International Concrete Abstracts Portal

SP-228CD This CD-ROM of Special Publication 228 contains the papers presented at the Seventh International Symposium on the Utilization of High-Strength/High- Performance Concrete that was held in Washington, D.C., USA, June 20-24, 2005. The symposium continued the success of previous symposia held in Stavanger, Norway, (1987); Berkeley, California (1990); Lillehammer, Norway, (1993); Paris, France, (1996); Sandefjord, Norway, (1999); and Leipzig, Germany, (2002). The symposium brought together engineers and material scientists from around the world to discuss topics ranging from the latest applications to the most recent research on high-strength and high-performance concrete. In the years since the first symposium was held in Stavanger, there has been worldwide growth in the use of both high-strength and high-performance concrete. In addition to more research and applications of traditional types of high-performance concrete, the use of self-consolidating concrete and ultra-high-performance concrete has moved from the laboratory to practical applications. This publication offers the opportunity to learn the latest about these developments.

The U.S. Federal Highway Administration recently constructed the first Ultra-High Performance Concrete (UHPC) vehicle bridge in North America. This prestressed concrete road bridge is composed of two bulbed double-tee girders, each having a 2.4 m deck width and a 0.84 m girder depth. The bridge spans 21 m. Structural optimization of the prestressed concrete girder/deck combination indicated that this pi-shaped section was an efficient girder for 21 to 30 meter spans. Fabrication and construction of this bridge is discussed.

The objective of this paper is to study the effects of the elevated internal temperature on the strength development and microstructure of high performance concrete with 40 % fly ash in mass structures. The concrete walls were designed using three different depths, being 1.5 m, 0.8 m, and 0.3 m. Temperature histories at different locations in the walls were recorded and the strength development of concrete at those locations was measured. In addition, the change of the degree of hydration, hydration products, and microstructure development of concrete at the different locations were investigated. Test results indicated that high elevated temperatures in mass concrete structures with fly ash significantly accelerate the strength development of concrete at the early ages, while the long-term strength development is decreased. The long-term strength loss is caused by the reduction of the degree of hydration and increased the total porosity and amount of smaller pores. The use of fly ash in mass concrete structure reduces the detrimental effect of high curing temperature on the strength development of concrete.

In this paper, an experimental investigation was conducted to identify the relationship between residual mechanical properties and explosive spalling occurrence of fibre-toughened high performance concrete exposed to high temperatures. The residual mechanical properties measured include compressive strength and tensile splitting strength, and fracture energy. A series of concretes were prepared employing OPC (ordinary Portland cement) and crushed carbonate. Steel fibre, polypropylene fibre, and hybrid fibres (polypropylene fibre and steel fibre) were added to enhance fracture energy of the concretes. After being subjected to high temperatures ranged from 200 °C to 800 °C, the residual mechanical properties of fibre-toughened high performance concrete were investigated. For fibre concrete, although residual strength was decreased by exposure to high temperatures above 400 °C, residual fracture energy was significantly higher than that before heating. Incorporating hybrid fibres seems to be a promising way to enhance resistance of concrete to explosive spalling.

In this paper, a national report on HPC technologies in China is presented. The paper covers development and application of ultra-fine mineral admixtures and study of the mechanism of their influence on properties of HPC, development and application of new types of superplasticizer, early-age properties of HPC, measurement and evaluation of HPC’s durability, and durability design of HPC. Proper exploitation, consumption, and recycling of natural resource, and saving of energy are an important subject associated with both concrete technology and ecology. In this respect, HPC is the main direction of concrete development in the future, owing to its high durability, long service life and more efficient application of natural resource. Besides the strength requirement, durability of concrete should be designed specifically for its application environment. Durability design is becoming more and more important. In China, especially in Western China where severe salt corrosion and frost action exist either in water or underground, a large number of bridges and railways are to be built. New type of HPC needs to be developed to meet the requirements of these construction projects.