Ceramics-Silikáty 58, (4) 260 - 268 (2014)

This study investigated the possibility of using biomass fly ash as an additive for ordinary Portland cement (OPC), where 5 %, 10 %, 15 %, and 25 % (by weight) of the Portland cement was replaced with biomass fly ash (BFA) and tribochemically activated biomass fly ash (AFA). The mixture was then hardened for 28 days in water at 20^oC. It is estimated that both additives are distinguished for very low pozzolanic activity. Under normal conditions, the BFA additive had a negative effect on the strength properties of cement. After 28 days of hydration, the compressive strength of samples with 15 wt. % BFA additive was more than 10 % lower than that of OPC (54 MPa), whereas the compressive strength of the sample with 25 wt. % additive (35 MPa) was 30 % lower than that of the OPC. Additional milling of biomass fly ash samples changes the particle size distribution and composition of the compounds. Tribochemically activated biomass fly ash additive significantly accelerates the hydration process of calcium silicates and had a positive effect on the strength properties of the samples, because up to 15 wt. % of the cement can be replaced with this additive without impairing the strength properties of Portland cement. Also, activated biomass fly ash impedes the alkali-silica reaction in cement mortars.