PHYSICAL CHARACTERISTICS OF BARITE PLASTER USED FOR X-RAY SHIELDING – PART ONE Filho,

Barite plaster has been largely used as shielding material in installations housing gamma radiation sources as well as x-ray generating equipment, in order to minimize exposure to individuals. However, some physical characteristics, such as density, plasticity, resistance to compression and radiation attenuation for the different types of barite plaster commercially available in Brazil are not well known. For this reason, this work was carried out aiming to determine specific density, consistency index (plasticity), resistance to compression and barite plaster composition, as well as the transmission factor and attenuation for x-rays in the ISO 60, 80, 110, 150 qualities for barite plaster produced in Brazil. Barite plaster is a compound of cement, sand, barium sulphate and water mixed in a controlled proportion. The basic ratio of cement to water determines plaster strength. Preliminarily, tests were carried out to determine the best amount of water to be added to manufacture the samples. After determining the quantity of water to be added to the mixture to obtain the optimum consistency index, seven samples (labelled A to G) were prepared by keeping constant the mass ratio of the components (one part cement, five parts sand and five parts barium sulphate). The only variable in the mixture was the barium sulphate, which was obtained from three mining companies located in the states of Bahia, Piauí and Minas Gerais, Brazil. The results obtained for the samples analyzed showed that the best consistency indexes were obtained for a mixture of 200 g of cement to 230 g of water, that is in a 1:1.2 proportion. On the other hand, samples “G” (Bahia) and “B” (Piauí) presented the highest resistance to compression (14.8 and 16.7 MPa, respectively). They were prepared by using a cement/water proportion of 1:1.2. It was also observed that sample “G” presented the highest specific density (2.40 g/cm) among all tested samples, with a consistency index of 20.25 cm and a plasticity of 0.049 cm.