Drying-Induced Cracking of Raw Earth Plaster
Abstract: The widespread adoption of raw earth materials in mainstream construction practices continues to encounter multiple challenges, where the main concerns with using earth plasters revolve around issues such as shrinkage, abrasion, and erosion (in the case of exterior application). This study aims to provide a better understanding of the drying-induced cracking patterns of raw earth plaster. It first tackles the formulations of plaster with two different types of clay, kaolinite, and montmorillonite, with various sand and water proportions, where the latter is added until observing a consistent paste. To quantify this rheological consistency, we performed a squeeze test to determine the yield stress. Then, we monitored the cracking behavior of samples on a varying-thickness slab experiment, from which we concluded the impact of the thickness, substrate, and clay content on drying patterns. To understand these cracking patterns, an oedometer test was conducted to observe the mechanical behavior under compression, air entry pressure estimated the capillary pressure significance in the cracking phenomenon, and a shrinkage laser test caught the initial drying behavior of the samples. Based on these results, we plan to formulate a crack-free earth plaster using montmorillonite, which is an abundant and affordable clay.
Keywords: Shrinkage, cracking pattern, clay formulations, compression, thickness.