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.

Ductility is an important factor in design of high strength concrete (HSC) members under flexure. A number of eight HSC beams with different percentage of ??& ???were cast and incrementally loaded under bending. During the test, the strain on the concrete middle faces and on the tension and compression bars and also the deflection at different points of the span length were measured up to failure. Based on the obtained results, the serviceability and ultimate behavior and especially the ductility of the HCS members are more deeply reviewed. Also a comparison between theoretical and experimental results are reported here.

This paper describes the first experience of using self-consolidating concrete for pretressed concrete bridge girders in North Carolina. Under construction in eastern North Carolina is a multi-span bridge which will use one hundred thirty AASHTO Type III girders, each 54.8 ft (16.7 m) long. To demonstrate the full-scale field production of self-consolidating concrete, and for comparative purposes, three girders from one production line of five girders were selected for the experimentation. Two of the girders were cast with self-consolidating concrete and one with normal concrete as control. The plastic and hardened properties of both the self-consolidating concrete and the normal concrete were monitored and measured. The plastic properties of self-consolidating concrete included unit weight, air content, slump flow, visual stability index (VSI), and passing ability measured by J-ring and L-box. Hardened properties of the two concretes included temperature development during curing, compressive strength, elastic modulus, and flexural tensile strength. The prestressing force was monitored by load cells. The transfer lengths of prestressing strands were determined by embedded strain gauges, and from the measured strand end-slips. Finally, the three girders were tested in flexure up to the design service load to determine and compare their load-deformation characteristics.

Large base slabs in the industry are exposed to different types of loading. In many cases, the restraint to imposed deformations due to temperature and shrinkage is decisive for the design. The most common loads for base slabs are introduced. In order to rationalize the fabrication of large slabs, a new concept for base slabs made of textile reinforced self-consolidating concrete (SCC) is presented. The advantages of textile reinforcement compared to ordinary steel reinforcement are pointed out. The main objective is to limit the crack width and to avoid expansion joints. Therefore, numerous tensile tests with differently prepared carbon rovings have been performed in order to analyze and advance the bond behavior of carbon reinforcement in SCC. These rovings serve as the basis for a technical textile as reinforcement for large base slabs.

It is widely recognized that addition of fly ash improves strength and durability of concrete, besides improving economy and ecology. In recent times the emphasis globally is on mixing high volume fly ash in high performance concrete. India produces 100 million tones annually out of which only 20 % is utilized. In an ongoing program, an experimental investigation is carried out to assess the performance of three types of concrete: one with ordinary Portland cement, another with blended cement and a third with site mixed high volume fly ash (with cement replacement level of 50 %). All three are exposed to acidic environment. A total of 180 cubes of 100 mm size are cast for the study. Batches consisting of 54 cubes in each are immersed in water, and 1 % solutions of H2SO4 and (NH4)2SO4 respectively. The changes in weight and compressive strength are monitored fortnightly for 90 days. Coefficient of water permeability is determined for these mixtures. Concrete with high volume fly ash showed better resistance when exposed to acidic environment, though strength decreased marginally. Concrete with blended cement is found more impermeable than concrete with fly ash mixed at site. It was concluded that high volume fly ash concrete is more durable than ordinary concrete.