RSM ANALYSIS AND STUDY ON THE 6 MONTHS COMPRESSIVE STRENGTH DEVELOPMENT AND SHRINKAGE BEHAVIOUR OF HIGH VOLUME FLY ASH RUBBERIZED ECC (HVFA-RECC)

The use of Crumb rubber (CR) and High Volume Fly Ash (HVFA) has been shown to enhance the ductility behavior of Engineered cementitious composite (ECC). However, the strength of the composite is known to be negatively affected by CR inclusion as well as the HVFA. Most research on these materials usually focus on the 28 days compressive strength development with very few that considered up to 90 days. No research has so far investigated the combined effect of HVFA and CR on the compressive strength development and shrinkage behavior of ECC beyond 90 days of curing. This paper is aimed at filling this gap by investigating this at 180 days (6 months) curing duration while adopting the RSM design and analysis approach. Result showed that HVFA affects the early strength development of RECC but proves beneficial at later days due to secondary hydration. The highest rate of development in compressive strength of 172% was recorded for a sample with 70% FA. Although the amount of CR negatively affects the strength and drying shrinkage of the composite, it plays no role in the rate of strength development. Response surface models were successfully developed and validated using the analysis of variance (ANOVA).