Interfacial characteristics of nano-engineered concrete composites

This study investigates the interfacial characteristics between aggregates and cement paste matrix in nanofillers modified concrete. A three-point bend test on the specimens composed of two pieces of aggregates bonded with a thin layer of cement pastes with/without nanofillers was carried out to characterize the interfacial bond strength of the composites. The scanning electron microscope observations and energy dispersive x-ray spectrometry analysis were also performed to characterize the interfacial microstructures and compositions of the composites. The experimental results indicated that the nanocomposites have higher interfacial bond strength and narrower interfacial transition zone thickness as well as more optimized intrinsic compositions and microstructures than that of composites without nanofillers. Specifically, the interfacial bond strength of nanocomposites can reach 7.67 MPa, which is 3.03 MPa/65.3% higher than that of composites without nanofillers. The interfacial transition zone thickness of nanocomposites ranges from 9 mu m to 12 mu m, while that of composites without nanofillers is about 18 mu m. The ratio of CaO to SiO2 in the interface of composites without nanofillers is 0.69, and that of nanocomposites increases to 0.75-1.12. Meanwhile, the nanofiller content in nanocomposite interface is 1.65-1.98 times more than that in the bulk matrix. The interfacial microstructures of nanocomposites are more compact and the content and crystal size of calcium hydroxide were significantly reduced compared with that of composites without nanofillers. (C) 2020 Elsevier Ltd. All rights reserved.