Design of Ultra High performance Concrete as an Overlay in Pavements and Bridge Decks

NUTC R321 Disclaimer The contents of this report reflect the views of the author(s), who are responsible for the facts and the accuracy of information presented herein. This document is disseminated under the sponsorship of The main objective of this research was to develop ultra-high performance concrete (UHPC) as a reliable, economic, low carbon foot print and durable concrete overlay material that can offer shorter traffic closures due to faster construction. The UHPC was optimized using supplementary cementitious materials (SCMs), proper combinations of aggregates, and adequate selection of fiber types and contents. Three types of SCMs, including silica fume, Class C and F fly ash, and ground granulated blast-furnace slag (GGBS) were used to optimize cement paste with high packing density. The optimized pastes were then used to produce UHPC materials with various contents of fine aggregates and fibers to prove the feasibility of using the UHPC for bonded overlay. The optimized materials were evaluated for workability, rheology, mechanical properties, and shrinkage, as well as their performance was compared to the reference UHPC. In addition, the robustness of the optimized UHPC mixtures to variations of the mixing and curing temperatures was also examined. Bond behavior and the effect of overlay thickness of the developed UHPC materials were also investigated in this study. The experimental study reported herein proved that the optimized UHPC mixtures can develop comparable performance to the commercially available UHPC proportioned with 100% silica sand and 25% silica fume replacement, which was used as the reference UHPC. Given the mix design of the reference UHPC, the UHPC mixtures developed in this study could be more environmental friendly and cost-effective overlay materials compared to the reference UHPC. It is important to note that the optimized UHPC materials can develop adequate mechanical properties without any accelerated curing or special treatment, which contributes to a reduction of overall construction cost of the overlay. The developed UHPC mixtures had equal to or lower drying shrinkage than the reference UHPC. The bond strength between the substrate concrete and the UHPC overlay was shown to be greater than that of the substrate concrete, and the use of the UHPC overlay led to significant increase in flexural strength and toughness over the monolithic beam cast with conventional concrete, regardless of the overlay thickness. These results indicate the feasibility of using the UHPC as a bonded overlay. and all the staff members of the Center for …