Influence Of Carbonation And Long-term Immersi On Multi Interface Microstructure Of Recycled Concrete

Recycled concrete as a green building materials is in line with the national energy conservation,environmental protection and sustainable development concept.Due to the internal defects of recycled aggregate,its durability has not been effectively guaranteed.The durability failure has become the main reason for the concrete structure failure in the normal use state,many related researchers widely used to overcome the difficulties to achieve the recycled concrete,puting a lot of manpower,material resources,financial resources.Recycled concrete with new old mortar interface(LG-XJ interface),the old new paste paste interface(LJ-XJ interface)and the old aggregate mortar interface(LG-LJ interface)is as a kind of porous structure and its full growth space is enriched with calcium hydroxide(CH),then three interfaces of recycle concrete are the weak link of regeneration concrete.The recycled concrete multi interface reconstruction model is builted through the use of innovatation,with accurately positing in three kinds of the interface under the premise,from the micro level to achieve the research of carbonation reaction and erosive medium(chloride and sulfate)on the damage mechanism of multi interface structure properties of recycled concrete,the related research contents are as follows:(1).the original concrete of C30,C45,C60 grade with standard curing prepared ahead of time by 18 months,on the basis of multiple interface reconstruction model of recycled concrete with pouring,curing and cutting to prepare of 100 mm × 100mm× 20 mm microhardness simples and 10 mm × 10 mm × 10 mm scanning electron microscope specimens.(2).with the test method of rapid carbonation,recycled concrete specimens have began to do rapid carbonization experiment,through studying the change of microhardness of LG-XJ interface,LJ-XJ interface and LG-LJ interface of recycled concrete and the change of morphology,determine the different strength grade of concrete with different recycled interfacial transition zone width of carbonation of recycled concrete,study carbonation for the influence of different interface microstructure of recycled conrete and the deterioration mechanism of carbonation of recycled concrete is revealed.The experimental results show that the microhardness of the three interfaces of recycled concrete is increased,and the width of the interface transition zone is decreased in different degrees.(3).with the test method of long-term immersion of respectively 3.5% NaCl solution and 5% Na2SO4 solution,recycled concrete specimen have began to do erosion medium long term immersion test.through studying the change of microhardness of LG-XJ interface,LJ-XJ interface and LG-LJ interface of recycled concrete and the change of morphology by respectively chloride erosion,sulphate erosion of different age regeneration,determine the different strength grade of concrete with different recycled interfacial transition zone width of chloride and sulfate erosion of recycled concrete and reveals the deterioration mechanism of chloride and sulfate erosion of recycled concrete.The test results show that with the growth of chloride erosion age,the microhardness of LG-XJ interface,LJ-XJ interface and LG-LJ interface of recycled concrete decreases,the width of the interface transition zone increases gradually,the rate of change of two are increasing trend;with the growth of sulfate erosion age,the microhardness of LG-XJ interface,LJ-XJ interface and LG-LJ interface of recycled concrete increases firstly and then decreases,the width of the interface transition zone decreased first and then increased.