Cement Stabilized Soil as a Road Base Material for use in Sri Lankan Roads

The elastic modulus of the lower quality coarse–grained sandy materials available in Sri Lanka is higher than the elastic modulus of fine–grained silty and clayed materials. Although these locally available soils can be stabilized using cement, due to the non-availability of appropriate guidelines, several issues can arise when they are stabilized. The strength of the materials can be measured using the California Bearing Ratio (CBR). However in certain specifications, it is the Unconfined Compressive Strength (UCS)that is specified for stabilized material. Therefore, the first phase of this study was focused on identifying the correct way to measure the strength of stabilized materials. The study confirmed that the strength of a Cement Stabilized Soil Base (CSB) should be measured using the UCS. Furthermore, in road pavements with a stabilized base, the most critical tensile stress and strain occur at the bottom of the stabilized layer. To minimize fatigue cracking, this tensile stress at the bottom of the stabilized layer has to be controlled. However, empirical design guidelines used in pavement designs cannot be used to analyse the mechanistic behaviour of pavement layers. Hence, during the second phase of this study, cement stabilized pavements were analysed using a Mechanistic-Empirical Method (MEM). A pavement design chart for pavements with a CSB layer was developed for various subgrade and traffic classes using the MEM software KENLAYER.