The Biocolonization Control Mechanism of Traditional Raw Earth–Rubble Walls in Fuzhou

Focusing on the R&D demand for green earthen building materials in coastal high-temperature and high-humidity areas, this study explores the biocolonization control mechanism of raw earth–rubble walls, taking the traditional raw earth–rubble walls of ancient buildings in Sanfang Qixiang, Fuzhou, as the research subject. FTIR, XRD, Raman, and SEM-EDS combined technologies were employed for characterization. The results show that the raw earth is rich in proteins, amino acids, and other nutrients, which provide the nutritional basis for plant growth. The raw earth and rubble share homologous mineral components. The rubble is fired from raw earth mixed with iron minerals such as hematite, with carbonaceous substances generated during the firing process. Iron, carbon, and potassium released from the weathered rubble may inhibit the growth of plant roots. The raw earth is relatively looser than the rubble, and the two form a dense–loose alternating structure. Combined with the secondary calcification mechanism in the raw earth, this structure resists the expansion and cracking of the wall and improves the viscosity and hardness of the wall. It is concluded that in a high-temperature and high-humidity environment, the raw earth first releases nutrients to promote plant growth. As time progresses, the relevant substances released by the rubble continuously inhibit root growth. Combined with the structural characteristics of the wall with high firmness and crack resistance, plants growing on the wall will not damage the wall structure. This finding provides a theoretical basis for the biocolonization control mechanism of raw earth–rubble walls and also offers practical references for the protection and sustainable reuse of raw earth buildings in similar areas.