Enhanced compressive strength of rammed earth walls stabilized with eco-friendly multi-functional polymeric system

This paper presents an efficient and eco-friendly soil stabilization method for binding the soil particles of rammed earth walls. The method uses a combination of a water-soluble acrylic acid–acrylic amide copolymer and an epoxy system containing a hardener. The results revealed that the unconfined compressive strength (UCS) of soil stabilized with the mixture of the copolymer and epoxy system was five times higher than that of soil treated with water and three times higher than that of stabilized soil (SS) with only the copolymer. The roles of the copolymer and epoxy system in UCS enhancement were determined based on morphology and apparent density (AD) and elucidated using proposed models. The soil stabilized with the copolymer and epoxy system exhibited the lowest AD and highest UCS. Further, its unique web-like morphology is consistent with the formation of an interpenetrating polymer network (IPN). The carboxylic and amide groups in the copolymer contribute to the formation of the IPN through interactions with the epoxy and amine groups of the hardener. The surface hydroxyl groups in the soil promote the coating of the polymer layer on the soil surface and the inter-particle cohesion, resulting in the formation of larger compacted lumps with a decreased AD and increased UCS. The hydrophilic copolymer acts as a stabilizer and plasticizer. The results confirmed that the epoxy system and copolymer significantly increased the UCS by forming an IPN. Thus, this study provides an efficient and eco-friendly water-soluble copolymer and epoxy system for enhancing the UCS of soil.