Primary kaolin waste as pozzolanic material in dry concrete: Mechanical properties and resistance to attack by sulphates

Abstract

This work reported to study the influence of metakaolin obtained from waste beneficiation of primary kaolin, the mechanical and durability properties of dry concretes for precast industry. The metakaolin was obtained by micronization of wastes and subsequent calcination at 800 °C for 2 h. Thermal and X-ray diffraction analyses were also carried out aiming at evaluating the consumption of calcium hydroxide by adding the material to be analysed. Was evaluated by replacing 10, 15 and 20% by weight of cement in concretes with 12, 15 and 18% of cement at 7, 14 and 28 days of age under ambient conditions. The substitution of 10 and 15% by weight of cement by metakaolin in the concrete with 12% of cement which provided, respectively, an increase of 12 and 6% in compressive strength compared to concrete without metakaolin. The durability was evaluated by exposure to sulphates whose results showed that, for all traits, using 10% of metacaulin promoted reduction of dimensional expansion. The results showed that the use of metakaolin obtained from waste in processing kaolin, can foster greater progress in resistance and durability in dry concrete from 28 days of cure.