JPS5930743A - Cement composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cement composition that suppresses the temperature rise due to the heat of hydration of mortar and concrete. The present invention relates to a cement composition in which a small amount is added to improve the temperature rise suppressing effect.

In the present invention, the water-soluble content of dextrin means the amount of dextrin dissolved in distilled water at a temperature of 21°C or 60°C. temperature 2
Add 150°C of distilled water at 1°C or 60°C, and bring it to that temperature.
After holding for a period of time, the dextrin was separated and the p solution was evaporated to dryness, and the obtained dextrin is shown in proportion to the sample dextrin.

In recent years, civil engineering and building structures have become larger, and mass concrete work is increasing. Along with this, the heat generation and accumulation of water from cement increases, causing the concrete temperature to rise rapidly in the early stages of the material's life, and when this temperature drops, the stress causes so-called thermal cracks in concrete. do.

To prevent this, the water soluble content at a temperature of 21℃ is 10 to 65.
Although a method of adding dextrin in the amount of % by weight has been proposed (Japanese Patent Publication No. 57-261), it is still not sufficient. As a result of further investigation, the present inventor found that in addition to the solubility at a low temperature of 21°C, the solubility at high temperatures and the dextrin production process also have an important effect on the temperature rise suppressing effect. This completes the present invention.

That is, the present invention is obtained by adding hydrochloric acid to starch and thermally decomposing it, and the water-soluble content is 1 at 21°C.
This is a cement composition containing 0.05 to 10% of dextrin based on cement, which is 0 to 50% by weight and 50 to 100% by weight at 60°C.

The present invention will be described in detail below. First, in the present invention, dextrin is limited to one produced by adding hydrochloric acid to starch and thermally decomposing it (hereinafter referred to as hydrochloric acid method dextrin). Dextrins are usually produced by adding dilute acids such as nitric acid or hydrochloric acid and thermally decomposing them, or by enzymatic decomposition of starch or condensation of glucose. Even if its solubility is appropriately controlled, the effect of suppressing temperature rise is smaller than that of hydrochloric acid dextrin.

However, in the present invention, even if the hydrochloric acid dextrin is used, sufficient effects will not be exhibited unless the water-soluble content is appropriate. That is, the water-soluble content at a temperature of 21°C is 10 to 50% by weight, and at a temperature of 60°C, it is 50 to 100% by weight.
% by weight, that is, the dextrin must be difficult to melt at room temperature but easily melt at high temperatures. As explained in the examples, when the water-soluble content at a temperature of 21°C is less than 10% by weight, the temperature rises to almost the same degree as when no dextrin is added, and
It exceeds 0% by weight and is effective in prolonging the time until the water utilization reaction starts, but after that the reaction occurs rapidly and the maximum temperature may be higher than when no dextrin is added. In either case, there is no effect of suppressing temperature rise.

The preferred water-soluble content at a temperature of 21°C is 20 to 40% by weight. On the other hand, the water-soluble content at a temperature of 60°C is required to be at least 50% by weight, preferably 60 to 9% by weight.
It is 0% by weight. If it is less than 50% by weight, the water soluble content will be small even if the temperature due to water utilization increases.
The temperature rise suppression effect becomes smaller.

The amount of dextrin added according to the present invention is 0.05 to 10% by weight based on the cement, and if it is added less than 0.05% by weight, the effect of suppressing the temperature rise will be small.
If the amount added exceeds 100%, the strength may be adversely affected. A particularly preferable addition amount is 0.1 to 2% by weight. Any type of cement can be used, including ordinary, early-strength, ultra-early-strength, medium-strength, white Portland cement, mixed cement containing silica, fly ash, blast furnace slag, etc., as well as expansion cement and rapid-hardening cement. As explained above, according to the present invention, cement contains a small amount of hydrochloric acid dextrin having a specific solubility. It has the effect of being able to significantly suppress it. In combination, this has the advantage of good water-reducing properties and long-term strength development.

Note that the dextrin according to the present invention can also be used in combination with other admixtures such as air entraining agents, water reducing agents, retarding agents, etc., and the effects of the present invention are not thereby lost.

The present invention will be further explained below with reference to Examples.

Example 1 100 parts by weight of ordinary Portland cement, 200 parts by weight of Sagami-use Ubukawa sand 5, 0.4 parts by weight of dextrin having various water-soluble components obtained by the method shown in Table 1, water-cement ratio 42 %, mortar adjusted to a kneading temperature of 20°C, height 30ci, inner diameter 16crIL, thickness 10cm
Put about 41 in a 1rL styrofoam cylindrical container, 20
The temperature at the center of the mortar was automatically measured using a thermocouple when it was cured in a constant temperature room. The results are shown in Table 2.
Experiment/162 is an example of the present invention, Experiment/161 and /i66~
A5 is a comparative example.

In addition, the compressive strength of a 5φ×10crrL specimen molded with the same mortar was measured when it was soaked in water at 20°C.

The results are shown in Table 3.

Table 1 Table 6 Example 2 100 parts by weight of ordinary portolan cement, 652 parts by weight of Ubukawa gravel for Sagami as coarse aggregate, 255 parts by weight of Ubukawa sand for Sagami 5 Nirashita as fine aggregate, water-cement ratio 56 parts by weight With the combination of
Adding the dextrin according to the present invention, kneading temperature 2
Concrete is adjusted to 0°C and has a thickness of 10°C.
The concrete was placed in a 50 x 50 x 50 steel mold box insulated on all sides with rIL Styrofoam and heat radiated on two sides, and the temperature at the center of the concrete was automatically measured with a thermocouple when it was cured in a constant temperature room at 20°C.

For reference, a similar test was conducted without the addition of gluconic acid and admixtures. The results are shown in Table 4. Experiment //67 is an example of the present invention, and Experiment Situation 6 and Demon 8 are reference examples.

Example 6 An experiment similar to Example 1 was conducted except that the dextrin according to the present invention was used and the amount added was varied.

Table 5 shows the maximum temperature and compressive strength at the center of the mortar.

Experiments A10 to A616 are examples of the present invention, Experiments 9 and A17
is a comparative example.

Table 5 Patent applicant Denki Kagaku Kogyo Co., Ltd.

Claims (1)

[Claims] It is obtained by adding hydrochloric acid to starch and decomposing it by heating, and its water-soluble content is 10 to 50% by weight at a temperature of 21°C.
A cement composition comprising 0.05 to 10% by weight of dextrin based on the cement, which is 50 to 100% by weight at a temperature of 60°C.