Abstract
Usually shrikage cracks occur in the restricted rich-mixed cement mortar under drying condition. In this paper, a new loading apparatus for the measurment of shrinkage is described, and the results of tests using this apparatus, with seven diferent types of cements are presented. According to the results, in each mortar under the restricted condition, shrinkage tesile-stress increases with lapse of time curring in the air. This stress-time curve shows a steep initial slope, and when the stress attains the mortar tensile strength the rupture occurs in the specimen. The time elapsed until the occurrance of the crack is four days in minnimum, and eleventh days in maximnm. On the other hand, according to the observed results of this experiment maximum free shrinkage strain is about 4 or 5×10^<-4> and the strain caused by shrinkage stress is about 1.3 or 1.6×10^<-4> at the crack point, so that, from the deduction of the each above value, we can obtain the creep-strain 2.7 or 3.4×10^<-4>. However, it may be given as a conclusion that, referring to the shrinkage crack, the value of free shrinkage-strain is significant.
