Reuse of woody biomass fly ash in cement-based materials

• Physico-chemical and mineralogical characterisation of pure woody biomass fly ash (WBFA).
• Treatments of WBFA to reduce detrimental effects on the technological properties of cement mixes.
• Technological feasibility of WBFA reuse as partial cement replacement material in cement mixes.
• Technological feasibility of WBFA reuse as a filler/partial sand replacement material in concrete.
• Hydraulic and pozzolanic activity of WBFA.

The reuse of woody biomass fly ash (WBFA) as a mineral admixture or as a filler/partial sand replacement material in cementitious mixes was investigated. Three different WBFAs were used, two coming from virgin wood and one from treated wood combustion. The physical and chemical characteristics of these ashes and the technological properties (workability, setting, compressive strength) of cementitious mixes incorporating WBFA were evaluated. It was found that, in spite of the satisfactory technological properties exhibited by most related blended cements, the studied WBFAs did not meet the UNI EN 450-1 requirements for reuse as mineral admixtures, even if they were subjected to a preliminary water-washing treatment. The reuse of raw wood fly ash as a filler/partial sand replacement material was found to be satisfactory and possible for low-quality concrete.