From mixing to microstructure: unraveling the effects of manual pound-mixing method on lime mortar through a laboratory-scale study

Traditional lime mortar is crucial for preserving historical structures, but knowledge of its mixing techniques remains limited. This study compared manual pound-mixing with conventional mechanical mixing to evaluate effects on mortar performance. Pure and fiber-reinforced hydrated lime mortars were tested. The results showed that pounding reduced lime particle size and increased specific surface area, producing a denser matrix. In fiber-reinforced mixtures, pounding also improved fiber dispersion and interfacial bonding while partially removing alkali-sensitive components from the fibers. These modifications led to higher strength, lower water absorption, and better durability, although drying shrinkage increased. Moreover, strength did not correlate with carbonation degree, indicating that pounding-induced microstructure governed performance. These findings reveal the scientific basis of traditional pound-mixing for improving lime mortars.