A novel high-performance lightweight concrete prepared with glass-UHPC and lightweight microspheres: Towards energy conservation in buildings

Improving energy conservation of buildings and promoting wastes recycling contribute to reducing CO₂ emissions. This work developed a green high-performance lightweight concrete (HPLC) with good thermal insulation for energy-saving purposes. The HPLC was comprised of lightweight microspheres and sustainable ultra high-performance concrete (UHPC), which was prepared with a large volume of waste glass. For the glass-based UHPC, the use of glass cullet led to mechanical decrement, while the workability and mechanical properties were improved with the replacement of 50% cement by glass powder. Combining glass aggregates and powder in UHPC significantly enhanced its thermal insulation properties. Meanwhile, incorporating two kinds of lightweight microspheres in the glass-based UHPC further lowered the density and thermal conductivity of HPLC. The performance of HPLC was dependent on the physical characteristics of lightweight microspheres rather than their chemical reaction based on molecular dynamics simulation. The developed HPLC exhibited a low density (<2000 kg/m³) and excellent mechanical properties (compressive strength >100 MPa and flexural strength >35 MPa). The superior performance of HPLC was ascribed to the high pozzolanic reactivity of glass powder and its promotion on cement hydration, the low thermal conductivity of glass, the chemical reactivity of microspheres as well as their hollow nature for impeding heat transfer. The good flexure and thermal insulation performance would make this eco-HPLC a promising material for applications in energy efficient buildings and long-span lightweight structures.