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.

摘要

本文用轻烧氧化镁和轻烧氧化镁与苛性白云石的混合物(质量比为1:3)制备了氯氧镁水泥混 凝土(MOCC),并将其应用于西北干旱地区道路工程中,分别修建了Road-L 和Road-D 两种MOCC 路面。通过抗压强度、抗折强度、物相组成及微观结构等性能测试,研究了MOCC 路面材料在两年 龄期内的性能变化规律。测试了28 d 龄期时试样的抗压强度,以及1、2、3、28、90、180、270、360 和720 d 龄期时预埋试件的抗压强度和抗折强度。采用X 射线衍射和扫描电镜对路面的矿物组成和微 观结构进行了分析。结果表明,养护3 d 龄期时Road-L 路段的抗压强度和抗折强度达到设计要求,而 Road-D 路段养护28 d 时达到设计要求,主要水化产物为5Mg(OH)₂MgCl₂ 8H₂O(5 相)和3Mg(OH)₂MgCl₂8H₂O(3 相)。经历两个雨季后,路段Road-L 和Road-D 的抗压强度和抗折强度均略有下降,服 役过程中5 相被雨水分解是导致MOCC 路面机械强度降低的主要原因。