International Concrete Abstracts Portal

This ACI Special Publication (ACI SP-253) CD-ROM contains 25 papers from the Fifth ACI/CANMET/IBRACON International Conference on High-Performance Concrete Structures and Materials that was held in Manaus, Amazon State (AM), Brazil, June 18-20, 2008. Topics include Durability, Self-Compactability, Curing, Retarders, and Abrasion Resistance. The Fifth Conference is a result of the collaboration of ACI and CANMET along with Sao Paulo University, Federal University of Goias, Amazon State University, and Brazilian Concrete Institute (IBRACON).

The galvanic couple effect decreases a few weeks after performing local repairs. Nonetheless, there is no information on the effect the anodic/cathodic area (aA/aC) ratio has on the magnitude of the galvanic couple. The selective use of stainless steel represents an alternative to repair of concrete structures, but it remains understudied, particularly in the tropical marine environments of the Gulf of Mexico. In this paper, we analyze and discuss the infl uence of the anodic/cathodic area ratio on the galvanic behavior of local repairs conducted on small beams made of low-quality concrete and 304 stainless steel (SS) bars. Results from this experiment indicate that an aA/aC ratio of more than 5 causes a signifi cant decrease in the galvanic couple of the adjacent areas.

This paper presents a review of the application of concrete to offshore structures in the last 35 years. The state-of-the-art technology available for offshore oil platforms and other offshore applications is also described. Currently, there are around 350 offshore gravity and floating concrete platforms in operation in the North Sea, Northern Canada, Australia, Netherlands, Congo, Nigeria, Indonesia, Russia, the Philippines, Brazil, and the Gulf of Mexico. More recently, an important LNG offshore terminal has been designed and is now under construction in Algeciras, near the Gibraltar Strait in Spain. Over the past 30 years there has been a considerable improvement in the design and construction aspects of concrete production. Water-reducing admixtures and additions, such as metakaolin and silica, allowed the development of concretes with improved performance. These new concretes can easily achieve much higher strengths and durability which make them much more suitable for offshore applications. The liberal use of lightweight aggregates is considered crucial for a total weight reduction of the structure and for floating considerations. The evolving technology for the design and construction of this type of structures is discussed.

Brazil generates annually around 190,000 tons of mud from the residue of processing marble and granite (MGBR). This has been causing a serious environmental problem because of a lack of destination for this residue. The objective of this work is the evaluation of the technique viability of the use of the MGBR, generated for three marble shops, of Goiânia city, state of Goiás, in Brazil, as partial substitution for portland cement in the production of concretes. Characterizations have been made to determine the physical, chemical, mineralogical, and the pozzolanic reactivity of the residue. Reference concretes mixtures and concretes mixtures with 5%, 10% and 20% substitution of the MGBR of the cement were produced. w/cm used were between 0.50 and 0.65. The properties of the concretes were determined, including workability, compressive strength, the modulus of elasticity, and absorption by immersion. The results show that the compressive strength of the concrete with the MGBR diminishes with contents of substitution at 10% and 20%. However, with 5% of substitution of the residue, the results of the analysis show that it did not have signifi cant variations in any of the analyzed properties, indicating the viability technique of the substitution of this percentage of residue.

Due to the different characteristics of higher strength concrete, some procedures traditionally used in the design of structures made of lower-strength concrete have to be changed. To evaluate the behavior of high-strength concrete (HSC) elements (fc > 50 MPa) with reasonable accuracy, an adequate compressive stress-strain relationship of concrete should be adopted. This is particularly important for predicting the behavior of columns - elements where the use of HSC is most advantageous. Different types of stress-strain relationships for HSC have been proposed for the nonlinear analysis of member behavior and for the ultimate state analysis of cross sections of elements under combined fl exure and axial load. In this work, simplifi ed rectangular stress blocks for the design of cross sections by different codes applicable to HSC structures are presented. It is shown that those concrete stress blocks can lead to quite different bending moment-axial load interaction diagrams and comparisons between experimental and calculated strengths of 403 tested columns give an idea of the level of safety related to the use of various concrete stress blocks.