Performance Evolution And Life Prediction Of Stiff Concrete In Dry Cold Corrosion Area Based On Green And Low-carbon Development

The initiative and implementation of "One Belt and One Road" brings new opportunities for the development of infrastructure in western region,and the increase of construction projects leads to the further upgrading of the contradiction of construction sand.The replacement of traditional construction sand by steel slag sand and aeolian sand is in line with the national strategy of recycling,energy saving,green and low carbon put forward by our country.The climate in northwest China is complex,with hot summer and cold winter,widespread distribution of salt lakes,and serious soil alkalization,which exposes concrete structures to the coupled environment of freeze-thaw cycle and sulfate erosion,which will accelerate the damage and deterioration of concrete structures.Therefore,It is urgent to study the service life prediction and durability of stiff concrete structures in dry cold corrosion areas.Based on Heruo Railway and combined with the actual engineering background,this study designed and carried out durability tests of stiff concrete under the action of single factor and double factor coupling according to the codes.Based on the apparent deterioration phenomenon and macro durability index of stiff concrete,the deterioration law of stiff concrete under the special environment of dry cold corrosion was explored.It is of great significance to guarantee the service life of stiff concrete structure and improve the research system of durability of stiff concrete to provide theoretical support for the service life prediction of stiff concrete.The main research results are as follows:(1)Combined with the actual situation of the site and the laboratory test study,on the basis of meeting the construction workability and economy,the test water-binder ratio was determined and the sand rate was adjusted to get the mix ratio of stiff concrete mixed with aeolian sand and steel slag sand;(2)In the freeze-thaw cycle test,the smaller the water-binder ratio is,the more complete the surface of the test block is,the smaller the damage degree is,the smaller the concrete mass loss rate is,the larger the corrosion resistance coefficient and relative dynamic elastic modulus are,and the stronger the frost resistance is.(3)In the sulfate attack test,the main appearance performance of indoor concrete specimens is similar to that of stiff concrete blocks in real environment,specifically: surface pitting,mortar falling off,fine aggregate exposed,fine aggregate falling off in layers,corner damage,exposed and spalling of coarse aggregate;In the sulphate attack test,the appearance change law and macroscopic index change law of stiff concrete block in the actual attack environment were studied.After analysis,it is concluded that the deterioration law of concrete obtained in laboratory accelerated test is consistent with the real environment after conversion.(5)In the coupled test of freeze-thaw cycle and sulfate attack,the variation regularity of macro-indexes of stiff concrete is similar to that of freeze-thaw cycle,but the deterioration degree is greater.The water-binder ratio has a great influence on the durability of concrete.With the increase of the number of cycles,the water-binder ratio is negatively correlated with the mass,compressive strength and relative dynamic elastic modulus of concrete.(6)Based on the theory of damage mechanics,the damage evolution model of stiff concrete under the coupling action of sulfate attack and freeze-thaw--sulfate attack was established.Based on the damage evolution equation,the expected service life of dry-hard concrete was predicted by combining the relationship between indoor accelerated test and outdoor service environment.