Investigation of recycled concrete aggregate utilization in road base and subbase layers

Sustainability is the common denominator of the proposed precautions and solutions these days, where natural resources are being depleted at a rate that cannot meet the needs of human life, and the negative effects of human-induced factors on the climate and ecosystem are gradually increasing. Sustainability is to establish a balance between the requirements of human life and natural resources. Considering both waste generation and natural resource consumption, the construction industry has critical importance in terms of ensuring this balance. In the past few decades, using as aggregate by recycling of concrete waste, which has the highest share in construction and demolition waste, has emerged as an effective way to control and manage these wastes. For this purpose, within the scope of the thesis, the usability of recycled concrete aggregates (GDBA) obtained from concrete wastes with compressive strengths ranging from 35-40 MPa, together with crushed limestone aggregate (KA), in unbound granular base and subbase layers were investigated. The main aim of this study is to compare GDBA with KA, a natural material, to investigate the compliance of GDBA with the specifications specified in the Highway Technical Specification (2013). For this purpose, 5 different mixtures were prepared by replacing GDBA with 0%, 25%, 50%, 75% and 100% KA. The strength, durability and hydraulic properties of the mixtures were investigated. According to the results obtained within the scope of the study, it was understood that the use of GDBA did not adversely affect the properties of the mixtures, except for permeability, and even showed superior performance in terms of flakiness index, wet CBR value, CBR value after freeze-thaw cycle and resilient modulus. In addition, it has been determined that the limit values specified in the Highways Technical Specifications (2013) are provided for use in the granular road foundation and sub-base layers of GDBA. As a result, within the scope of the thesis, the use of GDBA as a granular material in the road base and sub-base layers has proven to be a suitable solution to control waste management and protect natural resources.