Design and performance of cost-effective ultra-high performance concrete for prefabricated elements
"This study presented in this thesis aims to: (1) develop a mixture design methodology for cost-effective ultra-high-performance concrete (UHPC) incorporating high volume of supplementary cementitious materials and conventional concrete and masonry sands; (2) developed UHPC with adapted rheology incorporating lightweight sand, hybrid fibers, and nanomaterials with improved properties; (3) design prefabricated UHPC panels with fiber-reinforced polymers (FRP) for enhanced flexural properties of stay-in-place panels made with optimized UHPC; and (4) explore potential applications of such UHPC elements. The proposed design methodology produced UHPC mixtures with 28-days compressive strengths higher than 125 and 168 MPa under standard water curing and 1-d steam curing at 90 ⁰C. To further improve the properties, internal curing using pre-saturated lightweight sand, rheology control of the suspending mortar before steel fibers addition, and reinforcement of hybrid fibers and carbon nanomaterials, were employed. The outcome indicated: (a) the optimum replacement ratio of lightweight sand to river sand in the UHPC was 25% to increase mechanical properties and reduce shrinkage; (b) at steel fiber content of 2%, the optimal plastic viscosity of the suspending mortar was 53 ± 3 Pa·s to secure favorable fiber distribution and enhance flexural properties of the UHPC; (c) through use of hybrid steel fibers, the flexural strength, tensile strength, and autogenous shrinkage of UHPC can increase by up to 20%, 25%, and reduced by 40%, respectively; (d) adding nanomaterials at a volume fraction of 0.3% increased the tensile strength and energy absorption capacity of the UHPC by 55% and 185%, respectively. In the end, novel applications of the developed reinforced and non-reinforced UHPC-FRP systems were explored for various applications"--Abstract, page iii.
Missouri University of Science and Technology
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