Engineering interfacial transition zone with polymer/CNT nanocomposites coating: Break the dilemma between strength and damping

The conventional approach to enhancing the damping performance of mortar/concrete typically involves incorporating an excessive mass of soft polymer randomly, albeit at the expense of strength. In order to break dilemma between strength and damping, we propose a novel strategy involving the application of a thin layer of polyacrylic ester/carbon nanotube (PAE/CNT) nanocomposite onto aggregates, achieved through dip coating. The high modulus properties of the material effectively address stress concentration at the interfacial transition zone (ITZ) under external loads, thereby significantly enhancing its energy dissipation capability. Moreover, friction and microcrack at the nano-interface between CNT and the polymer matrix further contributes to markedly improved damping. Pore structure analysis of the composite mortar reveals that the coating layer densifies the ITZ and reduces the volume fraction of large capillary pores, consequently bolstering the concrete's strength. Backscattered electron (BSE) imaging results further confirm that the composite coating significantly reduces the porosity of the ITZ. Optimal results are achieved with a coating mass of 5 mg/g, resulting in a remarkable 10.2 % increase in compressive strength and a 33.3 % enhancement in the loss factor at 28 days.