JPH03909B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a construction method for cement mortar walls in houses, and particularly to a construction method for preventing cracks during and after the curing period of cement mortar walls.

A known traditional method for constructing mortar walls is to nail lumber to the frame structure of a house, fix a waterproof sheet and lath net with staples, and then apply mortar over the top.

In recent years, wall baseboards or cement boards have been developed, in which the surface of plate-like substrates such as plywood and fiberboard is coated with a coating material that is a mixture of resin or bituminous material with inorganic powder, particles, and foamed particles.
Another method is to fix inorganic boards such as ALC boards to the frame structure of a house and then apply or spray cement mortar on them. This method eliminates the need for recoating mortar and curing it, so it has the advantage of saving labor and shortening the construction period for wall construction.

However, during the curing period and after the curing period, when water moves and evaporates from the gel voids and capillary voids in the hardened cement mortar wall, a surface tension greater than expected acts on the cement mortar wall, which causes the voids to evaporate. It has the disadvantage that it applies tensile stress in the direction of shrinking the fibers, causing microscopic cracks called hair cracks.

Hair cracks not only spoil the aesthetic appearance of the wall surface, but also absorb and penetrate rainwater, corrode the staples and lath mesh that fixes the lath mesh when the wall base is made of lath, and cause damage even when the wall base plate is used. This causes delamination and flaking of walls.

Therefore, an object of the present invention is to provide a method of constructing a cement mortar wall that prevents the occurrence of such hair cracks. In the present invention, after wall preparation is performed on the frame structure of a house by a conventional method, a swelling agent and a nonionic surfactant are added to cement or a mixture of cement and aggregate, and then the mixture is mixed. Hair cracks can be largely prevented by preparing cement mortar by mixing with water and applying it by troweling or spraying.

The present invention will be described in detail below with reference to Examples.

We prepare the groundwork so that cement mortar can be applied directly to the frame structure of the house, such as columns and studs. This surface preparation may be done by the traditional method of lath nailing, pasting of a tarpaulin sheet, and pasting of lath netting, or may be done by nailing a wall base board. The wall base boards used include organic boards, inorganic boards, mixed boards of organic and inorganic materials, composite boards of organic boards and inorganic boards, etc., with synthetic resin on the surface, bituminous material, and attack material as necessary. , various aggregates, cement,
Various base plates are used in which a surface layer is formed by applying a coating material containing a dispersant, an antifoaming agent, a thickener, a surfactant, etc. These base plates may be treated with a sealer or waterproofed between them and the substrate. After these base plates are fixed to the frame structure of the house, joint treatment can be performed between adjacent base plates.

Cement mortar is prepared by mixing cement or a dry mixture of cement and aggregate, or mortar, with kneading water in which a swelling agent and a nonionic surfactant are added and mixed.

The cement may be any cement that is normally used for cement mortar walls, such as Portland cement or white cement.

Various aggregates such as sand, charcoal, silica sand, and perlite are also used.

Expanding agents refer to substances whose absolute volume increases during hardening of cement, and calcium sulfoaluminate (hereinafter referred to as CSA-based), lime-based, and gypsum-based expanding agents are used. The appropriate amount of expansion agent added is 0.5 to 20% based on the amount of cement in the cement mortar. If it is less than 0.5%, the effect of reducing shrinkage during mortar drying cannot be expected.
Moreover, if it exceeds 20%, the internal structure of the hardened mortar will be destroyed and the wall strength will be reduced.

CSA-based swelling agents include Desica CSA and Tuscon (trade name) manufactured by Denki Kagaku Co., Ltd., and Asano Dipcal (trade name) manufactured by Nippon Cement Co., Ltd., and lime-based swelling agents include Desica CSA and Tuscon (trade name) manufactured by Denki Kagaku Co., Ltd.. There is Onoda Expan (product name).
As a gypsum-based expanding agent, there is Zypton (trade name) manufactured by Onoda Cement Co., Ltd.

For example, CSA-based expansion agents are mainly composed of calcium sulfoaluminate clinker made from boxide (Al ₂ O ₃ ), lime (CaO), and gypsum (CaSO ₄ ), and the calcium sulfoaluminate clinker is 3CaO・3Al ₂ O ₃・_CaSO4 and CaO
CaSO ₄ and CaSO 4 are separated, and these generate the ettrin guide shown by the following formula through a hydration reaction.

