Marine durability of 15-year old concrete specimens made with ordinary portland, slag, and fly ash cements

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, 8 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-year 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-ion 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-year 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.