Fly ash from biomass combustion as replacement raw material and its influence on the mortars durability
Several types of industrial solid waste have been used as byproducts in the construction and materials industries. Some of the applications seem to be required from the environmental point of view as a contribution to circular economy. Nevertheless, durability of materials should be assessed to avoid future problems. This work evaluated the fly ash from forest biomass combustion as a potential additive replacing calcite in Portland cement-based mortars. Cement-based mortar formulations were prepared and characterized in the fresh and hardened states. In particular, the durability of samples cured for 1 year was assessed based on sulfate attack. Mortars cured for 360 days were pre-weighted and then totally immersed in a solution containing a well-defined concentration of sulfate. Seven-day immersion + drying cycles were carried out, and weight was determined after each cycle. Liquid solutions containing sulfate were renewed every 14 days. One set sample was kept soaked in tap water to be used as reference. The results revealed that replacing 20% of calcite by fly ash seems to be a suitable alternative concerning mechanical strength. However, sulfate attack tests showed that strength rapidly deteriorates using fly ashes as a replacement raw material.
KeywordsMortars Biomass fly ash Sulfates attack Durability
The authors thank Foundation for Science and Technology (FCT-Portugal) for the financial support (SFRH/BD/75182/2010—PhD grant and the project PTDC/AAC-AMB/098112/2008—Bias-to-soil—Biomass ash: Characteristics in relation to its origin, treatment and application to soil), and CNPq for the financial support of first author grant, Ciência sem Fronteiras Program—Postdoc modality: attracting young talent—BJT—MEC/MCTI/CAPES/CNPq/FAPs No. 02/2014.
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