Effect of bottom ash waste on the rheology and durability of alkali activation pastes

On a global scale, thermoelectric energy remains the main source of the energy industry. This process results in a large amount of coal waste. Among them, the bottom ash still has no suitable application in civil construction and usually is discarded in sedimentation basins. The objective of this investigation is to evaluate the valorization of bottom ash in alkali activation pastes. Rheological, mechanical, microstructure, and durability properties were assessed for application to external structures. Bottom ash and metakaolin were used as aluminosilicate and as an alkaline solution a mixture of sodium silicate and NaOH was made. A room temperature cure was adopted for all the samples. The findings show that the alkali activation of bottom ash (BA) was not satisfactory to achieve minimum strength and durability. BA samples require supplementation to improve its mechanical and durability properties. At 28 days of reaction, the formation of superficial cracks was observed, which contributed to the deterioration in the durability tests. However, metakaolin and bottom ash (MKBA) mixtures resulted in the best performance. It was observed an increase of reaction degree and compressive strength (47.9 MPa at 28 days), greater development of thermal conductivity, and reduced deterioration through wetting and drying cycles, marine environments, and sulfate attack.