JP2008184344A - Segregation-resistant cement admixture - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly segregation-resistant concrete admixture or mortar admixture added to produce high-fluidity self-compacting concrete or mortar. <P>SOLUTION: The cement admixture is one wherein, when a polysaccharide gum and a cement water reducing agent are used in order to obtain high-fluidity concrete or mortar, the polysaccharide gum is completely dissolved in a solution of the cement reducing agent. Its production method comprises adding a small amount of water or the solution of the water-reducing agent to the polysaccharide gum to knead the resulting mixture into a somewhat hard paste, agitating the paste while adding the solution of the water reducing agent thereto little by little to perfectly dissolve the polysaccharide gum in the cement reducing agent while keeping the water absorptivity of all the polysaccharide gum molecules uniform. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cement admixture excellent in separation resistance, which is added to produce a highly fluid self-compacting concrete or mortar, and further relates to a method for producing the admixture.

High-fluidity concrete, such as self-filling concrete, is prone to material separation and fluidity fluctuations when there is a change in the aggregate surface water ratio or when the amount of powder used is small. It was. In order to solve this problem, separation reducing agents and thickeners are used.
In general, separation reducing agents and thickeners are often powders and are manually added to the mixer. Therefore, it has been difficult to evenly disperse a small amount of additives. Moreover, since it had to be added separately from other concrete admixtures, operation became complicated.

  Patent Document 1 discloses a one-component concrete admixture in which welan gum is blended with a polycarboxylic acid cement admixture. According to this document, 0.1-1% by weight of welan gum is added to and dispersed in a high-performance water reducing agent solution and used as a one-component admixture with a viscosity of 100-200 cps that exhibits good fluidity. In this case, it is described that welan gum swells but does not completely dissolve.

  In Patent Document 2, PVA (usually called vinylon fiber) is blended at a blending amount of more than 1 to 3 vol%, and a biosaccharide thickener excluding welan gum is added to reduce shrinkage and self-filling properties. A strain-hardening cementitious composite material is disclosed. Further, in Patent Document 3, a fine powder polysaccharide (Dutan gum) having characteristics unique to S-657 effectively improves the rheological properties of the cement system and is used for self-filling grouts and the like. It is disclosed.

However, neither Patent Document 2 nor Patent Document 3 teaches that it is completely dissolved in a cement admixture solution. The present inventors have confirmed that these polysaccharide gums are not completely dissolved only by being dispersed in water. Further, these polysaccharide gums do not exhibit a sufficient effect in a state where they are not completely dissolved.
JP 2000-19518 A JP 2005-1965 A Special Table 2000-502314 US Pat. No. 5,175,278

  The present invention provides a cement admixture having sufficient separation resistance by fully expressing the separation reducing power inherent in polysaccharide gum and blended with concrete and mortar together with other cement admixtures. That is, it aims at providing the cement admixture which stabilizes the physical property of highly fluid concrete and highly fluid mortar, and has separation resistance.

  The composition of the present invention is characterized in that the polysaccharide gum is completely dissolved in the cement water reducing agent solution when using the polysaccharide gum and the cement water reducing agent in order to obtain a high fluidity concrete or mortar. Add a small amount of water or a water reducing agent solution to the polysaccharide gum, knead it into a hard paste, then stir while adding the water reducing agent solution little by little, while keeping the water absorption rate of all polysaccharide gum molecules evenly, It is characterized by being completely dissolved in a cement water reducing agent.

  In the present invention, the polysaccharide gum is kneaded into a hard paste using a small amount of moisture, and the entire polysaccharide gum is uniformly brought into an extremely initial swelling state. After that, it was found that the polysaccharide gum was completely dissolved in water without being damped by adding water little by little. Here, “dama” is a state in which the powder is gathered as a lump in the form of a powder or in a slightly swollen state, and its surroundings are covered with a sufficiently swollen powder, so that the substance inside does not dissolve stably in water. It is.

  According to the present invention in which the polysaccharide gum is completely dissolved in the water reducing agent solution, the separation resistance of the polysaccharide gum is sufficiently developed, and the characteristics that tend to separate the self-filling high-fluidity concrete and mortar are eliminated. Stable high-fluidity concrete can be provided. Furthermore, since the entire polysaccharide gum is moistened with the water of the water reducing agent solution and dissolved while supplying moisture evenly to all the polysaccharide gums, it was possible to completely dissolve the polysaccharide gum.

Examples of the water reducing agent of the present invention include polycarboxylic acid-based water reducing agents, naphthalene sulfonic acid-based water reducing agents, melamine sulfonic acid-based water reducing agents, aminosulfonic acid-based water reducing agents, and lignin sulfonic acid-based water reducing agents. Of these, polycarboxylic acid-based water reducing agents are preferred. The polycarboxylic acid water reducing agent is a carboxylic acid having a polyoxyethylene group or a salt thereof, and various compounds preferable for use in mortar and concrete are provided. The concentration of the polycarboxylic acid is 10 to 30% by weight, preferably 15 to 25% by weight. If it is less than 10%, the amount added to the cement increases, which affects the blending ratio of concrete and mortar. If it exceeds 30% by weight, the viscosity generally increases and it becomes difficult to handle.

  A cement admixture obtained by dissolving 0.05 to 2.0% by weight, preferably 0.10 to 1.0% of polysaccharide gum, in the liquid admixture of the polycarboxylic acid. When the polysaccharide gum concentration is 0.05% or less, sufficient separation resistance is not exhibited, and when it exceeds 2.0%, the viscosity is excessively increased, which may cause trouble in handling.

