*Proceeding Paper* **The Influence of the Ageing Process on the Mechanical Properties of Cement Mortars with Nano-SiO2 Admixture Initially Subjected to Thermal Treatment †**

**Elzbieta Horszczaruk ˙ 1,\* and Paweł Łukowski <sup>2</sup>**


**Abstract:** The research aimed to evaluate the effect of nano-silica (NS) on the strength recovery of the previously heated cement mortars. One hundred twenty cement mortar specimens were prepared with 1% to 5% of NS. The specimens were heated at temperatures ranging from 200 ◦C to 800 ◦C. Half of the samples, after heating and cooling, were mechanically tested. The other half of the specimens were stored for 24 months in 90% relative humidity. The presence of NS fostered partial recovery of the compressive strength of the heated mortars. The cement mortars regained more than 40% of their compressive strength after heating at 400 ◦C and about 25% after heating at 600 ◦C. The strength recovery phenomenon faded away at 800 ◦C.

**Keywords:** cement mortars; compressive strength; high temperature; nano-silica

**Citation:** Horszczaruk, E.; Łukowski, P. The Influence of the Ageing Process on the Mechanical Properties of Cement Mortars with Nano-SiO2 Admixture Initially Subjected to Thermal Treatment. *Mater. Proc.* **2023**, *13*, 20. https://doi.org/10.3390/ materproc2023013020

Academic Editors: Katarzyna Mróz, Tomasz Tracz, Tomasz Zdeb and Izabela Hager

Published: 14 February 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).
