Calcium silicate hydrate (C-S-H) gel provides cohesive strength that resists cracking and peeling of concrete. Mechanisms underlying C-S-H cohesion depend on complex molecular behaviors and mesoscale configurations, and remain poorly understood. Herein, bonding and cracking behaviors of C-S-H gel are explored via combining experimental information of decalcified C-S-H into statistical physics framework of aggregating nanograins. It quantifies the significant impact of inter C-S-H grain interaction on mechanical properties of hardened cement paste through experiments for the first time. Inter-grain interaction has little impact on pore structure, and yet determines the energy required for disintegration of grains stacked assembly. Huge gap of tensile properties between single molecular interface and multi-interface dense/porous grains assembly is elaborated, which decreases from a few gigapascals to tens to hundreds of megapascals. Full-range deterioration evolution picture of gel cohesion is constructed, as functions as inter-grain interaction and packing fraction, which gives the cracking threshold that bridges different concrete deterioration behaviors, and reconciles molecular-level characterizations, mesoscale configurations and its engineering applications.
 

水化硅酸钙,；粗粒化,；粘性材料