The unit cost of road construction in dollars per kilometer is the sum of the subunit costs of the road construction activities. Road construction unit costs are estimated by dividing the machine rates by the production rates for the various activities involved in road construction. The road construction activities considered here are surveying, clearing and grubbing, excavation, surfacing, and drainage.4.2 Surveying
The understanding of soil behavior in solving engineering and environmental issues as swelling soil especially expansive lateritic soils that can cause significant damage to road construction and other engineering application is the sole aim of geotechnical engineering (Abubakar, 2006; Oke and Amadi, 2008).One of the major causes of road accident is bad road which is usually caused by wrong application of constructional materials especially laterite as base and sub-base material by construction companies (Oke et al., 2009a; Nwankwoala et al., 2014). For a material to be used as either a base course or sub-base course depends on its strength in transmitting the axle-load to the sub-soil and or sub-grade (the mechanical interlock).
The characteristics and durability of any constructional material is a function of its efficiency in response to the load applied on it (Oke et al., 2009b; Nwankwoala and Amadi, 2013). The mineralogical composition of the lateritic soil has an influence on the geotechnical parameters such as specific gravity, shear strength, swelling potential, Atterberg limits, bearing capacity and petrograpic properties (Amadi et al., 2012). The rate at which newly constructed roads in Minna and environs developed cracks and later damage is worrisome. Hence this study will ensure that the right lateritic soils with the right criteria are used as a base or sub-base material for road construction in Minna and environs, North-Central Nigeria, thereby ensuring their durability.