Blocks for civil construction made with the sediment deposited in the Candonga dam

The use of the sediment deposited in the Candonga dam after the collapse of the Fundão dam is being considered as raw material for civil construction. Blocks were obtained by adding 5 % of sodium carbonate and 13 % of water to the dried dredged sediment, which was mixed and heat treated at 700 deg C and cooled slowly inside the oven to room temperature. The water absorption of the blocks was in the 12-16 % range, the loss of mass in water was (0.01±0.01) %, the density was (1.95±0.03) g/cm³ , the compression strength was (11.05±1.29) MPa (reference value ≥ 1.7 MPa), and the flexural strength was (4.42±0.69) MPa (reference value ≥ 3.5 MPa). Small cracks and pores, as well as the growth of white spots (efflorescence) were observed on the surface of the blocks, which can be avoided or attenuated by improving the compaction pressure and the heat treatment. (author)