Microstructure evolution and strength development for pozzolana blended cement mortar
Authors :- Jayswal S., Mungule M.
Publication :- Materials Today: Proceedings, Volume 80, Part 2, 2023, Pages 824-832
Replacement/Blending of cement with pozzolanic materials to reduce clinker content and analyzing its influence on resulting microstructure and strength development is an attempt in enhancing concrete sustainability. Present study compares microstructure development amongst pozzolanic materials with that of reference sample and monitors the process of microstructure evolution. Pozzolanic materials with two different replacement levels (namely 10 % and 30 %) based on its surface area have been considered. Mortar samples for all considered pozzolanic materials following constant water binder ratio have been studied. Microstructure evolution of the sample is monitored through usage of optical microscope with the pixel resolution of 17.3 µm. The observed images have been analysed through image processing tools to understand distribution of intensities, observed shift during evolution process and its comparison with control sample. The intensity distribution observed in histogram is further compared with line histogram of an image with identifiable features. Intensity values corresponding with white deposits in the sample are compared to be associated with Calcium Hydroxide (CH). Adopting threshold values over histogram at different time instants, estimates are drawn for presence of calcium hydroxide in the sample. As pozzolanic characteristics of the material is associated with consumption of CH, the evolutionary trend of this estimates is compared and is correlated to develop pozzolanic index. It measures transition of supplementary materials from filler to pozzolanic. Further, strength development at 28 and 56 days for both control samples and those with pozzolanic material have been compared and its variation correlated with pozzolanic index developed. From the test results and pozzolanic index is revealed that the initial strength enhancement is the combined effect of filler as well as pozzolancity.