Scope:
EXPOSURE CONDITIONS AT TREAT ISLAND, MAINE
CONCRETE MIXTURES
PROPERTIES OF FRESH CONCRETE
CASTING AND CURING OF TEST SPECIMENS
FREEZING-AND-THAWING RECORD AT TREAT ISLAND
In this study, the water-to-cementitious materials ratios of the concrete, in general, ranged from 0.40 to 0.60, and the percentage replacement of portland cement by supplementary cementing materials ranged from 0 to 80 percent by mass. The details of the various phases are as follows:
Phase I: Determination of performance of air-entrained concrete incorporating pelletized blast-furnace slag, and air-entrained and non air-entrained concretes incorporating high-range water-reducing admixtures (HRWRA) (superplasticizers)
Test prisms installed at Treat Island . . . . . . . . .1978 Phase II: Determination of the performance of air-entrained concrete incorporating fly ash and pelletized blast-furnace slag.
Test prisms installed at Treat Island . . . . . . . . .1979 Phase III: Determination of the performance of air-entrained semi-lightweight concrete incorporating pelletized blast- furnace slag.
Test prisms installed at Treat Island . . . . . . . .1980 Phase IV: Determination of the performance of air-entrained concrete incorporating fly ash.
Test prisms installed at Treat Island . . . . . . . . .1981 Phase V: Determination of the performance of air-entrained concrete incorporating ground granulated blast-furnace slag (ggbfs), and air-entrained and non air-entrained concretes incorporating silica fume.
Test prisms installed at Treat Island . . . . . . . . .1982 Phase VI: Determination of the performance of air-entrained, semi-lightweight steel fibre-reinforced concrete incorporating fly ash and silica fume.
Test prisms installed at Treat Island . . . . . . . . .1985 Phase VII: Determination of the performance of semi-lightweight concrete incorporating silica fume.
Test prisms installed at Treat Island . . . . . . . . .1986 Phase VIII: Determination of the performance of high-volume fly ash concrete.
Test prisms installed at Treat Island . . . . . . . . .1987 Phase IX: Determination of the performance of steel reinforced concrete incorporating pelletized blast-furnace slag or fly ash or silica fume.
Test prisms installed at Treat Island . . . . . . . . .1987 Phase X: Determination of the performance of semi-lightweight concrete incorporating silica fume.
Test prisms installed at Treat Island . . . . . . . . .1988 Phase XI: Determination of the performance of semi-lightweight high-volume fly ash concrete.
Test prisms installed at Treat Island . . . . . . . . .1990 Phase XII: Determination of the performance of beams that were unreinforced, reinforced, or reinforced with epoxy-coated reinforcement.
Beams installed at Treat Island . . . . . . . . . . . .1991 Phase XIII: Determination of the performance of high-volume fly-ash concrete (EPRI Project).
Test prisms installed at Treat Island . . . . . . . . .1992 Phase XIV: Determination of the performance of concrete containing silica fume and fly ash in controlling expansion and cracking of concrete due to alkali-silica reaction.
Test prisms installed at Treat Island . . . . . . . . .1994
EXPOSURE CONDITIONS AT TREAT ISLAND, MAINE
In 1936, the Concrete Laboratory of the Passamaquoddy Tidal Power Project established an exposure site at Treat Island in Cobscook Bay near Eastport, Maine. This island is within a few kilometres of the Canadian border, and is at the entrance to the Bay of Fundy. At the site, the test prisms are positioned on a rack at mid-tide level so that they are exposed alternatively to a marine atmosphere and to immersion in sea water twice daily. The alternating condition of immersion and exposure to the air provides on an average over 100 cycles of freezing and thawing per year. By using the above facility, deterioration patterns occurring in a study can be related to the behavior of concrete in investigations performed at Treat Island over the past 50 years.
Back to TopCONCRETE MIXTURES
The concrete for Phases I to XII mixtures were prepared under a CANMET contract, in the University of New Brunswick laboratory at Fredericton between 1978 - 1992 using a counter-current pan mixer; for the Phases XIII and XIV, the test prisms were made at CANMET, Ottawa, and were transported to the University of New Brunswick, Fredericton for installation at Treat Island, Maine. The details concerning the materials used and the mixture proportions are outlined below.Materials
Portland Cements
ASTM Types I and II cements were obtained from a plant in New Brunswick. The ASTM Type V cement was obtained from a plant in Quebec. The various types of cement used in different phases of the project are given in DATA Table.
