JPH0210788B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the creation of a method for producing hydraulic material products with excellent freeze-thaw resistance, and is capable of accurately producing cement and other hydraulic material products with excellent freeze-thaw resistance. The present invention aims to provide a method that can provide such a product that is excellent in stiffness, strength, and other properties.

It is generally known that when products made of cement or other hydraulic materials are used in cold regions or conditions with severe temperature drops, their strength gradually decreases and they become brittle or break. In order to avoid this, an air entraining agent is used in a kneaded product using powdered hydraulic substances such as cement as described above. However, in order to obtain the desired resistance to freezing and thawing in a kneaded product containing an air entraining agent in this way, it is necessary to use a relatively large amount of the air entraining agent. In this case, even if the resistance to freezing and thawing is increased, the strength of the obtained hydraulic material product is reduced.

The present invention was devised after repeated studies in view of the above-mentioned circumstances. and an air-entraining agent to obtain a raw mixture such as mortar or concrete by adding and kneading the mixed water and mixing the air-entraining agent to be added to one of the divided mixed waters. The above-mentioned aggregate is properly moistened and applied, and then this is mixed with the addition of a hydraulic substance, and the powder is adhered to the surrounding surface of the aggregate in a stable state, and then the other blended water is added and kneaded. This is a proposal to obtain a desired molded body.

In other words, according to the method of the present invention, the air entraining agent is added in whole or in part to the water, which is considerably smaller than the total amount of water added in the divided water mixture, to improve the quality of aggregate, especially fine aggregate. The surrounding surface is moistened, and a coating layer of hydraulic material powder such as cement is preferentially formed on this material, and after that, the remaining part containing no air entraining agent or the remaining part containing an air entraining agent is Since the other blended water is added and kneaded to form the desired kneaded product, a coating layer containing air bubbles is formed on the peripheral surface of the fine aggregate, resulting in favorable resistance to freezing and thawing as described above. It is possible to obtain the properties on the peripheral surface of the aggregate, and it is possible to effectively improve the resistance of the molded article in general to such freezing and thawing. Moreover, if all or most of the air entraining agent to be added is added to a divided portion of the total amount of water to be mixed, the amount of air bubbles entrained in the overall kneaded product can be relatively small, and the obtained It is possible to obtain preferable strength in the molded article.

To explain the present invention in more detail as described above, whether or not it has preferable resistance to freezing and thawing is determined by performing 300 cycles of freezing and thawing on a test piece obtained from a molded article. It is generally known that the evaluation is performed using the relative dynamic elastic modulus, that is, the elastic modulus after the freeze-thaw test over 300 cycles with respect to the elastic modulus before the test. Relative dynamic elastic modulus after freezing and thawing
For example, cement 309Kg/m ³ to obtain more than 95%,
Sand to gravel ratio S/a is 50%, water cement ratio W/C
The mixture of water 170/m ³ was added to give an air content of 55%, the air entraining agent was added to the mixture to give an air content of 4.9%, and these materials were simultaneously added and kneaded according to the conventional technique, and the present invention Divide the blended water according to the following, and the primary water will be approximately 100/m ³ and the air amount will be 2.9
% of the total amount of air entraining agent added to the aggregate and cement for 30 seconds and then the remaining 70/m ³
Water at a ratio of 3.1% was added as secondary water and kneaded for 2 minutes, and as primary water, half of an air entraining agent with an air content of 3.1% was added to 70/m ³ water to form aggregates. After mixing cement for 30 seconds, adding 100/m ³ of secondary water containing the remaining amount of air entrainment agent and kneading for 2 minutes, the air content,
The results of measuring the compressive strength after 28 days, the breathing rate, and the weight loss rate after 300 cycle tests are shown in Figure 1. In other words, with the conventional method, the air content is around 5%, the breathing rate exceeds 6%, the 28-day strength is 304Kg/cm ² , and the weight loss rate is 1.5%, whereas the air entrainment agent in the primary blended water In the case of the present invention ^, which uses the entire amount of
The weight reduction rate was an outstanding value of 1%, and it was confirmed that this was a very good product. The primary blended water is 70/ ^m3 , and this primary blended water and the remaining 2
In the case where the air entraining agent was added to the next mixed water in equal parts, the air content was slightly over 3% and the breathing rate was 2.70%, but the 28-day strength was 362Kg/cm ²
The weight reduction rate was also 1.1%, which was confirmed to be a better product compared to the value obtained by the conventional method. In addition, in the same formulation as above, concrete with an air content of 3.4 to 3.5% is mixed with the conventional method and the total amount of air entraining agent as described above is mixed with 1.
The results of measuring the relative dynamic elastic modulus and compressive strength after 28 days for the product added to the secondary water and the product of the present invention in which the air entraining agent is added in equal parts to the primary and secondary water are shown in the chart in Figure 2. That's right. That is, in this case, the conventional method was destroyed after about 200 cycles of the freezing test, and the relative dynamic elastic modulus at 180 cycles before this destruction was 48%, and the compressive strength after 28 days was 331 Kg/cm ² In contrast, in the method according to the present invention, the total amount of air entraining agent is reduced to 1
The relative dynamic modulus of elasticity after 300 cycles of freezing test was 96%, and the compressive strength after 28 days was
425Kg/cm ² , and when the air entrainment agent is divided into primary and secondary water, the relative dynamic elastic modulus is 95% and the compressive strength after 25 days is 410Kg/cm ² . It was confirmed that the relative dynamic elastic modulus and strength were significantly different.

