Experimental and analytical studies on shrinkage and creep behavior of RC walls and prisms

A component level experimental study has been carried out on four reinforced concrete (RC) walls subjected to a sustained compressive load for a period of 1 year and shrinkage tests on 10 prisms under ambient environmental conditions. Two extreme longitudinal reinforcement percentages and two grades of concrete were considered and their influence on the time-dependent behavior studied. It was observed that both longitudinal percentage of steel and concrete grade have a significant influence on the time-dependent strains. The evolution of time-dependent strain in RC member was also predicted, adequately accounting for the effect of reinforcement, using a theoretical model which can employ any linear viscoelastic constitutive law for concrete and a linear elastic constitutive law for reinforcing steel. The ACI 209 and fib MC 10 recommendations for creep and shrinkage of plain concrete have been used for the prediction of long-term strains. It is demonstrated that the analysis predicts the time-dependent strains reasonably well (with a statistical mean deviation error of 1.16 and 1.00) for the creep tests on RC walls, when the compliance function proposed by ACI and fib is used. However, in the case of shrinkage tests, the accuracy with both ACI and fib models was limited (1.64 and 1.66, respectively). It is further demonstrated that by suitably recalibrating the compliance and shrinkage parameters in both ACI and fib models, the accuracy of shrinkage prediction in the companion RC specimens improves significantly with mean deviation error of 1.07 and 1.05 for ACI and fib models, respectively.