Lightweight aggregate concrete modified with zinc oxide nanoparticles: compressive strength and carbonation resistance

ABSTRACT Zinc Oxide nanoparticles (ZnO nanoparticles) influence the concrete properties. This study evaluates mechanical strength and carbonation resistance of lightweight aggregate concrete (LWAC) modified with ZnO nanoparticles as an additive. Mixes adding 1 wt% and 2 wt% ZnO by cement weight were prepared and compared with unmodified LWAC. Fresh-state results showed a slight reduction in workability and a similar pH to the reference. Mechanically, ZnO-modified mixes exhibited lower early-age compressive strength, although they reached structural strength values after 28 days. LWAC modified with 1 wt% ZnO nanoparticles showed slower early-age strength development but stabilized and matched the reference strength gain rate after 14 days. In contrast, LWAC with 2 wt% ZnO nanoparticles exhibited a significant strength increase between 7 and 14 days, despite very low mechanical capacity during the first 7 days of the curing. Notably, ZnO-containing mixes demonstrated significantly improved resistance to carbonation under accelerated exposure at 5 % CO 2 , with reductions in carbonation depth of up to 58 % compared to the reference. These results confirm the potential of incorporating 1 wt% ZnO as an effective alternative to enhance LWAC durability against carbonation without significantly compromising its mechanical performance.