JPS6054955A - Cement additive - 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 additive for suppressing the temperature rise of concrete or mortar due to water heat utilization, and more particularly to a cement additive for water heat suppression containing dextrin and salicylic acid.

In the present invention, the cold water soluble content of dextrin refers to the amount of dextrin dissolved in distilled water at a temperature of 21°C, and more specifically, dextrin 10g
into a 200me flask and add 1 s of distilled water at a temperature of 21°C.
ome was added, maintained at a temperature of 20 to 26°C for 1 hour, filtered, and the filtrate was evaporated to dryness.
The cold water soluble content is expressed in proportion to the initial dextrin.

(1) - Dex having a cold water soluble content of 5 to 90 ts) It is already known that dextrin has the effect of suppressing the heat of hydration of mortar and concrete. However, the temperature at which this dextrin is used is usually about 25°C or higher, and if it is used at a low temperature of about 10°C, its effect of suppressing the heat of hydration is extremely low, and it is difficult to suppress the temperature rise in low-temperature regions or in winter. there were.

The present inventors have discovered that the combined use of a certain type of dextrin and salicylic acid significantly increases the effect of suppressing the heat of hydration at low temperatures such as in winter, and has thus completed the present invention.

That is, the present invention is a cement additive containing dextrin and salicylic acid having a cold water soluble content of 5 to 40% by weight.

To explain the present invention in more detail below, the dextrin used in the present invention is usually obtained by adding dilute acid to starch and decomposing it by heating, but it can also be obtained by any manufacturing method such as enzymatic decomposition of starch or condensation of glucose. However, it is necessary that the cold water soluble content is in the range of 5 to 40% by weight, and in particular (2) the range of 10 to 30% by weight is preferable. Cold water soluble content is 5
If it is less than 4% by weight, the dextrin is insufficiently dissolved.
If the weight ratio exceeds 0, the hardening retardation effect when added to cement becomes too strong.

By using the above-mentioned dextrin and salicylic acid in combination, the effect of suppressing the heat of hydration is significantly greater than that of using dextrin alone, and the effect of suppressing the heat of hydration is particularly remarkable when the implantation temperature is low, such as in winter. This is thought to be because salicylic acid appropriately promotes the dissolution of dextrin at low temperatures. Also effective are monochloroacetic acid, dichloroacetic acid, oxalic acid, malonic acid, maleic acid, and heptallic acid, which have large acid dissociation constants.

The amount of salicylic acid to be mixed is preferably 2 to 100 parts by weight per 100 parts by weight of dextrin as a cement additive, but is not limited thereto.

As the cement to which the cement additive is added, various Portland cements, mixed cements containing silica, fly ash, etc., and expanded (6) cements can be used.

The addition l of the cement additive is 1 o of cement.

It is preferable to use 05 to 10 parts by weight based on the weight of the skin. Added amount is 0
．． If it is less than 0.5 parts by weight, the effect of suppressing the heat of hydration is small, and if it exceeds 10 parts by weight, it will have an adverse effect on strength development.

As in the present invention, by using dextrin with a cold water soluble content of 5 to 40 ft% in combination with salicylic acid, the dissolution of the dextrin is promoted, and the effect of suppressing the heat of hydration is significantly greater than that of the dextrin alone. This is especially noticeable when the driving temperature is low, such as in winter.

The cement additive can also be used in combination with admixtures such as water reducing agents and setting retarders, and water-soluble polymers.

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

Example 1) Blend as in Experiments i63 to 8 in Table 1, add water to make the water-cement ratio A or 42%, and mix at a temperature of 10%.
The mortar adjusted to ℃ has a height of 3 degrees, an inner diameter of 13 cm, and a thickness of 10 C! The mortar was placed in a cylindrical container made of polystyrene foam with a temperature of about 3.5 mm, and cured (4) in a constant temperature room at 10° C., and the temperature at the center of the mortar was measured with a thermocouple. Table 1 shows the amount of temperature rise, the time to reach the maximum temperature (hereinafter referred to as peak time), and the compressive strength measured using a 4 x 4 x 16 CrIL specimen.

Cement: Denki Kagaku Kogyo ■Ordinary Voltland Cement Dex) IJn: Experiment/161-8 Cold water soluble content
20.0% experiment/I69-10 150.0 Salicylic acid: Reagent aggregate: Sagami-produced river sand 5rRrIL sewage: Tap water comparison example 1) For comparison, mix as in Experiment 7F61, 2, 9.10 in Table-1 The rest was carried out in the same manner as in the example, and the results are shown in Table 1.
Shown below.

Example 2) Blend as in Experiment A12 in Table 2, and knead at a temperature of 1.
The temperature was set at 0°C, and the complete adiabatic temperature rise of the concrete was measured using an adiabatic temperature rise measurement device manufactured by Ohmen Negaku.

289- Comparative Example 2) For comparison, the formulation was as in Experimental Flat 11 in Table 2, and the other procedures were the same as in Example 2), and the results are shown in Table 2.

Example 3) Concrete mixed according to Experiment J615.16 in Table 3 and adjusted to a mixing temperature of 20°C was made to a height of 30 CII.
Measurement was made using a Styro foam with an inner diameter of 60 cm and a thickness of 10 crn. The results are shown in Table-6. Also, 10αφ×20c
Table 3 also shows the results of the compressive strength determined by the IrL specimens.

Comparative Example 3) For comparison, the layers were blended as in Experimental Layers 13 and 14 in Table 6,
The rest was carried out in the same manner as in Example 2), and the results are shown in Table 3.

From here on, by using dextrin with a cold water soluble content of 5 to 40% by weight in combination with salicylic acid, the amount of temperature rise is reduced, the time to reach the maximum temperature is lengthened, and the strength is not reduced (water usage). It can be seen that the suppressive effect is exerted.

Patent applicant Denki Kagaku Kogyo Co., Ltd. (11) -901-

Claims (1)

[Claims] A cement additive comprising dextrin and salicylic acid having a cold water soluble content of 5 to 40% by weight.