Material performance lessons

The use of advanced technologies applying chemical and mineral admixtures, combined with conventional raw materials, can provide cost effective solutions to meet many of the challenges facing the concrete industry, especially with respect to production of cost effective durable structures, without the necessity of application of exotic new cementitious systems. The mechanisms controlling the performance of such concretes and the concepts of mix design are generally understood. Yet, in spite of this know-how, the performance on site frequently fails to meet the potential of these concretes. Some of the causes for this gap are associated with the influence of field practices which are often ignored, as well as the dependence on specifying and monitoring of concrete quality only on strength. The present paper discusses the various parameters and strategies which need and can be considered to change this state of affairs: quantifying the limitations of strength based specifications for durability, use of models and laboratory tests to optimize mix design for durability by considering expected curing effects, sensitivity of mineral additives to provide durability enhancement in different types of exposure conditions, as well as prediction of cracking which is based on quantifying the development of residual stresses in structures at early ages. (C) 2007 Elsevier Ltd. All rights reserved.