Experimental Study of Concrete Slab–Base Interaction for a Seamless Bridge–CRCP System

Conventional bridge systems make use of expansion joints to accommodate movements caused primarily by thermal changes. These joints may accelerate the deterioration of bridge elements and often require significant maintenance costs. Originally proposed in Australia, the seamless bridge concept eliminates the need for expansion joints between bridge decks and roadway pavements. Past applications of seamless bridges have utilized a continuously reinforced concrete pavement (CRCP) in which a transition zone is employed between the bridge deck and the CRCP to accommodate the longitudinal expansion and contraction of the bridge and pavement. A critical aspect of the system response is the longitudinal load transfer mechanism in the transition zone, which is governed by the restraint at the concrete pavement–base interface. This paper presents an experimental investigation of the concrete slab–base interaction through unit-cell direct shear tests and cyclic full-scale push-off tests. The load (shear) versus displacement behavior at the interface was evaluated for different interface materials (geotextiles, polyethylene sheets, and felt paper). Test results indicated double-sided textured linear low-density polyethylene sheets and felt paper, which presented coefficients of friction of around 0.4 and 0.7, respectively, were the most promising interface materials to be considered for the transition zone.

Seamless bridges provide a structural system that eliminates joints that permit corrosion-causing agents that adversely impact the super and substructure components. In seamless bridge systems, the bridge deck connects directly to a transition slab that provides a link with conventional pavement systems. The transition slabs deform to dissipate the thermal movements of the bridge. A critical element in the system is a bond breaker that allows the transition slabs to slide relative to the base foundation element. Too large of a coefficient of friction results in excessively wide cracks in the transition slabs, while too low of a friction coefficient results in excessive lengths of the transition slab region. This paper documents experimental studies on the performance of bond breakers to meet the needs of seamless bridge systems. The research considers the behavior of a wide variety of bond breakers with common bases used in bridge applications and recommends the most promising materials. These recommendations are critical to the successful implementation of seamless bridge systems in practice. The paper presents the results of a two-phase experimental program to identify the best bond breakers for seamless bridge systems and quantifies their interface resistance (coefficients of friction).