JP3367993B2 - Cement composition - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cement composition which suppresses temperature rise due to heat of hydration of concrete, mortar, grout and the like, and has improved retardability. 2. Description of the Related Art In recent years, civil engineering and building structures have become larger,
Mass concrete work is increasing, but the heat generated by the hydration of cement and its accumulation are increasing, and the concrete temperature rises rapidly in the early age of the material, and the stress when it falls causes the concrete. Then, so-called thermal cracks occur in the concrete. In order to prevent this, a method of adding dextrin having a water-soluble content of 10 to 65% by weight at a temperature of 21 ° C. has been proposed (Japanese Patent Publication No. 57-261), but it has not been sufficient yet. [0003] In view of such circumstances, an object of the present invention is to suppress a rise in temperature due to heat of hydration of cement, which causes cracks in concrete structures. [0004] In order to solve the above-mentioned problems, the present inventors have made intensive studies on various modified starches. As a result, the gelatinization starting temperature is 30 to 60 ° C and the paste liquid viscosity is 50 ° C. It has been found that a cement composition containing 0.05 to 10% by weight of a modified starch having a water content of 20 to 5000 centipoise in a 25% aqueous solution with respect to cement suppresses a temperature increase due to heat of hydration. Furthermore, the inventors have found that sugars and dextrins have the disadvantage of delaying the setting of the cement, whereas the compositions according to the invention have no such disadvantages. The modified starch used in the present invention is obtained by acid-decomposing, oxidizing, esterifying (acetate ester, phosphate ester, etc.), etherifying (hydroxyalkylating, carboxymethylating) potato, sweet potato, corn, tapioca, wheat and other raw starch. Cationization, alkylation, benzylation, etc.), cross-linking, and grafting by copolymerization of a synthetic polymer according to a conventionally known conventional method. [0005] The degree of chemical conversion of the modified starch of the present invention is represented by a decrease in the gelatinization start temperature at which starch particles that do not dissolve in cold water swell and gelatinize when heated in water, and a decrease in the viscosity of the gelatinized starch aqueous solution. It is. Here, the gelatinization start temperature means that 450 g of a 15% aqueous suspension of starch was mixed with an amylograph (two-blade paddle type manufactured by Brabender, measuring head: 700).
cmg, number of revolutions: 75 rpm, temperature rise: 1.5 ° C. /
Min) means the temperature at the point where it rises from the baseline of the amylograph. The gelatinization start temperature of the modified starch of the present invention is 30.
C. to 60.degree. C., preferably 35 to 55.degree. C., and if it is less than 30.degree. On the other hand, when the temperature exceeds 60 ° C., the effect of suppressing heat of hydration decreases. The viscosity of the modified starch of the present invention at 50 ° C. measured with a B-type rotary viscometer is 20 to 5 in a 25% aqueous solution.
000 centipoise, preferably 50 to 3000 centipoise, and if it is less than 20 centipoise, there is a delay. Further, when it exceeds 5000 centipoise, the effect of suppressing heat of hydration decreases. [0006] The modified starch of the present invention has a cement content of 0.1%.
