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.

This paper describes an approach used in developing a performance-based mixture design and optimization system for paving concrete. This system is being developed as part of a Federal Highway Administration (FHWA) project entitled “Computer-Based Guidelines for Job-Specific Optimization of Paving Concrete.” In this project, a new method of designing and optimizing concrete mixtures for pavement applications is being developed. The procedure includes two key elements: a knowledge base and mixture optimization routines. The former assists the user in selecting mixture design criteria based on site-specific conditions. It also allows for the user to quickly identify what combinations of concrete-making materials may be a starting-point for their site-specific conditions. The second element allows the user to optimize numerous properties of their concrete mixture including: w/cm ratio, cement content, the use of chemical and mineral admixtures, and gradation of aggregates. The optimization can be based on a variety of targets including cost, strength, workability, durability, and numerous other concrete mixture properties – both fundamental and phenomenological. Overall optimization of the selected targets is achieved using concepts of utility theory. When combined, these methods represent a rational approach to quantifying subjective decision-making criteria that is used in finding the optimum concrete mixture for specific conditions.

LCPC (Central Laboratory for Roads and Bridges, a French public research laboratory) has developed for five years a new concept of concrete pavement. It is based upon the following ideas: - High-Performance Concrete shows unique qualities with regard to pavement applications, like high tensile strength, durability, freeze-thaw resistance, abrasion resistance and prevention of steel corrosion; - but economy does not promote the use of HPC in conventional pavement, since the gain in flexural strength leads to a decrease in slab thickness, which does not compensate the increase of material unit cost (i.e. the cost per unit surface increases when replacing normal- by high-strength concrete); - HPC qualities are mostly desirable at the top surface of the pavement. Therefore, HPC Carpet consists in a thin, 60-mm HPC wearing course, reinforced by a welded wire mesh, cast upon a conventional concrete (or cement-treated material) structural layer. Thanks to a complex of polymer and geotextile, there is no bond between the two layers, so that reflexive cracking from the base to the course layer is avoided. However, cracking due to traffic loads is permitted in both directions, the dense reinforcement being supposed to maintain the course layer integrity. The paper will give an overview of this research, which encompassed design calculations, thermal instability verification, fatigue tests on a 10-m full scale model and an experimental construction site near Lyon (France). Here, a 120-m long test section has been built in 2003, and is currently submitted to a heavy truck traffic. To date, the behavior is excellent. In conclusion, the economical potential of this new concept will be highlighted. Rehabilitation of old concrete pavements – where slabs are partly cracked, with moderate rocking – appears as a promising market.

Design and construction of elements of Docklands Light Railway City Airport Extension in London are described. The scheme is 4.4km long and consists of sections at-grade, on embankment, on viaduct and in trough cuttings. Durability design was carried out to the new European Standard EN 206 and its British application document BS 8500. The paper concentrates on the concrete for the segments of the viaduct. A particular aspect of segment production was the need to meet high early strengths under winter working conditions in order to achieve 24 hour mould turn round and to meet the project schedule. In-situ strength for striking and lifting purposes was established by using the results of pull-out tests calibrated against cubes cured under the same conditions as the segments.

In recent years, a number of research projects have been conducted to investigate physical characteristics of rotary kiln expanded lightweight aggregates and engineering properties of high performance lightweight concrete. These research projects include academic research, laboratory research performed for and by the lightweight aggregate industry, and research projects conducted by the construction industry. Some of these research projects have already influenced design criteria and construction procedures on significant projects around the world. In the past, designers have had very little information on the behavior of lightweight aggregate concrete in applications requiring compressive strengths of over 6,000 psi (40MPa). Recent research projects provide reliable information on mechanical properties of high strength lightweight concrete such as modulus of elasticity, creep, shrinkage, coefficient of thermal expansion and chloride permeability. This paper will compile and present results of some of these research projects. It will discuss certain projects that have already been influenced. It will also discuss implications for design and construction of future projects, especially precast prestressed bridge girders, concrete frame buildings with post-tensioned floor slabs, post-tensioned bridge decks, segmental concrete bridges and other high performance concrete structures in severe environments such as off-shore oil and liquefied natural gas platforms.