Pozzolanic reactivity and drying shrinkage characteristics of optimized blended cementitious composites comprising of Nano-Silica particles

Measurement of reaction rate amid Pozzolans and portlandite (Ca(OH2) in the pore solution of cementitious system is the essential mechanism that need to be quantified for any blended cementitious system. So, in this study pozzolanic reactivity of multi-blended cementitious composites (binary, ternary and quaternary) was determined and corroborated using three different techniques i.e., strength activity index (SAI), selective dissolution method (SDM) and thermogravimetric analysis (TGA). In addition, efforts were made to correlate the measured drying shrinkage values of multi-blended cementitious mix with pozzolanic reactivity indices. Theory of particle packing which works on the basis of modified Andreasen and Andersen model was adopted to design the optimized blended cementitious mixes. It is observed that pozzolanic reactivity was found to be the highest for 3% nano-silica admixed binary cementitious mix, however, this binary mix reported that associated drying shrinkage is a cause of concern. Further measurement on ternary and quaternary blended mix revealed that SCMs at triplet scale (quaternary blended) is found to be equally pozzolanic and also sustainable with respect to the phenomenon of drying shrinkage. This is attributed to the fact that synergic effect of multiple SCMs (quaternary blend) triggered the pozzolanic activity by enhancing the CH consumption rate from the pore solution. From the results of the experimental investigation, it is also proposed that there exists a "three-phase drying system" for all kind of cementitious mixes. Drying shrinkage results also showed best fit in correspondence to measured pozzolanic reactivity indices.