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 presents an overview on durability of reinforced concrete in marine environment in China and relevant test methods based on comparison of results from laboratory and exposure tests. The test results of the reinforced concrete specimens, including ordinary concrete and high-performance concrete containing silica fume and other anticorrosion measures are comprehensively analyzed. The test data of the specimens exposed 3, 9, and 20 years in-situ in the South Sea and 3, 8, and 16 years in Huanghai Sea of China are reviewed. A comparison of test results between the laboratory and long-term exposure is made for evaluating their common characteristics and differences. Based on the Fick’s Law, the chloride ion penetration and diffusion characteristics in the concrete specimens exposed 16-20 years in marine environment are used to estimate the service life of reinforced concrete structures in marine environment. Recommendations for ensuring and improving the durability of the reinforced concrete in marine environment are provided.

This study investigates the effectiveness of low shrinkage-high strength concrete (LS-HSC) using expansive additive and shrinkage-reducing agent with regards to the time-dependent structural performance of reinforced HSC flexural members. Design equation for evaluating the flexural crack width and deformation of RC beams considering the effect of shrinkage/expansion before loading are proposed on the basis of JSCE (Japan Society of Civil Engineers) Design Code of 2002. The results show that autogenous shrinkage of conventional HSC with no additives can significantly affect the time-dependent serviceability performance of the RC beams, while LS-HSC can markedly improve its serviceability performance. In addition, time-dependent flexural crack widths of reinforced LS-/conventional HSC beam, can be evaluated by the JSCE Code Equation, which takes into account the strain change in the reinforcement bars from the state where the stress in concrete at the depth of tension reinforcements is zero. Also, time-dependent as well as instantaneous curvatures of reinforced LS-/conventional HSC beam can be accurately calculated by the proposed equation. This equation takes into account the effect of the change in curvature due to the release of restrained-shrinkage/expansion stress at cracked section.

This paper presents results of a study conducted to identify the drying shrinkage and compressive creep of high performance/high strength concrete (HP/HSC).The study included an experimental program and a comparison of available analyticalmodels for predicting creep and shrinkage. Results from creep and shrinkage tests performed on different mixes (with compressive strengths up to 90 MPa) were compared with those from prediction models available in the literature. The effects of pozzolanicmaterials the creep and shrinkage were also investigated. Results show that while fly ash increases the compressive creep of concrete, silica fume decreases it. Furthermore, thedrying shrinkage of silica fume concrete is higher than fly ash concrete. Adding fly ash could reduce the drying shrinkage of silica fume concrete. Moreover, current creep and shrinkage prediction models need to be revised for the HP/HSC mixture.

A new type of low-autogenous-shrinkage ultra-high-strength concrete with a compressive strength of more than 150 MPa has been developed for use in prestressed concrete structures. By using artificial aggregate with coal ash that has an internal-curing effect, in addition to a conventional expansive agent and shrinkage reducing agent, the effects on autogenous shrinkage reduction and compressive strength were investigated experimentally. The experimental results showed that although the artificial aggregate with coal ash causes a loss of compressive strength, it greatly contributes to the reduction of autogenous shrinkage; autogenous shrinkage of ultra-high-strength concrete can be effectively reduced by adjusting the quantity of aggregate used and the combination of admixtures used. The mechanical properties of ultra-high-strength concrete with low-autogenous-shrinkage were also evaluated, and it was confirmed that currently used estimation formulas are applicable.