Variability of Creep and Shrinkage of Concrete

So far only few reports on the variability of creep and shrinkage have been published. In many practical cases, however, it is necessary to know the probability of occurence of extreme values. Therefore four different test series, each consisting of indentical concrete specimens with a given mix proportion, have been prepared. Shrinkage and creep have been measured for 300 days. For the creep experiments a load of 20% and 40% of the corresponding prism strength has been applied. In each test series between four and eight identical specimens have been tested. Experimental results have been evaluated statistically. For shrinkage a coefficient of variation in the range of 0, 07 and 0, 14 was found. For the total time-dependent deformation (creep plus shrinkage) the coefficient of variation after 300 days of loading was found to be between 0, 05 and 0, 10. Creep recovery was measured for 28 days.