the hydraulic cement composition suitable for casting work without adding any delay agent or water reducing agent. You That is, the present invention, the present invention, a hydraulic cement composition 100 parts by weight of the hydraulic cement, 1-50 parts by weight of calcium aluminate-based minerals and a hydraulic cement composition containing a suitable amount of water formwork The present invention provides a method for producing a cement molded body, which comprises casting the molded body at a temperature of 70 to 110 ° C without pre-curing to obtain a cement molded body.

(Cement composition) The hydraulic cement composition comprises 100 parts by weight of cement, 0 to 400 parts by weight of fine aggregate, 0 to 200 parts by weight of coarse aggregate,
20-50 parts by weight of water and calcium aluminate mineral 1
~ 50 parts by weight.

(Cement) Examples of hydraulic properties include ordinary Portland cement, early-strength Portland cement, intermediate heat Portland cement, sulfate resistant Portland cement, white Portland cement, blast furnace cement, silica cement, fly-ash cement, and expanded cement.

(Fine aggregates) Fine aggregates include river sand, crushed sand, silica sand, artificial lightweight sand, etc. These are 0 parts by weight to 100 parts by weight of cement, 100 parts by weight, 100% in the case of mortar and concrete products.
Used at a ratio of up to 300 parts by weight. As coarse aggregate, river gravel,
Crushed stone is common and is not compounded when obtaining mortar moldings, but 200-4 when manufacturing concrete moldings
It is generally used in a proportion of 00 parts by weight and a proportion of fine aggregate of 27 to 45% by weight. Water is added in an amount necessary for the hydration reaction of cement, and the amount of the cement mixture is maintained such that the cement mixture is fluid so that it can be easily placed in a mold.

(Calcium aluminate-based minerals) As calcium aluminate-based minerals, CaO / Al
₂ O ₃ , CaO ・ 2Al ₂ O ₃ , 3CaO ・ Al ₂ O ₃ , 12CaO ・ 7Al ₂ O ₃ , calcium haloaluminate (for example, 11CaO ・ 7Al ₂ O ₃・ Ca
F ₂ ), calcium sulfoaluminate (eg 3CaO ・ 3A
l ₂ O ・ 3Al ₂ O ₃・ CaSO ₄ ), alumina cement, etc. can be used.

This calcium aluminate mineral is used in a proportion of 1 to 50% by weight with respect to cement. If it is added in any amount other than this, poor curing or reduction in strength will occur.

(Optional components) These cement compositions may be mixed with CaSO ₄ , CaSO ₄
1 / 2H ₂ O, CaSO ₄・ 2H ₂ O, Al ₂ (SO ₄ ) ₃ , Al ₂ (SO ₄ ) ₃ nH
₂ O, AlK (SO ₄ ) ₂ , AlK (SO ₄ ) ₂・ 12H ₂ O, AlNH ₄ (S
_{O 4) 2, AlNH 4 (} SO 4) 2 · 12H 2 O, AlNa (SO 4) 2 · 12H 2
Inorganic sulfates and carbonates such as O, Na ₂ CO ₃ , K ₂ CO ₃ and CaCO ₃ , gluconic acid, citric acid, tartaric acid or their N
A particle size selected from oxycarboxylic acids such as a, Li, K, Sr, Ca salts or retarders such as salts thereof, Al ₂ O ₃ · 3SiO ₂ , ZrSiO, diatomaceous earth, bentonite, silica sand, kaolin. A silica-based compound having a particle size of not more than 1 micron, preferably not more than 1 micron, a water-reducing agent such as a naphthalene / sulfone formalin condensate, a melamine resin sulfonate, a pigment, etc. may be blended in a ratio of 5% by weight or less of the cement.

In the case of concrete with a large amount of unit water, rapid heating and curing causes expansion and cracking. Therefore, the use of a water reducing agent is preferable because it reduces the amount of unit water. As the water reducing agent, any general water reducing agent for concrete can be used. What is called a superplasticizer is particularly effective.

Silica powder suitable as an admixture, fly ash,
Addition of pozzolan, blast furnace slag, etc. has the effect of increasing the strength and improving the durability of the cement molded body.

(Manufacture of cement molded body) Even if the hydraulic cement composition is cured at room temperature,
Although a cement molded product can be manufactured, in the present invention, in order to shorten the molding cycle, it is subjected to rapid high temperature curing at a temperature of 85 ° C. or higher for molding.

That is, hydraulic cement, calcium aluminate-based minerals, water and aggregate (fine aggregate such as sand and coarse aggregate such as gravel or crushed stone or both), and if necessary, other accelerators, retarders, Add an admixture such as a water-reducing agent, knead, and put (fill) into the mold.

After casting, it may be possible to take a pre-curing time (pre-curing) at room temperature, but in order to increase the production cycle of the cement molded body, a rapid temperature rise is immediately performed without pre-curing after the completion of casting. The rate of temperature rise is 40 ° C./hour or more, preferably 60 to 120 ° C./hour, and no adverse effect occurs on the obtained cement molded product in this rate range. The curing temperature is 85 ℃ or higher,
Preferably, the high temperature of 90 to 110 ° C. is maintained for 15 to 60 minutes. An airtight curing device is required when performing high temperature curing above 100 ° C. For example, if the molded body is wrapped in a sheet and pressurized steam is aerated, high temperature curing exceeding 100 ° C can be performed.

