Uncovering the compensatory effect of aggregate size on the mechanical performance of lightweight aggregate concrete (LWAC): An experiment and simulation study

Mitigating the low strength of lightweight aggregate (LWA) on the degradation of mechanical properties of concrete has vital significance in optimizing field applications of lightweight aggregate concrete (LWAC). This research systematically investigated the matching relation between the variations of LWA’s size (0.075-0.6 mm, 0.6-1.18 mm, 1.18-4.75 mm, and 4.75-10 mm) and different strength matrices (ultra-high strength, high strength, and normal matrices) on the compressive strength compensation of LWAC. Furthermore, a mechanical model was established using the peridynamic theory to analyze the effect of aggregate size on the mechanical properties of LWAC. The experimental results indicated that the reduction of LWA’s size effectively enhanced the compressive strength of concrete, where the enhancement effect was more pronounced in combinations of LWA and ultra-high strength matrices. The compressive strength of UH-LWA0.6 reached 96.3 MPa at a density of only 1887 kg/m3, which was 75.5% of the guaranteed compressive strength compared with UH-Ref. The simulation results revealed that the reduction of aggregate size adequately unleashed the advantages of transgranular fracture in LWAC, where The number of broken bonds increased by 62.0%, 48.9%, and 43.8% from ultra-high strength to normal concrete, respectively. Meanwhile, the elastic modulus of ultra-high strength and high strength matrices mixed with 0.075-0.6 mm LWA improved significantly, reaching 42.97 and 39.06 GPa, respectively. This research provided an economical and practical approach to promote the mechanical properties of LWAC. • The reduction of LWA’s size enhance the compressive strength of concrete. • LWA below 0.6 mm can produce concrete with compressive strength exceeding 100 MPa. • Damage process of LWAC under compression is analyzed via peridynamic model. • The trans-granular fracture mode of LWA transforms the damage of concrete under compression.