The influence of different concrete additions on the properties of lightweight concrete evaluated using experimental and numerical approaches

Lightweight concrete is a building material used for better insulation and lower energy consumption. The material properties of lightweight concrete, such as compressive strength and thermal conductivity, are strongly affected by the characteristics of its aggregate, binder, and other concrete additions. This study aims to investigate the effects of different concrete additions on the performance of lightweight concrete. Six different materials were used as concrete additions: limestone powder, expanded clay (Liapor®), fine fly ash, fly ash, and fine and normal sand. For lightweight concrete specimens, expanded glass granulate, i.e., Liaver®, was used as a lightweight aggregate to clarify the effects of concrete addition type, with all specimens designed so as to have a density between 800 and 950 kg/m³. The effects of different concrete additions on the characteristics and properties of lightweight concrete were investigated using several approaches; X-ray micro-computed tomography (μ-CT) was adopted to examine microstructural characteristics, with both the mechanical and thermal properties of the materials being measured using experimental tools. Numerical analysis was also conducted to validate the performance of the materials. The results show that supplementary materials can improve the performance of lightweight concrete with regard to both compressive strength and thermal conductivity.