Influência de areias artificiais de rochas britadas na estrutura e nas propriedades de concretos de cimento portland

Abstract

Eleven series of concrete mixtures were made, with the following characteristics: cement content: 350 kg/m3; water-cement ratio: 0,54; slump: 70 ± 10 mm; mortar ratio in relation to the total of dry materials in concrete: (46 ± 1)%; replacement of natural sand by crushed stone sand (gneiss and limestone), percent by weight: 0, 20, 40, 60, 80 and 100; concrete ages: 3, 7 and 28 days. In this research, the characteristics ofaggregates and concrete (fresh and hardened) were analyzed, under some aspects: compressive strength, splitting tensile strength, flexural tensile strength, elastic modulus (elastic and dynamical), microstructure characterization by scanning electron microscopy (SEM) and mineralogical analysis (X-ray diffraction). It sands natural and gneiss sand with behavior slowly reagent; concrete with good workability; increase of 14,3% in the splitting tensile strength for diametrical compression (ftD) and 19,6% in the flexural tensile strength (fctM), in concrete mixtures with artificial sand of aggregates, relatively to the concrete mixture with natural sand; in the scanning electronmicroscopy (SEM), it is noticed intimate contact between the calcium carbonate and the paste of moisturized cement.