  Examples of polysaccharide gums include dutan gum, welan gum, guar gum, gellan gum, tamarind gum, locust bean gum, xanthan gum and the like. Among them, bio gums such as dutan gum and welan gum are preferable, and detan gum is particularly preferable.

  Dutan gum is a product produced by microorganisms described in detail in Patent Document 4, S-657. S-657 is a microbial polysaccharide produced by the organism Xanthomonas ATCC 53159 under carefully controlled aerobic fermentation conditions. Its structure consists of repeating units of linear tetrasaccharides of D-glucose, D-glucuronic acid, D-glucose and L-rhamnose.

The polysaccharide gum is moistened with a small amount of an aqueous solution of 10-30% by weight of a water reducing agent. Stir well to allow the wettability to spread throughout the polysaccharide gum, making it a slightly stiff paste-like mass. At this point, all polysaccharide gums are in a very early swollen state. Next, the mixture is thoroughly mixed while adding a small amount of a water reducing agent solution, and the whole polysaccharide gum is always thinned so as to maintain a uniform swelling state.
Since these polysaccharide gums have a remarkable swelling property, when part of them swells, they tend to absorb water prior to other parts and not swell other parts. These polysaccharides dissolve after passing through a swollen state. Therefore, it is important for complete dissolution that all gum powders are swollen evenly.

Dutan gum (manufactured by Sanki Co., Ltd.) was used as the polysaccharide gum, and Super 200 (trade name, manufactured by Grace Chemicals, polycarboxylic acid-based water reducing agent) was used as the water reducing agent.
200 g of Super 200 was dissolved in water to make a total volume of 1000 ml. 1000 ml of 20% aqueous solution of Super 200 and 4 g of dutan gum were prepared. A small amount of Super200 aqueous solution was added to the total amount of Dutantham and kneaded to obtain a hard paste. Thereafter, the super 200 aqueous solution was added little by little, and the dutan gum was diluted while uniformly kneaded to produce a water reducing agent containing completely dissolved dutan gum. The one-component separation-resistant cement admixture thus obtained was used as an experiment No. Table 1 shows the concentration of Super 200, the concentration of Dutan gum, the viscosity of the admixture aqueous solution, and the state thereof.

  Experiment No. 1-5 and Experiment No. 7-9, except that the solid content concentration of the super 200 and the solid content concentration of the dutan gum were varied as shown in Table 1. In the same manner as in No. 5, a Dutan gum completely dissolved super 200 aqueous solution was produced, and its viscosity and state were observed and are also shown in Table 1.

  As Comparative Example 1, the usage amounts of Super 200 and Dutan gum were the same as those in Experiment No. In the same manner as in 5, all of Super 200 and Dutan gum were blended, and the mixer was vigorously rotated and mixed. The obtained one-component separation-resistant cement admixture is such that after 1 day, a lump covered with fully swollen dutan gum floats up, and the miso soup standing at the bottom settles down. The fluffy material settled. The results are also shown in Table 1.

  As Comparative Example 2, the usage amount of Super 200 and Dutan gum was set as Experiment No. Same as 5. The whole amount of detan gum was stirred and mixed with a small amount of Super 200 aqueous solution, and the whole amount of the remaining Super 200 was added and mixed. At first glance, a one-component type separation-resistant cement admixture that seemed to be completely dissolved in dutan gum but did not completely dissolve was obtained. The cement admixture initially seemed stable, but after 5 days a hazy sediment also formed in the lower part. The results are also shown in Table 1.

From Table 1, the viscosity of deuteron gum does not increase linearly with increasing water reducing agent concentration or with increasing concentration of detan gum itself. It can go down.
Experiment No. shown in Table 1 5 and the cement admixtures of Comparative Example 1 and Comparative Example 2 were used to prepare mortar. As the cement, three equivalent mixed cements made by Taiheiyo Cement, Ube Mitsubishi Cement, and Sumitomo Osaka Cement were used. As the sand, land sand from Oigawa was used. High-fluidity mortar was manufactured with the formulation shown in Table 2.

  Furthermore, a mortar to which only super 200 was added without adding dutan gum was also prepared. The mortar flow of the obtained high fluidity mortar was measured, and the stability was judged from the appearance. Separation is a state in which a water layer appears to be formed on the top surface of the mortar, and further, fine sand is sinking to the bottom.

  From the above table, by completely dissolving the polysaccharide gum in the water reducing agent solution, the characteristics possessed by the polysaccharide gum were fully expressed, and the present invention succeeded for the first time in providing an excellent separation-resistant cement admixture.

Claims (6)

In using polysaccharide gum and cement water reducing agent to obtain high fluid concrete or mortar,
Separation resistant cement admixture characterized in that polysaccharide gum is completely dissolved in a cement water reducing agent solution. The separation resistant cement admixture according to claim 1, wherein the polysaccharide gum is at least one selected from the group consisting of dutan gum, welan gum, guar gum, tamarind gum, locust bean gum and xanthan gum. 3. The separation resistant cement admixture according to claim 2, wherein the polysaccharide gum is detan gum. The separation-resistant cement admixture according to any one of claims 1 to 3, wherein the cement water-reducing agent is a polycarboxylic acid-based cement water-reducing agent. 5. The solid content concentration of the cement water reducing agent is 10 to 30% by weight, and the solid content concentration of the polysaccharide gum is 0.05 to 2.0% by weight. Separation-resistant cement admixture described in 1. Add a small amount of water or cement water reducing agent solution to polysaccharide gum, knead it into a hard paste, and then stir while adding small amount of cement water reducing agent solution while keeping the water absorption rate of all polysaccharide gum molecules equal. A process for producing a separation resistant cement admixture characterized by being completely dissolved in a cement water reducing agent.