STUDY ON THE BLOCKGE IN CONCRETE PUMPING WITH PRECEDING MORTARS

摘要

Before concrete pumping, a special mortar premixedwith cement, fine aggregate and chemical admixture wasapplied as a preceding mortar. Excessively long-termpumping, however, caused blockage for which possiblemechanisms were investigated. As a result, followings were found.(1)The pumped concrete preceded the preceding mortar andseparated into cement paste and aggregates which formed amajor part of the blockage.(2)Coarse aggregate content in the blockage was 3 to 6percentlarger than the designed mixture proportion.(3)When the special preceding mortar was used, degradation ofpumped concrete quality was not found even near the blockage.