Restrained Shrinkage of High Performance Concrete Comprising Silica Fume and Fly Ash

Abstract

High performance concrete (HPC) is stronger/more durable than conventional concrete and its popularity has been widespread over the recent past. The composition of HPC is unique, for instance, it comprises high paste/aggregate volume, supplementary cementitious materials, etc. Consequently, some HPC characteristics are distinguished to be stern and one of those is shrinkage. For instance, HPC structures that are subjected to restrained conditions could experience undesirable non-structural cracking. In this context, this study assessed the restrained shrinkage behaviour of five HPC mixes conforming to the ASTM C1581 procedure. The mixes were designed for 50 MPa target cylinder compressive strength and comprised supplementary cementitious materials (SCMs) of 0-10% silica fume (SF) and 0-30% fly ash (FA). The results showed that the control and 10%SF/30%FA mixes had comparatively lower cracking potential under restrained conditions whereas the highest cracking potential was with the 10%SF/0%FA and 10%SF/10%FA mixes. Hence, shrinkage exaggerated with the addition of SF whereas that undesirability was compensated with the addition of FA. Meanwhile, the compressive strength of the control mix was enhanced approximately by 48% with the inclusion of 10%SF whilst the FA inclusion to the 10%SF mix reduced the compressive strength fairly proportional to the FA content. Overall, the strength varied in the range of 49 – 73 MPa. Mix 10%SF/20%FA had 26.5% higher compressive strength than the control mix and showed low risk on restrained shrinkage cracking. Hence, it was identified as a promising HPC combination. Similarly, 10%SF/30FA mix showed similar strength and crack potential characteristics to the control mix. That mix was accordingly identified as an ideal sustainable concrete mix for highstrength concrete applications.