INVESTIGATION OF THE USE OF CONSTRUCTION AND DEMOLITION WASTE AS FILL MATERIAL AND GEOPOLYMER BINDERS IN ROAD PAVEMENT STRUCTURES

This study investigates the feasibility of using construction and demolition waste as fill material and geopolymer binder in road pavement structures to reduce environmental impacts and support sustainable material use. Six different mixtures (T1–T6) containing glass powder, brick powder, and recycled concrete aggregate were prepared with fine contents ranging from 2% to 12%. The mixtures were prepared as Type-A for the subbase layer class and as Type-C for the base layer class, in accordance with the Highway Technical Specifications. Modified Proctor and CBR tests were conducted to determine the engineering properties of the mixtures. The Modified Proctor results indicated that increasing fine content increased the maximum dry unit weight while decreasing the optimum moisture content. From T1 to T6, the optimum moisture content decreased from 12% to 8.5%, whereas the maximum dry unit weight increased from 2.02 g/cm³ to 2.16 g/cm³. The CBR test results showed that the increase in fine-grained material ratio significantly improved the bearing capacity. For the T6 mixture, CBR values of 94.8% and 159.6% were obtained at 2.5 mm and 5.0 mm, respectively. Using 4M NaOH solution, these values increased to 136% and 223.9%, respectively. In addition, SEM and EDS analyses showed that increasing molarity led to a denser and more homogeneous structure. As a result, construction and demolition waste was evaluated to be suitable for use as a subbase material.