Investigating the effect of polycarboxylate-ether based superplasticizer on the microstructure of cement paste during the setting process

There is limited measure available to quantify the effect of polycarboxylate-ether based superplasticizer (PCE) on the microstructure of cement-based systems during the first 24 h. To fill this gap, the backscattered electron image analysis (BSE-IA) alongside the ternary technique is used in this study to separate composed phases quantitively and then calculate the average spacing between cement particles. Besides, together with an examination of hydration heat, the skeleton development of reaction products is investigated. The results show that cement hydration is not a constant process, and the developing mode for hydration products region varies with the particle size of cement. In this regard, numerous hydration products may gather around small cement particles and then adsorb other unhydrated particles, forming the continuous region. By contrast, the particles possessing relatively large size are surrounded by noticeable pores, which interrupt the continuity of the hydration products region. When introducing PCE, the agglomeration of cement particles and the average spacing between cement particles reduced, manifesting as an enlarged hydration products region alongside a decreased porosity at the area surrounding large particles. However, this leads to a decreased hydration degree for cement and extends the setting time of cement paste.