The Effect of Using Desert Sands and Cement to Stabilize the Base Course Layer of Roads in Libya

Abstract

This paper investigates using a mixture of natural sand, Portland cement, and manufactured aggregates to stabilize the base course layer for low-volume roads. Compaction and resistance to deformation California Bearing Ratio (CBR) results are measured and guidelines provided with consideration for hot desert areas like Libya. These tests have been conducted to provide relevant statistical conclusions and recommendations as to how much round-shaped sand may be used versus manufactured crushed sand for various traffic loads. In the last 15–20 years, Libya, along with many other developing countries in the area, has undergone a sizeable move towards modernization, including upgrading the road infrastructure that services the growing population. Such a project runs into challenges in areas with lower population density, that require that roadwork projects be kept under sharp cost constraints. Using a mixture of sand cement to stabilize the base course has been common for decades because the properties of cement improve the characteristics of natural sand; furthermore, when the road is built in a sandy desert, the use of desert sand is an obvious solution to containing costs. Nonetheless, natural sands have been rounded by years of mechanical action by environmental forces, and are therefore rounder and more prone to shifting than angular manufactured sand. Manufactured aggregates need to be imported from elsewhere in the country and so have higher costs and environmental considerations, both of which give these projects incentives to use the local desert sand. This paper only considers the use of manufactured aggregate of 0–5 mm in the base course and examines how using local desert sand in the aggregate mix can reduce costs. This solution brings with it many problems because, due to natural sand’s lower inherent stability with regards to manufactured sand, the road surface will degrade faster. The solution to this problem, presented here, is to relocate some of the strength of the road from the surface layer to the base course layer. This is done by reducing the thickness of the asphalt course to a minimum, and introducing more structural strength in the base course layer by means of a cement-stabilized base layer.