Document Type

Report

Publication Date

10-2018

Abstract

This study investigated the use of a locally produced ultra-high performance concrete (UHPC) as an alternative to typical overlay materials. Several bond strength tests including slant-shear, splitting tension, and direct tension tests were performed to assess the bond strength between UHPC and normal strength concrete (NSC) substrate with varying surface textures. Tests were also conducted to assess the early-age and longer-term shrinkage behavior and coefficient of thermal expansion of the UHPC as well as rapid chloride permeability testing. Good bond between UHPC and NSC substrate was observed even with inadequate surface texture. Combined shrinkage and thermal effects were investigated for NSC slabs overlaid with the non-proprietary UHPC by analyzing five slab-overlay sections. Each slab-overlay had a single parameter varied to isolate the effects of thickness of the NSC substrate, substrate reinforcement ratio, and exposure conditions. Increased steel reinforcement and thickness of the NSC substrate were observed to reduce the effect of UHPC overlay shrinkage. The final major experiment was to overlay a full-scale channel girder to assess the response of a high-performance concrete, pre-stressed bridge girder with a 1-in. (25-mm) UHPC overlay to flexural loading. The girder was subjected to 1000 load-unload cycles to specified service load conditions. Cyclic loading was applied both before and after application of the UHPC overlay to provide a comparison of global behavior and performance of the girder and overlay. Finally, the girder with overlay was loaded to failure to investigate post-cracking and ultimate behavior of the composite member. Little to no visible distress was observed in the overlay until loads were applied that were significantly greater than expected under normal service conditions. The results indicated that the non-proprietary UHPC has the potential to serve as an overlay material as long as proper measures are used to prepare the substrate surface and ensure a high quality bond with the existing deck.

Comments

Tran-SET Project No. 17CNMS01

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