JPH07115901B2 - Concrete admixture - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a concrete admixture, and more specifically, it enhances the fluidity of concrete, which is a hydraulic cement mixture, and prevents the fluidity from decreasing with time. The present invention relates to a concrete admixture capable of improving workability.

Conventionally, a cement mixture prepared by mixing cement, water, and if necessary, sand, gravel, and an admixture (agent) has undergone physical and chemical agglomeration of cement particles over time after kneading, The fluidity is gradually lost, and the workability and workability deteriorate over time. Therefore, the cement compound has a drawback that the workable time (potable time) is limited. In addition, the cement mixture is often transported to the setting site by an agitator car (fresh concrete mixer car) after kneading,
The time required for transportation varies greatly depending on the transportation distance or traffic congestion. For this reason, it is extremely difficult to obtain a certain level of workability because the fluidity of each agitator vehicle is different at the driving site.

Also, when pumping cement mix, when pumping is temporarily interrupted due to lunch break or step change, and then trying to restart pumping, the fluidity of the cement mix in the pipe decreases, and when pumping restarts There are also many problems such as sudden increase in pumping pressure or blockage.

Further, in the case of centrifugal compaction concrete or mortar, it is often the case that after the kneading, the centrifugal molding formwork is filled with concrete and the centrifugal compaction is started at the time when the filling of several formwork is completed. In this case, if it takes a long time to fill the mold, the fluidity of the concrete is lowered, and it becomes difficult to perform centrifugal compaction.

For this reason, several methods have been devised to prevent the fluidity deterioration of cement formulations.

For example, there is a method of adding a curing retarder such as oxycarboxylic acid for the purpose of preventing chemical aggregation. Although this method can delay the hydration reaction of cement, it is difficult to prevent physical agglomeration, and therefore slump loss has not been prevented. In addition, disadvantages such as early reduction of strength of concrete and mortar occur.

Also, granulating concrete fluidizer such as β-NSF,
There is a method for preventing slump loss by adding it to concrete or the like and gradually dissolving this granular fluidizing agent (Japanese Patent Laid-Open No. 139929/54). With this method, slump loss can be prevented to some extent, but defects such as a decrease in strength and durability occur due to the granular particle mobilizing agent locally remaining in the concrete after hardening.

Further, there is a method of maintaining the fluidity of concrete for a long time by dividing or continuously adding a fluidizing agent such as β-NSF to concrete (Japanese Patent Publication No. 51-15856). This method is effective as a slump loss prevention method, but it takes time to add the fluidizing agent, and the addition of the fluidizing agent such as concrete in the pumping pipe for pumping and concrete in the centrifugal compaction frame is added separately. It is impossible to prevent concrete slump loss under difficult conditions.

These conventional methods for preventing fluidity deterioration of cement compounds have some problems and cannot be said to be satisfactory.

The present invention has been made to improve the above-mentioned drawbacks of the conventional method, and contains the following components (a) and (b) as essential components, and the ratio of component (a) / component (b) is 90 / 10-99.8 /
The present invention provides a concrete admixture characterized by being 0.2.

(A) Component Naphthalenesulfonic acid formalin condensate or salt thereof (b) Component Polyoxyethylene having an average molecular weight of 80,000 or more The component (a) of the present invention is a known cement dispersant. Mighty 150 (manufactured by Kao Soap Co., Ltd.) is suitable as the formalin condensate of naphthalene sulfonic acid or a salt thereof, and the naphthalene sulfonic acid formalin condensate described here is naphthalene sulfonic acid or alkylnaphthalene sulfonic acid, or One or two of sulfonates of compounds containing these components, such as creosote oil, naphthalene oil, and components such as pitch produced in the process of coking of coal, or compounds having a naphthalene ring such as coal liquefied oil.
It also includes at least one formalin condensate or formalin cocondensate.

The component (b) of the present invention is preferably polyoxyethylene. As polyoxyethylene, PEO-1, PEO-3, PEO
-8 and PEO-15 (both manufactured by Iron and Steel Chemical Co., Ltd.) are good. These polyoxyethylene average molecular weight 8000
0 or more, preferably 150,000 or more.

The ratio of the component (a) to the component (b) is 90/10 to 99.8 / 0.2, preferably 95/5 to 99.5 / 0.5. If this ratio is less than 90/10, the dispersibility will be remarkably low and the addition amount will be large, which is uneconomical, and adversely affects air entrainment and delay of setting and the like. Further, if this ratio is larger than 99.8 / 0.2, the slump retention becomes low.

When the components (a) and (b) of the present invention are mixed, the compositions of the respective components may be used separately or in a dispersed liquid form if a uniform solution is not obtained. May be. Also, after mixing the acid of the component (a) and the component (b),
When partially or completely neutralized, a good morphology is often obtained.

The addition amount of the concrete admixture of the present invention is 0.10 as the solid content% by weight with respect to the cement of the hydraulic cement composition.
~ 2.5 is good. If it is 0.10% or less, a sufficient dispersing effect and slump loss preventing effect on the cement particles cannot be obtained. Further, if it exceeds 2.5%, it is economically disadvantageous or excessive dispersion of cement particles causes breathing or paste separation.

It is most preferable that the concrete admixture according to the present invention is added to the hydraulic cement composition in the form of an aqueous solution. However, even if the components (a) and (b) are added separately, the slump loss preventing effect can be obtained. To be In addition, the time of addition can be such that the admixture is dissolved in the mixing water, added at the same time as the mixing water, added to the hydraulic cement composition that has been kneaded, or added to the cement composition in powder form. Is. Further, the admixture of the present invention can be added dividedly at each stage.

In addition to the concrete admixture of the present invention, other cement dispersants, water-soluble polymer compounds and the like are used. Other cement dispersants include lignin sulfonate, formalin condensate of melamine sulfonic acid, and polycarboxylic acid. As the lignin sulfonate, Chemical Admix
Pure lignosulphonate with properties close to the molecular weight distribution, such as the analytical values described on pages 5 to 9 of tures for concrete (MRRIXOM, E & F.N.Spon Ltd), is good.

The present invention will be described below with reference to examples of the present invention, but the present invention is not limited to these examples.

Example 1) Concrete mix and materials used 2) Test conditions A kneading test into concrete was conducted using various concrete admixtures shown in Table 2. The method of adding the concrete admixture and the method of kneading the concrete were performed by either of the following method 1 or method 2.

Method 1: Concrete admixture is dissolved in water in advance by kneading, and at 25 ° C, 40 l is kneaded in a gradient mixer.
The concrete shown in Table 1 was obtained, and the number of revolutions was further kept at 2 rpm for a predetermined time to measure the slump and the change with time in the air amount. Measurement of slump, air content, compressive strength, and sampling of strength specimens were all performed in accordance with JIS.

Method 2: The same as in Method 1 except that the concrete admixture was added at the same time as the mixing water.

3) Test results Test results are shown in Tables 3 and 4.

From the results shown in Tables 3 and 4, it is clear that the product of the present invention has an extremely excellent effect on the slump residual rate.

Claims (1)

[Claims] 1. The following (a) component and (b) component are contained as essential components, and the ratio of (a) component / (b) component is 90 / 10-9.
Concrete admixture characterized by being 9.8 / 0.2. Component (a) Naphthalenesulfonic acid formalin condensate or salt thereof (b) Component Polyoxyethylene having an average molecular weight of 80,000 or more