International Concrete Abstracts Portal

Cement-based composites are used in the construction of a wide range of structures. During their service life, many of these structures are exposed to various types of aggression; their durability is generally controlled by their diffusivity and permeability of the cement-based composite. Since the assessment of these two properties by laboratory or in situ tests is often difficult and generally time-consuming, a great deal of effort has been made towards developing microstructure-based models to predict them. A critical review of the most recent developments in this field is presented in this paper. The report begins with a survey of the various mathematical concepts developed to characterize the structure of porous media. Empirical and physical models are reviewed in separate sections. Special emphasis is placed on recent innovations in the field of numerical and digital image analysis based modeling. Each model is evaluated on the basis of its ability to predict the mass transport properties of a wide range of cement-based composites and its potential application to the study of other micro- and macro-structural properties.

Presents basic information on a newly developed electrically conductive concrete. The concrete differs from previous inventions in that both high conductivity and mechanical strength are simultaneously achieved. The electrical and mechanical properties of the conductive concrete developed at Institute for Research in Construction, National Research Council of Canada are given. The material has superior electrical conductivity values and excellent mechanical strength. Experimental results of a laboratory-scale study on the application of conductive concrete to deicing and/or snow melting are presented in this paper. The results indicate that heat can be uniformly produced by the conductive concrete heating element when the element is activated by an external electric power supply. The new method is effective for deicing purposes. Power output of the conductive concrete heating element is stable over a wide range of temperature. The minimum heater power output required for deicing at various air temperatures was determined. This value is linearly dependent on the air temperature, ranging from 150 to 855 W/m 2 as air temperature varies from -5 C to -30 C.

SP-154 In 1995, The Canadian Centre for Mineral and Energy Technology (CANMET), in association with the American Concrete Institute and other organizations sponsored a second conference on Advances in Concrete Technology. The objectives of this conference was to bring together representatives from industry, universities, and government agencies to present the latest information and explore new areas of needed research and development. Thirty two papers from 20 countries were reviewed and accepted for inclusion in this new publication based on the symposium subject, advances in concrete technology. The range of subjects is varied due to the wide range of experts involved in this project.

Describes improvements in the performance characteristics of cement- based matrices when reinforced with pitch-based carbon fibers. Under tension and flexure, increases both in strength and strain capacity were reported as a result of fiber reinforcement. Carbon fiber reinforced cement composites were also much more impact resistant that the parent matrix. Under compression, however, no increases either in the compressive strength or in the elastic modulus were noticed. Crack propagation in these composites was characterized using crack growth resistance curves (R-Curves) in which it was demonstrated that carbon fibers lead to a higher resistance to both nucleation and growth of cracks. This paper emphasizes the desired durability characteristics of these composites and discusses their current and future applications.

The Japanese economy has been highly developed through foreign trade. Port facilities have been supporting this economic growth; many concrete port structures have been constructed and maintained during the past few decades. Recently, various social and economical demands have required port facilities to be multi-functional. New facilities are being constructed to meet this trend. These changes include new types of breakwaters, revetment, and undersea tunnels which improve aesthetics and reduce cost, labor, and construction time. Fresh concrete used in the construction of these new types of structures is often required to have high flowability and to be self-compactible because of the complicated shape and densely arranged reinforcements of these structures. To meet these demands, the authors have developed super workable concrete using viscous admixture (segregation-reducing admixture) and super plasticizer. In this paper, the mix design and material properties of this supe rworkable concrete and examples of its application to new port concrete structures are presented.