Experimental assessment of freezing-thawing resistance of rammed earth buildings
2021
Abstract The use of earth as a building material is worldwide encouraged thanks to its low environmental impact and its high hygrothermal performances. In wet and cold regions, the durability of earthen constructions is a major preoccupation because of water attack and frost damage. The variety of raw earth, compaction method and exposition to water increases the complexity to agree on a representative testing protocol to assess the frost resistance of earthen buildings. In this context, various molding and testing configurations are proposed to evaluate the impact of repeated freezing and thawing (F-T) cycles on earthen compacted samples. The experimental protocol is adapted from ASTM D560 standard which recommends 12 F-T cycles of −23 °C/+23 °C. A series of cylindrical samples were made from two types of earths (unstabilized and cement-stabilized) compacted following two compaction methods (dynamically and statically). They were experimentally investigated under two kinds of freezing-thawing cycles that can affect earthen buildings. One with water absorption aimed at reproducing the combined effect of capillary rise and frost action. The other one consisted in testing samples at their manufacture saturation ratio in a moist environment in order to analyze the frost resistance at early age. After each cycle, frost damage was evaluated through the amount of mass lost by scaling, as well as water content and the volume changes. The results indicated that surface scaling affected all samples exposed to freezing and thawing, even if cement stabilization upgraded frost resistance. The impact of the freeze-thaw cycles on water uptake within the samples was analyzed, and some considerations were given in order to develop a dedicated test to assess freezing-thawing resistance of earthen building materials in milder conditions.
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