Use of Natural Rubber Latex (NRL) in Improving Properties of Reclaimed Asphalt Pavement (RAP)

Abstract

Many issues, especially cost, need to be looked at when a new asphalt materials are considered for road construction. One major factor that impacts the cost is the volatility in oil price and stock availability. Consequently, this factor affects both road construction and maintenance by creating uncertainty and financial challenge for Thai manufacturers. Furthermore, all economies, either national or local, depend on adequate road infrastructure and their sound maintenance for growth and development.  One strategy for reducing the overall cost of road construction is through reclamation of existing pavement surfaces that are being repaired or replaced. A process of recycling asphaltic concrete pavement known as Reclaimed Asphalt Pavement (RAP) has been employed in many countries. However, one drawback associated with this practice is the costly investment in the mixing equipment which mechanically rejuvenates the old asphalt pavement by blending it with new asphalt binder. In addition to the high cost of investment, the required quality of the RAP has not been assured due to the lack of enough evidence. The addition of Natural Rubber Latex (NRL) to the process of the recycling asphalt pavement with the aim of reducing production costs and improving the quality of the RAP, offers a promising solution. This paper describes the results of an investigation into the properties of reclaimed asphaltic concrete mix with added NRL. The properties investigated include the Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR). The results show that properties of the NRL modified RAP mix meet the required engineering specifications. The results show that mixing NRL content of 5-15% by weight with RAP and cement content of 3-7% produced a mixture that meet the specification of Thailand Department of Highways in terms of UCS and CBR value for use in layers of pavement. Apart from the positive environmental impact of using recycle material of RAP, the economic and financial benefits to Thailand and  rubber farmers make it worthwhile to use this NRL modified RAP for road construction and maintenance.