Experimental Study On Impact Mechanical Property Of Concrete After Frost-thaw Cycling

In order to study the dynamic impact mechanical properties under tri-axial load or in freeze-thaw environment，a large diameter (φ74) Spilt Hopkinson Pressure Bar and a static compressiontesting machine are used. Impact compression tests of two groups of concrete samples are usedunder one-dimensional and tri-dimensional stress state with different strain rates, the other group isused for comparison. Axial stress and strain as well as toroidal stress and strain of the specimensare measured, and average strain rates are calculated. The stress-strain curves under one-dimensional stress state and the effective stress-strain curves considered the effects of steel sleeveunder three-dimensional stress state are drawn. As the passive confining pressure, the ability ofresistance damage evolution of the concrete material is obviously bigger than one-dimensionalstate.By used of ultrasonic nondestructive testing technology combined with experimentalobservation on concrete materials’ erosion phenomenon, the damage evolution for concrete isresearched. The experimental results are analyzed. Due to the function of high and lowtemperatures alternating frequently, there is original damage of concrete samples such as microholes, and micro cracks suffered after freeze-thaw cycling, and water in it turns into ice and meltsrepeatedly. The expansion force of ice seriously affected the mechanical properties for concrete. Itmakes the original damage aggravated and the mechanical properties of materials are declined. Nomatter whether concrete samples are confined by steel sleeves or not, the laws of varies ofultrasonic wave velocity in the impact compression tests are the same. With increasing of impactstimes, the ultrasonic wave velocity of concrete is reduced overall while increased in local zone. Thephenomenon is increased with decrease of the frost-thaw temperature of concrete material.