A summary of studies of bonded concrete overlays

This report summarizes major findings of Research Project 457, "Thin bonded concrete overlay implementation". The performance of bonded concrete overlays (BCO) in terms of pavement condition, deflection, fatigue life, and load transfer after overlay is described along with the warrants of BCO. A field experimental program, performed on a stubout of State Highway 225, at IH-610 in Houston, is summarized. The objectives of the experimental program are to identify significant construction variables and to evaluate their effects on the bond strength between a CRCP overlay and an existing CRCP. Variables considered in the investigation were surface preparation, moisture condition, use of grout, vibration level, location of core, and season. Various BCO material types in terms of reinforcement types (fibrous concrete versus steel mat reinforced concrete, and CRCP versus JCP) and bonding agents (portland cement grout versus epoxy resin) are evaluated. Problems associated with the use of silicious river gravel as aggregates of the concrete mix are presented. A summary of recommendations for the BCO construction are also presented. Several case studies conducted using Rigid Pavement Rehabilitation Design system (RPRDS) are described. They include comparison of BCO design lives (20 versus 40 year design), effect of early construction of BCO, comparison of asphalt shoulder and PCC shoulder, importance of directional and lane distribution in design effect of construction time on the traffic delay cost, and the effect of selecting different surface preparation methods on the total cost (A).