Geotechnical and Petrographic Characterisation of the Birimian Granitoids in Southern Ghana as an Aggregates for Sustainable Road Construction
( Vol-5,Issue-3,March 2018 )

Isaac Ahenkorah, Evans Mensah Awuah, Anthony Ewusi, Michael Affam


Cape Coast (G1), Dixcove (G2), Granitoids, Granite, Road Construction.


Granitic aggregates are mostly used for civil construction and other engineering works in Ghana. In this project, the characteristics of the Cape Coast (G1) and Dixcove (G2) granitoids for sustainable road construction were assessed. Physical and mechanical properties of the rocks were evaluated. Hand specimen description revealed that, amphibole is the major mafic mineral in the G2 and biotite as the dominant mafic mineral in the G1 granitoids. Petrographic study of the grains showed that, the large grains interlocked with fine grains (well-graded) with irregular grain boundaries in the matrix of the G2 gives the rocks a higher strength to withstand compressive loads than the G1 granitoids which have micro fractures in them that acts as weak planes in the rock. Geotechnical tests performed on the rocks gave an average Aggregate Crushing Value (ACV) of 11.6 % for Dixcove and 20.1 % for the Cape Coast, Aggregates Impact Value (AIV) of 6.1 % for Dixcove and 11.02 % for Cape Coast, Aggregate Abrasion Value (AAV) of 16.60 % for Dixcove and 26.0 % for Cape Coast, Specific Gravity of 2.74 for Dixcove and 2.66 for Cape Coast and Water Absorption of 0.18% for Dixcove and 0.51 % for Cape Coast granites. These values indicate that, both rock aggregates have relatively high strengths. However, G2 granitoids have relatively high resistance to compressive stresses under crushing, impacts and abrasion of traffic loads hence more suitable for sustainable road construction according to the global standards.

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