Experimental study on double-K fracture parameters of concrete exposed to sulfate environment

Abstract

The deterioration regularity of double-K fracture parameters of concrete under sulfate attack and drying-wetting cycle environment was investigated by three-point bending beam test in order to assess the performance of concrete due to sulfate attack and provide references for fracture analysis.The initiation,propagation and unstable development of crack in the concrete were monitored by pasting some strain gauges onto the pre-crack tip based on the fracture mechanics.The load-crack mouth opening displacement(P-CMOD) curves under different sulfate attack periods were obtained by the experiment.Taking the erosion coefficient as an evaluation index,the unstable fracture toughness and the initial fracture toughness were calculated according to the double-K criterion.Experimental results indicated that the ratio of the initial cracking load to the unstable fracture load(PQ/Pmax) approximately varied between 0.55 and 0.90.Both unstable fracture toughness and initial fracture toughness obviously increased during the early stage of sulfate ingression,and reduced continuously and slowly with a turning point at 60 and 30 days respectively.The initial fracture toughness was more sensitive to sulfate attack than the unstable fracture toughness.