Shrinkage-cracking behavior of OPC-fiber concrete at early-age

The current paper presents the results of early-age restrained shrinkage (RS) tests on Ordinary Portland Cement (OPC) concretes incorporating admixed polypropylene fiber (PP). Four concrete mixtures made with OPC containing various volume fractions of PP fiber were tested. Two identical specimens of each mixture were tested: one subjected to fully restrained conditions and the other allowed to shrink freely, both under the drying conditions of 23°C and 50% relative humidity at the age of 24 h. Direct and indirect tensile tests were also performed in the same concretes to monitor the tensile strength development. With increasing fiber contents in mixture, the tensile strength, creep and elastic modulus characteristics have not significantly changed during the first week of age. Increasing the volume fractions of PP fiber significantly delayed the time of cracking owing to the delayed onset of RS, which is beneficial to crack resistance.