Microproportioning paste with crushed aggregate filler by use of specific surface area

It is necessary to understand how to combine the fines with various cementitious and pozzolanic binders and admixtures, in order to develop the use of crushed aggregate fines in concrete, obtaining target rheological properties. Following previous studies on the effect of crushed aggregate fines specific surface area (SSA) and its relation to rheology, we extended this approach to all materials and still find that SSA relates to rheology measurements on largely different powders: crushed fines ,Portland cement, blended cements (fly ash ground with clinker) and also additional bulk fly ash.

First, we developed a single method for powder particle size distribution (PSD) and SSA using an X-ray Sedigraph covering all powders of the filler modified paste. Then we investigated both mixes with constant and varying solid fraction and found that they correlated reasonably well to rheology at constant SP dosage, in spite of the big differences in both powder composition and higher range of SSA values compared to the early filler studies.

The current study reports some additional experiments,where mixes incorporating also silica fume and variable SP-dosage have been included, with the purpose of further understanding the suitability of using the SSA of all the powders in a mix as the main parameter for developing a practical concrete micro-proportioning tool.