Mechanical Properties, Durability and Leaching Toxicity of Cement-Stabilized Macadam Incorporating Reclaimed Clay Bricks as Fine Aggregate

Abstract

The utilization of reclaimed clay brick (RCB) from construction and demolition (C&D) waste is an extremely troublesome problem, which is beneficial and necessary for environmental protection and resource conservation. The objective of this study is to evaluate the mechanical properties, durability and environmental impact of cement-stabilized macadam (CSM) incorporating RCB. The physical and chemical properties of RCB were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) technologies. RCB exhibited a porous surface micro-morphology, high water absorption and pozzolanic activity. The higher RCB substitution ratio resulted in a lower unconfined compressive strength of CSM. Meanwhile, the higher the RCB substitution ratio was, the larger the 90 d indirect tensile strength of CSM at the late curing period. The RCB substitution ratio within 50% was beneficial for the freeze-thaw resistance of CSM. Additionally, RCB had a smaller aggregate size, causing a negative influence on the anti-scouring property of CSM. CSM incorporating RCB had an overall increasing accumulative water loss rate, and average coefficients of dry shrinkage and temperature shrinkage, except that 20% RCB substitution ratio resulted in an excellent dry shrinkage property. Based on the chemical analysis of EDTA-2Na, the pozzolanic RCB reacted mainly at later curing to form the crystal structure, enhancing the interfacial transition zone. Additionally, the leaching solutions could meet the identification requirements for extraction toxicity, surface water and groundwater referring to Chinese standards. Utilizing RCB in road engineering as the substitute for natural aggregate would be a promising step forward to sustainable development and green construction.