Abstract
In this article factors that affect the comminution behavior of heterogeneous diorite rocks obtained from two quarry locations in Botswana were investigated. Diorite rocks are in great abundance in Botswana and they are increasingly viewed as a relatively inexpensive and reliable alternative construction material to sustain the infrastructure growth in Botswana. The diorite rock samples collected from both the Central and North-Eastern districts were studied for structural similarities and mineral composition. These two are the main factors that influence material hardness, fracture toughness and particle size distribution (PSD) following breakage, which are important material properties in construction applications (Barry & James, 2016). The aim of the investigation was to comminute and compare the behavior of the rock sample types, under similar experimental conditions in a laboratory jaw crusher as well as in a planetary ball mill. The product PSD was used to theoretically determine and compare power requirements. The experimental results show that the diorite rock sample collected from the central region required 41.58 KWht-1 while the one collected from the north-eastern region required 38.33KWht-1 to fragment from a particle feed in the -50 + 40 mm size range to a product in the -11.2 + 6.3 mm size range, which is a typical construction aggregate size range. The diorite sample collected from the central district was largely characterized by amorphous phase constituents and high silicate/quartz content (12.4%) while the north-eastern diorite was characterized by a high crystalline phase percentage and lower silicate/quartz composition (6.94%). The experimental results show that inherent diorite rock properties play a significant role in determining cost of production and product application in the quarry industry of Botswana.