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Performance of Slag Concrete in Marine Environment by ProQuest

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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). [PUBLICATION ABSTRACT]

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									 ACI MATERIALS JOURNAL                                                                                  TECHNICAL PAPER
Title no. 105-M71


Performance of Slag Concrete in Marine Environment
by Michael D. A. Thomas, Allan Scott, Ted Bremner, Alain Bilodeau, and Donna Day

This paper reports the findings from an evaluation of concrete            revealed some interesting trends in terms of the relative
containing ground pelletized blast-furnace slag after 25 years of         performance of the concrete mixtures after 10 to 15 years of
exposure in a marine tidal zone. Twelve large concrete blocks (305 x      exposure and these have been reported elsewhere.1
305 x 915 mm [1 x 1 x 3 ft]) were retrieved from the exposure site          In 2003, a decision was made to retrieve one of the two
and were sampled for evaluation in the laboratory. The specimens
                                                                          blocks from each of the mixtures as they reached an age of
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             25 years for testing in the laboratory. The testing will include
concrete mixtures contained 0, 25, 45, or 65% slag by mass of total       the determination of mechanical properties, depth of chloride
cementitious materials.                                                   penetration, and the measurement of various mass transport
   Severe surface erosion was observed for concretes containing           properties. This paper reports the results from testing the
higher levels of slag (45 or 65%) with a w/cm of 0.50 or 0.60, the        blocks from Phase I, which were placed in 1978, that
extent of damage increasing with increasing slag levels. The              contained up to 65% of a pelletized slag.
surface condition, however, was satisfactory for all concretes with
a w/cm of 0.40. Laboratory testing included the determination of                        RESEARCH SIGNIFICANCE
the depth of chloride ion penetration, compressive strength,                The Treat Island exposure site provides a unique opportunity
modulus of elasticity, splitting strength, chloride permeability
                                                                          to study the performance of concrete under very severe
(ASTM C1202), chloride diffusion, and hardened air-void parameters.
                                                                          exposure conditions. This paper presents long-term data,
   The depth of chloride penetration after 25 years of exposure was
greater than 100 mm (4 in.) for all the control concretes (that is,       few of which exist already, for concrete with various levels
without slag) regardless of the w/cm. The slag concretes showed           of ground pelletized blast-furnace slag. Such data are essential
significantly greater resistance to chloride ion penetration (generally   for determining the real effect of supplementary cementing
<50 mm [2 in.] for 45 and 65% slag), the depth of penetration             materials, such as slag, on the ability of concrete to resist the
decreasing with increasing slag content and decreasing w/cm.              penetration of chloride ions. The long-term diffusion data
The beneficial effect of slag in terms of reducing mass transport         from this study will serve as valuable input for emerging
was confirmed by laboratory tests with the slag concretes                 mathematical models for predicting the service life of
showing more than tenfold reductions in chloride permeability             concrete exposed to chloride ions and freezing-and-thawing
and diffusion coefficients.                                               conditions in service.
   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                         EXPERIMENTAL INVESTIGATION
concrete in a very aggressive marine environment provided the                Twelve concrete blocks (305 x 305 x 915 mm [1 x 1 x 3 ft])
w/cm is kept low (that is, w/cm ≤ 0.40).                                  from Phase I of the investigation were collected from the
                                                                          marine exposure site at Treat Island, Maine, on August 19,
                      INTRODUCTION                                        2003. The blocks had been exposed to tidal conditions in the
   In 1978, the Canadian Centre for Mineral and Energy                    Bay of Fundy for 25 years representing approximately
Technology (CANMET) initiated a study on the marine                       18,250 cycles of wetting and drying and 2500 cycles of
performance of concrete containing supplementary                          freezing and thawing. The concrete specimens were produced
cementing materials (SCM), which involved placing large                   from three series of mixtures with different w/cm values of
concrete blocks (305 x 305 x 915 mm [1 x 1 x 3 ft]) in the                0.40, 0.50, and 0.60. At each w/cm, there were four blocks
tidal zone of the marine exposure site at Treat Island,                   with slag replacement levels of 0, 25, 45, and 65%. Mixture
Maine.1 Between 1978 and 1994, 16 different series of                     proportions for the concrete mixtures are given in a previous
concrete mixtures were placed at Treat Island; these                      paper.1 The slag used was a ground pelletized blast-furnace
mixtures had water-cementitious material ratios (w/cm) in                 slag from Hamilton, ON, Canada. The portland cement used
the range of 0.40 to 0.60 and various levels (up to 80% by                met the requirements of ASTM C150 Type I. The chemical
mass of cementing
								
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