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During 1994, a new 50,000 m 2 warehouse and similar area of external pavement was constructed at Ingleburn near Sydney, Australia. The client required that the warehouse meet very onerous performance criteria that required the construction of a very flat, prestressed concrete floor that would be crack free, with excellent abrasion resistance, and having a minimal number of joints. The design required that the concrete base provide the wearing surface for the floor without application of a surface topping. A second industrial project which required the construction of high performance concrete floors is a new integrated printing facility for a major newspaper, commenced at Chullora near Sydney in late 1994. The plant is highly automated; sections of the floor are designed to be frequently loaded with turning transporters carrying full rolls of newsprint. Such floors require exceptional abrasion resistance. The designers decided to seek a level of abrasion resistance even higher than that provided at Ingleburn. To minimize joints and cracking, the concretes were designed to have 56- day drying shrinkage of less than 450 microstrain and to exhibit an abrasion resistance, when tested in situ using the Chaplin abrasion machine, of less than 0.10-mm depth of wear. This marks the first time such a direct measurement of abrasion resistance has been specified and assessed in Australia. Key elements of both projects were the high performance concrete floors, which were required to meet tolerances on surface flatness ¦ 2 mm on 3-m straight-edge and ¦ 4 mm overall. These and other strict performance criteria were met consistently during construction providing clients with world class low maintenance warehouses.

A superworkable concrete, which has excellent deformability and resistance to segregation and can be placed in heavily reinforced formwork without vibrators, was developed and employed in the construction of a 70-story building. The height of the building is 296 m, and the height of the superworkable concrete in the tubular columns is about 40 m. Some of the columns have two diaphragms with opening ratio of seven percent at each joint of column and beams. Before actual construction, the placing of the concrete into three model columns was conducted. From the tests, it was confirmed that the superworkable concrete had excellent filling ability and left no voids under the diaphragms. A 6-m high removable column was set on top of the 40-m high column of the building to check the quality of filled concrete. The superworkable concrete was placed successfully into 66 columns of the tallest building in Japan.

Presents an overview of the technical aspects of concrete for a major bridge project in Eastern Canada. The bridge is unique in that it is being designed, finances, and constructed by the private sector; it will also be subsequently operated by the private sector. Private sector partnering with government is a relatively new concept in Canada. This project is an example of the merits of such agreements. The design life of this structure being constructed in a marine environment is 100 years. The length of the bridge will be 12.9 km, constructed in upwards of 35 meters of water. Ice floes throughout the winter and early spring have a major influence on the design and resultant configuration of the structure. Durability of the concrete with respect to chloride ingress, sulfate attack, freezing and thawing, abrasion resistance, and alkali-aggregate reactivity are addressed in the proportioning of concrete mixtures and in the structural design. Extensive use is made of silica fume and fly ash as a measure to reduce chloride diffusivity and heat rise in the more massive sections.

Presents the results of an ongoing experimental research program on creep and shrinkage behavior of high-strength concrete loaded at an early age (16 hours) and a normal age (28 days). The experiments were carried out on high-strength concrete with three types of aggregates (crushed gravel, granite, and limestone). The concretes were dried and loaded at ages of 16 hours and 28 days after casting. Loading levels with stress/strength ratios ranging from 0.15 to 0.70 were adopted in the experiments. The creep deformations were measured for a duration ranging from 90 to 210 days. The experimental results are compared in this paper with the predictions of CEB-FIP Model Code 1990, the modified MC90 model, and the model proposed by ACI Committee 209. The aging effect (in particular, at early ages) is emphasized and the influences of various factors on the aging effect are discussed.

The resistance of rice hull ash (RHA) concrete to freezing and thawing in saline environment was studied in the laboratory, for non-air- entrained high performance and normal concrete. The Swedish standard test for concrete resistance to freezing and thawing in saline environment was used. Although the number of tests was limited, the results were very promising for the use of RHA in non-air-entrained normal or high performance concrete. The laboratory salt scaling for concrete with 15 to 30 percent replacement of portland cement with RHA indicated that RHA concrete without air entrainment would be fairly resistant to freezing and thawing in most applications except for in very severe climates. No indications on an accelerated scaling rate over time was observed for RHA concrete, as opposed to the accelerated scaling rate found for a non-air-entrained high performance silica fume concrete tested.