JPH0146478B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to lightweight mortar. Using this mortar, lightweight structures can be built without autoclaving, curing, or steam curing, and it can also be used as a repair material for lightweight cellular concrete. <Prior art and its problems> Generally, lightweight mortar is made by kneading Portland cement, lightweight aggregate, thickener, etc., but it takes a long time to harden, causing volume reduction (breathing) before hardening. It is known to have drawbacks such as subsequent drying shrinkage. Therefore, a curing accelerator,
For example, CaCl ₂ has been added to speed up the curing process, but this has led to problems such as rusting of the reinforcing bars and cracking after drying, and the curing speed has not been sufficient. There is also a lightweight mortar made by kneading alumina cement, slaked lime, etc., but the curing speed is insufficient and the durability is poor.
On the other hand, lightweight mortar made by kneading rapidly hardening cement such as jet cement, lightweight aggregate, and thickener is
It sets too quickly, making it difficult to work with, and its strength deteriorates due to pounding. Moreover, since the color of rapid hardening cement used to be gray, there was a problem in that even if white cement was mixed with it, it was not possible to make it a color close to white. <Means for Solving the Problems> In view of the above-mentioned prior art, the present invention improves workability when kneading lightweight mortar, reduces material separation, and quickly hardens after 5 to 30 minutes. The first object of the present invention is to provide a lightweight mortar that has reduced volumetric shrinkage after curing, reduced drying shrinkage, and significantly increased early strength. The composition of the present invention that achieves this objective consists of 15-25% by weight of lightweight aggregate, 82-72% by weight of Portland cement, and 3-7% by weight of hardening accelerator, as well as small amounts of thickeners and setting modifiers. . As the lightweight aggregate, perlite, vermiculite, anti-firestone, pumice, ALC scrap, etc. can be used, and the appropriate specific gravity is 0.2 to 0.7, and the blending amount is preferably 15 to 25% by weight. Various types of Portland cement can be used, such as white Portland cement, ordinary Portland cement, early strength Portland cement, etc., and the blending amount thereof is preferably 82 to 72% by weight. As a hardening accelerator, a mixture of calcined alumite and slaked lime can also be used, but if a mixture of these and an alkali metal carbonate is used, a large effect can be expected with a small amount. The appropriate amount of the hardening accelerator is 3 to 7% by weight, and the hardening agents include: 65 to 85% by weight of calcined alumite, 15 to 25% by weight of alkali metal carbonate, and 1 to 10% by weight of slaked lime. % formulations are preferred. As the thickener, methyl cellulose, polyethylene oxide, ethyl cellulose, etc. can be used, and methyl cellulose is particularly suitable, and its blending amount is preferably 0.05 to 0.15% by weight. As a coagulation modifier, oxycarboxylic acid salts such as citrate and tartrate can be used, and as dispersants, melamine sulfonate, β-naphthalene sulfonate, etc. can be used, and the blending amount is 0.05 to 0.3% by weight. is preferred. <Function> For the lightweight mortar of the present invention, the water ratio is 0.5 to 0.75.
When you add water and knead to make a mold, it hardens quickly. As explained in detail in Japanese Patent Application No. 59-116627, hardening accelerators include: calcined alumite,
The synergistic action of alkali metal carbonates and slaked lime can shorten the curing time and significantly increase the initial strength. Moreover, since a small amount of a setting modifier is added to delay setting to some extent, it will not harden during kneading. In addition, since the thickener prevents material separation, workability is improved and cracking after drying can be prevented. In the present invention, when white Portland is used as the Portland cement, a color close to white can be ensured, and furthermore, by adding a pigment, it is easy to color the cement into any desired color. <Example> Example 1 Samples 1, 2, 3, formulated as shown in Table-1
Add water to the material in step 4 so that the water ratio is 0.65, mix it with a mortar mixer, pack it into a 4 x 4 x 16 cm mold, and evaluate the flow, curing time, shrinkage rate, age of 3 hours and The compressive strength for one day and the absolute dry specific gravity of the mortar were measured. The results are shown in Table-2.

[Table] (Note) Numbers indicate parts by weight. As the methylcellulose, the product name ``Methocel 8000'' manufactured by Shin-Etsu Chemical Co., Ltd. was used.

[Table] However, pearlite A in Table 1 has a specific gravity of 0.24 and a particle size of 1.2 to 0.3 mm, and pearlite B has a specific gravity of 0.21 and a particle size of 0.3.
mm or less. The hardening accelerator used in samples 2 and 3 was a mixture of 75% by weight of calcined alumite, 20% by weight of soda ash, and 5% by weight of slaked lime, and the hardening accelerator used in sample 4 was It is a mixture of 75% by weight of limestone and 25% by weight of slaked lime. As is clear from the results shown in Table 2, Samples 2, 3, and 4 containing a curing accelerator had a shorter curing time and higher early strength than Sample 1. In addition, samples 2 and 3 used a mixture of 75% by weight of calcined alumite, 20% by weight of soda ash, and 5% by weight of slaked lime as hardening accelerators.
The effect is remarkable. Furthermore, by adding sodium citrate as a coagulation regulator, the coagulation time of sample 4 can be adjusted. If a thickener is not added, material separation will be significant, resulting in a dry mortar. Example 2 65 parts by weight of water was added to the formulations of the examples and comparative examples shown in Table 3, mixed in a mortar mixer, poured into a formwork with internal dimensions of 30cm long, 30cm wide and 2cm deep, and hardened. I let it happen. The mortar according to the example started to harden 10 minutes after being poured, the surface could be finished with a trowel after 15 minutes, and it could be demolded after 2 hours.
Note that there was no change in volume after 1 day. On the other hand, the mortar according to the comparative example started to harden 3 hours after pouring, but 1 mm of breathing was observed from the mold surface, and the volume change rate after 1 day was -7.5.
It was %.

[Table] Example 3 Diameter of lightweight aerated concrete plate approximately 10 cm, depth approximately 5
To repair the concave part of a cm mortar, apply a 10-fold diluted commercially available vinyl acetate emulsion solution to the concave part, and after drying, apply water to the materials of Examples and Comparative Examples shown in Table 4. In addition, when appropriately softened mortar was filled in and piled up, the mortar according to the example hardened after 15 minutes, and after 40 minutes it was possible to finish it by carving it flat with a sharp knife. When I inspected the finished part the next day, I found that it was finished so well that it was hard to tell the repaired part from other parts.
On the other hand, the mortar according to the comparative example was cured after 3 hours and was ground flat with a knife. However, when observed the next day, the repaired area had sunk by approximately 0.05 mm, and cracks had spread into a network.

[Table] <Effects of the Invention> As explained above in detail based on Examples, the lightweight mortar according to the present invention can be made into a lightweight mortar that does not shrink or crack in an extremely short time without autoclave curing or steam curing. Can be done. In addition, to adjust the specific gravity of the mortar, it is sufficient to appropriately select a lightweight aggregate such as perlite and the cement/aggregate ratio.Also, to color the mortar, for example, use white cement, white calcined alumite, or any other suitable material. Coloring pigments may be used. The lightweight mortar of the present invention allows lightweight structures to be built in a short period of time without the risk of cracking, can repair lightweight cellular concrete, and can also be widely used as an adhesive.

Claims (1)

[Scope of Claims] 1. A lightweight mortar comprising 15 to 25% by weight of lightweight aggregate, 82 to 72% by weight of Portland cement, 3 to 7% by weight of a hardening accelerator, and small amounts of a thickener and a setting modifier. 2. The lightweight mortar according to claim 1, in which a mixture of calcined alumite, slaked lime and alkali metal carbonate is used as a hardening accelerator.