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.

Mix design and technology of very high strength rapid-hardening concrete (VHSC) on the base of composite cements produced by «intergrinding» (IG) and «interblending» (IB) have been developed, and their characteristic properties have been studied. The use of mechanical-chemical activation of binders in combination with both new generation superplasticizers based on polycarboxilates and traditional ones and efficient dispersed fine mineral additives (silica fume, metakaoline, etc) allows to obtain VHSC. The strength ranged from 50-80 MPa after 24 hours and 125-140 MPa after 28 days of normal curing for self-leveling concrete mixtures (slump value 22-25 cm). Intensive concrete hardening starts after either 10 hours (IG) or 15 hours (IB) from mixing time. With the increase of hardening temperature ranging from 40 to 500C, the induction period decreases by 2-2,5 times, and strength of concrete exceeds 50 MPa in 8-10 hours after mixing (IG and IB, respectively). Volumetric water absorption of coarse aggregate concrete produced with water/binder ratio of 0.24-0.28 amounts to 2.2-3.3%, and that of fine-grained concrete, with water/binder ratio of 0.32-0.39, to 3-3.4%. Waterproofness of such concrete exceeds W20 (water tightness relating to Russian standard testing of cube specimen 150 mm in diameter and 50 mm in height under 2 MPa pressure during 6 hours), and their freezing-thawing resistance surpasses 600 cycles. Physical and mechanical properties (initial modulus of elasticity, tensile strength) are in line with the normal indices for corresponding concrete classes. Shrinking deformations of heavy weight concrete after 28 days of normal curing are 10x10-2 – 17x10-2 mm/m and those of fine-grained concrete are 29x 10-2 – 48x10-2 mm/m.

A large number of models have been developed recently in an attempt to link the parameters of the Bingham equation to concrete composition [1]. On the other hand, concrete mixture proportioning methods based on a rheological approach usually do not provide direct input of measurable rheological parameter(s) into the proportioning ex-pression. The theories underlying the design methodologies are usually based on a rheological model, but the parameter associated with the rheology of the system (for instance, the magnitude of the relative viscosity) is an adjustable (arbitrary) constant. Consequently, in a broad sense, a universal method for concrete mixture proportioning based on rheological characteristics has not been proposed until now. In this paper, an attempt has been made to associate the rheological quantity involved in an analytical model for mixture proportioning with a measurable rheological characteristic. To do this, the results from evaluation of concrete rheology using a newly developed capillary viscometer are compared with calculated apparent viscosities by the model on a series of concrete mixtures (conventional and self-consolidated). The agreement of the experi-mental results with the theoretical prediction of the model proved to be encouraging. The application of the approach and a new viscometer for self-consolidating concrete technology is believed to be innovative.

Since the 1970’s the concrete industry has seen major developments in high strength/ high-performance concrete (HPC). New materials, design codes and construction methods have enabled us to design and build taller, slimmer, lighter, more attractive and more durable concrete structures. Through research and development and practical applications we have improved our knowledge on strength, ductility, durability, constructability, appearance and other properties to where technology is not the limiting factor, but rather our ability to utilize what we know and to promote our ideas for more sustainable and competitive concrete structures. HPC is now covered by a number of design codes and high-performance structures can be produced almost anywhere with selected local materials and competent workmanship. The volume of available literature on HPC has increased almost exponentially in recent years. Large research and development programmes have been executed and shown to produce remarkable results and provide very satisfactory returns on the investment. HPC still constitutes only a small part of the output of the concrete industry and is largely limited to marine structures, large span bridges and prestigious buildings and to some extent precast components. The market of ordinary structures is still dominated by ordinary concretes with ordinary performance. The paper discusses some aspects related to the evolution of high strength concrete (HSC) and high performance concrete and how the concrete industry, for the benefits of the clients and its own performance and image, needs to more actively utilize the proven HPC technology.

One of the breakthroughs in concrete technology is ultra-high-performance concrete with a steel like compressive strength of up to 250 N/mm2 and a remarkable increase in durability compared even with high-performance concrete. In combination with steel fibres it is now possible to design sustainable filigree, lightweight concrete constructions with or even without additional reinforcement. Wide span girders, bridges, shells and high rise towers are ideal applications widening the range of concrete applications by far. In addition e.g. to some pedestrian bridges heavily trafficked road bridges has been build in France and in the Netherlands. Bridges are already under construction in Germany as well. A wide range of new concrete formulations has been developed to cover an increasing number of applications. Technical recommendations have recently been published in France and in Germany covering material as well as design aspects. The paper will report on the state of research and application of UHPC in Europe, on material and design aspects of UHPC and will present the state-of-the-art based on an International Symposium on UHPC held in Kassel in 2004.