Mechanical and durability properties of mortars prepared with untreated sugarcane bagasse ash and untreated fly ash

Mechanical and durability properties of mortars containing mineral admixtures were analysed. Mortar mixtures were prepared with a water-to-cementitious materials ratio of 0.60 and a cementitious/sand ratio of 1:3.5. A partial replacement of Ordinary Portland Cement (OPC) by 10% and 20% of untreated sugarcane bagasse ash (UtSCBA), and by 10% and 20% of untreated fly ash (UtFA) was used practically “as received”. The only post-treatment was to sieve SCBA and FA through No. 200 and No. 100 sieves, respectively. Compressive Strength (CS), Ultrasonic Pulse Velocity (UPV), Electrical Resistivity (ER) and the Rapid Chloride Permeability (RCPT) tests were carried out on cylindrical specimens. The addition of 10% and 20% of UtSCBA and 10% and 20% UtFA to the mortars had the following effects: the CS decreased generally for all the mortars at early ages but after 90 days was similar or surpassed the level of the control; the UPV decreased generally for all the mortars, except for the 10% UtFA mortar which surpassed the control at 180 days; the ER increased generally for all the mortars after only 14 days, especially when UtSCBA was used; the level of permeability decreased generally in all the mortars, but was especially true for the 20% UtSCBA mortar. Correlations between the results of the different tests evidence the need for further investigation of the influence of additives in mortar mixtures in order to develop more reliable predictions on the behaviour of the properties of cementitious materials.