"Marine Durability of 15-Year Old Concrete Specimens Made with Ordinary Portland, Slag,and Fly Ash Cements"

Abstract

Marine durability of 15-year old plain and reinforced concrete cylindrical specimens exposed in marine environments for 15 years is presented here. The specimens were made with ordinary portland, slag (Type A, B, and C) and fly ash (Type B) cements. Water-to-cement ratios were 0.45 and 0.55. Compressive strength of concrete, corrosion of steel bars, and chloride-ion concentrations in concrete were evaluated. After 15-years of exposure, compressive strength of concrete increases compared to its 28-day's strength for the investigated cements, except fly ash cement. Slag cement of Type C shows the best performance against chloride ingress and corrosion of steel bars in concrete. Accumulation of chloride-ions at the surface of concrete made with slag and fly ash cements is observed. The presence of voids at the steel-concrete interface causes the formation of corrosion pits irrespective of the type of cement. The use of seawater as mixing water causes an earlier strength development at the 28-day and does not cause the strength of concrete to regress after 15-years of exposure. However, it causes more corrosion of steel bars at a lower cover depth. At the deeper cover depth, no significant corrosion of steel bars is found irrespective of the type of mixing water.