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The requisite for a careful design of pavement subgrades and subbases has been stressed by the failures caused by fallacy in understanding the variability and uncertainty associated with material properties (Jung et al. 2012). This study emphasizes the improvement of California bearing ratio (CBR) found in the expansive soil after treating with lime and fly ash through probabilistic evaluation. The variability associated with the CBR values is studied for twenty soil specimens stabilized with lime and fly ash at varying proportions. A comprehensive analysis has been carried out in a probabilistic framework for a complete understanding of the variability range. The aftermath of the investigation can be suitably beneficial for a reliable and reasonably economical design of pavement subgrades.

Reclaimed asphalt pavement (RAP) is a term given to removed and/or milled pavement materials containing asphalt and aggregates. This material is obtained from recycling the existing flexible pavements which have reached the end of their design life or shown excessive cracking. The use of RAP has grown widely reducing the use of virgin material thus helps to conserve the natural resources. It also reduces the amount of construction debris reaching the landfills. RAP can be used in construction of base/subbase of a new pavement which results in huge savings. A 100 % RAP cannot be used directly in base/subbase layers because of its inferior properties such as unconfined compressive strength (UCS), California bearing ratio (CBR) and resilient modulus (Mr). This is because RAP material has a very low or limited bonding as the particles are coated with aged bitumen. These properties can be improved by using RAP in combination with virgin aggregates (VA) and/or calcium based additives such as lime, cement or fly ash. Calcium rich fly ash and a fraction of VA have been used in the present study to evaluate the strength in terms of UCS and stiffness in terms of Mr of RAP to promote as a pavement base/subbase material. The RAP material was collected from an ongoing national highway (NH) expansion project in India. Class “C” fly ash was collected from Neyveli Lignite Corporation (NLC), Tamil Nadu for stabilization studies. Specimens were prepared with 100 % RAP, 80 % RAP + 20 % VA and stabilized with 10, 20, 30 and 40 % dosages of fly ash by weight. In this study, emphasis is given to the mixing methodologies adopted to amend base materials and stabilizer. Traditionally, addition method is preferred for stabilization studies and replacement is preferred for mixture of two materials by weight of the principal material. Two methodologies were compared in terms of results obtained from the Mr and UCS studies and a balanced method was suggested. To know the level of interaction of

Chemical stabilization of clays is widely accepted in many countries and was proved to be effective in mitigating the expansive behavior. Several cases are reported that described premature failures in clay subgrades after stabilization. The reasons for these failures could be the ineffectiveness of stabilizer dosage or due to loss of stabilizer from soil over a period of time due to rainfall infiltration. The main objective of the present research project was to study the cause of premature failures in stabilized clays. Four soils showing expansive behavior were selected for this study and were studied with different stabilizer dosages of Lime and Portland cement. Accelerated curing was adopted in the current research as it saves time and provides better results. Leachate apparatus, an experimental set up used to study the soil specimens for stabilizer loss and how it replicates the moisture inflow was used in this research. Calcium concentration, pH and Unconfined Compressive Strength (UCS) of the soil specimens were monitored thorough out the experiment. It was found out that stabilizer loss has not much impact on the stabilizer ineffectiveness of a treated soil.