Incorporation of magnetite powder as a cement additive for improving thermal resistance and gamma-ray shielding properties of cement-based composites

摘要

In this contribution, the effect of waste magnetite powder (MP), obtained from a rock crushing process, as an additive to cement pastes exposed to elevated temperature and gamma-ray radiation, is evaluated. Cement pastes with different magnetite powder to cement ratios, up to 50% by mass, and exposed to temperatures of 200 degrees C, 300 degrees C, 450 degrees C and 600 degrees C, were prepared. The thermal conductivity, mass loss, compressive strength and shielding efficiency against gamma-rays (Cs-137) of the specimens were determined and the results compared with theoretical values obtained according to the WinXCom program, at different energy levels. The results demonstrate that the addition of MP significantly increases paste density, thermal conductivity, as well as the specific heat of cement stone. Moreover, the inclusion of MP contributes to strength improvements in both heated and unheated states. Likewise, the presence of MP leads to a decrease in mass loss and surface cracking on exposure to high temperature. In conclusion, it is argued that the incorporation of MP results in a significant improvement in gamma-ray shielding properties, as compared to plain cement pastes. (C) 2019 Elsevier Ltd. All rights reserved.