Study On The Degradation Rule Of Hydraulic Concrete Materials Under The Action Of Multi-factor Combined Effects

The study of hydraulic concrete structure durability has gradually become research hotspot in the field of hydraulic structure engineering at home and abroad,because of the special working environment regarding the hydraulic concrete structures in the cold drought area of northwest China,which leading to the concrete structures suffer from freezing and thawing cycle or ion erosion.The article aimed at the key environment factor which causing degradation of hydraulic concrete materials in cold and arid regions of northwest China,that is freeze-thaw cycle,salt ion erosion and the combined action between the two,the testing program regarding multi-factor effects of hydraulic concrete materials durability have been designed based on the relevant test specification.Then,targeted experiments have been conduct to explore durability and degrading characteristics of hydraulic concrete materials under the action of single factor and multi-factor effects,the composite mechanism and utility about environmental factors have been uncovered,at the same time,the life forecast and reliability degree models regarding hydraulic concrete materials under freeze-thaw cycle have been established.The article select Gansu province Jingtaichuan electric-irrigated area（hereinafter referred to as Jingtai electric irrigation region）as object of study,concerning the environmental erosion problems regarding hydraulic concrete materials such as cracking and spalling,on the basis of combing colleges science and technology innovation talents support program of Henan province——the study of durability regarding hydraulic concrete structure based on several coupling effect in irrigated area,the following contents have been implemented:The article focusing on researching the degradation rules of hydraulic concrete material under action of rapid freeze-thaw cycle and combined action between sulphate attack and freeze-thaw cycle in cold and arid regions,the degradation processes of dynamic modulus of elasticity,compressive strength and quality have been clarified under action of rapid freeze-thaw cycle and combined action between sulphate attack and freeze-thaw cycle.Conclusions have been summarized as followings:（1）Concrete materials with smaller water-binder ratio could possess stronger the frost resistance durability,the concrete with appropriate coal ash not exceeding 30% could reduce material cost and ensure the anti-frost property of concrete.Meanwhile,the concrete with appropriate air entraining agent could significantly enhance the material anti-frost property.（2）Under the coupled effect of freeze-thaw cycle and sulphate attack,the quality loss and compressive strength loss of hydraulic were all greater than single freeze-thaw erosion,in addition,the relatively dynamic elastic modulus of hydraulic concrete were all less than the test results of single freeze-thaw erosion.（3）Under the environment of freeze-thaw cycle,the compressive F_cu·k and dynamic modulus E_d of concrete material emerged positive correlation relationship,then,sulphate attack could promote degradation of concrete material under action of freeze-thaw cycle.In addition,the service life predictive methods have been explored based on bearing capacity and the degradation process of hydraulic concrete material under action of freeze-thaw cycle,and then calculated degree of reliability and forecasted service life regarding reinforced concrete structure under freeze-thaw cycle environment.The study could provide beneficial reference for optimization design and material repair technology of hydraulic concrete structure durability.