Sulfate attack research - whither now?

Sulfate attack research is at a critical stage. In spite of meaningful adva nces in the past few years, this problem is still not well understood. Due to its complicated mechanism, the reaction between cement hydration product s and sulfate-bearing solutions manifests itself in a variety of ways. In o rder to provide adequate means for selection of materials for concrete expo sed to such aggressive environments, additional research is necessary to fu rther clarify the interaction between concrete and sulfate-bearing solution s. Specifically, the role of the cation in the sulfate solution, and the ef fects of formation of various products like gypsum, ettringite, and thaumas ite, on the extent of damage need to be investigated. The available testing methods for sulfate aback have been subject to some criticism lately. Alth ough these test methods can give an indication of the mechanisms involved i n sulfate attack, prediction of field performance using lab studies is diff icult. Efforts are needed to introduce appropriate changes in the tests in order to obtain field-like conditions in the laboratory. Combined with good monitoring methods, this would enable the prediction of service life of st ructures exposed to sulfate solutions. Recent advances in nondestructive te sting techniques can be applied to the task of monitoring field structures, although there is a significant effort necessary to calibrate these method s for sulfate attack-related scenarios. In order to produce efficient concr ete designs for service in aggressive environments, it is imperative to dev elop reliable models. Modeling can help in selecting the appropriate materi als and their proportions, as well as in determining service life parameter s. As a first step towards modeling, critical parameters, which serve as an indicator of deterioration, need to be recognized and established. This pa per discusses these issues, and cites some interesting recent developments. Finally, some recommendations for future studies are provided. (C) 2001 El sevier Science Ltd. All rights reserved.