Engineering petrology for roads in South Africa

The thirty different types of rock used by engineers in South Africa for road construction are described and the suitability of these rocks, and their weathering products, for road construction is discussed in the light of the South African geology and climate. Unconsolidated windblown sand, alluvial deposits and soil are not included.

The thirty types of rocks are divided into nine groups according to their petrological and road engineering properties. In some cases this grouping cuts across the traditional genetic classification of rocks.

Special attention is drawn to the importance of quartz in determining the quality and durability of rock to be used as aggregate in road construction.