Characterizing properties of magnesium oxychloride cement concrete pavement

Abstract

The performance of magnesium oxychloride cement concrete (MOCC) in road engineering in the arid region in northwest China was investigated over a two-year period. Two categories of MOCC pavement, light-burnt magnesia concrete road (Road-L) and dolomite concrete road (Road-D), were prepared with light-burnt magnesia and a mixture of light-burnt magnesia and caustic dolomite (1:3 by mass), respectively. Variations in the properties of the MOCC pavement, such as compressive and flexural strength, mineralogical phase, and microstructure, after being exposed to two rainy seasons in the field were monitored. The compressive strength of the cored samples were conducted after being aged for 28 d, and the compressive and flexural strength were tested at ages of 1, 2, 3, 28, 90, 180, 270, 360 and 720 d. The mineralogical phase and microstructure of the pavement were also analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results demonstrate that MOCC pavement obtained desirable compressive and flexural strengths after curing for 3 d for Road-L and 28 d for Road-D. Both of the compressive and flexural strength of Road-L and Road-D decreased slightly after experiencing two rainy seasons, with the major hydration products being 5Mg(OH)2·MgCl2·8H2O (Phase 5) and 3Mg(OH)2·MgCl2·8H2O (Phase 3). The decomposition of Phase 5 is mainly responsible for reducing the mechanical strength of the MOCC pavement.