Interaction of Superplasticizers with C3A: Understanding the Superplasticizer Compatibility with Cement

The incompatibility between the superplasticizer (SP) and cement can cause problems with the cementitious materials’ fresh and hardened qualities, such as unstable workability, uncontrollable setting times, excessive air entrainment, and so on. In this paper, five various types of SPs were prepared. Their interaction with pure tricalcium aluminate (C3A) and its hydration products were investigated and their effect on the generation of Ettringite (AFt) and single-sulfur calcium sulphoaluminate hydrate (AFm) in paste and their compatibility with cement were also studied. The results demonstrate that after 15 min of cement hydration, the AFt and AFm content of mixture with polycarboxylate SP and sulfonated acetone-formaldehyde superplasticizer (PCA-SAF) is 124.6% and 24.8% higher than that of SAF, respectively, which decreases the consumption of SPs molecules and improves the compatibility of SAF with cement. Compared with polynaphthalene sulfonate superplasticizer (PNS), PCA-PNS dramatically enhanced the SP’s compatibility with cement. Accelerating the production of AFt and AFm during the early stages of cement hydration may be one method to increase SP–cement compatibility.