Title:
Performance of Slag Concrete in Marine Environment
Author(s):
Michael D. A. Thomas, Allan Scott, Ted Bremner, Alain Bilodeau, and Donna Day
Publication:
Materials Journal
Volume:
105
Issue:
6
Appears on pages(s):
628-634
Keywords:
DOI:
10.14359/20205
Date:
11/1/2008
Abstract:
This paper reports the findings from an evaluation of concrete containing ground pelletized blast-furnace slag after 25 years of exposure in a marine tidal zone. Twelve large concrete blocks (305 x 305 x 915 mm [1 x 1 x 3 ft]) were retrieved from the exposure site and were sampled for evaluation in the laboratory. The specimens were from three series of mixtures with a water-cementitious material ratio (w/cm) of 0.40, 0.50, and 0.60; within each series, the concrete mixtures contained 0, 25, 45, or 65% slag by mass of total cementitious materials. Severe surface erosion was observed for concretes containing higher levels of slag (45 or 65%) with a w/cm of 0.50 or 0.60, the extent of damage increasing with increasing slag levels. The surface condition, however, was satisfactory for all concretes with a w/cm of 0.40. Laboratory testing included the determination of the depth of chloride ion penetration, compressive strength, modulus of elasticity, splitting strength, chloride permeability (ASTM C1202), chloride diffusion, and hardened air-void parameters. The depth of chloride penetration after 25 years of exposure was greater than 100 mm (4 in.) for all the control concretes (that is, without slag) regardless of the w/cm. The slag concretes showed significantly greater resistance to chloride ion penetration (generally <50 mm [2 in.] for 45 and 65% slag), the depth of penetration decreasing with increasing slag content and decreasing w/cm. The beneficial effect of slag in terms of reducing mass transport was confirmed by laboratory tests with the slag concretes showing more than tenfold reductions in chloride permeability and diffusion coefficients. These data indicate that the use of slag at relatively high levels of replacement by North American standards (for example, 45 to 65%) results in a significant increase in the performance of concrete in a very aggressive marine environment provided the w/cm is kept low (that is, w/cm = 0.40).