On the early Volume Change of Concrete after Placing

The Authors measured the early volume changes of concretes which were placed under least friction in the moulds by own method and by devided rapid exact method, and obtained following results. 1) In the cases of Portland Cement of normal properties, the settling amount up to 10 minutes after placing of concrete indicates increased values from 40×10-4 to 100×104 (cowpared with initial unit length) as increasing W/C and slump values. Then the volume change stops for a short time and after 1-2 hours from initial placing, shrinkage due to cement paste in concrete of the order (3-1)×10-4 reciprocal to W/C and to settling amount, appears. 2) Abnormal Portland Cements which showed the tendency of early craking at concrete building jobs, showed the abnormal settling in above described apparatus in laboratory continued till 60 minutes after placing of test concrete, and large shrinkage followed the rest period.