JP3343428B2 - Hydration heat inhibitor for cement - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an agent for suppressing heat generation due to hydration of cement for suppressing heat generation due to hydration of cement and thereby preventing cracking of hardened concrete due to heat generation (hereinafter referred to as temperature cracking). .

[0002]

2. Description of the Related Art The main reason for the occurrence of temperature cracks is that the heat generated by the hydration of cement causes a temperature difference between the inside and outside of concrete, and the stress caused by this temperature difference exceeds the tensile strength of hardened concrete. Because. Therefore,
Suppressing the heat of hydration of cement and reducing the temperature difference between the inside and outside of concrete are effective means for preventing temperature cracking. Based on such an idea, conventionally, a hydration heat generation inhibitor for cement comprising the following substances has been proposed. a) Urea (Japanese Patent Application Laid-Open No. 62-223048) b) A heat storage substance having a melting point or a transition point at 5 to 60 ° C. (Japanese Patent Application Laid-Open No. 3-69542) c) Cold water-soluble content of dextrin of 5 to 90% by weight (JP
55-75950) d) Hydrolyzable tannin (JP-A-63-117941)

The mechanism by which the above substances suppress the heat of hydration of cement is considered as follows. That is, a and b use the endothermic action of the substance itself, and urea absorbs heat when hydrolyzed in concrete, and the heat storage substance absorbs latent heat during melting or phase transition. This suppresses the heat of hydration. On the other hand, the above c and d are to suppress the heat of hydration by delaying the hydration reaction of the cement, dextrin releases dextrin molecules by dissolving the powder, and hydrolyzable tannin is hydrolyzed. These substances, which release tannin molecules and are released into the liquid phase of the concrete, delay the hydration reaction of the cement and suppress the heat of hydration.

[0004]

However, since the endothermic amount of the above-mentioned urea and heat storage material depends on the amount of addition, a large amount of these materials must be added to concrete in order to obtain a significant effect. However, when a large amount of urea is added to concrete, a large amount of carbonic acid and ammonia is generated by hydrolysis, and these cause the promotion of neutralization of the concrete and the odor. In addition, the heat storage materials are expensive, and have a practical problem such as a significant increase in cost. On the other hand, the dextrin and the hydrolyzable tannin can suppress the heat of hydration by adding a relatively small amount (hereinafter, referred to as a suppressing action), but at the same time, delay the hydration start time of the cement (hereinafter, referred to as a delaying action). ), These actions are inseparable.
Therefore, particularly when the concrete is placed at a high temperature such as in summer, the delay effect becomes remarkable, and problems such as prolongation of the mold release time and increase in the amount of breathing are likely to occur.
The present invention relates to a conventional cement hydration heat generation inhibitor,
In view of the above circumstances, an object of the present invention is to provide a cement hydration heat generation inhibitor that exhibits a large heat generation suppression effect even when added in a small amount and does not cause the above-mentioned problem caused by a delayed action even at a high temperature. And

[0005]

To achieve this object, the present inventor has proposed:
As a result of studying the mechanism of the hydration exothermic inhibitor involved in the hydration reaction of cement in more detail, the following findings were obtained, and based on this finding, hydration of cement that did not cause problems due to delayed action We have completed the heat generation inhibitor. In general, the hydration of cement goes through a period of several hours after contact with water until the hydration reaction starts (hereinafter referred to as an induction period), and then shifts to a period in which the hydration reaction is active (hereinafter referred to as an acceleration period). It is known. The present inventor has found that the delayed substance released from the hydration heat generation inhibitor exhibits a retarding action in the induction period and a suppressing action in the accelerated phase. Regarding the dextrin, dextrin containing 5 to 90% by weight of the cold water-soluble component of the above c is added to 150 ml of water at a temperature of 21 ° C., 10 g of this is added, and the temperature is kept at 20 to 23 ° C. for 1 hour. In this case, the dextrin containing 5 to 90% by weight of dextrin dissolved in water is added to the concrete. When the dextrin is added to the concrete, the dextrin molecules are eluted into the liquid phase of the concrete during the induction period of several hours. Delay. In particular, when the concrete pouring temperature or the environmental temperature is high, the amount of dextrin eluted is further increased, the delay action is increased, and the induction period is lengthened, so that the demolding time is greatly delayed. Further, the hydrolyzable tannin of d also releases tannin molecules by a hydrolysis reaction immediately after kneading of the cement, and shows the same phenomenon.
Based on the above findings, the hydration heat generation inhibitor of the cement according to the present invention, the release time of the delayed substance is adjusted,
In the induction phase of the hydration reaction, it hardly releases a retardant,
It is mainly composed of a substance having a property of releasing a delayed substance until the acceleration period.

