Experimental study on bond enhancement between hammered lime mortar layers and sandstone in moist environments

Abstract

Abstract Delamination and detachment of hammered lime mortar layers threaten sandstone relic stability. This study enhances hammered lime mortar–sandstone bonding by innovatively applying composite material bridging effects through interfacial fiber incorporation. Direct shear tests evaluated fiber type, embedment length, strand number, width, end treatment, and curing age impacts in humid conditions. Results confirm method feasibility: fibers significantly increase peak shear strength (up to 28.56%), with fiber type being most influential. Enhanced strand number, width, embedment length, and knotted ends all improved shear resistance. The technique effectively mitigates interfacial sliding and mortar detachment. Aligned with minimal intervention principles, it provides theoretical and practical guidance for outdoor stone heritage preservation.