不同干燥温度下水工混凝土脱水与变形规律及机制OA

The hydraulic concrete undergoes slow but non-negligible deterioration under drying-wetting cycles.While laboratory accelerated testing serves as an effective research approach for investigating this process,two key issues persist:drying shrinkage acts as the intrinsic driving force of deterioration under drying-wetting cycles,yet the multi-scale deformation mechanism remains unclear;and the absence of unified standards for drying temperatures directly affects the determintaion of the drying rate,deformation patterns,and degradation mechanisms.Multi-scale drying tests on concrete,mortar,and paste were performed in this study,combined with microstructural analyses such as 1H and 29Si nuclear magnetic resonance spectroscopy,to characterize dehydration,deformation patterns,and the evolution of hydration products.Results show that both water loss rate and shrinkage of concrete,mortar,and paste increase with drying degree and temperature,exhibiting a development pattern of initial slow acceleration fol-lowed by rapid acceleration.Concrete shrinkage is mainly governed by shrinkage stresses induced by water loss from pores of various sizes.Elevated temperature promotes water loss from smaller pores and leads to continuous consump-tion of gel water and interlayer water,thereby intensifying nonlinear shrinkage.High temperatures cause irreversible damage to hydration products,manifested as loss of crystalline water and phase transformation of aluminate phases,as well as polymerization/depolymerization of calcium silicate hydrate gels,fundamentally altering the deformation mechanism.A predictive model was established between shrinkage rate and water loss rate and a recommended drying temperature threshold of 60 ℃ was proposed,providing theoretical support for accurate long-term performance prediction of hydraulic concrete.