Reuse of Woody Biomass Ash Waste in Cementitious Materials

There is an increased interest in the reuse of ash waste from biomass combustion, being a sustainable source of energy. This paper investigates the partial replacement of cement and sand in building materials with fly ash waste generated from combustion of woody biomass waste. The results show that the ash widens the particle size distribution of cement and has minerals complementary to portland cement, thus justifying its application as cement replacement, but with a relatively high amount of free CaO and MgO that may exert significant expansion. With ash addition, the rate of hydration, strength, and workability decreased. The optimum dosage showed 15 % of ash, replacing 5 % of cement and 3.33 % of sand, which can still produce a structural grade cementitious material with acceptable workability and mechanical properties. The ash exhibits hydraulic and pozzolanic activity that initially increases and subsequently decreases the amount of Ca[(OH).sub.2] in the hydrated material.Key words:biomass ash, blended cement, hydration, sustainability, waste reuse