Development and Evaluation of Nano-silica Sustainable Concrete

Abstract

The concrete industry is one of the main contributors in the emission of carbon dioxide. Yet, it is the most used man-made material. In the past few decades, different pozzolanic materials were used as a partial replacement of Portland cement. These materials played a major role in reducing the carbon footprint associated with the production of Portland concrete. Furthermore, they greatly improved the concrete's strength and durability. However, these materials are also responsible of causing significant shortcomings to the concrete such as the slow rate of strength development. In the last decade, the nanomaterials made a major breakthrough in the concrete industry in terms of reinforcing the concrete with unique properties. In this study, 1% and 2% dosages of nano-silica were added to concrete mixtures that contain 30% and 70% ground granulated blast-furnace slag (GGBS) dosages. Adding 1% of nano-silica to the 30% GGBS concrete mixture showed an increase in the compressive strength by 13.5%, 7.8%, 8.1%, and 2.2% at 1-day, 3-day, 7-day, and 28-day, respectively. The 2% of nano-silica increased the 30% GGBS concrete mixture's compressive strength less effectively by 4.3%, 7.6%, and 4.9% at 3-day, 7-day, and 28-day, respectively, when compared to the 1% dosage. On the other hand, adding 1% and 2% of nano-silica reduced the 70% GGBS concrete mixtures' compressive strength. Moreover, nano-silica reduced the deformability of the mixtures significantly which caused the increase in the Young's modulus. The flexural strength of the 30% GGBS concrete mixtures had similar behavior as the 28-day compressive strength. On the other hand, the flexural strength of the 70% GGBS concrete mixtures increased as the nano-silica's dosage increased. Nano-silica addition improved the microstructure and the interface structure of the mixtures due to its high pozzolanic activity and the nano-filler effect which is confirmed by the rapid chloride permeability test's (RCPT) results, and the scanning electron microscopy (SEM) images. Life-365 service life modeling showed that the 1% and 2% dosages of nano-silica extended the service life of the 30% GGBS concrete mixtures by 2.5 and 4.9 years and the 70% GGBS concrete mixtures by 11.2 and 24.7 years, respectively.