JPH0453828B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing concrete in which a mixing agent for reducing separation is added, and particularly to a method for producing concrete suitable for pouring in water, the sea, or muddy water. Traditionally, when constructing concrete structures in the sea or underwater, such as bridge piers and abutments, which are the substructures of bridges, it has been known that the concrete used for normal concrete structures easily separates in water, the sea, or muddy water. In order to reduce this separation, for example, concrete mixing agents (mixtures for reducing separation) made of cellulose-based polymers such as powdered carboxymethyl cellulose have been added. However, this type of mixture develops viscosity in concrete, which is alkaline, and can suppress the separation of the constituent materials of concrete, but it increases the viscosity of concrete, causing the following problems. was. In other words, as the viscosity increases, the load on the concrete mixing equipment (for example, a batch mixer) becomes extremely heavy, and a mixer with a small mixing capacity cannot perform sufficient mixing, which not only increases the size of the equipment but also increases the There is a problem that it takes time to knead, and furthermore, if the kneading is insufficient, the mixture is not uniformly dispersed and its function cannot be utilized effectively. Moreover, it is of course difficult to clean concrete adhering to the equipment used for mixing with water, and the larger the equipment, the more complicated the removal becomes. Furthermore, since the viscosity of concrete mixed with an admixture increases over time, there is also the problem that the time required from mixing and stirring the admixture to pouring is longer than with regular concrete. . One way to solve the above-mentioned problems to some extent is to add a powdered mixture to base concrete that has been mixed with cement, water, aggregate, and an admixture. When they come into contact, viscosity immediately occurs at the contact area, which tends to form flocs, which necessitates even more thorough stirring, resulting in a problem of poor workability. This invention was made in view of the above-mentioned conventional problems, and its purpose is to improve handleability without deteriorating workability, and to
It is an object of the present invention to provide a method for producing concrete mixed with a mixture for reducing segregation, in which the mixture for reducing segregation can be effectively used. To achieve this objective, the present invention provides a method for producing concrete in which a separation-reducing admixture that increases in viscosity in the alkaline region is added to a base concrete prepared by kneading cement, water, aggregate, and an admixture.
The mixture is a PH mixture made by adding an organic acid to water.
is dissolved in an acidic aqueous solution of about 3%, and is added and kneaded to the base concrete at the casting site in a range of 0.1 to 0.5% based on the weight of the cement, and the water in the base concrete is mixed with the mixture. It is characterized in that the amount corresponding to the water content of the agent is reduced in advance before being kneaded. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is an explanatory diagram showing an embodiment of a method for manufacturing concrete to which a mixture for reducing separation according to the present invention is added. In the manufacturing method shown in the figure, a base concrete 12 is manufactured using a mixer 10 in a plant B installed at a location away from a pouring site A in the same manner as for ordinary concrete. This base concrete 12 includes cement,
It is mixed with water, aggregate, and admixtures as appropriate, and then transported to the pouring site A by a ready-mixed concrete truck or the like. Then, the base concrete transported to the pouring site A is transferred to an agitator 14, and a mixture 16 is added thereto. In this case, the mixture 16 is prepared by adding a miscellaneous acid (organic acid) such as acetic acid to water to create an acidic aqueous solution with a hydrogen ion index (PH) of about 3, and then dissolving the powder into a slurry. The water content of the base concrete is reduced in advance by an amount corresponding to the water content contained in the mixture 16 before being kneaded. In this way, by dissolving the powdered mixture in an acidic aqueous solution,
The mixture 16 easily becomes a slurry, and
The prepared mixture 16 is applied to the base concrete 12
It has been confirmed that it takes time (for example, about 10 to 15 minutes) for concrete to develop viscosity after it is added and kneaded, so caution can be taken in the work. In particular, by setting the pH of the acidic aqueous solution to about 3, it is possible to suppress the adverse effects on concrete that occur in the case of strong acids. As the mixture 16, for example, a powdered cellulose polymer such as carboxymethyl cellulose is used as shown in the previous example. Cellulose-based polymers suppress the separation of concrete in water and the sea, and increase the viscosity in the alkaline region, and since the mixed concrete exhibits alkalinity, it increases the viscosity of concrete. Figure 2 shows an example of the properties of the mixture 16, where the vertical axis shows the viscosity and the horizontal axis shows the pH. The viscosity was measured after the mixture was added and left to stand for 1 hour. As is clear from this figure, the mixture 16 has a pH of about 3, has a low viscosity, and easily becomes a slurry. The concrete in which the separation reducing mixture 16 is added to the base concrete 12 in this way is
Water is supplied via baskets, pumps, tremie pipes, etc.
It will be placed in the sea. Now, use the method described above to create base concrete 12.
When concrete for pouring is created by adding and kneading the mixture 16 for reducing separation, the mixture 16 is not added at the time of mixing and preparing the base concrete 12, so there is no need to increase the size of the mixer 10 in the plant. Regular equipment can be used as is by simply changing the formulation slightly. Furthermore, equipment such as the mixer 10 used to create the base concrete 12 does not contain the mixing agent 16, which is difficult to clean, and can therefore be easily cleaned with water. Furthermore, since the addition and kneading of the mixture 16 is carried out at the casting site, the time constraints from the addition and kneading to the casting can be greatly alleviated. What should be particularly noted here is the following points. That is, the mixture 16 for reducing separation is previously prepared in the form of a slurry, and added to and kneaded into the base concrete 12. In particular, in the present invention, the mixture 16 is previously dissolved in an acidic aqueous solution and made into a slurry. As a result, the mixture 16 can be quickly and uniformly dispersed in the base concrete 12 without causing flocs, ensuring good workability, and the function of the mixture 16 is utilized extremely effectively, allowing it to be easily dispersed in water or under the sea. The concrete poured into the concrete has a dense structure. The inventors of the present invention confirmed this point from the test results shown in Table 1 below. As shown in Table 1, the tests were conducted on two types: one in which the powdered mixture for reducing separation was added to the base concrete as it was and kneaded, and the other in which the powdered mixture was previously made into a slurry form and added to the base concrete using the method of the present invention. These are the results of comparing the unconfined compressive strength (σ) after 7 days and after 28 days.

