Mechanical Properties and Pore Structure Analysis of Nanoparticle-Enhanced Alkali Activated Slag

Abstract

Concrete is the most abundantly used construction material in the world because of its low-cost and high-durability; however, using concrete in such high quantities has consequential environmental impacts that cannot be overlooked. Concrete production and usage accounts for over 5% of all annual CO2 emissions, and this number is only rising as concrete usage increases. The CO2 emissions associated with concrete can be reduced by altering the material design such that ordinary Portland cement (OPC) powder, which leads to CO2 emissions in both its extraction and manufacturing processes, is replaced with an alkali-activated material (AAM), such as alkali-activated Ground Granulated Blast Furnace Slag (AAS). AAS is a sustainable option; however, it has been observed to experience micro-cracking, which results in poor structural strength. This thesis investigates methods of strengthening AAS and reducing the effects of micro-cracking by adding zirconium dioxide (ZrO2) nanoparticles and multi-walled carbon nanotubes (MWCNTs) to strengthen the cement matrix. The impacts of adding nanoparticles were assessed by analyzing tensile strength, compressive strength, stiffness, and pore size distribution of samples with concentrations of 0%, 0.05%, and 0.1% of the two nanoparticle types over a 28 day period. The results showed that adding MWCNTs at a concentration of 0.1% MWCNTs led to a 29% improvement in compressive strength and a 5% improvement in stiffness while adding ZrO2 nanoparticles at these concentrations demonstrated no substantial improvement in strength or augmentation of the pore size distribution over time.