Fracture mechanics of cementitious materials

Abstract

The concepts of classical fracture mechanics were first applied to cementitious materials by Kaplan in 1961; since then, an enormous literature on this topic has emerged, the more recent publications emphasizing the nonlinear fracture mechanics approach. Unfortunately, this body of literature is highly fragmented. It appears in a bewildering number of journals and conference proceedings, and is often highly contradictory in its conclusions. This is at least one reason why the fracture mechanics approach has not been much used in the analysis and design of concrete structures. Thus, the present book by two widely respected researchers, Brian Cotterell and Yiu-Wing Mai, is particularly welcome at this time. It brings together in one place a detailed discussion of well over 400 studies of the fracture of cementitious composites, supplemented by the considerable experience of the two authors. The book is aimed primarily at graduate students, and at structural engineers who may be interested in finding out what advantages the fracture mechanics approach may bring. The coverage of the book is very broad. Since fracture mechanics is little taught to civil engineers at the undergraduate (or even the graduate) level, it begins with a brief but lucid introduction to fracture mechanics itself. This is followed by a description of the nature of the fracture process in cementitious materials, with particular emphasis on the fracture process zone and on the fibre bridging zone in fibre reinforced cements and concretes. Chapter 3 deals with the experimental determination of the fracture parameters, which will be of particular value to graduate students embarking on an experimental study of the fracture of concrete. The next two chapters deal, in considerable detail, with the theoretical models for the fracture of cementitious materials and fibre reinforced cementitious composites, respectively. The statistical aspects of the fracture process are then discussed, with some emphasis on size effects. Chapter 7 deals with the timedependency of the fracture process, devoted primarily to slow crack growth and creep problems. A notable omission, unfortunately, is the almost complete lack of any discussion concerning the applications of fracture mechanics to dynamic (blast or impact) loading of concrete, since this is an area of great current interest. Finally, the book concludes with an all-too-brief discussion of the application of fracture mechanics to the design of concrete structures, probably because there have been relatively few such applications in practice. While the authors do not present any new theories regarding the applications of fracture mechanics, they do present a balanced and comprehensive review of what is now known. Moreover, they do this in a way that makes the fracture mechanics approach understandable even to those with little previous exposure to this method of analysis. This book should help to overcome the mistrust with which most stmctural engineers view fracture mechanics. It is highly recommended for graduate students, for structural engineers, and indeed for anyone concerned with the strength and mechanical behaviour of cementitious composites.