DETAILED DESCRIPTION OF THE INVENTION In the segregation reducing agent for a hydraulic composition of the present invention, the thickener on the surface of the powder particles dissolves in, for example, concrete to give the concrete high resistance to segregation.
Further, the particles of the core swell in the concrete to form calcium gel particles.
Thus, the segregation reducing agent gives the concrete high fluidity and high filling ability based on the bearing effect of the calcium gel particles.
The .
beta.
-1,3-glucan is a polysaccharide composed of glucoses which are primarily bonded through .
beta.
-1,3-glycosidic linkages.
Specific examples thereof are curdlan, paramylon, pachyman and the like.
In this invention, curdlan is especially preferred.
Curdlan is a polysaccharide primarily composed of .
beta.
-1,3-glucose joined to each other through .
beta.
-1,3-glycosidic linkages, and is generally thermo-gelable, namely gelable on heating in the presence of water, as described in vol.
20, No.
10, pp.
49-57 (1978) in New Food Industry.
Any microorganism can be used in the present invention so long as it is capable of producing .
beta.
-1,3-glucan.
When the .
beta.
-1,3-glucan is curdlan, examples of the microorganism include microorganisms belonging to the genus Alcaligenes, microorganisms belonging to the genus Agrobacterium and the like.
As examples of the microorganisms belonging to the genus Alcaligenes, there are Alcaligenes faecalis var.
myxogenes 10C3K [Agricultural Biological Chemistry, Vol.
30, p.
196 (1966)], a mutant NTK-u (IFO-13140) of Alcaligenes faecalis var.
myxogenes 10C3K (JP-B 48-32673, U.
S.
Pat.
No.
3,754,925) and the like.
As examples of the microorganisms belonging to the genus Agrobacterium, there are Agrobacterium radiobacter (IFO 13127) and its mutant U-19 (IFO-13126) (JP-B 48-44866) and the like.
When the .
beta.
-1,3-glucan is paramylon, examples of the microorganisms to be used in the invention include microorganisms belonging to the genus Euglena.
Specific examples thereof include Euglena gracilis Klebs NIES-47, Euglena gracilis Klebs NIES-48, Euglena gracilis var
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Molecular Biology 
