A discussion of the paper “The use of tension testing to investigate the effect of W/C ratio and cement type on the resistance of concrete to sulfate attack” by Andrew J. Boyd, Sidney Mindess

Abstract

This brief discussion comments on a recent research study (Boyd and Mindess, 2004) on concrete specimens that were cast and partially immersed in a solution for varying periods of time up to 1 year. The study found that water/cement (w/c) ratio had a greater influence on the resistance of the concretes to than did cement type. In addition, the pressure tension test appeared to be more sensitive than the compressive strength test in detecting internal damage, particularly at early ages. In this commentary, Hime takes the researchers to task for failing to be clear about the distress mechanisms discussed or even the study results. Hime contends that the term sulfate attack is not adequately defined, nor is the distress under investigation necessarily confined to at all; it may be due to physical salt due to precipitation of sodium as either thenardite or mirabilite or both. Hime also notes that the authors fail to provide any explanation why the tests fail to show any loss from the initial measurement of the prisms in sodium solution, except for one type of cement studied. Lastly, the authors failed to make any study of the tested cylinders to determine the actual mechanisms for distress.