STUDY ON UNIAXIAL DYNAMIC COMPRESSIVE MECHANICAL PROPERTIES OF FREEZE-THAW DETERIORATED CONCRETE IN FROZEN CONDITIONS

To study dynamic mechanical properties of freeze-thaw deteriorated concrete under frozen conditions, uniaxial compressive loading tests at different strain rates (1.0×10^-5,1.0×10^-4,5.0×10^-4,1.0×10^-3,5.0×10^-3 and 5.0×10^-3 s^-1) after different freeze-thaw cycles (0,10,20,30 and 40 cycles) were carried out with a 10 MN dynamic and static triaxial apparatus.The variation laws of peak stress with different strain rates and degrees of freeze-thaw deterioration were studied.The sensitivity of strain rates and degrees of freeze-thaw deterioration to strength was analyzed.The results showed that at the same degree of freeze-thaw deterioration,the peak stress of frozen concrete increased with increase of the strain rate;increasing with freeze-thaw degrees,the peak stress of frozen concrete increased first and then decreased, without significant difference in failure modes.The slower the strain rate was, the more serious the exfoliation of mortar was on the surface of concrete, and more coarse aggregates were exposed.When strain rates were high,the main cracks on the surface of concrete were very clear.The uniaxial compressive strength of concrete under frozen states still was of a rate effect,and the bonding effect of porous ice crystals on concrete compostion world gradually change to isolation effect with the increase of contents.The sensitivity of freeze-thaw degradation degrees to peak stress was higher than that of strain rates to peak stress.