Evidence collected from extensive field studies has indicated that the bond of the aggregate-mortar interface at an early age is one of the most significant factors affecting the development of delamination and eventual spalling, which is a distress type that plagues both jointed and continuously reinforced concrete (CRC) pavements. Coarse aggregates generally occupy about 70 to 80% of the volume of concrete, and form the skeleton of concrete. Therefore, a better understanding of the contribution of aggregates to the bonding performance of concrete is of great importance to the successful construction practice for using aggregates to prevent delamination and spalling distresses. In this study, a fractional factorial design (the Taguchi method) was applied to investigate how important the aggregate effect plays on the aggregate-mortar interfacial bond among key construction design factors, and what kind of aggregates can provide best performance. In this Taguchi design, four factors (i.e., aggregate type, water/cementitious ratio, replacement of ultra-fine fly ash, and curing method) with three levels for each factor based on the orthogonal array were considered. A fracture mechanics parameter, fracture toughness (KIf), was used to represent the aggregate-mortar bond strength. The associated comprehensive investigation of aggregate characteristics through physical, geometric, and chemical categories, and the overall evaluation of aggregate properties based on a rating system using utility theory provided not only better understanding of the contribution of aggregate to the bonding performance of concrete, but also valuable recommendation on selecting right aggregate type in concrete paving construction.
Abstract