As a heating medium for high temperature curing, high temperature pressurized steam used in general steam curing is suitable. Other heating and curing methods such as electric curing, electrothermal curing, high frequency curing, heated air curing, and infrared heating curing can be used without any trouble.

The cement molded body is immediately demolded after steam curing at high temperature, and the whole manufacturing process is completed. In order to increase the thermal efficiency of curing, it is effective to perform natural cooling (soaking) for a while (10 minutes to 2 hours).

In this way, the cement molded product (cement, mortar or concrete product) obtained in a curing time of 1 to 4 hours has no defects such as expansion, foaming and cracks on the surface and internal structure of the product, and it is necessary and sufficient for demolding. Strength (100-200kg / c
m), and the increase in strength after demolding is equivalent to that of ordinary steam curing products.

In the practice of the present invention, calcium aluminate-based mineral, in the rapid high temperature curing of hydraulic cement formulation,
It is considered that the cement composition acts to suppress expansion, foaming, and cracks and accelerate hardening.

[Effect of the Invention] According to the method of the present invention, it is easy to place a hydraulic cement mixture in a mold, and a compressive strength immediately after demolding of 100 kg / cm ² or more can be obtained in an extremely short time. It has the advantage that a cement molded product with a smooth surface can be manufactured under atmospheric pressure using an open mold. Further, in the method of the present invention, since it is not necessary to secure a large vapor pressure in the compartment as in the conventional high temperature and high pressure curing method, there is no need to attach any special pressure holding means to the curing equipment, and the conventional normal pressure The steam curing equipment can be used as it is. As for the mold, it is not necessary to use a closed mold, which requires high equipment and operating costs, and a normal open mold can be used as it is.

That is, according to the present invention, rapid high temperature curing can be performed safely without fear of expansion phenomenon, so that problems such as early strength development, shortening of curing time, and increase of production cycle can be solved by the equipment cost of the mold and curing device. It can be easily achieved without incurring an excessive increase in cost, and also in terms of the quality of the molded body itself, the pore volume in a relatively large pore radius can be reduced, or the freeze-thaw resistance can be improved. It has an improving effect such as suppressing neutralization.

Next, Tables 1 to 5 show the examples and comparative examples of the present invention in which the hydraulic cement composition was cured by high temperature steam by changing the kind and the addition amount of the admixture.

Example 1 100 parts by weight of ordinary Portland cement, 200 parts by weight of standard sand, and 50 parts by weight of water were mixed with the calcium aluminate mineral shown in Table 1 at a ratio shown in the same table, and the mixture was kneaded to obtain a hydraulic cement. A composition was prepared.

While the flow value of the cement mixture was 100 mm or more, the cement mixture was filled in the open-type preparation form and placed in the curing tank.

Immediately introduce steam without pre-curing for 10 minutes in 90 minutes
After raising the temperature to 0 ° C. and introducing steam for 30 minutes at the same temperature for curing, the steam was stopped, the hardened cement product was immediately taken out from the mold, and its compressive strength (JIS R-5201) and appearance were examined. Appearance is determined by expanding, foaming,
The presence / absence of cracks, the size, and the number were visually observed.

Appearance: Excellent-Completely cured Good-No blisters and fine dandruff is found in one or two places.

No-A lot of cracks and blisters are seen.

Example 2 A hydraulic cement composition prepared by mixing 100 parts by weight of ordinary Portland cement, 200 parts by weight of standard sand, and 50 parts by weight of water with 12CaO · 7Al ₂ O ₃ at a ratio shown in Table 2 was used. Cemented body was obtained by casting, curing with high temperature steam, and demolding.
Table 2 shows the flow value, compressive strength and appearance.

Example 3 A hydraulic cement composition prepared by blending 100 parts by weight of ordinary Portland cement, 200 parts by weight of standard sand, and 50 parts by weight of water with 12CaO.7Al ₂ O ₃ and anhydrous gypsum in the proportions shown in Tables ₃ and 4, In the same manner as in Example 1, hardened cement was obtained by casting, curing with high temperature steam, and demolding. The flow value, compressive strength and appearance are shown in Tables 3 and 4.

Example 4 100 parts by weight of ordinary Portland cement, 200 parts by weight of standard sand, 45 parts by weight of water, 5 parts by weight of 12CaO · 7Al ₂ O ₃ and condensate of sodium naphthalenesulfonate sodium formalin (solid content 45%) 1
The hydraulic cement composition blended in a ratio of parts by weight was cast, cured at high temperature and demolded in the same manner as in Example 1 to obtain a hardened cement product.

 The flow value, compressive strength and appearance are shown in Table-5.

Claims (2)

(57) [Claims] 1. A hydraulic cement composition in which 1 to 50 parts by weight of calcium aluminate mineral and an appropriate amount of water are mixed with 100 parts by weight of hydraulic cement, is cast into a mold and is not precured. A method for producing a cement molded product, which comprises obtaining a cement molded product by high temperature curing at a temperature of 85 to 110 ℃. 2. A temperature rising rate at which a curing temperature of 85 to 110 ° C. is set to 40 ° C. after the hydraulic cement composition is placed in a mold.
1 / hour or more
A method for producing a cement molded product according to item.