Assessment of Rock Aggregate for Construction Using Comminution Theory

In this research, grinding energy of selected rock samples collected from South West Nigeria was determined using comminution theory in order to evaluate suitability of rock for aggregate production. Bond Work Index (BWi), Aggregate Impact Value (AIV) and Aggregate Crushing Value (ACV) of samples was characterized and correlated. The work index of the charnockitic rock, granite gneiss, porphyritic granite –labelled PG1 and porphyritic granite –labelled PG2 of samples was found to be 17.12 kWh/t, 13.72 kWh/t, 13.64 kWh/t and 12.76 kWh/t respectively. The ACV of the charnockitic rock, granite gneiss, porphyritic granite (PG1) and porphyritic granite (PG2) was determined to be 26.2 %, 27.3 %, 27.6 % and 27.8 % respectively; while the AIV of the samples, in same order, was 11.2 %, 13.2 %, 19.1 % and 18.4 % respectively. Following high correlation coefficient of 0.98% between BWi and ACV, hardness of rock materials are classified as ‘very difficult’, ‘difficult’, ‘medium’, ‘easy’ and ‘very easy’ for grinding energies in the range of >18 kWh/t, 14-18 kWh/t, 10-14 kWh/t, 7-10 kWh/t and 0-7 kWh/t respectively. Based on the classification, rock materials with grinding energy >10 kWh/t could be suitable for aggregate production and usable for civil construction purposes. Keywords- Aggregate,  Aggregate impact value, Aggregate crushing value, Comminution, Grinding energy.