Properties of biomass fly ash-phosphogypsum based pastes

Abstract

Biomass fly ash (BFA) and phosphogypsum (PG) are by-products of wood biomass combustion in thermal power plants and phosphoric acid production. PG is formed during the decomposition of phosphate raw materials by sulfuric and phosphoric acids. About 1.5 million tons of PG waste is generated in Lithuania each year, whereas the BFA waste amount will triple by 2035 compared with the 2008 levels. This paper investigated the effect of PG content on the rheological properties and physical-mechanical properties of pastes based on BFA and PG. Increasing the PG content from 0 to 100 wt% in the paste increases the highest exothermic temperature (from 29.5 to 47.4 ℃) and compressive strength (from 3.02 to 26.53 MPa after 28 days of curing). XRD analysis shows that increasing the PG content increases gypsum crystallization.