High-performance Reactive Magnesium Cement Incorporating Hollow Natural Fiber and Silica Sand

Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China

^* Corresponding author: bwuar@connect.ust.hk

Abstract

Global warming caused by CO₂ emissions makes reactive magnesium cement (RMC) increasingly attractive due to its ability to sequester CO₂, however, the diffusion of CO₂ in RMC is severely limited by the dense hydrated magnesium carbonates (HMCs) formed on the outer layer. This work utilizes hollow natural fiber (e.g., sisal fiber) to facilitate the diffusion of CO₂ into the deep part of the RMC specimen. Combining with adding silica sand as a filling agent, the mechanical strength can be enhanced from 42.4 MPa of the control group to 92.6 MPa of the specimen with 2 vol.% sisal fiber, this is attributed to that the addition of sisal fiber significantly enhances the carbonation depth. FTIR and XPS results further prove that the addition of 2 vol.% or more sisal fiber can improve the carbonation degree by over 200%, leading to a sharp reduction of CO₂ emission from 37 kg/(m³>MPa) of the control group to 12.1 kg/(m³∘MPa) of the specimen with 2 vol.% sisal fiber. Therefore, adding hollow natural fiber and silica sand to RMC can be a promising approach to make RMC stronger and more sustainable.