Chemical admixtures dose optimization in pervious concrete paste selection - A statistical approach

Making good-quality portland cement pervious concrete (PCPC) requires utilization of chemical admixtures. Several types of admixtures, including superplasticizers (SPs), viscosity modifying admixtures (VMA), and set-retarding admixtures (RE) are commonly used in PCPC. These chemical admixtures significantly influence the flowability, film-forming ability and film-drying time (setting time) of the paste component. Consequently, the workability of the PCPC mixtures is greatly affected by the type and amount of chemical admixture added. This paper shows how the Box-Behnken (BBD) response surface design can be used to characterize the individual and combined effects of SP, VMA and RE on pervious concrete paste. The paste properties evaluated include flowability, film-forming ability and film-drying time. Using the BBD technique, ranges of admixture combinations were studied with a reasonable amount of data points. Finally, mathematical equations (models) and response surfaces were developed. The models and the response surfaces could be used to select admixture doses for different type of PCPC mixtures. Therefore, this method is highly recommended for situations where concrete producers are required to create PCPC mixtures, which have variable mixture composition and material properties. (C) 2015 Elsevier Ltd. All rights reserved.