混凝土抗冻融破坏性能研究进展OA北大核心

The freeze-thaw resistance of concrete is a crucial factor determining its service life in cold regions.This review represents recent research progress on concrete freeze-thaw resistance based on freeze-thaw damage mechanisms,influencing factors,damage models and service life prediction,as well as measures to enhance freeze-thaw resistance. The freeze-thaw damage mechanisms of concrete mainly are based on powers hydraulic pressure theory,osmotic pressure theory,the Setzer's micro-ice lens theory,Scherer and Bresme's crystallization pressure theory,and the salt frost theory.These theories provide insights into the damage mechanisms of concrete during freeze-thaw cycles from different perspectives.However,a unified theory is not yet established,and a further research is thus needed. Some factors influencing the freeze-thaw resistance of concrete can be classified as direct and indirect factors.The direct factors primarily encompass pore structure characteristics(such as porosity,pore size distribution,air void spacing factor,etc.)and degree of saturation,with the air void spacing factor being the decisive element affecting concrete's performance in resisting freeze-thaw cycles.The indirect factors can be classified into two categories,i.e.,material composition and environmental conditions.In terms of material composition,the type of aggregates,water to cement ratio,mineral admixtures,and various chemical admixtures play important roles.Using lightweight aggregates or reducing the water to cement ratio can enhance the freeze-thaw resistance.The addition of mineral admixtures like silica fume and fly ash can optimize concrete pore structure and improve the freeze-thaw resistance.Chemical admixtures such as air-entraining agents and water reducers can enhance concrete freeze-thaw resistance from different aspects.The application of fiber materials and nanomaterials has a potential in improving concrete freeze-thaw performance,primarily via enhancing its mechanical properties and microstructure.The environmental conditions like freeze-thaw temperature,curing conditions,and freeze-thaw rate are key factors affecting concrete freeze-thaw resistance.Lower temperatures and rapid freeze-thaw cycles often exacerbate concrete damage,while appropriate curing conditions can significantly improve its freeze-thaw durability.These environmental factors interact with material composition factors to collectively determine concrete performance in cold environments. Recent work propose various freeze-thaw damage models to describe the performance evolution of concrete under freeze-thaw cycles.These primarily include models based on cumulative damage,probability distribution models(such as the Weibull distribution),and multi-scale numerical simulation models.These models provide a theoretical basis for predicting the service life of concrete structures.However,some limitations remain in parameter determination and practical application. To enhance concrete freeze-thaw resistance,some improved techniques are proposed.These mainly include:1)adding chemical admixtures such as air-entraining agents,superabsorbent polymers,and antifreeze agents;2)incorporating mineral admixtures like silica fume,fly ash,metakaolin,rice husk ash,and ground granulated blast furnace slag;3)using fiber materials such as steel fibers and polypropylene fibers;4)adding nanomaterials like nano-silica,nano-alumina,and carbon nanotubes;and 5)applying surface coating treatments,such as using hydrophobic materials like silane.These techniques primarily aim to improve concrete freeze-thaw resistance via enhancing its pore structure,reducing internal free water,and strengthening its internal structure. Summary and Prospects This review represents recent research status on concrete freeze-thaw damage,encompassing key mechanisms,influential factors,damage models,and remedial measures,thereby establishing a basis for future investigations.However,the existing research still faces some challenges,from microscale freeze-thaw damage mechanisms to macroscale performance evaluation,with some aspects that need to be resolved.A future research needs to make breakthroughs in multiple directions,including an in-depth exploration of microscopic mechanisms,the development of new materials,the optimization of damage models,the study of composite environmental effects,and the improvement of evaluation standards and test methods.These efforts will drive concrete technology towards more sustainable and intelligent directions,enhancing the service life of concrete structures in cold regions,while meeting growing engineering demands and environmental requirement.The research can focus on the following directions,i.e.,in-depth investigation of freeze-thaw damage mechanisms and their interactions at the microscale;development of new frost-resistant materials,such as novel supplementary cementitious materials,chemical admixtures,and nanomaterials;optimization of multi-scale damage models to improve their prediction accuracy and applicability;study of concrete durability under coupled environments;improving evaluation standards,test methods,and design specifications for concrete frost resistance.These research directions will help to enhance the service life of concrete structures in cold regions,promote the development of concrete technology towards more sustainable and intelligent directions,thereby meeting the growing engineering demands and environmental requirements,while providing more reliable theoretical foundations and technical support for the frost-resistant design and service life prediction of concrete structures.