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.