[0006]

Specifically, the present invention relates to a cement hydration heat generation inhibitor having the following structure. (1) An inhibitor for hydration heat generation of a cement mainly composed of a non-easily soluble component obtained by removing water-soluble components from dextrin. (2) The cement hydration heat generation inhibitor according to the above (1), which is mainly composed of a powdery material composed of insoluble components obtained by removing water-soluble components from dextrin and gradually dissolves under weak alkalinity. (3) The cement of (1) or (2), wherein the powder has a particle size of 0.1 to 2000 μm.

[0007]

[Detailed Description] Dextrin as a raw material is obtained from starch, cellulose, hemicellulose, or a derivative thereof by thermal decomposition, hydrolysis, enzymatic decomposition, or the like.
A mixture of more than one species. The non-soluble component obtained by removing the component soluble in water from dextrin is, for example, 2%.
A component in which dextrin is dispersed in water at 5 to 40 ° C. and kept at this temperature for 1 to 10 hours, and then components dissolved in water are separated and removed by centrifugation, filtration or a combination thereof. Specifically, the dissolution temperature and dissolution time of dextrin are selected within the above ranges according to the upper limit of the concrete pouring temperature and the environmental temperature, and the length of the induction period of hydration of cement. The amount of water used for dispersing the dextrin is suitably a water / dextrin ratio of 10 or more, preferably 15 or more by weight, in order to obtain good dispersion. As described above, the hydration heat generation inhibitor of the present invention comprises an insoluble component obtained by removing a component soluble in water from dextrin.

The separated insoluble components are dried and pulverized, or made into a slurry by adding water, and then into a granular material by spray drying. The powder may be formed by other methods. The particle size of the powder is suitably from 0.1 to 2000 μm, preferably from 1 to 1000 μm. If it is smaller than 0.1 μm, it is not preferable because, when added to the cement, the elution of the retardation substance tends to occur from the induction period of the hydration reaction. On the other hand, if the particle size exceeds 2000 μm, elution during the acceleration period becomes insufficient.

The amount of the non-soluble component added to the cement is suitably 0.05 to 5 parts by weight based on 100 parts by weight of the cement. If the addition is less than 0.05 part by weight, the effect of suppressing the heat of hydration is insufficient, and if the addition amount exceeds 5 parts by weight, the strength development becomes slow. The method of addition is not limited, and for example, it is directly added to the cement in a dry state, or at the time of kneading concrete, the above-mentioned insoluble powder is dispersed in kneading water and used. In addition, the type of cement used is not limited, and is used for known cements such as ordinary Portland cement, moderately heated Portland cement, blast furnace cement, fly ash cement, high belite cement, early-strength cement, and expanded cement. can do.

Further, the hydration heat generation inhibitor for cement according to the present invention includes an AE agent, a water reducing agent, an AE water reducing agent, a high performance water reducing agent, a fluidizing agent, a shrinkage reducing agent, a setting accelerator, a waterproofing agent, and a rust preventive. It can be used in combination with a well-known concrete admixture such as an agent.

When the hydration heat-inhibiting agent for cement according to the present invention is used by adding it to cement, it gradually dissolves under weak alkalinity in the cement. Phase hardly elutes during the period,
In the accelerated period in which the temperature rises due to the heat of hydration of the cement, the elution of the retardant proceeds. Therefore, there is no problem of delaying the start time of the hydration reaction.On the other hand, during the accelerated period of the hydration reaction, the temperature rises due to the heat generated by the hydration of the cement, and the amount of the delayed substance eluted increases, so that the inhibitory effect is reduced. It increases and the heat of hydration is effectively suppressed.