Aggregates
The characteristics of the fine and coarse aggregates used in the various phases of the investigation are described in DATA Table. The fine aggregate was natural sand in all cases. In phases dealing with normal weight concretes, the coarse aggregate was either crushed limestone or river gravel with 19-mm nominal maximum size, except in phases I and II when river gravel with a nominal maximum size of 37.5 mm was used. In phases concerned with lightweight concretes, the coarse aggregate was expanded shale lightweight aggregate from various sources, with a nominal maximum size of either 12.5 or 19 mm. The gradings of the fine aggregates and the various types of coarse aggregate were within the limits of ASTM Standards.
Fly Ashes
For investigations of Phase II in 1979, the fly ash (ASTM Class F) was obtained from a plant in Detroit, MI; for the Phases IV, VA, VI, VIII, IX, XI and XIV, the fly ash was obtained from a plant in Lingan, Nova Scotia. For Phase XIII, the fly ashes were from the sources in the U.S.A.Ground Blast-Furnace Slags
Pelletized blast-furnace slag was obtained from a plant in Hamilton, Ontario and granulated blast-furnace slag was from a plant at Sparrows Point, Maryland.Silica Fume
The silica fume used in the various phases was of uncompacted form, and was obtained from a silicon and ferrosilicon plant in Becancour, Quebec.Air-entraining Admixture
A sulphonated hydrocarbon air-entraining admixture was used throughout the investigations.High-Range Water Reducing Admixture (Superplasticizer)
The high-range water reducing admixture (HRWRA) used throughout these investigations was a naphthalene-based product of Japanese or Canadian origin except for specimens SP5 and SP6 of Phase I when a melamine-based HRWRA was used.Mixture Proportions
The mixture proportions for each phase are summarized in Tables 2 to 15. When supplementary cementing materials were incorporated into the mixtures, these were used as a direct replacement for cement by mass. All concrete mixtures without HRWRA were proportioned to give a slump of 75 ± 25 mm, whereas concrete mixtures with HRWRA were proportioned to produce slumps varying between 75 and 250 mm for the various phases. The target air content was 6 ± 1 percent for all air-entrained concrete mixtures. When lightweight aggregates were used, these were soaked in water for 24 hours prior to use in concrete. The mass of the aggregates are given in a saturated-surface dry basis with the exception of the lightweight aggregates which are given in an oven-dry basis.PROPERTIES OF FRESH CONCRETE
The properties of the freshly-mixed concrete, i.e., temperature, slump, unit weight, and air content are given in DATA Tables Phase1 to 14.CASTING AND CURING OF TEST SPECIMENS
The large test prisms, 305 x 305 x 915-mm in size, were cast in two layers of equal depth with each layer vibrated with an internal vibrator. Upon completion of the vibration of the filled mold, the excess concrete was struck off with a wooden straight edge. As soon as the bleed water had evaporated, the concrete was floated with a wooden trowel, and the concrete covered with a sheet of plastic. The concrete prisms were demolded after 24 hours curing in the laboratory air, and then covered with a wet burlap and a plastic sheeting. After three days, the prisms were moved into the moist-curing room where they were stored on their ends. The high slag-content mixtures had a relatively slow rate of strength gain and as a result, additional moist curing was required before they could be moved. All prisms cast in 1978 were moist cured for 28 days, whereas all the subsequent prisms were moist cured for at least 90 days prior to being shipped to Eastport for subsequent transport by boat to Treat Island.
In addition to the large prisms, a number of 152 x 305-mm cylinders were cast from each mixture for strength testing. The specimens were cast according to the ASTM procedures, and were kept in a moist-curing room until required for testing.FREEZING-AND-THAWING RECORD AT TREAT ISLAND
An XL-800 data logger was used to record temperatures at Treat Island from about October 18, 1991 to about March 31 the following year. Temperature sensors are located in the concrete at the centre of a 152 x 152 x 508-mm prism. The prisms are located at mid-tide level, and subjected to repeated cycles of freezing and thawing during the winter months. The number of freezing-and-thawing cycles experienced at each of the sensors is shown in DATA Table . The number of cycles of freezing and thawing the concrete is exposed to, is normally reported as the number of times the temperature at the centre of the 152 x 152 x 508-mm prism drops below -2.2°C. Using the above criteria, the number of freezing-and-thawing cycles was 75 for the winter of 1991/92.