FRACTURE PROPERTIES OF PLAIN AND STEEL-POLYPROPYLENE-FIBER-REINFORCED HIGH-PERFORMANCE CONCRETE LASTNOSTI LOMA NAVADNEGA IN VISOKOZMOGLJIVEGA BETONA, OJA^ANEGA S POLIPROPILENSKIMI VLAKNI

doi:10.17222/mit.2014.180 The aim of this research was to establish the fracture properties of high-performance concrete (HPC) containing two widely used types of fibers. The experimental investigation consisted of the tests on cubes, cylinders and notched prismatic samples made of plain HPC and fiber HPC (FHCP) with variable contents of steel or/and polypropylene fibers ranging from 0.25 % to 1 %. Extensive data on compressive, splitting and flexural tensile behaviors, modulus of elasticity and fracture energy were recorded and analyzed. The experimental investigations showed that HPC in fracture mode I exhibit brittle/softening behavior. The FHPC materials showed a more ductile behavior compared to that of the HPC materials. Fiber bridges cracked on the fracture surface during the loading and delayed cracking, thus the element did not break. The results of the bending tests showed an extended post-peak softening behavior. The shape of the descending branch was dependent on geometrical and mechanical properties as well as the quantity of the fibers used. The results of the research were evaluated and it was shown that the fibers contributed considerably to the structural integrity and stability of the HPC elements, thereby improving their durable service life.