Valorization of waste wood fly ash in environmentally friendly lime-based plasters with enhanced strengths for renovation purposes

Abstract

Waste wood fly ash (WWFA) generated during wood chips combustion in a power plant does not have any application nowadays and is commonly disposed of or landfilled. Nevertheless, considering its composition and reactivity in the presence of calcium hydroxide, it is one of the promising materials that could be used as an active admixture for modification and partial replacement of lime in lime plasters. This solution seems to be a suitable step to both improve the properties of the traditional lime plaster and reduce carbon dioxide emissions. Therefore, this comprehensive study describes a wide range of properties of lime plaster with WWFA (up to 50 wt% lime replacement) as an active admixture. Compositions of studied plasters were firstly analyzed with the help of XRD, DSC, and SEM, and then the effect of WWFA on the physical, mechanical, hygric, and thermal properties was investigated. The obtained results showed that the application of WWFA led to lower total porosity, highly improved mechanical properties, higher thermal conductivity, and lower water transport capability, which could be attributed to its pozzolanic activity. The performed experiments fundamentally broadened the existing insufficient knowledge about the utilization of WWFA for lime-based plasters improvement. All tested lime-based plasters (with 10, 20, 30 and 50% lime replacement by WWFA) have a high potential for common use in practice, especially in the historical buildings renovation. The originality of this paper lies, among others, in using a specific type of fly ash (originating from waste wood, not coal) and in testing a wider range of characteristics and properties of designed lime-based plasters with WWFA with respect to their changes over time, which enables prediction of plasters' durability.