Optimization and performance evaluation of crushed stone waste as an alternative material in flexible pavement base layers

Exhaustion of conventional non-renewable natural assets like coarse and fine aggregates used in the construction sector is the major issue currently faced by the construction industry. To overcome this problem of depletion of aggregates, an initiative has been taken in the current work to replace Gravel Chips (GC) of size 10mm to 4.75mm and M Sand (MS) with crushed stone sludge waste (CSSW) up to a percentage of 50% as part of base and sub-base layers in flexible pavement structure. CSSW is a dust waste from stone crusher units produced during the crushing of stones, rocks etc., which when utilized as replacement to GC and MS will cut down on amount of waste being disposed in surrounding environment, consequently reducing environmental pollution. Expenses responsible for discarding the waste can be reduced, material costs related to purchasing of coarse and fine aggregates for flexible pavement base and sub-base layers can be minimized, resulting in a construction that is both cost-efficient and eco-friendly. Peak MDD of 2.14 gm/cc and 2.08 gm/cc was attained for GC replaced with 40% CSSW and for MS replaced with 30% CSSW respectively due to filling of the voids within GC and MS with finer CSSW. Optimum replacement of GC with CSSW was 40% - 50% whereas, that of MS was 30% - 40% based on maximum CBR strength achieved by the mix. A reduction in pavement thickness by approximately 34.2% and 51% was achieved for GC and MS replaced with 40% CSSW respectively.