Development of Sustainable High-Strength Self-Consolidating Concrete Utilising Fly Ash, Shale Ash and Microsilica

Abstract

With high flowability and passing ability, self-consolidating concrete (SCC) does not require compaction during casting and can improve constructability. The favourable properties of SCC have enabled its widespread adoption in many parts of the world. However, there are two major issues associated with the SCC mixes commonly used in practice. First, the cement content is usually at the high side. Since the production of cement involves cal- cination at high temperature and is an energy-intensive process, the high cement content imparts high embodied energy and carbon footprint to the SCC mixes. Besides, the exo- thermic reaction of cement hydration would cause high heat generation and early thermal cracking problem that would impair structural integrity and necessitate repair. Second, the strength is usually limited to around grade 60, which is considered as medium strength in nowadays achievable norm. With a view to develop sustainable high-strength self-consoli- dating concrete (HS-SCC), experimental research utilising fly ash (FA), shale ash (SA), and microsilica (MS) in the production of SCC has been conducted, as reported herein. by adopting low W/CM ratios through the use of polycarboxylate-ether-based superplasticiser (SP). A series of 12 SCC mixes incorporating FA, SA and MS have been produced for laboratory testing. From the experimental results, all the concrete mixes have the required workability and flowability of self-consolidating. The flow values have satisfied the respective ranges of slump-flow classes SF1, SF2 or SF3 according to the European guidelines for SCC, there has been no problem of segregation instability as revealed from visual observations. mean 28-day compressive cube strengths of the SCC the range from 80.2 to 108.5 MPa, could grade C70 to C90. (EE) For comparison on at so concurrent improvement in and by and demonstrated, by more achieved. Overall the results have concluded successful development sustainable HS-SCC superior compared mix