Research On Freeze-Thaw Resistance Of Damaged Concrete

The durability of concrete structure under freeze-thaw condition has been a popularissue in academic circles, which has been explored beneficially by scholars from theworld. But it gets less results about the effect of mechanical damage on frost resistance ofconcrete. The concrete structure, because of the action from incidental load includingaccidental impact and earthquake and so on, may get diffrent damage degree, which canaggravate deterioration of concrete structure under freeze-thaw condition. So it is verynecessary to research the frost resistance of damaged concrete.The issue is studied by two stages containing precast damage and freeze-thawexperiment. Using compression testing machine to exerte pressure to make intial damagein advance, which is calculated by damage variable based on concrete ultrasonic wavevelocity before and after damage. And the damage degree of test specimens are variedfrom0.0to0.3. Meanwhile, concrete participating in freeze-thaw experiment are dividedinto four groups, which including C30undamaged concretes and damaged ones withdamage degree0.0~0.1,0.1~0.2and0.2~0.3.In order to study the influence of intial damage on concrete properties subjected tofreeze-thaw cycles. The test specimens, investigated by adopting quickly freeze-thawexperiments in laboratory, were quantified by both rate of mass loss and relative dynamicmodulus of elasticity deriving from GB/T50082-2009—“Standard for test methods oflong-term performance and durability of ordinary concrete”. Experimental results showthat the freeze-thaw resistance about damaged concrete gets poor compared with thereference. The intial damage within0.0to0.1has a little effect on concrete performance,and its maximum cyclic number is more than95%of that about control one, which couldbe ignored. However, the intial damage exceeding by0.1has a significant effect onconcrete performance, and its maximum cycle times is lower than70%of that aboutreference one. Also, the mechanical damage evolution equation of concrete includingboth stress damage and freeze-thaw damage was established by the analysis offreeze-thaw damage evolution process. Results show that the fitted value of mechanical damage variance was in agreement with the experimental result. The result from thisresearch can be a significant guide in the aspect of assessing the concrete structuredurability.