Development of polymer-modified cement-based hybrid fiber reinforced lightweight composite

Concrete is a brittle material, it shows a linear elastic behavior under low loads. When the load is increased, plain concrete loses its bearing capacity from the first crack. "Engineered Cementitious Composites (ECC)", is a new generation building material that can exhibit multiple crack behavior under tensile loads and has higher energy absorption capacity than plain concrete thanks to the micron size fibers it contains. In this thesis, the mixing water of ECC was replaced with different amounts of polymer emulsion (12.5%, 25%). ECC's were designed with the use of two different fibers and their hybrids. The fibers that used are " High Tenacity Polypropylene Fiber - HTPP" and "Polyvinyl Alcohol (PVA)". The composite contains total 2% by volume of these fibers; It is prepared by using 1.5% - 0.5% and 1%-1%. Digital Image Correlation (DIC) method was used to observe the effects of changes made in composites on crack development. The polymer emulsion used is of "Styrene Acrylic Rubber (SAR)" origin. The polymer modification supported the lightweight composite production due to the air entraining effect of the polymer, and thanks to the film it formed, it achieved a 28% increase in tensile strength. However, depending on the polymer percentage, a certain increase in the crack-forming capacities of the polymer-modified ECCs and a reduction in higher rates were observed. It has been determined that the polymer film formed in ECC prevents the development of multiple cracks by increasing the resistance of the matrix to cracking after a certain density. To increase the fracture toughness of ECC, 3% by volume granulated glass powder was added to the matrix and the multiple crack behavior of the composite was supported, which increased the average number of cracks by 20%.