Furthermore, in the case of the present invention, in which an air entraining agent is added so that the air content becomes 3.2 to 3.5%, and the entire amount of the air entraining agent is added to the primary blended water, the amount of water that is attached to the surface of the aggregate in advance Fig. 3 shows the results of an investigation of various changes in . That is, in this case, it is effective when the amount of primary water (W ₁ ) is 15% to 50%, especially 20 to 35%, relative to the amount of cement, and in the case of this 20 to 35%, 300%
It was confirmed that the relative dynamic elastic modulus after the cycle freeze-thaw test was all 95% or higher, and the product strength was also high.In terms of the breathing rate, W ₁ /C
It was found that the amount can be reduced to 2% or less within the range of 15 to 45%.

Further, the same relationship as shown in FIG. 3 was examined for the case where the air entraining agent was added separately to primary and secondary water, and the results are shown in FIG. 4 below. That is, even in this case, 50% of the air entraining agent to be added is
% is mixed in the primary water, so the W ₁ /
Excellent results are obtained when C is 15-35%, 40-
It is clear that even with a ratio of 50%, favorable results can be obtained compared to the conventional method.

According to the present invention as explained above, when obtaining concrete or other products made of a hydraulic substance such as cement, the mixing water necessary to obtain the raw mix is divided, and an air entraining agent is added to one side. By adding all or most of it to form a coating layer containing air bubbles around the aggregate surface, it is possible to provide a product with excellent freeze-thaw resistance, and the air entrainment necessary to obtain the desired resistance. This invention has many excellent effects such as being able to reduce the amount of the agent and maintaining the strength of the resulting product at a sufficiently high level, so it is an invention that is industrially very effective.

[Brief explanation of drawings]

The drawings show the technical contents of the present invention, and Figure 1 shows the amount of air required to make the relative dynamic elastic modulus 95%, the strength in that case, the breathing rate, and the weight loss rate after the freeze-thaw test. Figure 2 shows the relationship between relative dynamic elastic modulus and strength when the air content (3.4 to 3.5%) is kept constant between the conventional method and the present invention. Fig. 3 is a chart showing the relationship between the relative dynamic elastic modulus, strength, and breathing rate in the case of the present invention in which the entire amount of the air entraining agent is added to the primary blended water. The figure is a chart showing the relative dynamic elastic modulus and breathing rate in relation to the variation in the amount of primary water, similar to Figure 3, in the case of the present invention in which the air entraining agent is added separately into primary and secondary water. It is.

Claims (1)

[Claims] 1 Adding mixed water and an air-entraining agent to fine aggregate or aggregate consisting of fine aggregate and coarse aggregate to hydraulic substance powder such as cement and kneading to obtain a raw mixture such as mortar or concrete. For this, the mixed water is divided, and a mixture of all or a part of the air entraining agent to be added to one of the divided water is applied to the entire surface of each particle of the aggregate, and then hydraulic A material powder is added and mixed to form a hydraulic material coating layer on the surface of the fine aggregate in which the water-cement ratio is lower than that in the final kneaded product, and then an air entraining agent is not mixed or the remaining air entrainment is carried out. 1. A method for producing a hydraulic material product having excellent freeze-thaw resistance, which comprises molding a kneaded product obtained by adding and kneading water mixed with an agent.