Polycarboxylate and Polyether Admixture Compatibility with Different Cement Compositons

摘要

The use of polycarboxylate (PC)- and polyether (PE)-based superplasticizers often generates segregation, inadequate flowability or similar problems due to the incompatibility between the cements and admixtures used. In light of the widely varying composition of these admixtures, not all cement-and superplasticizer-related factors which could affect compatibility have been defined to date. In this study, therefore, Theological trials were conducted with a rotational viscometer and adsorption tests were conducted in a total organic carbon (TOC) analyzer to explore the compatibility between different PC - PE admixtures and cements employed in a variety of compositions and additions.rnThree admixtures (PC_, PC_2, and PC_3) with different carboxylate (CA) and polyether (PE) group contents were used, along with seven standard cements whose chemical and mineralogical compositions and active additions varied.rnThe structural characteristic of the admixtures affecting compatibility most intensely was found to be the carboxylate (CA) to polyether (PE) group ratio. In cements with no active additions, characteristics such as fineness and the C_3A to calcium sulphate and C_3S to C_3A ratios were also observed to have marked effect on compatibility. On the other hand, in cements with limestone or fly ash additions, no fundamental differences were identified with respect to a standard CEMI _(42.5)R cement in terms of admixture compatiblity.rnIn calcium aluminate cement (CAC) the fluidizing effect of polycarboxylate superplasticizers led to very significant declines in yield stress.