[Table] As is clear from this table, even if concrete is mixed with the same mix of base concrete and the same amount of mixture for reducing separation, the slump, flow value, and air content are almost the same. The concrete produced by the method of the present invention, in which the mixture is prepared in advance in the form of a slurry and kneaded, can significantly increase the compressive strength both after 7 days and after 28 days. In addition, the amount of the above-mentioned separation-reducing mixture added is preferably 0.1% to 5.0% of the weight of cement in terms of economical efficiency and the amount of water for slurrying. As described above in detail in the examples, the method for producing concrete to which the mixture for reducing segregation is added according to the present invention is such that the mixture can be added at the pouring site to improve handling without deteriorating workability. By adding and kneading this in the form of a slurry, the mixture can be quickly and uniformly dispersed, and its functions can be effectively and reliably utilized.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of the concrete manufacturing method according to the present invention, and FIG. 2 is a graph showing the properties of the mixture for reducing separation. 10...Mixer, 12...Base concrete, 14...Agitator, 16...Mixing agent.

Claims (1)

[Claims] 1. In a concrete production method in which a separation reducing mixture that increases viscosity in the alkaline region is added to base concrete made by kneading cement, water, aggregate, and an admixture, the mixture is created by adding an organic acid to water. The pH of the base concrete is dissolved in an acidic aqueous solution of about 3, and is added to the base concrete at the casting site in a range of 0.1 to 0.5% based on the weight of the cement, and the water in the base concrete is A method for producing concrete to which a mixture for reducing separation is added, characterized in that the mixture is kneaded by reducing an amount corresponding to the water content of the mixture in advance.