Development and characteristics of novel high-strength lightweight core-shell aggregate

The need for high-strength lightweight concrete for cost-effective and energy-efficient building construction drives the need to develop high-strength lightweight aggregates. In this study, a novel high-strength lightweight core–shell aggregate (HLCSA) was developed and compared with commercial available artificial lightweight aggregates (LWAs). The loose bulk density, water absorption, and crushing strength of the developed aggregate were optimized by changing the water/binder ratio of the shell, core materials, shell/core ratio, and curing methods and time. XRD, TGA, and X-CT were utilized to analyze the hydration degree, microstructure, and pore structure of the shell and core of the core–shell aggregate. The results showed that a suitable water/binder ratio of 0.20–0.22 for the shell and a core material (cenosphere) were optimal for producing the HLCSA. The size, loose bulk density, crushing strength, and strength efficiency of the pelletized aggregate were all found to increase with the shell/core ratio. The curing method and curing time played an important role in affecting the crushing strength. The microstructure and porosity of HLCSA analyzed by optical microscopy and X-CT showed that it was a hollow shell structure with a porous core that was well coated by a dense shell, which ensued the high strength and lightweight features at the same time. The developed HLCSA (with shell/core of 1.6) had a crushing strength of 6.93 MPa and a loose bulk density of 834 kg/m³ with a high strength efficiency of 8,309 Pa·m³/kg, which was much higher than the common commercial LWAs.