Strength and Microstructure of Mortar Containing Nanosilica at High Temperature

• Published in: ACI materials journal Vol. 111; no. 2; p. 163
• Main Authors: Ibrahim, Rahel Kh, Hamid, R, Taha, M R
• Format: Journal Article
• Language: English
• Published: Farmington Hills American Concrete Institute 01.03.2014
• Subjects: Bond strength; Cement; Concrete; Construction industry; Crystals; Decomposition; Flexural strength; Heat; Hydration; Mechanical properties; Microstructure; Moisture content; Mortars; Nanostructure; Residual strength; Seismic engineering; Slaked lime; Strength
• ISSN: 0889-325X; 1944-737X
• DOI: 10.14359/51686497

The effect of high temperature on the mechanical properties and microstructure of nanosilica-incorporated mortars has been studied. Results show that the incorporation of nanosilica increases both compressive and flexural strengths significantly at both ambient and after a 2-hour exposure to 752 degree F (400 degree C) temperatures; the strengths increase with the increase of nanosilica content. A significant decrease in strength was recorded for all control and nanosilica-incorporated mortar specimens after a 2-hour exposure to 1292 degree F (700 degree C) heat; however, nanosilica-incorporated specimens show higher residual strength than those without nanosilica. Microstructural analysis shows that nanosilica reduces the calcium hydroxide crystals to produce more calcium silicate hydrate, the process that contributes to the strength and the residual strength of the material. In addition, the material exhibits a stable structure state up to 842 degree F (450 degree C), while exposure to higher temperatures results in a decomposition of hydration products.