The contribution of alkali-soluble proteins to the performance of traditional sticky rice-lime mortar

Traditional sticky rice-lime mortar, a remarkable ancient building material, derived its effectiveness from the synergistic interaction between lime and sticky rice pulp. While the role of starch has been studied, the specific activation mechanism and microstructural templating effect of its protein components (constituting about 10% of rice) remained unclear. This study systematically investigated the use of alkali-treated sticky rice pulp, a process inspired by traditional slaking practices and modern industrial starch modification, to activate these proteins. The results showed that alkaline pretreatment enhanced protein dissolution, induced a conformational change, and increased surface hydrophobicity. Critically, these activated proteins acted as organic templates, directing the formation of uniform CaCO 3 spheres in solution and promoting a reinforced, interlocking microstructure in the hardened mortar. Macroscopically, the mortar with alkali-treated sticky rice pulp demonstrated superior workability, optimal dimensional stability (lowest drying shrinkage of 2.3% and no cracking), and improved durability, although its long-term strength development was moderated by reduced carbonation. This work revealed the alkali-activation mechanism of proteins in sticky rice pulp and their consequent templating role, providing a scientific basis for optimizing traditional materials for cultural heritage conservation.