Estudo da expansão por umidade (EPU) em blocos cerâmicos do Estado da Paraíba.

Abstract

Moisture expansion has been little studied here in Brazil, and there is no information concerning structural clay-based products. Thus, the purpose of this work is to study the problem of moisture expansion in ceramic blocks in the State of Paraiba, concerning your evolution and mechanical behavior, in a laboratory scale, seeking an adequate understanding of the phenomena involved, in order to foresee future behavior of masonry constructions in high freatic level or flood prone regions. Initially samples of three plastic masses used in the production of red clay holed ceramic blocks were collected, coming from different areas in the State of Paraiba, as well as samples of the ceramic blocks manufactured with those raw materials. The masses were characterized by chemical analysis, differential thermal analysis, thermal gravimetry, X ray diffraction, granulometry analysis and plasticity analysis. Test pieces manufactured in the laboratory, fired at the temperatures of 700, 800, 900, 1000 and 1100°C, and those cut from the ceramic blocks collected in the industry, were subjected to ceramic tests, moisture expansion and mechanical flexural resistance, before and after moisture expansion. Some of the test pieces made in the laboratory, fired at 900°C, were subjected to X ray diffraction, mercury porosimetry, infrared spectroscopy and specific area measurement (BET) before and after moisture expansion under boiling water conditions and autoclaving. It happened the erosion of the test pieces during the test to determine the moisture expansion, masking the values obtained by direct measurement, concluded that the dilatometry have a great advantage about the direct measurement. Generally speaking, the results of moisture expansion show that the increase in severity of the test conditions causes a significant increase in moisture expansion and a significant decrease in the mechanical resistance. In all the cases, at 900°C the moisture expansion values were high, above the standard value stated for ceramic blocks, suggesting the presence at this temperature of a highly reactive and amorphous phase. No modification in the crystalline structure of the samples was registered after the moisture expansion tests. The infrared spectroscopy showed variations in the absorbance of the samples before and after the moisture expansion tests, probably as a result of the moisture expansion.