Improved conductive and self-sensing properties of cement concrete by PDMS/NCB-impregnated recycled fine aggregate

Abstract

Polymer emulsion impregnation is a common method for strengthening recycled fine aggregate (RFA). By mixing Nano carbon black (NCB) into the polymer emulsion, highly conductive modified RFA (MRFA) can be simultaneously obtained. In this paper, highly conductive and self-sensing concrete was prepared by using the MRFA impregnated with the NCB and polydimethylsiloxane (PDMS) solution. The microstructure of MRFA and MRFA concrete physico-mechanical properties were studied. The effects of replacement ratio of MRFA, temperature, water content, and loading rate on the conductivity and self-sensing of prepared MRFA concrete was explored. The results show that the PDMS fills the pores of the RFA surface. The water absorption decreases by 2.53%, the apparent density and fineness modulus increased by 1.5% and 8.3%, respectively. With the increase of MRFA replacement ratio, the resistivity of concrete gradually decreases, and a sharp decline appears from 60% to 70%. The percolation threshold of concrete is calculated to be 3.37vol% of NCB. Meanwhile, the MRFA concrete has good temperature sensitivity and humidity adaptability. Under the stress cycle loading, the stress sensitivity of the MRFA concrete with 70% replacement ratio MRFA is as high as 4.45%/MPa. Besides, the stress sensitivity of MRFA concrete decreases as the loading rate increases.