Hydration of Portland slag cement in the presence of nano silica

Abstract

The cement industry accounts for nearly 7% of carbon dioxide (CO2) emissions globally and is facing tremendous pressure to reduce the emission intensity. Supplementary cementitious materials (SCM) are a quick and effective lever to lower CO2 emissions. The cement hydration process is a sensitive mechanism and is greatly influenced by many factors such as hydration environment, type of SCM, and the amount used in the cement, which affect the cement's physical and mechanical performance. The SCM adversely impacts cement performance, especially prolonged setting and slow initial compressive strength development, compared to ordinary Portland cement (OPC). The importance of nanomaterials has been known for decades; their usage in cementitious materials is now accelerated as they can play an essential role by offsetting the adverse effects of the high usage of SCMs in cement. They help in reducing the intensity of CO2 and offer value-added features. A lab experiment is carried out to understand the role of nano SiO2 at different dosages on the Portland slag cement (PSC) hydration by studying heat evolution profiles, compressive strengths, TG-DTA, XRD, and SEM images. Results have revealed that 1% nano SiO2 accelerates early settings time and compressive strength compared to OPC. It will promote slag-based blended cement (PSC) and replace ordinary Portland cement in the construction industry to reduce the CO2 footprint of the cement and construction industry. A model of NS's role during PSC hydration is also given.