An Experimental Study On The Evolution Of The Chloride Diffusivity Of Ordinary Concrete With Time

The evolution of the chloride diffusivities of cement paste and concrete with time is studied in this thesis through experiment. Based on the experimental results, the effects of the water/cement ratio, aggregate volume fraction, and curing age on the chloride diffusivity are analyzed. The effect of the salt and water saturation on the chloride diffusivity is also discussed. Through analyses, the following conclusions are drawn:(1) The chloride diffusivity of cement paste decreases with the increase of the curing age. When the curing age is from 118 to 358 days, the decrease value of the chloride diffusivity is only half that from 28 to 118 days.(2) The chloride diffusivity of concrete decrease with the increase of the curing age, with a larger rate of decrease in early ages and a smaller rate of decrease in latter ages. The decrease value from 28 to 118 days is approximately 2 times that from 118 to 358 days.(3) After cement paste and concrete experience a salt and water saturation process, the chloride diffusivities decrease with the increase of the curing age and are slightly smaller than those of cement paste and concrete without experiencing this process.(4) For the curing ages of 358 to 718 days, the chloride diffusivity of concrete seems not to decreases any more and basically keeps constant.(5) For a given aggregate volume fraction, the chloride diffusivity of concrete increases with an increase in water/cement ratio and a larger water/cement ratio results in a more significant decrease in the chloride diffusivity of concrete with time.(6) For a given water/cement ratio, the chloride diffusivity of concrete decreases with increasing the aggregate volume fraction and a larger aggregate volume fraction results in a more significant decrease in the chloride diffusivity of concrete with time.