Studying effects of chemical admixtures on the workability retention of zeolitic Portland cement mortar

In this paper, the effects of three superplasticizers, namely, poly-carboxylate ether, calcium ligno-sulfonate, and Naphthalene Sulfonate Formaldehyde, on the workability retention of NZ blended mortars were investigated. In addition, simultaneous inclusion of either tripolyphosphate type retarder or Na2SO4 admixtures was examined as a measure to mitigate the workability loss of NZ blended mortars. Thereafter, the compatibility of zeolitic cement with three different superplasticizers was studied in more details by performing adsorption isotherm test, zeta potential test and also pH measurement of pastes at different time intervals. Obtained results indicated that for ligno-sulfonate and naphthalene sulfonate superplasticizers, reduction in the amount of electrostatic charge (which occurred by NZ inclusion) is an influential parameter contributing to the higher workability loss. On the other hand, for poly-carboxylate ether admixture, the results implied that the significantly high polymer adsorption is the major reason for the observed workability loss of NZ blended mortars. (C) 2014 Elsevier Ltd. All rights reserved.