Microchemical Analysis of Rammed Earth Residential Walls Surface in Xiaochikan Village, Guangdong

Xiaochikan Village, located in Guangdong Province in South China, is one of the few remaining traditional rammed earth dwellings of the Cantonese ethnic group in the Lingnan region. However, the influence of Zhuhai’s subtropical maritime monsoon climate has led to continuous physical and chemical erosion of the rammed earth walls. For example, cracking occurs due to high temperatures and heavy rain, accelerated weathering occurs due to salt spray deposition, and biological erosion occurs due to high humidity and high temperatures. Therefore, two experimental analysis techniques, X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectrometer (SEM-EDS), were used to explore the structural anti-erosion mechanism of the ancient, rammed earth buildings in Xiaochikan Village. The results show that (1) the morphological characteristics of the east and west walls of the rammed earth dwellings in Xiaochikan Village are more similar. The particles on the east wall are regular spherical or polygonal, small, and evenly distributed, while the particles on the west wall are mainly spherical and elliptical, with consistent size and less agglomeration. The surfaces of the particles on both walls are relatively smooth and flat. (2) The core element bases of the four wall samples are consistent, with C, Si, Al, Ca, and Fe as the core, accounting for more than 93%, reflecting the base characteristics of the local alluvial soil “silicate skeleton–carbonate cementation–organic matter residue” and reflecting the “local material” attribute of rammed earth. Except for the south wall sample, the Cl content of the remaining samples exceeds 1%. In the thermal map, Cl shows “pore/interstitial enrichment”, which confirms that the salinization process of marine aerosols with rainwater infiltration and evaporation residue is a common influence of marine climate. (3) The rammed earth walls in Xiaochikan Village consist of three main minerals: Quartz (SiO₂, including alpha-type SiO₂), Calcite (CaCO₃, including synthetic calcite), and Gibbsite (Al(OH)₃).