JPS6325251A - cement dispersant - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] interjection The present invention relates to cement dispersants.

Cement dispersants are added to improve the dispersibility of cement compounds such as cement paste, mortar, and concrete, and to reduce the moisture content of the compositions.

As such a cement dispersant, a naphthalene sulfonic acid formalin condensate has conventionally been used, but its effect has not yet been sufficient.

On the other hand, with changes in concrete aggregate conditions, the adverse effects of alkaline aggregate reactions have become a problem. When an alkaline aggregate reaction occurs, it expands and cracks occur after construction. In order to suppress the alkaline aggregate reaction, it is possible to use low-alkali cement or to limit the number of aggregates and use good aggregates. However, the use of alkaline cement increases costs, and good aggregates are becoming difficult to obtain, both of which are difficult to implement.

JP-A-60-235756 discloses a method for producing a calcium salt of an aromatic sulfonic acid formalin condensate since the amount of alkali metal in the cement dispersant may not be ignored in the alkali aggregate reaction. ing. However, as mentioned above, this type of cement dispersant does not have sufficient performance6. Furthermore, the use of polyethylene sulfonate or its copolymer as a cement dispersant is disclosed in Japanese Patent Application Laid-Open No. 51-525, No. 64527, No. 57-156355, and No. 60-46956, and a calcium salt is also indicated as one of the salts, but there is no description regarding the alkaline aggregate reaction. In addition, the above-mentioned Japanese Patent Application Laid-Open No. 51-525 states that when the degree of sulfonation of polystyrene sulfonate is low, it exhibits hydrophobicity and the initial dispersibility and strength enhancement effect become insufficient. It has been shown that it is desirable to substitute an average of 0.5 or more, preferably 0.7 or more, sulfonic acid groups per group. However, there is no suggestion of the effect of higher sulfonation rates.

The present invention provides a cement dispersant that is unlikely to cause an alkaline aggregate reaction and provides good dispersibility.

HighlightsThe cement dispersant of the present invention has a weight average molecular weight of 5,000.
~50,000, ooo, and is characterized by containing polystyrene sulfonate calcium salt with a sulfonation rate of 80% or more.

The weight average molecular weight of the polystyrene sulfonate calcium salt needs to be from s,ooo to sO,ooo. If the molecular weight is less than 5,000, the amount of adsorption is small, and if it is larger than 50,000, sufficient dispersion performance cannot be obtained in either case due to aggregation effect, and the sulfonation rate is low. It is necessary to set it to 80% or more. Initial dispersibility can only be achieved by increasing the sulfonation rate and introducing an average of 0.8 or more sulfonic acid groups per styrene nucleus.

The polystyrene sulfonate calcium salt of the present invention is produced by directly sulfonating it using a sulfonating agent such as sulfuric anhydride and fuming sulfuric acid by a conventional method, and then removing unreacted polystyrene from door to door and neutralizing it with slaked lime, calcium carbonate, etc. It can be obtained by removing by-product gypsum.

Unreacted polystyrene sulfonate calcium salt is added to cement mixtures such as cement paste, mortar, and concrete, and the amount thereof is 0.02 to 3.0 parts by weight, preferably 0.02 to 3.0 parts by weight per 100 parts by weight of cement. 0.
0.04 to 2.0 parts by weight is suitable. If the blending ratio is too small, initial dispersion performance cannot be obtained, while if it is too large, the cement will be extremely dispersed, causing a separation phenomenon, making it impossible to obtain the initial strength.

In the dispersant of the present invention, other known additives can also be used together with polystyrene sulfonate calcium salt. Examples of such additives include polyvinyl alcohol (Japanese Unexamined Patent Publication No. 57-20354), oligosaccharides (Japanese Unexamined Patent Publication No. 109522), reaction products of unsaturated dicarboxylic acids and alkenes (Japanese Unexamined Patent Application Publication No. 52-109522), Showa 55-95
No. 656).

The cement dispersant of the present invention may be added or blended into a cement mixture in any form such as solid, powder, or aqueous solution, and there is no particular restriction on the timing of addition, starting from the preparation stage of the cement mixture. It can be added at any time up to just before construction.

According to the present invention, by using a calcium salt of polystyrene sulfonic acid having a specific molecular weight and sulfonation rate as a cement dispersant, dispersibility is imparted to the cement mixture and an excellent water-reducing effect is achieved. This makes it possible to effectively prevent the occurrence of cracks and the like due to shrinkage. In addition, since the alkali aggregate reaction occurs and the mixture is dried, cracks due to expansion do not occur, and mortar and concrete with sufficient strength can be obtained. Therefore, the cement dispersant of the present invention is extremely useful in fields such as civil engineering and architecture, as well as in fields dealing with secondary concrete products.

Hereinafter, the effects of the present invention will be explained more specifically in Examples.

Calcium salt of polystyrene sulfone was placed in a four-piece separable flask with internal volume IQ.

Take 585g of dichloroethane and add 45g of polystyrene (
Weight average molecular weight: 5,500) was added and dissolved with stirring.

Next, 35 g of sulfuric anhydride was added dropwise while maintaining the reaction temperature at 25 to 30°C, and after the dropwise addition was completed, the mixture was stirred at the same temperature for 30 minutes. Thereafter, 320 g of water was added to extract polystyrene sulfonic acid and filtered. The P solution was carefully neutralized with 19 g of slaked lime, and the by-produced calcium sulfate was removed from door to door to obtain an aqueous solution of calcium salt of polystyrene sulfonic acid. The average molecular weight of the product was 10.000 as determined by GPC. Furthermore, the sulfonation rate was 80% as determined by 1H-NMR measurement.

Using calcium salts with different weight average molecular weights and sulfonation rates of polystyrene sulfonic acid, the water reduction rate and swelling amount were evaluated. In addition, sodium salts and conventional dispersants were also evaluated, and the above results are shown in Table 1 below.
It was shown to.

In the table, those with an x on the right shoulder of the material Nα are comparative examples, and the others are examples of the present invention.

The water reduction rate is concrete with a slump of 181 in accordance with JIS A-6204! It was made and evaluated.

The dispersant has a solid content of 0.3 based on the weight of cement.
% added.

The expansion rate was determined by testing the possibility of an alkaline-aggregate reaction occurring in accordance with ASTM C227, "Test Method for Potential Alkaline Reaction of Cement-Aggregate." In addition, in order to promote the alkaline aggregate reaction, a small amount of Bertin Opal, which is a reactive aggregate, was added. Further, the dispersant was added in an amount of 0.5% in terms of solid content based on the weight of cement. The composition is 1 part of ordinary Portland cement (Na, O: 0.6%), 2 parts of Fuji sand (specific gravity: 2.61), Bertin Opal (
The specific gravity is 2.61) 0.1 part, and the water is 0.45 part (0.55 part when no dispersant is added).

From Table 1, weight average molecular weight 5,000 to 50,000
, ooo, it can be seen that a remarkable water reduction rate is exhibited at a sulfonation rate of 80% or more. Furthermore, it can be seen that the product of the present invention has a clearly smaller expansion amount than the product containing an alkali metal, and is approximately equivalent to the product without the use of a dispersant.

(Margin below)

Claims (1)

[Claims] 1. A cement dispersant characterized by containing a polystyrene sulfonate calcium salt having a weight average molecular weight of 5,000 to 50,000 and a sulfonation rate of 80% or more.