Concrete is frequently used in marine and estuarian environments where it has long been recognised that the cement paste matrix is readily attacked. Other high sulphate environments occur in arid climates, where sulphates may attack underground concrete as well as slabs at grade. In moist climates, clay formations may also contain significant soluble sulphate. The aggressiveness of sulphate has led to classification schemes for ground waters as well as to the development of supposedly sulphate-resistant varieties of Portland cement (SRPC). To put the problem in perspective, even sea water, whose sulphate concentration is low, c. 0·05 M, is damaging to concrete.
In recent decades, perceptions of the sulphate attack problem have shifted. First, external attack by sulphates is controlled in part by the cation: MgSO4 is more damaging than sodium sulphate. Second, a host of other durability related problems seem to be associated with sulphate attack, including alkali—aggregate reaction and warm curing. Finally, the perception also exists that the resistance of cement to sulphate attack has somehow diminished over the past 70 years, since SRPC was developed.
Against this background, a conference was organised. The refereed papers resulting from the meeting have been edited by Skalny, Marchand and Odler—all distinguished researchers in the field. The chapter contributions integrate well to give an overall picture of current and ongoing research and development in the field.
In their search for the truth, the authors note that the complexities of sulphate deterioration have led to ‘honest controversies’ and ‘that while they have their own preferences of interpretations … they tried to present a multitude of views represented in the literature’. They have, in my view succeeded. The literature review is extremely thorough and comprehensive. The book certainly deserves a place in any technical library on cements and concretes.
This is not to say the book is without problems. It clearly reads as though written by several authors. The prose style ranges from lucid to turgid and imprecise. Its chemical formulae and mineral names are often inaccurate and the book has not been adequately proofread; for example on page 177 we read ‘The building boom of the 1980s and 1990s led to a situation in which the recommendations with respect to the type of cement were usually followed by the bear (sic) minimum cement content was used …’. One has to grin and bear it!
While chapter headings follow in a logical sequence, the contents often do not. For example, one might expect the authors to open by offering a definition of ‘sulphate attack’: does it include the cation or not? Early chapters approach a definition obliquely and it is not until Chapter 4, page 43, before the editors preferred definition is offered.
Are we closer to understanding the causes and cure for sulphate attack? The book provides criteria for the distinction of sulphate attack from other types of degradation. But it also offers hope that with proper mix design, workmanship and cure, sulphate attack can be avoided. This is in my belief, difficult to sustain for external attack but one which may be attainable for internal attack. External sulphate attack represents an approach to thermodynamic equilibrium; we may have some control over the rate at which attack occurs, but occur it must. With respect to internal attack, there is still much to be learned. By highlighting many of the outstanding divergences of opinion, the book serves a very useful purpose. The gulf between our understanding, on the one hand, of chemistry and mineralogy, and on the other of mechanical and physical properties still remains wide.
