Combined effect of Polypropylene fibers and Silica Fume to improve the durability of concrete with natural Pozzolans blended cement

Early age shrinkage and cracking, water permeability and carbonation depth of concretes with natural Pozzolans blended cement (NPC) were investigated in order to assess the combined effect of Polypropylene short fibers (PPF) and Silica Fume (SF) on some durability parameters. The addition of 10% of SF increased compressive strength, shrinkage and cracking, permeability and carbonation depth. But, the combination of 10% SF and 0.07% PPF volumetric fraction mitigated early age cracking and significantly reduced water permeability and carbonation depth. The use of PPF in NPC concrete combined with SF can be recommended to reduce long-term impact of early age cracking, and enhance durability. However, cement should not be reduced when SF is added to mixtures without PPF, because lower CaO reserves may affect final pH, leading to concretes more sensible to carbonation. (C) 2015 Elsevier Ltd. All rights reserved.