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.

High strength concrete, which is characterized by a low water to cement ratio, has a greater cement content than ordinary concrete. Even if the cross sectional area of reinforced concrete member is reduced on account of high strength, significant temperature rise at an early age can be observed because of the higher cement content per unit mass of concrete. This can jeopardize durability and the appearance of concrete members due to early age cracking. Regarding this problem, it is of vital importance to be able to predict the temperature history in concrete members. This is especially true in the case of small section members where the temperature dependency of cement hydration is difficult to predict. In this study, temperature distribution in concrete members made of ultra high-strength concrete with water to cement ratio of 0.15 is investigated. In order to predict the temperature distribution, a cement hydration model which takes into account temperature effect on the rate of cement hydration is proposed. Also, a finite element analysis considering temperature dependent heat production is conducted for evaluating temperature history and distribution in concrete. The proposed hydration model and analysis method are discussed along with experimental results.

A new generation of cemen titious composites, ultra high performance fiber reinforced concrete (UHPFRC), represents an important breakthrough for addressing civil engineering challenges. The most significant feature of UHPFRC is the nearly elasto-plastic ductile behavior in tension, which allows safe exploitation of the tensile and shear capacity in structural elements, while also potentially benefits the dynamic behavior of concrete structures. Where traditional steel elements have shown fatigue resistance problems at the connections in orthotropic slab bridge decks, an attractive application of UHPFRC has been developed within MIKTI coordinated R&D French national project. It consists in a thin 2D-ribbed slab, pre-stressed transversally, made of 2.5 m-long segments connected by post-tension, further connected to conventional longitudinal steel beams which take advantage of the slab lightness. A major critical aspect of the project consists in the safe accounting for local with respect to global bending, even under repeated local fatigue loading. Moreover, safety barriers have to be anchored at the edges of such a thin structure. The capacity of the deck to withstand the load representative of a truck shock, without being damaged before the fuse connecting system of the barrier yields, appears as highly critical also. The detailed design of this innovative structure has been carried out applying French interim recommendations for UHPFRC [1-3]. However, detailed verifications of the local bending (corresponding to a wheel load directly applied and concentrated over the center of one “honeycomb” delimited by the transverse and longitudinal ribs) and of the behavior of the transverse joint under representative bending loads, require refined Finite Element analyses. Both general design and detailed analyses are being compared to scale one experiments.

This report presents the results of an experimental program dealing with ultra high strength concrete (UHSC) under concentrated load. The implemented tests should be used for the determination of the bearing capacity under concentrated load and for the observation of the failure behavior. Specimens made of plain and reinforced concrete were tested, whereby a helical reinforcement was used. The results were compared with an extrapolation of existing design rules established for normal and high strength concrete. In this context, two different UHSC and one high strength concrete for comparison were investigated in order to recognize the influence of concrete strength and composition on the load bearing behavior under concentrated load. The results showed that the bearable concentrated load depends on the compressive strength and also on the concrete composition. Furthermore the under-proportional increase of the tensile strength in relation to the compressive strength has an important influence on the bearing behavior of UHSC.

In order to decrease cross sectional area of structural members, ultra high strength concrete with compressive strength over 150 MPa is required for building structural members, which needs no steam curing. In the present study, concrete is made of silica fume cement which is composed of low heat type cement and silica fume and demonstrates high compactability. Compressive strength of the concrete with water to binder ratio of 0.15 and the effect of hydration heat of binder on compressive strength are investigated experimentally. Effectiveness of expansive additive on reduction of autogenous shrinkage is also investigated. According to the experiment, compressive strength over 150 MPa is gained by adopting appropriate aggregates without steam curing at early ages, while the strength of full sized specimens decreased about 10 % at the age of 91 days. Autogenous shrinkage was reduced from more than 700x10-6 to 0 by expansive additive and shrinkage-reducing admixture. However, expansive additive leads to strength reduction of about 10 %.