Lightweight ultra-high-performance concrete (UHPC) with expanded glass aggregate: Development, characterization, and life-cycle assessment

Ultra-high-performance concrete (UHPC) has high mechanical strengths and durability, but its density and carbon footprint are usually high. This paper developed a lightweight UHPC with low cost, low carbon footprint, low energy consumption, low thermal conductivity, and high ductility, by using three types of lightweight ingredients: hollow glass microsphere (460 kg/m³), expanded glass aggregate (800 kg/m³), and polyethylene fibers (970 kg/m³). Underlying mechanisms were investigated through thermogravimetry, X-ray diffraction, and mercury intrusion porosimetry analyses. Results showed that the hollow glass microsphere reduced the thermal conductivity of concrete; the expanded glass aggregate mitigated shrinkage while enhancing compressive strengths and flexural properties of concrete through internal curing; and the polyethylene fibers promoted multiple cracks, increasing ductility and toughness of concrete. With 20 % hollow glass microsphere, 1.5 % polyethylene fiber, and 25 % expanded glass, UHPC mixtures were developed to achieve high compressive strength (>127 MPa) and high flexural strength (>21 MPa), while reducing the density by 20 % and carbon footprint by 16 % as well as embodied energy by 27 %.