Análise macro e microestrutural em concretos preparados com calcário de alta resistência.

Abstract

The understanding of the microstructure of concrete offers subsidies and tools to improve their properties, specially durability and mechanical resistance. Thus, this project directs its research in a macro and microstructural analysis in concrete prepared with high density limestone of the Ceara's cariri. A comparative analysis with the concrete prepared with crushed granite and low density limestone was performed with secondary aim. Specimens were prepared with 35 mm diameter and 70 mm height on the dash 1:2:2:0,5. In the conventional concrete was used crushed granite as coarse aggregate and the alternatives were prepared with high and low density limestone. Then the specimens were subjected to the tests: XRD for phase identification of the constituent materiais of the aggregates that were used, XRF to identify the chemical elements of aggregates, strength testing for the concrete compression, pH testing, real specific mass and SEM of the concrete samples for analysis of transition zone. The two high density concrete kinds found in the field in the Ceara's cariri presented on their chemical composition the CaO predominating in 73% to white limestone and 65% to the grey limestone, however the grey type presented 4,5% of silica in its composition against only 1,84% found in the white type. The concretes prepared with high density limestone presented on average 16% higher resistance to compression than the conventional concretes. The micrographs obtained in the SEM showed a transition zone with low occurrence of cracks or fractures and low porosity in the concretes prepared with limestone, on the other hand on those prepared with crushed granite were found cracks along its interface and high porosity.