It is preferable to add about 05 to 10% by weight, and if the addition amount is less than 0.05% by weight, the effect of suppressing hydration heat is small, and if the addition amount exceeds 10% by weight, the strength may be adversely affected. . A particularly preferred addition amount is 0.1 to 2% by weight. The cement is Portland cement such as various Portland cements and mixed cements containing silica, fly ash and the like, and the mortar for grout is breathing (which exhibits proper strength without showing settlement, For example, lime, calcium aluminate, those using swelling force by hydration by adding gypsum etc. to calcium sulfoaluminate as necessary, those using oxidation of iron powder, or a mixture of these as a main component It is a mortar that uses, for example, a thickener such as polyvinyl alcohol and carboxymethyl cellulose, a foaming agent such as aluminum, and a necessary amount of various types of cement dispersants added thereto, and the like. Anything that indicates
Specifically, calcium sulfoaluminate-based minerals,
An expanding component such as calcium aluminate and gypsum, blast furnace slag, lime, magnesia or the like is added to cement, or calcined and ground so that these substances are present in the cement clinker. Hereinafter, the present invention will be further described with reference to examples. The present invention will be described in more detail with reference to the following Examples and Comparative Examples, which by no means limit the present invention. In the following, “parts” and “%” mean “parts by weight” and “% by weight”, respectively, unless otherwise specified. Example 1 100 parts of ordinary Portland cement, river sand 5 mm 200
Parts, 0.5 parts of the modified starch in Table 1, a 42% water-cement ratio, a mortar adjusted to a kneading temperature of 20 ° C., a height of 30 c
Approximately 3.5 l was placed in a styrene foam cylindrical container having a diameter of 13 m and an inner diameter of 13 cm and a thickness of 10 cm, and the temperature of the mortar center when cured in a constant temperature room at 20 ° C. was automatically measured with a thermocouple. Table 1 shows the results. In addition, Table 2 shows the results of a compressive strength test when the same mortar having a test piece size of 4 cm × 4 cm × 16 cm was cured in water at 20 ° C. [Table 1] [Table 2] Example 2 Ordinary Portland cement, calcium sulfoaluminate-based grout admixture, modified starch shown in Table 3, natural sand and water were mixed and kneaded, and a cement mortar for grout having a temperature of 20 ° C. was kneaded. This is 30cm high, 1 inner diameter
Approximately 4 liters were placed in a 3 cm, 10 cm thick styrofoam cylindrical container, and the temperature at the center of the mortar when cured in a constant temperature room at 20 ° C. was automatically measured with a thermocouple. Table 3 shows the results. In addition, these cement mortars for grout have no bleeding and settlement, and have a grout allowance (thickness) of 3 cm.
Filling rate of mortar when this mortar is spontaneously injected from one side to a 3 cm thick 10 cm wide 20 cm long barrier provided at the center of a mold frame of cm × width 40 cm × length 170 cm and capacity 20 l , And all were 100%. Further, Table 4 shows the results of the compressive strength test of the samples having different age. [Table 3] [Table 4] Example 3 90 parts of ordinary Portland cement, 10 parts of a commercially available cement expander, 200 parts of natural sand, 42 parts of water and 0.1 part of modified starch.
6 parts, water cement ratio 42%, kneading temperature 20
Mortar adjusted to ℃, height 30cm, inner diameter 13c
m, 10 cm thick in a styrofoam cylindrical container about 3.
The temperature of the central part of the mortar when 5 l was put and cured in a constant temperature room at 20 ° C. was automatically measured with a thermocouple. Table 5 shows the types and results of the cement expander and the modified starch. The same mortar specimen size 4cm x 4cm x 16c
Table 6 shows the results of the compressive strength test when the m was cured in water at 20 ° C. [Table 5] [Table 6] The gelatinization starting temperature of the modified starch used in Examples 1 to 3 and the size liquid viscosity at 25% and 50 ° C. are as follows. Oxidized starch: 35 ° C., 30 centipoise, starch acetate: 39 ° C., 210 centipoise, hydroxypropylated starch: 38 ° C., 410 centipoise, carboxymethylated starch: 36 ° C., 780 centipoise, 4
Grade cationized starch: 45 ° C., 860 centipoise, phosphate-crosslinked starch acetate: 57 ° C., 2500 centipoise, polyacrylic acid grafted starch: 52 ° C., 2800 centipoise, dextrin for comparison: gelatinization started due to cold water solubility Temperature 30 ° C. or less, 10 centipoise, oxidized starch comparative product: 57 ° C., 5500 centipoise. By adding the modified starch of the present invention to cement, it was possible to suppress the temperature rise due to the heat of hydration of concrete, mortar, grout, etc., and to improve the retardability.

Claims (1)

(57) [Claims 1] The gelatinization start temperature is 30-60 ° C and 50
Esterification, etherification, cross-linking,
Chemical engineering group consisting of grafting by copolymerization of synthetic polymer
Of which, one or a combination of two or more
A cement composition comprising 0.05 to 10% by weight of powder based on cement.