JPH0832580B2 - Admixture for cement - Google Patents

Description

TECHNICAL FIELD The present invention relates to an admixture for cement, and more specifically to an admixture for cement obtained by incorporating a dispersant for cement in an organic hydrogel.

(Prior Art) Generally, when producing concrete, mortar, paste and the like using cement, a dispersant for cement called a water reducing agent, a high performance water reducing agent or a fluidizing agent is used. Since this dispersant can greatly reduce the amount of water used,
It is used for high-strength concrete, fluidized concrete, etc. because it gives a hardened product with high strength and can obtain sufficient workability even if the amount of water used is reduced.

However, the cement composition in which the dispersant is kneaded exhibits excellent fluidity immediately after kneading, but the initial maintainability of the consistency is poor, and the fluidity of the cement composition decreases rapidly with the passage of time. Have. This decrease in fluidity is called slump loss, and for this reason, when manufacturing fluidized concrete, a method is used in which a dispersant is added at the casting site to raise the slump to a specified value and then immediately poured. , And the personnel for the equipment and quality control for that are necessary.

Also, after the dispersant is added to the truck agitator, it is necessary to stir and mix the drum of the truck agitator at medium speed or high speed, which causes noise and exhaust gas, which is a problem for the health of local residents and field workers in urban areas. Becomes

Several methods have been proposed for such problems. For example, (1) a method in which the dispersant is dividedly added several times (JP-B-51-19856), (2) a method in which a retarder is used in combination, (3) a method in which the dispersant is added in a granular form (special Kaisho
54-139929 and 60-221354), but the method (1) may complicate the work and is not practical, and the method (2) sufficiently prevents slump loss. The effect is not obtained, and the method (3) requires a granulation operation, which is disadvantageous in terms of cost and has a drawback that undissolved dispersant remains and localized breathing occurs. Was there.

(Problems to be solved by the invention) Therefore, as a result of intensive studies to solve the above-mentioned drawbacks, the present inventors have found that when a dispersant is contained in an organic hydrogel, a decrease in fluidity due to a slump loss is prevented and a constant value is obtained. It was found that the fluidity of the above can be maintained, and the present invention has been completed based on this finding.

(Means for Solving the Problems) Thus, according to the present invention, there is provided a cement admixture characterized by containing a dispersant for cement in an organic hydrogel.

The cement admixture of the present invention comprises an organic hydrogel containing a cement dispersant.

Specific examples of such a hydrous gel include starch-
Acrylonitrile graft copolymer system, carboxymethyl cellulose system, polyacrylonitrile system, polyethylene oxide system, vinyl acetate-acrylate copolymer system, vinyl alcohol-acrylate copolymer system, polyacrylate system, olefin-maleic anhydride copolymer In the presence of an aqueous dispersant solution such as a hydrogel obtained by absorbing an aqueous dispersant solution into a super absorbent polymer such as a polymer system, or a polycarboxylic acid salt such as a polyacrylic acid salt or an olefin-maleic anhydride copolymer salt. Examples thereof include hydrogels obtained by reacting with a crosslinking agent.

The types of the above-mentioned superabsorbent polymer and polycarboxylic acid are not particularly limited, and any commercially available one can be used.

The amount of dispersant and water contained in the organic hydrogel is not particularly limited, with respect to the superabsorbent polymer and polycarboxylic acid, usually 1 to 20 times the solid content, 1 to 40 times the amount of water.
It is 0 times.

The organic hydrogel has a granular shape, a plate shape, a rod shape or the like, and is not particularly limited depending on the method of use, but it is preferably used as a granular gel in terms of ease of mixing.

Water to be used is not particularly limited, but tap water, ground water, etc. are usually used.

The dispersant for cement used in the present invention may be any as long as it is generally used as a dispersant for cement, and specific examples thereof include a resin acid salt, a lignin sulfonate, an oxycarboxylic acid salt, and a polyol complex,
Melamine sulfonic acid formalin condensate or salt thereof, creosote oil sulfonic acid formalin condensate or salt thereof, naphthalene sulfonic acid formalin condensate or salt thereof, polycarboxylic acid or salt thereof (AE) water reducing agent, superplasticizer or A high performance water reducing agent is exemplified.

Above all, when a fluidizing agent or a high-performance water reducing agent is used, the effect of the present invention for preventing slump loss is remarkable.

Mighty FD is a typical commercial fluidizer.
(Manufactured by Kao), NP-10, NP-20 (manufactured by Nisso Master Builders), Work 500 (manufactured by Zeon Corporation), Sunflow FBF
(Made by Sanyo Kokusaku Pulp Co., Ltd.) and the like. A high-performance water-reducing agent has a high water-reducing function and can usually reduce about 20 to 30% of kneading water. Typical commercially available products thereof are Mighty 150 (manufactured by Kao Corporation) and Mailment F-10.
(Manufactured by Showa Denko KK), M-10 (manufactured by Zeon Corporation) and the like.

In the present invention, the mixing amount of the organic hydrogel is an amount capable of supplying the required amount of the dispersant.

The amount of the dispersant used is appropriately selected depending on the type of the dispersant and the required performance of the target product, but is usually 0.01 to 5% by weight, preferably 0.02 to 3% by weight based on the solid content of the cement. Used in proportion.

The type of cement to which the admixture for cement of the present invention can be applied is not particularly limited. As a specific example, for example,
Normal Portland cement, early strength Portland cement, moderate heat Portland cement, alumina cement,
Examples include fly ash cement, blast furnace cement, silica cement, various mixed cements, and slag cement.

The timing of addition to the cement mixture can be appropriately selected depending on the purpose of use. For example, a method of adding to the cement in advance, a method of adding the compound after kneading the compound in advance, and the like can be mentioned. Although the cement admixture of the present invention may be used alone, it is generally used in combination with another aqueous dispersant solution.

The hydrous gel thus added can gradually release the contained dispersant by the calcium hydroxide in the cement and maintain a certain fluidity. The release rate can be controlled by changing the water absorption capacity of the dispersant solution contained in the hydrogel.

(Effects of the Invention) Thus, according to the present invention, it is possible to obtain a cement composition having less slump loss and good fluidity as compared with the prior art.

(Example) Hereinafter, the present invention will be described more specifically with reference to Examples. In addition, parts and% in the examples, comparative examples and reference examples are based on weight unless otherwise specified.

Reference Example 1 Various dispersant solutions shown in Table 1 were made to absorb water in a super absorbent resin to obtain organic hydrogels (I) to (VIII).

Example 1 The performance of the organic hydrogels (I) to (VIII) obtained in Reference Example 1 as an admixture for cement was evaluated according to the following concrete test conditions.

The following components were weighed and kneaded to a kneading amount of 40 l, and kneaded with a tilting mixer having a capacity of 50 l for 3 minutes. After that, the number of revolutions of the mixer was set to 2 rpm, and the slump value after a certain period of time was measured according to JIS A1101.

 The results are shown in Table 2.

Mixtures of concrete Cement: Mixed three brands of ordinary Portland cement Fine aggregate: River sand from Oigawa, specific gravity 2.61 Coarse aggregate: Crushed stone from Ome, specific gravity 2.64 Admixture: Hydrogel (I) to (VIII) Dispersant: Table 2 As shown in From Table 3, it can be seen that the slump loss can be greatly reduced in the example of the present invention.

Claims (1)

[Claims] 1. An admixture for cement, which comprises an organic hydrogel containing a dispersant for cement.