Experiment study of chemo-mechanical coupling behavior of leached concrete

This paper deal-with concrete behavior under chemical and mechanical degradation. Experimental investigations were described where the effects of the calcium leaching process of concrete on its mechanical properties were highlight. The compressive strength and the stress–strain relationship of leached concrete with different leaching degradations were investigated experimental. As leaching grew, a loss of stiffness and strength were observed and an obvious decrease of peak strain was noted. The leaching degradation was measured by nondestructive or local-damage methods such as phenolphthalein solution, ultrasonic wave and pH value in pores, which showed the better linear relationship of the compressive strength of the leached concrete. The uniaxial compression failure mode of leached concrete was a shear mode under the experimental condition. Then the analytical regression for the stress–strain relationship of leached concrete were given, which could be directly used in theoretical and numerical analysis as well as practical engineering design of leached structures. To quantify the leaching evolution, the leached concrete was analyzed by MIP and TGA. The results showed that the dissolution happened both in portlandite and C–S–H gel during the leaching duration and at the early stages of leaching CH dissolution is the main cause of mass loss. The number of harmful pores with size above 200 nm increased which was associated with the leaching of portlandite, was considered to significantly affect the durability of leached concrete.

Research highlights
► The stress-strain relationship curves of normal size leached concrete were investigated experimental.
► The inclination angle between the failure plane and the vertical load plumb of leached concrete was larger than normal one.
► Phenolphthalein indicator was an optimum local damage method to characterize the degradation of leached concrete structure.
► The analytical regression for the stress-strain relationship of leached concrete were given, which could be directly used in theoretical and numerical analysis.