Investigations of Distress in Precast Concrete Piles at Rodney Terminal, Saint John, New Brunswick
J. Khanna,P. Seabrook, B. Gerwick, Jr., and J. Bickley
Appears on pages(s):
air entrainment; chlorides; concrete piles; deterioration; freeze-thaw durability; marine atmospheres; precast concrete; sulfates; prestressed concrete; repairs; sea water; thermal stresses; Structural Research
The Rodney Terminal is a 610 m long, 37 m wide, L-shaped container wharf of concrete construction. It was constructed during 1974-75 and utilized about 1750 24 in. (600 mm) hollow core octagonal precast piles. Soon after construction, pile distress began to be noted. Forty piles were repaired in 1978 and seven piles were replaced in 1982. Since the pile deterioration was rapid and progressive, extensive investigations were carried out to determine the causes of the pile deterioration and possible remedial measures. Later, studies were carried out to investigate whether the piles had met the contract specifications. These investigations revealed that distress was primarily vertical cracks in the outer half of the pile walls. Scouring and freezing and thawing spalling, over time, caused loss of the pile wall. The vertical cracks were related to thermal stresses during the winter months and possibly high thermal gradients during steam curing at the time of manufacture. The rapid freezing and thawing deterioration was due to inadequate air-entrainment of the concrete. The pile distress was also caused, in a few cases, by manufacturing defects. The investigations suggested that the following changes to the original design and specifications may have reduced the problems: 1) higher percentage of circumferential steel; 2) air-void system determinations on samples of the hardened concrete to insure that the specification intent was being met; and 3) use of solid instead of hollow core piles. Remedial steps at the Rodney Terminal have included epoxy-grouting (unsuccessful), pile replacement (expensive), fiberglass jacket over reinforced grouted annulus, insulated fiberglass jackets over reinforced grouted annulus, air-entrained and steel fiber reinforced concrete jackets, and insulated jackets.