Linking stability characteristics to material performance of self-consolidating concrete-equivalent-mortar incorporating fly ash and metakaolin

Abstract

Properly designed self-consolidating concrete (SCC) should have high deformability while maintaining high stability to secure homogeneous properties of hardened concrete. This paper aims at correlating the stability characteristics to material performance of self-consolidating concrete-equivalent-mortars (SCCEMs) made with various binary and ternary cement blends of fly ash (FA) and metakaolin (MK). The stability characteristics of the mixtures were determined using mini-column segregation, mini V-funnel flow time, visual stability index (VSI), and hardened visual stability index (HVSI) to assess both static and dynamic stability. A response surface method (RSM) was conducted to mathematically evaluate the level of significance of mixture parameters and their coupled interactions on the performance of SCCEMs. Trade-off contour diagrams between investigated mixture constituents and the modeled responses were illustrated.Test results indicate that binder composition have substantial influence on dynamic and static stability. Based on the established correlation between stability and overall performance, SCCEMs with a higher segregation index (SI) values are expected to have lower fresh and hardened properties. A ternary combination of 25% FA and 25% MK with a SI value of 5 achieved the highest overall material performance among the tested binary and ternary cementitious systems. The slump flow and V-funnel flow time tests are shown to be an efficient tool for controlling static segregation of mixtures. Mixtures with higher level of fluidity and lower flow time exhibited lower segregation resistance.