Abstract

Variation of rock densities and durability with rock petrologic types has been evaluated. The evaluation followed collecting ten rock samples of different petrologic types viz: igneous rocks, pelitic argillites and contact metamorphic rocks from quarry units of Albian Asu-River Group. The rock samples were each divided into two portions and the first portion subjected to density tests to determine their matrix and bulk densities. The second portion was subjected to short soaking and partial drying degradability test to determine their susceptibility to intra-seasonal degradability (durability). Results of the density tests show that the difference in matrix and bulk density (ρmat-bulk) for the pelitic argillites ranges from 0.09 to 0.12g/ cm3; ρmat-bulk for the contact metamorphic rocks ranges from 0.04 to 0.07g/cm3 while ρmat-bulk for the igneous rocks ranges from 0.01 to 0.01g/cm3.

Results of the degradability test show that the percentage of mass lost (Mlost) by the pelitic argillites ranges from 11.63 to 26.76%; Mlost by the contact metamorphic rocks ranges from 0.12 to 0.8% while Mlost by the igneous rocks ranges from 0.00 to 0.03%. The results revealed that amongst the analyzed rocks, pelitic argillites have the highest ρmat-bulk and least durability; the contact metamorphic rocks have intermediate ρmat-bulk and durability while the igneous rocks have least ρmat-bulk and highest durability. This work has shown evidence that densities and durability can serve as relative indices in distinguishing different rock petrologic types.

Keywords: Bulk density; Matrix density; Degradability; Pelitic argillite; Durability