Assessment of mechanical strength of nano silica concrete (NSC) subjected to elevated temperatures
Journal of Structural Fire Engineering
ISSN: 2040-2317
Article publication date: 28 February 2019
Issue publication date: 28 February 2019
Abstract
Purpose
This paper aims to inspect the effect of indirect elevated temperature on the mechanical performance of nano silica concrete (NSC). The effect on both compressive and bond strengths is studied. Pre- and post-exposure to elevated temperature ranges of 200 to 600°C is examined. A range covered by three percentages of 1.5, 3 and 4.5 per cent nano silica (NS) in concrete mixes is tested.
Design/methodology/approach
Pre-exposure mechanical tests (normal conditions – room temperature), using 3 per cent NS in the concrete mix, led to the highest increase in both compressive and bond strengths (43 per cent and 38.5 per cent, respectively), compared to the control mix without NS (based on 28-day results). It is worth noticing that adding NS to the concrete mixes does not have a significant effect on improving early-age strength. Besides, permeability tests are performed on NSC with different NS ratios. NS improved the concrete permeability for all tested percentages of NS. The maximum reduction is accompanied by the maximum percentage used (4.5 per cent NS in the NSC mix), reducing permeability to half the value of the concrete mix without NS. As for post-exposure to elevated-temperature mechanical tests, NSC with 1.5 per cent NS exhibited the lowest loss in strength owing to indirect heat exposure of 600°C; the residual compressive and bond strengths are 73 per cent and 35 per cent, respectively.
Findings
The dispersion technique of NS has a key role in NSC-distinguished mechanical performance with NSC having lower NS percentages. NS significantly improved bond strength. NS has a remarkable effect on elevated temperature endurance. The bond strength of NSC exposed to elevated temperatures suffered faster deterioration than compressive strength of the exposed NSC.
Research limitations/implications
A special scale factor needs to be investigated for the NSC.
Originality/value
Although a lot of effort is placed in evaluating the benefits of using nano materials in structural concrete, this paper presents one of the first outcomes of the thermal effects on concrete mixes with NS as a partial cement replacement.
Keywords
Acknowledgements
The authors would like to express their deep appreciation to The STDF for supporting this research through Grant No. 4354. Also, the authors extend their gratitude to The NRC administration and staff, for facilitating and supporting us, through all the official and technical procedures.
Citation
Elkady, H.M., Yasien, A.M., Elfeky, M.S. and Serag, M.E. (2019), "Assessment of mechanical strength of nano silica concrete (NSC) subjected to elevated temperatures", Journal of Structural Fire Engineering, Vol. 10 No. 1, pp. 90-109. https://doi.org/10.1108/JSFE-10-2017-0041
Publisher
:Emerald Publishing Limited
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