Performance and mechanism of the structure formation and physical-mechanical properties of concrete by modification with nanodiamonds

Abstract

Nanomodifying additives in the building materials production is a relevant and widely studied topic in current building materials science. Nanodiamonds are used in various fields of science and technology. However, they were not used as a modifying additive in the production of building composite materials. The purpose of this study is to investigate the mechanism of interaction of chemically pure cavitation synthesis nanodiamonds (КНА-НС) with cement concrete on the structure formation and mechanical properties of fresh and hardened concrete. These KHA-HC nanodiamonds are carbon sp3 hybridized nanoparticles with a diamond-like structure and a particle size in a cross section of not more than 3nm, shaped close to spherical and a clear mono modal distribution throughout the entire fractional composition, with a maximum of 1nm to 3nm. During the research, the initial components were selected, the compatibility of these components was checked, including the formation of test samples, the properties of fresh concrete, the density of hardened concrete, compressive and flexural strength at various ages of hardening (2, 7, 14 and 28 days) were studied using standard methods, and X-ray diffraction and scanning electron microscopy of concrete were also carried out. It has been established that the addition of KHA-HC accelerates the process of concrete strength gain. The greatest effect was recorded for concrete aged 2 days. With an optimal KHA-HC content of 0.4%, the increases in compressive and flexural strength were 28.6% and 26.1%, respectively. The addition of KHA-HC in all considered ranges from 0.1% to 1.0% has a positive effect on the strength properties of concrete. The most effective dosage is 0.4%. The increases in compressive and flexural strength of concrete at an age of 28 days were 15.1% and 15.7%, respectively. Nanomodification of concrete with the KHA-HC additive does not affect the phase composition of concrete. The effect of “self-reinforcement of cement matrix” put forward in this study is confirmed by images of the microstructure of the cement matrix with a large accumulation of calcium hydrosilicate zones.