[0012]

As described above, the heat generation inhibitor for hydration of cement according to the present invention can effectively suppress the heat of hydration of cement even with a small amount of addition, and can surely prevent problems such as temperature cracking. be able to. In addition, even during construction at high temperatures, the induction period of the hydration reaction is not prolonged, and the concrete strength in long-term aging is not adversely affected.

[0013]

Examples and Comparative Examples Examples of the present invention are shown below together with comparative examples. This embodiment is an exemplification, and does not limit the scope of the present invention. Production Example To 1500 g of water at a temperature of 25 ° C., 100 g of dextrin containing 50% by weight of a soluble component in cold water was added, and the mixture was stirred and dispersed.
After that, the slurry was centrifuged and dehydrated to obtain an insoluble component. While suction-filtering this insoluble component,
After washing with 200 g of water at 25 ° C., drying at 80 ° C., further pulverizing in a mortar, and classifying, 35 g of a powder having a particle size of 1 to 100 μm
I got

Examples 1-3 520 g of ordinary Portland cement, 1040 g of Toyoura standard sand,
In a JIS mortar of 338 g of water, 0.3 g (1.56 g) and 0.35 g (1.
82 g) and 0.4 part by weight (2.08 g) were added and kneaded, and the compressive strength and temperature of the mortar were measured as in Example 1, Example 2 and Example 3, respectively. The compressive strength was measured on a mortar formed into 4 × 4 × 16 cm, cured in water and aged 7 and 28 days. In addition, the method of measuring the temperature is as follows.The whole kneaded mortar is packed in a polyethylene bag of 8.5 cm in diameter and 24 cm in height, and the bag is inserted into a stainless steel dewar with an inner diameter of 10 cm and a height of 28.5 cm. The temperature at the center of the mortar was automatically measured by covering with a cork through a thermocouple. The above mixing, molding, curing in water, and temperature measurement were all performed in a constant temperature room at 30 ° C.

Comparative Examples 1-2 The JIS mortar used in Examples 1-3 was added without addition.
Alternatively, 0.35 parts by weight (1.82 g) of dextrin having a soluble content of 50% by weight in cold water was added to 100 parts by weight of cement and kneaded, and the mixture was used as Comparative Example 1 and Comparative Example 2 in the same manner as in Examples 1 to 3. The compressive strength and temperature of the mortar were measured by the method and conditions. Table 1 shows the measurement results of the compressive strength of the above Examples and Comparative Examples, and FIG.
It was shown to.

As shown in FIG. 1, the maximum temperatures of the mortars of Examples 1 to 3 are lower than those of Comparative Examples 1 and 2, and it can be seen that the mortar has a remarkable effect of suppressing hydration heat generation. on the other hand,
Even when the conventional dextrin of Comparative Example 2 was added, the temperature of the mortar rapidly increased after 30 hours of the material age even at the same amount of addition as in Example 2, and the temperature significantly exceeded that of Examples 1 to 3. become. This is because conventional dextrin inhibitors have a large amount of water-soluble components, and most of them are eluted during the induction period of the hydration reaction. Because. Further, as shown in Table 1, the mortars of Examples 1 to 3 had a 28-day material strength higher than those of Comparative Examples 1 and 2, and had no adverse effect on the long-term material strength.

[0017]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a graph showing the change over time in mortar temperature in Examples and Comparative Examples.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-305799 (JP, A) JP-A-55-75950 (JP, A) JP-A-1-3055838 (JP, A) JP-A-4- 139047 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C04B 24/38

Claims (3)

(57) [Claims] 1. A hydration heat-inhibiting agent for cement, comprising as a main component a powdery material comprising a non-soluble component obtained by removing a component soluble in water from dextrin. 2. The hydration heat-inhibiting agent for cement according to claim 1, wherein the agent is mainly composed of a powdery material composed of insoluble components obtained by removing water-soluble components from dextrin and gradually dissolves under weak alkalinity. 3. The particle size of the powdery granules is 0.1 to 2000 μm.
m.