Reduction of calcium leaching in cement hydration process using nanomaterials

Continuous efforts are being made to understand the mineralogical and morphological properties of cement hydration at the early stages for speedy construction. Use of nanoparticles may provide faster kinetics due to their high surface/volume ratio. Spherical dispersed silica nanoparticles were prepared by employing the sol-gel method. Scanning electron microscope (SEM) and X-ray diffraction (XRD) studies revealed that the prepared nanoparticles are amorphous and uniform in size (similar to 50 nm). Further, these particles were incorporated into cement paste and investigated through SEM, XRD and thermogravimetric analysis techniques. Incorporation of silica nanoparticles into cement paste improved the microstructure of the paste, and calcium leaching is significantly reduced as silica nanoparticles react with calcium hydroxide (CH) and probably form an additional calcium-silicate-hydrate (C-S-H) gel. It was found that the CH content in the silica nanoparticle incorporated cement paste reduced by similar to 86% at 1 day and up to similar to 62% at 28 days of the hydration process. The XRD studies revealed that the addition of 2.5% (w/w) silica nanoparticle powder was found to be optimal to significantly digest the CH. Morphological features as studied through SEM showed that the microstructure of silica nanoparticle incorporated cement paste becomes significantly denser, and a more compact C-S-H gel is formed, thereby improving the mechanical properties of the resulting cement paste. Insight and tuning of cement based materials at nanolevel may thus greatly help in achieving ultrahigh performance concrete for durable and sustainable construction.