PRODUCTION OF UNCALCINED AGGREGATE

摘要

PROBLEM TO BE SOLVED: To obtain a concrete reduced in drying shrinkage by adding water to a powder consisting essentially of coal ash, compacting the admixture and boiling the steam-cured aggregate. SOLUTION: A raw powder consisting essentially of coal ash and blended with a cement powder (e.g. ordinary Portland cement) and various additives such as silica fumes and gypsum, as required, is mixed with an appropriate amt. of water (ordinarily, 10-40wt.%) and compacted. The obtained compact is steam-cured at 60-80 deg.C for 3-20hr. and then boiled. In this case, the steam- cured and sufficiently hardened aggregate is placed in boiling water and boiled for 0.5-10hr. An aggregate with the void of the pores having <=75nm radius decreased to <=120mm<3> /g is obtained by the boiling. Ordinarily, the void of the pores having <=75nm radius is >=150mm<3> /g in the case of an unboiled uncalcined aggregate. The grain size is controlled by the conventional method after boiling to obtain a product. The boiling can be performed after grain size control.