Avaliação do comportamento mecânico de misturas de concretos reforçados com microfibra de vidro e microfibra de polipropileno

Abstract

This study investigates the comparison of conventional concrete with microfiber reinforced concrete at the ages of 7, 14, 21, 28, 60 and 90 days. In order to increase the ductility and mechanical strength of the concrete against compressive, tensile and bending loads, the addition of microfibers can be implemented to reduce the problems associated with the brittleness of the concrete. The research evaluated the workability of fresh concrete, physical, chemical and morphological characteristics by XRD and SEM/EDS, the mechanical properties of compressive strength, tensile strength and flexural strength reinforced with glass microfiber and polypropylene microfiber. Considering the amount of fiber and cement used, compression and tension specimens with dimensions of (10×20) cm and bending beam specimens with dimensions of (50×15×15) cm were prepared. The microfibers have an average diameter and length of 18 μm and (12 to 15) mm, respectively, demonstrated in a microscopy test. The results of the X-ray diffraction data confirm the electronic microscopy data regarding the composition of the mixtures with glass microfiber and polypropylene microfiber. Experimental results indicated that workability was highly influenced by microfibers in concrete, regardless of type. The additions decreased the workability of the cementitious mixture in greater proportion in polypropylene microfibers by 38%. The two fiber types improved the compressive strength by 5.68% for MPV and 7.95% for MFPP; flexural strength in 15.67% for MFV and 17.65% for MFPP; tensile strength of 7.50% for MFV and 20% for MFPP at 90 days. Additions of polypropylene microfibers increased mechanical strength more effectively than glass microfibers. The properties of conventional concrete were improved with the addition of fibers, justifying their viability.