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.This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (no. 2012R1A2A1A05026406) and carried out as a partial research of the ‘‘Development of Ultra High Performance Concrete for Hybrid Cable Stayed Bridges’’ in the Korea Institute of Construction Technology