SUSTAINABLE USE OF RAP-INCLUSIVE CONCRETE FOR THE CONSTRUCTION OF RIGID PAVEMENTS

Abstract

At present, about 98% of roads, in India, are paved with bituminous material produced from oil refineries importing crude oil from other countries, whereas less than 2% are concrete pavements. Past experiences have shown that these bituminous roads are prone to damage and require frequent periodic maintenance due to adverse climatic conditions such as rains, snow, cold and hot weather prevailing in different parts of the country. Concrete pavement, on the other hand, when properly designed and built out of durable materials, can provide many decades of service with little or no maintenance. India is a developing country with depleting natural resources in terms of availability of natural stone quarries to supply natural aggregate for construction of concrete pavement. Secondly, with government’s plan to convert the existing bituminous pavements into concrete ones, it is imperative to search for a cheap and an already existing alternative for natural aggregates. This is where Recycled Asphalt Pavement (RAP) material comes into play. The aim of the thesis is to find out the optimum replacement level of RAP material in the construction of concrete pavement. The two replacement levels considered in this thesis were 75% and 100% with additions of certain mineral admixtures viz. Fly Ash (FA), Silica Fume (SF) and Bagasse Ash (BG). The adverse effect of dust on the properties of concrete containing fine RAP is minimized by utilizing higher doses of superplasticizers in combination with fly ash, silica fume and bagasse ash. It was found that 75F mix requires at least double amount of SP for achieving the recommended workability. Moreover, the improvement in the fresh workability was found to enhance the hardened properties of 75F mix significantly. The inclusions of considered mineral admixtures were found to further enhance the compressive strength, splitting tensile strength and abrasion resistance, however, inclusions of BG and FA provided with comparable flexural strength. The determination of water absorption and permeable voids was found to be affected by the melted asphalt film suggesting to conduct the same at a temperature lower than 50ºC. Based on the results, it is suggested that natural fine aggregates can be optimally replaced up to 75% with the addition of certain mineral admixtures without having any adverse effect on durability properties of concrete. Replacement level of 100%, however, is not recommended.