Research on mechanical and electromagnetic shielding properties of cement paste with different contents of fly ash and slag

Abstract

This paper studied the mechanical properties and electromagnetic shielding effectiveness of cement paste (CP) mixed with fly ash and slag. With pure CP as the control group, 10%, 20%, and 30% cement contents were replaced by fly ash and slag. Then the compressive and flexural strength of the samples were tested. Wet resistance and dry resistance of samples were tested by the four-probe technique. The electromagnetic shielding effectiveness of the sample in the 3.94 GHz–5.99 GHz band was tested. Finally, based on the mercury intrusion porosimetry (MIP) test and backscattered electron and energy-dispersive X-ray spectroscopy (BSE-EDS) test, the impact mechanism of fly ash and slag on the electromagnetic properties of CP was expounded from the pore structure and element distribution. The results show that with the increase of fly ash or slag, the strength of the sample decreased. Mineral admixtures had little effect on wet resistance, while dry resistance showed an increasing trend with the increase of mineral admixture content. The reflection loss had the greatest impact on electromagnetic shielding effectiveness. With the increase of mineral admixture content, the reflection loss and multiple reflection loss of the sample increased, but the absorption loss decreased. The reason for the effect of compounding different proportions of fly ash and slag on the electromagnetic shielding effectiveness of CP is mainly due to the change in the proportion of mesopores with an aperture less than 100 nm and the content of metallic elements (e. g. Fe) in the specimens.