Estudo da resistência à compressão do concreto por meio de testemunhos de pequeno diâmetro e esclerometria

Abstract

The current method for the verification of the concrete strength to compression consists in molding test cylinders or taking cores of the structure elements. The Brazilian Code ABNT NBR 7680:2007 recommends the extraction of cores with a minimum diameter of 100 mm, preferential. The reduced diameter cores have the objective of facilitating and optimizing the evaluation of existing structures, avoiding steel sectioning, reducing costs and allowing the increase of the number of samples. In this line, the sclerometry (for testing the surface hardness) is a non-destructive technique to evaluate the concrete uniformity, the evolution of strength along with time, and to estimate the final concrete s strength. This study presents the results of an experimental research to estimate the compressive concrete s strength using the sclerometry and the extraction of reduced diameter cores. Some factors which have relevant influence in the extraction and testing of cores will be hereby discussed. The investigated variables were: the nominal dimension of the aggregate and the core s diameter. The sclerometry variability results in the blocks it was studied too. In the program of rehearsals three concrete series were used with gravel 0, with gravel 1 and with gravels 1 and 2, maintaining the same relationships for water-cement and aggregatecement. The sclerometric tests were conducted in concrete blocks of 40 cm x 40 cm x 80 cm and cylinders specimens with 150 mm diameter. The analysis was conducted by comparison of the results of drilled cores from the blocks with diameters of 150 mm, 100 mm, 50 mm, 32 mm and 25 mm, test specimens with diameters of 150 mm, 100 mm and 50 mm, and sclerometry testing of specimens of 150 mm diameter. Although the limitations in relation to the number of specimens and some discrepancies between the used techniques the results had indicated a trend in terms of concrete strength variation.