Abstract: For construction of a high core-wall clay earth-rock dam at negative air temperature, it is common to see compactability degeneration and structural defects (e.g. frost heave, thawing settlement and structure crack) after short-term frozen or freeze-thaw cycles, leading to working performance deterioration in strength and impermeability. Conventional measures, e.g. covering thermal insulations, interfere severely with core-wall clay paving and filling, and suffer difficulty in maintaining continuous construction. In this work, a phase change material-incorporated clay (PCM-clay) is used as core wall material; anti-freezing performances of the lower PCM-clay are investigated considering the effect of an upper loose-covering layer. We analyze the impact of PCM content on thermal characteristics, and verify the effectiveness of a homogenization model for thermal conductivity through thermal tests. Then, heat transfer and thermal performance of the upper layer is examined by conducting thermal cycling tests. Under 48-hour typical temperature, construction time extension for the core wall clay with 4% and 8% PCM contents are 22.6 and 24.9 hours, respectively. For 4% PCM-clay, the total continuous construction time in 2 days is 45.8 hours; 8% PCM-clay even keeps above positive temperature for 48 hours. The results indicate that the anti-freezing measures of PCM-clay and upper loose covering provide a theoretical basis and potential way to extend winter construction time, thus helping accelerate the construction progress of core walls in cold regions.

Key words: core-wall clay earth-rock dam, winter construction, phase change material-incorporated clay (PCM-clay), thermal property, anti-freezing performance, loose-covering