Compressive strengths of mortar cubes from hydrated lime with cofired biomass fly ashes

This document comprehensively compares strength of 5 cm mortar cubes made from binders of hydrated lime and cofired biomass fly ashes. Samples of cement only, with the same binder mass, provide controls and comparisons. Compressive strengths are tested from one to 12 months and samples were cured under carbonation free conditions. Four cofired (coal and herbaceous/woody) biomass fly ashes consistently develop two to three times that of Class C and F, indicating that cofired biomass fly ashes need more reevaluation as an admixture in concrete rather than exclusion by ASTM C 618 because of its “non coal” origin. However, the investigation does suggest that pure woody biomass fly ash may represent unacceptable pozzolans for use in concrete.