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.

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.

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.

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.

The Federal Highway Administration (FHWA) encourages the use of high performance concrete (HPC) to improve the long-term performance of the nation’s infrastructure at lower life-cycle costs. For its purposes, the FHWA uses 11 performance criteria to define high performance concrete, and it designates three levels of performance for each criterion, with Grade 3 being the most stringent. For FHWA projects, the specifier is expected to select the criteria necessary for a given element, and then select an appropriate performance grade. It’s not necessary or desirable to specify the same performance grade for all characteristics. Guide Specification for High Performance Concrete for Bridge Elements provides mandatory language that the specifier can cut and paste into project specifications, as well as guidance on what characteristics should be specified in a given case, and what criterion is needed to ensure satisfactory performance. It includes commentary that tells how to obtain the desired performance for each characteristic. In cases where two performance criteria are in conflict, the commentary advices the user how to balance conflicting requirements.