Rheological properties, strength characteristics and flexural performances of engineered cementitious composites incorporating synthetic wollastonite microfibers with two different high aspect ratios

In this study, synthetic wollastonite microfiber (SWM) with high aspect ratio (44:1/SWM-I) developed with a special technique was used in different proportions instead of cement (C), fly ash (FA) and cement + FA (C-FA) in Engineered Cementitious Composites (ECC). SWM-I decreased the workability as a result of interlocking during flow due to its acicular particle structure. When SWM-I was used instead of C, it was determined that the compressive strength decreased and the ductility improved significantly due to the increased SWM-I content. The use of SWM-I instead of FA improved the mechanical performance up to 6% in terms of compressive strength and flexural performance. However, the mixtures prepared by using SWM-I instead of C-FA provided optimum data, considering both ''increasing deformation capacity'' and ''maintaining the bearing strength by fiber bridging after crack''. Therefore, the effect of SWM-II (30:1) was tested by using instead of C-FA. SWM-I with a higher aspect ratio has been improved the mechanical properties of ECC and reduced the workability of ECC more than that of SWM-II. Increasing FA content in ECC has been provided higher ductility but decreased significantly the compressive strength. The bearing strength and deformation capacity of the ECC designed with finer aggregate has been achieved the higher levels compared to larger aggregate size. As a result of all obtained findings, the data of the optimum mixture has been determined as follows: the compressive strength, flexural strength and ductility of ECC incorporating 6% SWM-I instead of C-FA have been reached higher levels than that of 19.0%12.5%, 12.0%-8.2% and 56.2%-25.5% at 7-28 days, respectively.