ACI 212.3R

Abstract

<strong>Introduction</strong> <br>An admixture is defined as "a material other than water, aggregates, hydraulic cement, and fiber reinforcement used as an ingredient of concrete or mortar, and added to the batch immediately before or during its mixing" (American Concrete Institute 2010; ASTM C125). Chemical admixtures are primarily water-soluble substances used to enhance the properties of concrete or mortar in the plastic and hardened state. These benefits include increased compressive and flexural strength at all ages, decreased permeability and improved durability, corrosion reduction, shrinkage reduction, initial set adjustments, increased slump and workability, improved pumpability, finish and finishability, rheology modification, improved cement efficiency, alkali-silica reaction (ASR) reduction, and concrete mixture economy. <br>An admixture or combination of admixtures may be required to achieve the specific desired results; however, proper mixture designs are required for optimum benefits. In certain instances, a desired objective may be best achieved by mixture changes in addition to proper admixture usage. Chemical admixtures are not a substitute for suitable concrete mixture proportions and acceptable construction practices. <br>This report deals with commonly used admixtures other than those assigned to other ACI committees. Materials, such as mineral admixtures, used to produce concrete are not discussed in this report. <br>The chemical admixtures are classified generically or with respect to their characteristics. Information to characterize each class is presented with brief statements of the general purposes and expected effects of each group of materials. The wide scope of the admixture field, the continued entrance of new or modified materials into this field, and the variations of effects with different concreting materials and conditions preclude a complete listing of all admixtures and their effects on concrete. Summaries of the state of the art of chemical admixtures include Ramachandran and Malhotra (1984), Ramachandran and Mailvaganam (1992), Mather (1994), Nkinamubanzi and A&#239;tcin (2004), Collepardi and Valente (2006), and "Chemical Admixtures for Concrete," <em>ACI Education Bulletin</em> E4-03 (ACI Committee E703 2003).