This study focuses on the surface materials of rammed-earth walls of Fujian Tulou in Xiaoshu Village, exploring the microscopic characteristics of rammed earth in different orientations and the microclimate adaptation mechanism and degradation law of the walls. Specimens were collected from the inner and outer surface soil layers of the four directional walls of a representative Tulou. SEM, XRD, and XRF analyses were performed to characterize the materials’ microstructure, mineral composition, and elemental distribution, with the test results correlated to the microclimatic conditions of each wall orientation. The conclusion is as follows: (1) The microscopic particle size of rammed earth exhibits significant directional differences at dual scales of 300 nm and 2 μm. Solar radiation duration and wind speed are positively correlated with the coefficient of variation in particle size. (2) The southeast and north walls were the most severely damaged (soil loss, quartz enrichment: 79.9%), the west wall had minor cracks, the north wall showed slight salt crystallization (Halite = 0.3%), and the east wall exhibited moisture-related moss growth. (3) Traditional organic additives (bamboo strips, rice husks) mitigate deterioration and enhance structural integrity. (4) The diversity of soil color (related to hematite and iron oxide) can serve as a simple indicator of deterioration. This study has proposed differentiated protection schemes for the “microclimate-compounds” on walls facing different directions on the rammed-earth surface of the Tulou. The findings provide a theoretical basis for orientation-specific conservation of Tulou heritage and offer scientific references for the modification of modern rammed-earth materials.
Yan et al. (Sun,) studied this question.