ABSTRACT
This chapter discusses the performance of high-efficiency, pozzolanic admixtures like silica fume, metakaolin, and rice husk ash. To understand the behavior of such high-end pozzolanic admixtures clearly, the methodology of establishing the general and percentage efficiency factors for silica fume is explained in detail. The various combinations of constraints used with different researchers have been compiled and presented to arrive at the limitations. It is obvious from the findings that these materials containing higher amounts of amorphous silica present a significant advantage in terms of limiting the total cementitious material contents to reasonable limits to ensure lower water requirements. Such an approach to arrive at a very low effective cementitious material content after considering the pozzolanic efficiency of materials like silica fume will result in high-strength concretes. Naturally being fine powders, these materials also have a significant filler and pozzolanic effect to reduce permeable porosity and thus improve strength as well as performance. The need for establishing specific cementitious efficiency factors for other such materials is also emphasized in this chapter. Similar to Chapter 6, nomograms for arriving at the appropriate mix of constraints at the different percentages of replacement possible are also developed and presented. This chapter also discusses the effect of fiber constituents in such high-strength and high-performance materials.
