Durability of Marine Concrete with Nanoparticles under the Joint Effect of Dry–Wet Cycles, Cl− Erosion, and Carbonation

Abstract

This study aimed to investigate the durability performance of marine concrete incorporated with nano–SiO2 and nano–Al2O3 under the joint effect of dry–wet cycles, Cl− erosion, and carbonation. Free Cl− content and carbonation depth were used as durability evaluation indexes of concrete with nanoparticles under the joint effect of the three factors. Scanning electron microscope (SEM), energy dispersive spectrometer (EDS), backscattered electrons (BSE), and X-ray diffraction (XRD) were used to analyze the morphology and phase composition of the concrete. The test results showed that the free Cl− content and carbonation depth of the concrete were significantly reduced after incorporating nanomaterials, indicating that nanomaterials improved the resistance of the concrete to Cl− erosion and carbonation under the joint effect of dry–wet cycles, Cl− erosion, and carbonation. Compared with plain concrete at 56 cycles, both nanomaterials showed the most significant improvement at a dosage of 1.8%, with a 20% and 37.5% reduction in free Cl− content and carbonation depth, respectively, for nano–SiO2 concrete, and 16.67% and 31.66% reduction, respectively, for nano–Al2O3 concrete. The improvement effect of nano–SiO2 was better than that of nano–Al2O3, and the free Cl− content and carbonation depth of nano–SiO2 concrete were reduced by 3.33% and 5.84%, respectively, compared with those of nano–Al2O3 concrete at the optimal dosage. The microscopic test results showed that incorporating nanomaterials promoted the hydration process of cement and refined the pore structure of the concrete, improving the durability of the concrete under the joint effect of dry–wet cycles, Cl− erosion, and carbonation.