Lowering cement clinker: A thorough, performance based study on the use of nanoparticles of SiO2 or montmorillonite in Portland limestone nanocomposites

Nanotechnology has changed the way we perceive science, our world and consequently the built environment. Cement sustainability is of primary importance and nanotechnology can offer new alternatives towards lowering the CO₂ footprint by reducing clinker, by increasing the by-products content and by creating more durable formulations. This paper presents an optimization protocol of ternary Portland limestone nanocomposites through the addition of nanosilica or nanomontmorillonite (nMt) particles. Thermal gravimetric and X-ray diffraction analyses, confirmed the Ca(OH)₂ consumption towards the production of C–S–H. Mercury intrusion porosimetry (MIP) and long-term relative density measurements coupled with field emission scanning electron imaging (FESEM) confirmed the microstructural changes leading to strength enhancement. Lastly, limitations were determined through the extensive study of the addition of nanosilica particles at four different dosages (0.1, 0.5, 1.0, 1.5% addition by total mass of solids) or three different nMt dispersions at five different dosages (0.5, 1.0, 2.0, 4.0 and 5.5%). Strength tests and characterization were carried out at day 1, 7, 28, 56, 90 and 170 to assess both the short- and long-term effects. Nanosilica and inorganic nMt particles were found to be the most effective at lower dosages for strength, hydration and microstructural improvements.