Influência da temperatura e de tratamentos alcalinos na remoção dos extrativos da biomassa de madeira e seus efeitos na hidratação de pastas de cimento e de bioconcreto

Abstract

In this work, wood sawdust has undergone different pre-treatments to reduce the amount of extractives. Therefore, the water temperature was varied between 25 and 95°C, the immersion time between 0.5 and 48h, and the sawdust mass:water volume ratio between 1:4 and 1:10, carrying out one washing cycle. Washing in alkaline solutions was also tested. Aiming the reuse of the washing water for the bioconcrete production, nanofiltration and reverse osmosis was tested. Initial and final setting time of pastes were determined by Vicat apparatus in order to evaluate the washing temperature, the immersion time, and the sawdust mass:water volume ratio. Isothermal calorimetry was used to evaluate cement pastes produced with water from the filtration processes. Adiabatic calorimetry and ultrasonic pulse velocity were performed in bioconcretes. The results showed that water heated at 80°C removes a greater amount of extractives. The amount of solubilized extractives with the immersion time of 30 min is sufficient. The use of reverse osmosis was efficient on the treatment of waste water and pastes produced with these waters presented isocalorimetric curves similar of the curve of paste with deionized water. The nanofiltration allowed the passage of the chloride ions and accelerated the hydration of the cement paste. LCA results showed that the best treatment was to wash the wood biomass in solution of 4% CaCl2. Overall, bioconcretes produced with wood biomass washed in solution of 4 % CaCl2 showed the best results.