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Abstract While ultra-high performance concrete (UHPC) offers numerous advantages, it also presents specific challenges, primarily due to its high cost and excessive cement content, which can pose sustainability concerns. To address this challenge, this study aims to develop cost-effective and sustainable UHPC mixtures by incorporating ground granulated blast furnace slag (GGBFS) and limestone powder (LP) as partial replacements for portland cement. Eight fiber-reinforced UHPC mixtures were investigated, with a water-to-cementitious materials (w/cm) ratio of 0.15. In four of the UHPC mixtures, 25% of the cement was replaced with GGBFS, and further, LP was added as a mineral filler, partially substituting up to 20% of the cement. In the remaining four mixtures, cement was replaced with only LP up to 20% (without GGBFS). The 28-day compressive strength of the UHPC mixture with 25% GGBFS and 20% LP was 149 MPa, 3.50% lower than the mixture without GGBFS. Its 28-day flexural strength decreased by 30%. Increasing LP replacement reduced drying and autogenous shrinkage, with a 29% shrinkage reduction at 20% LP replacement. Moreover, UHPC mixtures with GGBFS exhibited lower shrinkage compared to those without GGBFS for all LP replacements up to 20%. For evaluating the sustainability of UHPC mixtures, the cement composition index (CCI) and clinker to cement ratio (CCR) were determined. For 20% LP replacement with 25% GGBFS, CCI was 3.6 and the CCR was 0.5, 38% decrease from the global clinker to cement ratio. Overall, 20% LP replacement UHPC mixtures with and without GGBFS can produce UHPC class performance and reduce the environmental impact.
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An Experimental and Statistical Study of Normal Strength Concrete (NSC) to Ultra High Performance Concrete (UHPC) Interface Shear Behavior
With number of existing bridges in U.S, classified as structurally deficient and many bridges nearing end of their design service life, there is a need for a durable and accelerated construction solution. Recently, several state DOTs developed innovative solutions using Ultra-High Performance Concrete (UHPC) as infill material between prefabricated bridge components or as an overlay over existing structural elements. The normal strength concrete (NSC) to UHPC interface behavior is critical for overall performance of such structures. Experimental investigation consisting of 10 push-off specimens was performed to investigate shear transfer behavior at NSCUHPC interface. In general, the results showed that increasing roughness depth and reinforcement area has positive effect in interface shear capacity. The experimental results were compared with current AASHTO LRFD, ACI and PCI design guidelines. Though the design guidelines were conservative; they were not accurate in predicting the interface shear strength. Additionally, a database including results from past push-off tests on NSC-UHPC interface was developed and a reliability analysis was carried out with respect to AASHTO LRFD design guidelines. The reliability index was found to be lower than the target reliability index in standard design practices.
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- Award ID(s):
- 1662963
- PAR ID:
- 10107165
- Date Published:
- Journal Name:
- Second International Interactive Symposium on Ultra-High Performance Concrete
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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