Concrete Bond and Behavior of Nonproprietary Ultrahigh-Performance Concrete Bridge Slab Joints

Abstract

The purpose of this study was to evaluate a nonproprietary ultrahigh-performance concrete (UHPC) mix design in terms of bond strength and behavior as a slab joint material. Composite modulus of rupture and direct pull-off tests were conducted to evaluate bond strength using sandblasted, wire-brushed, and exposed aggregate substrates. The two methods for obtaining a saturated substrate included covering the substrate with wet burlap or power washing the substrate and either leaving pooled water or patting the surface dry. In addition, several specimens were constructed by joining two full-scale normal strength concrete slabs with a UHPC joint containing shortened reinforcing bar embedment lengths. These specimens were used to evaluate structural behavior when subjected to both static and cyclic loadings. Each test was compared to an identical test using the proprietary UHPC product Ductal. Bond testing showed that power washing of the substrate was required to produce comparable bond strengths to Ductal. For full-scale slabs, the nonproprietary mix performed comparably to Ductal as a bridge joint material, despite having lower compressive strength.