Revamp of the sticky rice-lime binder with metakaolin and natural fiber for restoration: Properties and characteristics

Abstract

• Revamped binders were designed based on ancient formulas from practical cases. • Coupled aging test involving freeze-thaw cycles and salt erosion was conducted. • Sticky rice starch facilities the formation of C-S-H or C-A-H gel in lime-metakaolin binder. • Microscopic characteristics of hybrid adhesives before and after aging were studied. Metakaolin and natural hemp fiber were selected to revamp sticky rice-lime binder with reference to ancient formulas from practical cases. Three types of hybrid lime adhesives were fabricated: sticky rice-lime putty, fiber-reinforced sticky rice-lime binder, and fiber-reinforced sticky rice-lime-metakaolin binder. The consistency, drying shrinkage, mechanical strength, pore structure, and durability assessed by the resistance against freeze-thaw cycles and freeze-thaw cycles in salt solution were evaluated. The XRD, FT-IR, SEM, EDS, and NMR analysis were used to investigate the mechanism of the obtained properties. The pore size distribution and microstructure characteristics after freeze-thaw were also studied by the NMR and SEM analysis. Fiber admixture effectively play a reinforcing role, manifested as the better shrinkage, flexural strength, and freeze-thaw resistance of revamped binders. Metakaolin admixture imparted hydrsaulicity into revamped binder and evidently improved the resistance towards freeze-thaw cycles and salt erosion. Sticky rice addition promoted carbonation and regulated CaCO 3 crystallization. Besides, sticky rice starch was conducive to the formation of a relatively dense microstructure aggregated by smaller-sized CaCO 3 crystals and amorphous gel, which facilitated the resistance against salt erosion. The formulated fiber-reinforced sticky rice-lime-metakaolin binder proved to be suitable for restoration with the superior mechanical, physical and durability properties.