Prediction of Shrinkage of Concrete Containing Fly Ash and/or Silica Fume Using Composite Modeling

摘要

Partial replacement of Portland cement by industrial by-products such as fly ash and silica fume (collectively known as mineral admixtures) in the normal concrete diverts the deposition of those by-products from landfills, reduces CO_2 emissions, and produces durable and sustainable concrete. Shrinkage strain is a major parameter for concrete durability. No systematic data are available to predict the shrinkage of concrete containing mineral admixtures from paste properties to coupon level. In this study, composite modeling was developed from paste level to coupon level for 10 concrete mixtures containing fly ash, and, silica fume, individually as well as in combination, at two different w/cm ratios. Then a two-step composite model was used; firstly to find the shrinkage of mortar from the paste and then the range of the concrete shrinkages was determined using the shrinkage of the mortar and the Hashin-Shtrikman bounds (1963) with the corresponding elastic modulus. The prediction model agreed well with experimental data. The predicted shrinkages from the ACI 209R and CEB M90-99 were computed and the predicted model was found to be in close agreement with the experimental results.