Effect of Hydroxypropyl Methylcellulose on the Properties of Hemp Concrete

Hemp concrete, the most widely researched bio-aggregate concrete made from hemp shiv and lime, is highly valued in the building envelope for its negative carbon balance, thermal-acoustic insulation, and moisture regulation properties. However, its weak strength and vulnerability limit wider application and make it prone to damage, prompting research to improve its durability and strength without compromising hygrothermal performance and sustainability. This study evaluated the effect of hydroxypropyl methylcellulose (HPMC) on lime-hemp composites, examining their impact on thermal-mechanical and water absorption properties. At the same time, the phase composition of the matrix was studied using Thermogravimetric (TG). Results show that with 0.5-5% dosage, HPMC minimally impacts hemp concrete's thermal performance but significantly enhances strength and reduces capillary water absorption. Especially adding 5% of HPMC boosts compressive strength by 89%, reduces water absorption by around 21%, and slightly increases thermal conductivity. These effects stem from fiber-bridging, pore-filling, carbonation promotion, and cellulose's hydrophilic water retention.