Packing density of cementitious materials: part 2—packing and flow of OPC + PFA + CSF

Abstract

The wet packing method developed in Part 1 [Wong HHC, Kwan AKH (2007) Packing density of cementitious materials: part 1 measurement using a wet packing method. Mater Struct (Paper No. MAAS3281)] has been successfully applied to measure the packing densities of cementitious materials containing ordinary Portland cement (OPC), pulverised fuel ash (PFA) and condensed silica fume (CSF). The test results for non-blended materials revealed that whilst the addition of a superplasticiser would always increase the packing densities of OPC and PFA, the addition of a polycarboxylate-based superplasticiser could decrease the packing density of CSF. On the other hand, the results for blended materials showed that the packing density could be improved by double blending OPC with either PFA or CSF, and further improved by triple blending OPC, PFA and CSF together in appropriate proportions. A maximum packing density of 0.752 has been achieved and a ternary packing density diagram for determining the mix proportions for maximum packing density has been produced. Furthermore, the positive influence of a higher packing density on cement paste rheology has been demonstrated using the mini-slump cone test. Based on these results, the concept of excess water ratio, which is the major factor governing the rheology of a paste, is introduced.