Combined effect of expansive and shrinkage-reducing admixtures on the properties of ultra high performance fiber-reinforced concrete

In order to investigate the combined effect of expansive and shrinkage-reducing admixtures on shrinkage and mechanical properties of ultra high performance fiber-reinforced concrete, a series of experiments including three types of shrinkage tests, compressive and flexural tests, and penetration-resistance test were performed. Test results showed that about 51-53% of free shrinkage and 35-49% of restrained steel strains were reduced by adding 1% shrinkage-reducing admixture along with 7.5% expansive admixture with slight change of strength. Elastic stress, residual interface pressure and degree of restraint from ring specimens were also significantly reduced by using expansive and shrinkage-reducing admixtures. Although the elastic stress of the ring specimen without expansive and shrinkage-reducing admixtures was higher than the tensile strength, no shrinkage crack was observed for all test specimens due to the relaxation effect.