Experimental Research on Material Properties of Ancient White Bricks in the Yichun Region, China

Abstract

ABSTRACTThe ancient white bricks in the Yichun region occupy a special place in Chinese cultural heritage. In order to study the material properties of these unique bricks, a series of experimental studies were conducted, including measurement of density, compressive strength, thermal conductivity, chemical composition, phase composition, pore structure, micro morphology, and firing temperature. These material properties were tested and analyzed using a variety of methods including X-ray fluorescence (XRF) spectrometry, X-ray diffraction (XRD), scanning electron microscopy (SEM), mercury injection test, thermal expansion test, etc. The material properties of the ancient white bricks were also compared with the material properties of the traditional red bricks and of the traditional blue bricks. The results reveal that while the thermal conductivity of the ancient white bricks is lower than that of the traditional red bricks and of the traditional blue bricks, the ancient white bricks’ density is actually slightly higher than that of the traditional red bricks and of the traditional blue bricks. An additional finding is that whereas the compressive strength of the white bricks from the ancient city walls is higher than that of the traditional red bricks and of the traditional blue bricks, the compressive strength of the white bricks from the traditional residential walls is similar to that of the traditional red bricks and of the traditional blue bricks. The main components of these two types of ancient white bricks are basically consistent with the constituents of the natural clay originating in the Yichun region, such as Al-Mg compounds and silicide, furthermore the proportion of each of these main elements is also similar. The phases of these two types of ancient white bricks are mainly composed of γ-Fe2O3, FeCO3, FeS, enstatite, gaylussite, talc, calcite, quartz, and corundum. The pore size of the two types of ancient white bricks is mainly concentrated in the interval between 0.1 μm and 1 μm, which is similar to the traditional blue bricks’, but is smaller than the traditional red bricks’. The firing temperature of the white bricks from the ancient city walls is between 650°C and 700°C, and the firing temperature of the white bricks from the traditional residential walls is approximately 600°C. These results can provide the basis for the excavation of traditional techniques and a scientific conservation strategy for the ancient Chinese white bricks.