Dual Functionality of Silica Fume in Very-High-Strength   Heat-Resistant Concrete

Zhwan Anwar Noori; Ferhad Rahim Karim; Hardy Kamal Karim

doi:10.38027/ICCAUA2026EN0296

Authors

Zhwan Anwar Noori Department of Civil Engineering, college of Engineering, University of Sulaimani, Al-Sulaimanyah, Iraq
Ferhad Rahim Karim Department of Civil Engineering, college of Engineering, University of Sulaimani, Al-Sulaimanyah, Iraq
Hardy Kamal Karim Department of Civil Engineering, college of Engineering, University of Sulaimani, Al-Sulaimanyah, Iraq

DOI:

https://doi.org/10.38027/ICCAUA2026EN0296

Keywords:

Bulk dry density, Compressive strength, Split tensile strength, Silica fume, Very-high strength heat-resistant concrete, Water absorption

Abstract

Very-high strength heat-resistant concrete (VHSHRC) is intended to withstand high
temperatures without significantly degrading its characteristics. This research highlights the
effect of silica fume on the properties of VHSHRC, and it was employed as a partial substitute
for Portland cement at various ratios of 11.5%, 12%, 12.5%, and 13%. The properties, such as
compressive and split tensile strength, bulk dry density, and water absorption, were measured
under normal and different heating temperatures and durations. 165 cubes were used to
determine compressive strength, and 150 specimens were examined for split tensile strength,
bulk dry density, and water absorption. The results show that the optimal silica fume
replacement ratio in VHSHRC was 12.5%, resulting in a 3.72% increase in compressive
strength at 125°C and a 32.18% reduction in water absorption due to the improvement in
pozzolanic reaction by silica fume and its ability to reduce the number and size of micro-pores.