Assessing the individual impact of magnesia and titania nano- particles on the performance of alkali-activated slag mortars

Abstract

The present investigation aims to evaluate the impact of prepared magnesia nanoparticles (MNP) and titania nanoparticles (TNP) on engineering properties of Alkali Activated Cements (AAC) based on granulated blast-furnace slags (GFS). Either MNP or TNP was incorporated to Alkali Activated Slags Matrices AASMs (Paste or Mortar) with different ratios (0, 1, 3 and 5 wt%). Fresh and hardened properties of AAC-GFS with or without nanoparticles were evaluated. The results revealed that both MNP and TNP have a positive impact on the physicomechanical properties: compressive strength, flexural strength, setting times, dry shrinkage, total porosity and flow rate. Complementary, the M3-MNP (containing 3 wt% MNP) and M1-TNP (containing 1 wt% TNP) mixes revealed the highest mechanical strengths, in addition to a significantly reduction in drying shrinkage, total porosity and flow rate and lower setting times comparing to control samples. Compressive strength for specimens cured at 25 °C and 70 % RH for 30 days increased by 25.7 % and 21.1 %, while flexural strength significantly enhanced by 51.7 % and 47.1 % for mixes incorporating 3 wt% MNP and 1 wt% TNP respectively compared with control specimens (without nanoparticles). Maximum reduction in drying shrinkage reaches 60 % and 70 % for mixes incorporating 3 wt% MNP and 1 wt% TNP respectively compared with control specimens up to 180-days of curing and 70 % RH. This fact can be due to the synergistic formation of CSH gel in parallel with hydrotalcite CH24O23Mg6Al2 (Hct), CTiSH and C4TiH13 phases, which have a potential impact on the performance of geopolymerization system.