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Earthen sites with important historical, cultural, artistic, social, and scientific values have been seriously damaged. Basal erosion, which is caused by soluble salts, water runoff, and sand-driving wind, is an extremely threatening erosion pattern for earthen sites. A cushion layer which has a damp-proofing function and good physical and mechanical properties can effectively decrease basal erosion. The primary aim of this study is to investigate material selection for the hydrophobic cushion layer for earthen sites in northwest China. The results indicate that cooked tung oil and sticky rice liquid, traditionally used in China, cannot meet the fundamental requirements of sufficient hydrophobicity for the cushion layer. Although polyvinyl alcohol (PVA) solution and tung oil exhibit similar properties in terms of soil hydrophobicity, water vapour permeability, water resistance, surface hardness, and colour difference for samples with 0.0-1.0% content, the PVA solution is significantly better than tung oil in unconfined compressive strength, deformation modulus, wave velocity, and viscosity. Therefore, the PVA solution should be preferentially selected as a hydrophobic cushion layer material according to the results of this work. When the mixing method is adopted, 0.6-1.0% PVA content is the best choice. [ABSTRACT FROM AUTHOR]

To determine thermal parameters of porous building materials for building thermal and energy analysis, an experimental study is presently carried out, which applies constant relative humidity controlled by the saturated salt-water solution under isothermal conditions. The principle of isothermal vapor sorption is discussed and the method for temperature and humidity control is proposed. Experiments are first performed using the routine materials of concrete, mortars, and clay brick whose experimental data widely existed in the previous studies, to confirm the present experimental work. Insulation materials of expanded polystyrene, extruded polystyrene, and polyurethane are tested for determining their water vapor permeability and isothermal sorption. These materials are considered due to the fact that they are mostly used as building insulation materials in China but lack thermalhygro parameters for actual applications. The humidity-bound ranges 11.3-96.7%, which basically covers the whole range of building thermal-hygro environment is encountered. The least square method is used to fit the experimental data obtained, and finally to present regression equations for the three materials. Results of this study are expected to provide key parameters for the model of heat and moisture transfer in the materials for real buildings in hot-summer and cold-winter regions of China, where the transfer of moisture is exhibited significantly in building energy. [ABSTRACT FROM AUTHOR]