3CaO・3Al ₂ O ₃・CaSO ₄ ＋6CaO＋8CaSO ₄ ＋
96H ₂ O → 3 (3CaO・Al ₂ O ₃・3CaSO ₄ )・32H ₂ O These large acicular or columnar ettringite crystals fill the gel voids in the hardened cement and cause volume expansion.

Crystal formation and volume expansion also occur with lime-based and gypsum expanding agents.

When a wall base plate is used in wall base treatment, the cement mortar and wall base plate are restrained by strong adhesion, chemical prestress occurs, the initial expansion is converted into internal stress, and then the cement mortar The contraction and associated stress relief allows expansion, thereby preventing initial cracking. However, although the initial cracking of the hardened cement mortar can be prevented by mixing an expanding agent, it has been found that the voids in the capillary with a small diameter radius of about 100 to 1500 Å increase. Hair cracks caused by capillary voids can be prevented by adding a nonionic surfactant.

Nonionic surfactants include polyoxyethylene, polyoxyethylene alkyl ether, polyoxyethylene alkylamine, polyoxyethylene fatty acid ester, glycerin ester, glycerin fatty acid ester, polyoxyethylene higher alcohol, and alkylene oxide addition of lower alcohol. things are used. The appropriate amount of addition is 0.5 to 8% based on the amount of cement in the cement mortar. By adding a nonionic surfactant, the kneading water is adjusted to have a surface tension of 40 dyn/cm ² or less.

If the amount of nonionic surfactant added is less than 0.5%, it will not be possible to reduce the tensile stress caused by surface tension during moisture movement during drying of cement mortar, and the tensile stress will increase to more than 8%. However, the hair crack preventing effect cannot be increased in proportion to the increase in the amount added. Therefore, the upper limit of the amount of nonionic surfactant added is not critical.

Further, the nonionic surfactant preferably has a molecular weight of 1000 or less. If the molecular weight exceeds 1000, it will be difficult to dissolve in water, and it will also be difficult to enter the capillary pores, reducing the cracking prevention effect.

Further, the HLB value of the nonionic surfactant is preferably in the range of 5 to 15. If the HLB value is less than 5, air bubbles in the cement mortar will be extinguished, resulting in poor trowel separation during troweling, reducing work efficiency, and poor adhesion between mortar during topcoating, resulting in a decrease in wall strength. let When the HLB value exceeds 15, there will be excessive air bubbles in the cement mortar,
This also reduces wall strength.

Furthermore, if an anionic surfactant is used instead of a nonionic surfactant, it will be adsorbed on the surface of the cement particles, impairing its penetration into the capillary pores, delaying the hardening of the cement itself, and causing the cement mortar layer to deteriorate. It tends to dry out, leading to a decrease in wall strength.

In addition, the above cement mortar may contain vinyl acetate, vinyl chloride, ethylene/vinyl acetate, Epoquin, acrylic resin or MBR, as necessary.
A latex or emulsion solution of a synthetic resin such as NBR or SBR may be added and mixed in an amount of 1 to 20% by weight based on the amount of cement in the mortar.

As mentioned above, when using a cement mortar prepared by adding and mixing cement or a mixture of cement and aggregate with kneading water containing a swelling agent and a nonionic surfactant, crystal formation and expansion due to the swelling agent and chemical precipitate may occur. The initial drying shrinkage is compensated by the generation of internal stress due to the stress effect, and the addition of a nonionic surfactant reduces the surface tension associated with water movement within the capillary cavity, thereby reducing the tensile stress generated. Therefore, cracks in the finished wall surface can be almost completely prevented.

Claims (1)

[Claims] 1. After preparing the groundwork for applying cement mortar to the frame structure of a house such as pillars and studs,
A method for constructing a wall surface in a house, characterized by applying or spraying cement mortar mixed with kneading water in which a swelling agent and a nonionic surfactant are added to cement or a mixture of cement and aggregate. . 2. The method according to claim 1, characterized in that 0.5 to 20% by weight of an expanding agent and 0.5 to 8% by weight of a nonionic surfactant are used based on the amount of cement contained in the cement mortar. Method.