Experimental studies of c and d waste as a geo material for road construction

Abstract

The present work proposes a framework for recycling of construction and demolition waste(CDW) as geo-material for construction of sub base and base course of flexible pavement. It was based on the results of experimental studies of physical and engineering properties of recycled CDW aggregates compared to standard requirements as per MoRTH (Ministry of Road Transport & Highways) specification of road and bridge works (2001),which was supported through field testing and performance evaluation of 3 km trial stretch of road constructed using recycled waste. The physical and engineering properties like specific gravity, grain size distribution, density-moisture relationship by Proctors compaction test, aggregate crushing value, Los angles abrasion value test, and California bearing ratio (CBR) of recycled CDW aggregates have been tested in laboratory and compared with that of new virgin materials as specified in codal specification. It is observed that most of the physical and engineering properties of recycled CDW aggregates fulfil the standard code specification else the effect of variation of property has been analysed and suitable remedial proposals are incorporated in the proposed frame work. The CDW aggregates have variable characteristics as they are extracted from diverse spectrum of materials used in old buildings and structures. This frame work suggests laboratory tests to assess the variation in quality of waste aggregates and suggested the parameters for design of flexible pavements layers using waste materials. The field investigation and performance evaluation of trial stretch designed as per codal provisions using CDW aggregates, has been carried to investigate the effect of use of this waste as sub-base and base course. Thereafter the performance of sub-base and base course was evaluated through field testing of density of compacted pavement, relative density and relative compaction, plate load test of compacted pavement for assessment of settlement on application of loads and modulus of sub grade reaction. The safe bearing pressure from plate load test at the settlement of 1.25 mm has been found in the range of 450-650 kPaat the top of base course, without the laying of bituminous layers of 130mm thickness. These layers further contribute to the load bearing capacity of pavements. As the permissible axle load in India is 100kN, it can be safely assume that this pavement even with the impact of moving wheel loads may not cause structural failure. The pavement performance monitoring and evaluation has been carried out for a period of seven years and compared with normal maintenance requirements of typical flexible pavement. The comparison has revealed that the performance of flexible pavement constructed using CDW aggregates is comparable to the natural aggregates. The present work proposed a frame work for recycling of CDW aggregates in flexible pavements in the form of systematic flow charts and a step by step methodology for utilisation of CDW in field as an economically viable and environmental friendly material with partial or full substitution of standard natural materials in construction of flexible pavements.