Bond Strength between UHPC and Normal Strength Concrete (NSC) in accordance with Split Prism and Freeze-Thaw cycling tests

Civil Engineering CE 5990 Graduate Seminar
Three graduate students will present their research topics in our Civil
Engineering Seminar. This Thursday- 4-5PM 11/10/2011, Dow 642

Miguel Angel Carbonell

CEE Graduate Student

Abstract

The rehabilitation of concrete structures, particularly within transportation infrastructure network is a major challenge for transportation agencies in the United States. This is especially true for concrete bridge decks, which are often subjected to severe operating conditions, both environmental and man-made. Often, the most appropriate strategy to preserve or rehabilitate these structures is to provide some form of a protective coating or barrier. These surface treatments have typically been some form of polymer, asphalt, or low-permeability concrete, but the application of UHPC (Ultra High Performance Concrete) has shown promise for this application mainly due to its negligible permeability, but also as a result of its excellent mechanical properties, self consolidating nature, rapid gain strength and minimal creep and shrinkage characteristics. However, for widespread acceptance, durability and performance of the composite system must be fully understood, specifically the bond between UHPC deck and normal concrete typical for bridge decks. It is essential that the bond offers enough strength in order to resist the stress due to mechanical loading or thermal effects while also maintaining an extended service-life performance.

An experimental study was performed to assess the bond performance of UHPC for overlay applications. Pre-wetting conditions, surface preparation, freeze-thaw cycling and indirect tensile strength were variables taken into account to study such performance. A total of 60 composite and 7 monolithic concrete specimens, 102x76x394 mm, were cast to test in indirect tension. Experimental results showed that samples subject to 300 freeze-thaw cycles present greater bond strength than samples of the same age without freeze-thaw cycles, and all samples in which the moisture condition of the substrate is saturated before placing UHPC achieves excellent bond strength which amply satisfies the range specified in the ACI Concrete Repair Guide.