Uso de dregs em substituição da cal hidratada em argamassas mistas de revestimento.

Abstract

The significant volume of wastes generated by pulp and paper mills and the consequent environmental liability associated with the composition of these wastes motivated this present work, which proposes to partially replace hydrated lime with green liquor dregs in cement/lime coating mortars. These mortars were dosed based on Santos et al., (2018), using the following materials: Portland cement, quartz sand, hydrated lime and green liquor dregs generated by CMPC Celulose e Papel. Lime was replaced by dregs in percentages of 10%, 15%, 20% an d 30%. The materials were characterized according to their chemical compositions and granulometry. Tests in the fresh and hardened state were carried out in accordance with current standard procedures. In addition, wetting/drying cycles were performed, simulating the aging of the mortars based on the performance standard and, later, their effect was evaluated in compression and tensile bending. In general terms, both the results obtained with the tests in the fresh and hardened states, indicated a high degree of similarity between the studied mortars. Therefore, dregs acted in a similar way to CH -I in the production of these mortars, and, in this sense, among the mortars, the one with 30% replacement of lime by dregs can be highlighted as the most promising one due to environmental and economic reasons. The SEM images indicated that the presence of dregs in the mortars did not change their mechanism of formation of C-S-H crystals, which corroborates the high degree of similarity of the evaluated properties. The effect of accelerated aging promoted a gain in compressive strength, which indicates that post-hydration mechanisms of the cement may have occurred. Also, the improvement in this property over time indicates that the damage induced by the artificial agi ng benefited the mortars.