Evaluating the performance of high volume fly ash-blended-cement mortar individually containing nano- and ultrafine micro-magnesia

• Published in: Journal of Building Engineering Vol. 36; p. 102129
• Main Authors: Abdel-Gawwad, Hamdy A., Metwally, Khaled A., Tawfik, Taher A., Mohammed, Mona S., Hassan, Hassan Sultan, Heikal, Mohamed, El-Kattan, Ibrahim M.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.04.2021
• Subjects: Compressive strength; Early-hydration; Environmental pollution; Fly ash; Nano-magnesium oxide; Fly ash; Compressive strength; Environmental pollution; Nano-magnesium oxide; Early-hydration
• ISSN: 2352-7102; 2352-7102
• DOI: 10.1016/j.jobe.2020.102129

This work focuses on the individual impact of nano- and ultrafine micro magnesia (N–MgO and UM-MgO, respectively) on the early performance of high volume fly ash (FA)-blended-cement mortar (CM). N–MgO and UM-MgO were synthesized using a thermal treatment of lightweight hydromagnesite at 550 and 1100 °C, respectively. Different contents of MgOs (1, 3, and 5 wt% by weight of powder) were individually added to FA-blended-CM. The results revealed that the N–MgO exhibits higher efficiency in the acceleration of early PC-FA system hydration compared to UM-MgO at all addition levels. The addition of 1, 3, and 5 wt% N–MgO to FA-blended-CM has resulted in the enhancement of 3-days compressive strength value by ~26, 94, and 103%, respectively; whereas the UM-MgO shows a modest effect. The small particle size, low crystallinity, and high hydration reactivity are the dominant features of N–MgO, which reflect on the enhancement of FA-pozzolanic activity accompanied by the acceleration of strength-giving-phases formation at early ages of hydration. To achieve the sustainability, we have recommend the use of N–MgO, as it contributes to cost minimization, energy saving, and the mitigation of carbon footprint. •Nano- and micro-MgO were used to enhance the performance of fly ash cement mortar.•Nano-MgO exhibited higher hydration reactivity compared with ultrafine micro-MgO.•Cement mortar containing 5 wt% nano-MgO exhibited the highest early performance.•The properties of cement mortar depend on the particle size and reactivity of MgO.•MgO interacts with amorphous aluminosilicate, yielding magnesium silicate hydrate.