Interfacial reinforcement behavior of lightweight aggregates–binder matrix in high-strength mortars incorporating carbon nanotubes

Abstract

In lightweight high-performance concrete with low water-to-cement ratios, pre-saturated lightweight aggregates (LWA) can increase the interfacial transition zone (ITZ) porosity owing to rapid internal water release. This study investigated the feasibility of improving ITZ morphology and strengthening aggregate–binder bonding in lightweight high-strength mortars through the incorporation of carbon nanotubes (CNTs). CNTs acted as nucleation sites and formed mechanical interlocks, reducing ITZ thickness and heterogeneity, particularly near pre-saturated LWA. Well-dispersed CNT-incorporated lightweight mortars achieved up to 120 % higher compressive and flexural strength than the control specimens (compressive strength: 72 MPa, flexural strength: 4.54 MPa), whereas the ITZ thickness adjacent to the LWA decreased from 35 to 15 μm. Overall, the synergistic effect of LWA internal curing and CNT reinforcement offers an effective strategy to enhance the ITZ microstructure and improve mechanical performance in lightweight high-strength mortars.