MEASURING EARLY AGE DIFFERENTIAL SHRINKAGE OF HIGH PERFORMANCE CEMENTITIOUS MATERIALS

摘要

Over the last several decades, advances in concrete technology have led to the use of many high performance cementitious materials. One of the major concerns in the use of such materials has been with durability issues. The importance of early age shrinkage as one of the key durability parameters has been recognized and studies have shown the potential for such shrinkage to lead to undesirable cracking. This paper presents the results of part of an experimental study using the image analysis technique to monitor early age shrinkage strains at various depths from the exposed surface (i.e. early age differential shrinkage) of high performance cementitious materials exposed in a controlled environment (RH of 65% and Temp of 30℃). Shrinkage monitoring was initiated 30 mins after adding water to the mix. A comparison with the sealed companion specimens was also carried out. This paper also deals with the effects of initial measurement time, "the time zero value", used on the shrinkage strains monitored. The results show that the early age differential shrinkage strain values differ significantly and vary according to the depth from exposed surface. The selection of the time to initiate measurement of the strains affects significantly the early age shrinkage strains when plotted against time during the first 24 hours after adding water to the mix.