Effect of silica fume type, mixing sequence, and curing regime on workability and compressive strength of UHPC Available to Purchase

The impacts of silica fume (SF) type, mixing sequence, and mixing time on the workability and compressive strength of ultra-high-performance concrete (UHPC) were examined. The effects of demolding time and curing regimes on the compressive strength and microstructure of UHPC were also investigated. The results indicated that undensified SF was more effective than densified SF in enhancing the workability and strength of UHPC. The mixing sequence and mixing time also influenced concrete workability and strength development. From the results of this work, it was concluded that incorporating SF in slurry form at the beginning and adding high-range water reducer in a single dosage with mixing water is more beneficial for achieving a homogenous UHPC mix. The preferable concrete demolding time is after 24 h. Any delay in demolding time for concrete made with a very low water/binder ratio may cause a reduction in strength development owing to insufficient hydration and the formation of shrinkage cracking. Water curing at 60°C was found to be more favorable for compressive strength development than water curing at 28°C and jute bag curing for up to 56 days. After 56 days, there was no significant variation in compressive strength of all the specimens subjected to different curing regimes.