The effect of elevated temperature on the properties of cement mortars containing nanosilica and heavyweight aggregates

In this contribution the effect of nanosilica (NS) on the behavior of cement mortars containing quartz aggregate and two types of heavyweight aggregates (magnetite and barite) exposed to elevated temperature will be investigated. The cement mortars have been modified with nanosilica in quantities of 1%, 2%, 3%, 4% and 5% (by weight of cement). The samples were exposed to the elevated temperatures of 200 degrees C, 400 degrees C, 600 degrees C and 800 degrees C, respectively. The mass loss, flexural and compressive strength of the cooled specimens were determined. Additionally, by means of scanning electron microscopy (SEM) and optical microscopy the structure defects have been determined. The results clearly demonstrate that there is an optimal nanosilica content, in the cement mortar containing quartz and magnetite aggregate, improving the thermal resistance and preventing the crack extension (especially in the range of 200-400 degrees C). However, the study has also shown that cement mortars containing barite aggregate tend to crack and exhibit spalling as a result of low thermal resistance of the aggregate. (C) 2017 Elsevier Ltd. All rights reserved.