Setting behaviour of alkali activated slag concrete mixes - Effect of chemical additives
  Manjunath R. and Mattur C. Narasimhan
  As efforts are on towards making the alkali activated concrete (AAC) systems as a practically viable, economical and greener concrete technology, rapid-stiffening and consequent rapid-loss of workability characteristics of such mixes is delaying their large-scale application in major constructions. Hence herein, a detailed experimental study was conducted towards increasing the workability of alkali activated slag concrete (AASC) mixes and to retain them for long, in field conditions, by increasing their initial setting times by using different chemical additives. Additives like Lime, Sucrose, Phosphoric acid, Citric acid, Tartaric acid, Borax and Sodium phosphate are taken in appropriate dosages and effect of their addition on workability and stiffening behaviour of a candidate AASC mix is evaluated. An attempt is also made to study the effect of using cold water and cold alkaline solution, while mixing, on the workability and setting behaviour of AASC mixes. From the experimental results obtained, it is concluded that appreciable increase in initial setting times and workability can be obtained with an addition of Sodium phosphate and Borax, at optimum dosages of 2.0% and 0.4% respectively, with respect to total binder content.
 

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