Development of flaw tolerant fiber reinforced cementitious composites with calcined kaolin

Abstract Flaws naturally occur in the structure of the cementitious composites or concrete. When brittle composites (ceramics, concrete) are loaded up to their ultimate capacity, micro-cracks initiate and propagate from these flaws in a sudden manner. As an exception, Engineered Cementitious Composite (ECC) surprisingly has an ability to transform its flaw structure into an advantage by exhibiting multiple cracking behavior with improved mechanical properties. On the other hand, presence of polymeric fibers in ECC design can rise some challenging situations such as workability and fiber distribution. Both flaw structure and workability of ECC can be improved by using inert and pozzolanic powders in matrix phase. In this study, five sets of composites were prepared at three different water to cement and fine material to cement ratios by using high tenacity polypropylene fibers (HTPP). Calcined kaolin was used for the first time in order to improve fresh state properties and fiber distribution performance of composites. The flaw tolerances of composites were studied by adding polyethylene beads (diameter of 3 mm by 6% of total volume) as artificial flaws into matrix. Results showed that, flaw tolerant ECCs exhibiting saturated multiple cracking with a flexural strength of 10.9 MPa and a deflection capacity of 13.2 mm can be prepared successfully by using HTPP fibers and calcined kaolin.