Benefits of using expansive and shrinkage-reducing agents in UHPC for volume stability

This study investigated the effects of expansive agent (EA) and shrinkage-reducing agent (SRA) on the mechanical and shrinkage properties of ultra-high-performance concrete. Along with a reference specimen, the work considered five different specimens with different ratios of SRA (1% and 2%), EA (5% and 7.5%) and a combination of 1% SRA and 7.5% EA. The test results revealed that compressive strength varied with the inclusion of SRA and EA, while tensile strength decreased according to the admixing of SRA and EA. The free shrinkage strain was obviously reduced by including SRA and EA, and the specimen with 7.5% EA showed the lowest shrinkage strain. The inner steel strain was also decreased by incorporating SRA and EA, and the specimen with a combination of 1% SRA and 7.5% EA exhibited the smallest strain even though it showed a larger free shrinkage strain than the specimen with 7.5% EA. Furthermore, the specimens with EA exhibited a decrease in steel strain after nearly 10 d due to the tensile creep effect.