Microstructure model of fresh cement paste in the presence of superplasticizer
The microstructure of fresh cement paste (FCP) in the presence of superplasticizer was investigated in this study. A Morphologi G3 microscope was applied to directly observe the microstructure of the FCP with the emphasis of the real organization structure of cement particles in the paste. Based on the microstructure characterization, the working mechanism of superplasticizer on the flowability of FCP was analyzed. Combined with the real microstructure of multi-sized cement particle suspension and the working mechanism of superplasticizer, the contents of different types of water in cement suspension and the volume fraction of solid phase were calculated. Finally, a generalized multi-scale microstructure model of FCPs at varied superplasticizer dosages and water to cement ratios was established, which was verified by the experimental results of yield stress of the FCPs.
1 Introduction
Flowability has been considered one of the important properties of fresh cement-based materials due to their essential roles in the construction process as well as their effects on the mechanical properties and durability of hardened ones. Basically speaking, the macroscopic flowability is primarily determined by the microstructure of the materials, e.g. the packing state and the contents of solid phase in the cementitious suspension systems etc. [1-3]. In the fresh cement paste (FCP), the agglomeration of cement particles immediately takes places upon the contact of cement to...
