Exposure to elevated temperatures has detrimental effects on the properties of concretes based on the Portland cement, leading to irreversible changes, up to total failure. One of solutions to improve resistance of structures after exposure to high temperatures may be the use of cement-based materials modified at the nanoscale. The influence of complex nanomodification with polycarboxylate ether superplasticizer, ultra- and nanofine mineral additives and volume fiber-reinforcement by thermal stability basalt fibers on the behavior of Portland cementing materials exposed to elevated temperatures was investigated. After 1 and 7 days of curing period the concrete specimens were exposed to elevated temperatures of 105, 200, 400 and 600 °C typical for fire environment. The mass loss, flexural and compressive strength, porosity, shrinkage, water adsorption of the specimens exposed to the elevated temperatures were determined. The nanomodified Portland cementing materials are characterized by high strength at early and later age, exhibit enhanced stability of mechanical properties when exposed to temperatures in a range of 105 to 600 °C. The compressive strength of nanomodified concrete after 1 and 7 days of hardening at normal conditions and exposed to temperatures from 400 °C is increased to 89.8 and 107.4 MPa respectively. The adding of thermal stability basalt fibers is provided additional strength increase of nanomodified fiber-reinforced concrete. The possibility of obtaining nanomodified rapid hardening Portland cementing materials with high thermal resistance is provided by water demand reducing, system particle packing optimization, increasing cement matrix density, stimulating nucleation processes in the intergranular space, acceleration of hydration process and pozzolanic reaction, three-dimensional reinforcement of structure. Lower water/cement ratio and higher degree of water binding into hydration products decreases the total porosity, shrinkage and the rate of shrinkage of the nanomodified fiber-reinforced concrete by providing the rigidity increasing of the solid matrix to resist deformation.
1. Qianmin M., Rongxin G., Zhiman Z., Zhiwei L., Kecheng H. (2015), Mechanical properties of concrete at high temperature – A review Construction and Building Materials, No. 93, pp. 371–383.
2. Wang G., Zhang C., Zhang B., Shui Z. (2015), Study on the high-temperature behavior and rehydration characteristics of hardened cement paste, Fire Material, No. 39, pp. 741–750.
3. Sikora P., Elrahman M. A., Stephan D. (2018), The influence of nanomaterials on the thermal resistance of cementbased composites–A Review, Nanomaterials, No. 8, pp.465–498.
4. Horszczaruk E., Sikora P., Cendrowski K., Mijowska E. (2017), The effect of elevated temperature on the properties of cement mortars containing nanosilica and heavyweight aggregates, Construction and Building Materials, No. 137, pp. 420–431.
5. Seungmin L. (2015), Effects of nanosilica addition on increased thermal stability of cement-based composite, ACI Materials Journal, Vol. 112, Issue 2, pp. 305–316.
6. Dvorkin L. Y., Babych Y. M., Zhytkovsky V. V., Bordyuzhenko O. M., Filipchuk S. V., Kochkarov D. V., Kovalyk I. V., Kovalchuk T. V., Skrypnyk M. M. (2017) Vysokomitsni shvydkotverdnuchi betony ta fibrobetony. [Highstrength rapid hardening concretes and fiber reinforced concretes]. Rivne, NUVGP, 331 p. (in Ukrainian).
7. Sanytsky M., Marushchak U., Kirakevych I., Stechyshyn M. (2015), Vysokomitsni samoushchilniuvalni betony na osnovi dyspersno-armovanykh cementuuchyh system. [High strength Self-compacting concretes based on the fiber-reinfrorced cementitious systems], Budivelni materialy ta vyroby, No. 1, pp. 10–14. [in Ukraine].
8. Koňácová D., Chácová M., Doloželová M., Scheinherrova L., Vejmelkova E. (2016), Hightemperature resistance of concretes produced of two different cements, Cement, vapno, beton, No. 5, pp. 295–309.
9. Maruchchak U., Rusyn B., Olevych Y. (2018), The properties of Rapid hardening fiberreinforced concretes at elevated temperatures, 20. Internationale Baustofftagung, Weimar, Vol. 2, pp. 905–912.
10. Marushchak U., Sanytsky M., Olevych Y. (2017), Effects of elevated temperatures on the properties of nanomodified rapid hardening concretes, MATEC Web of Conferences, Vol. 116, p. 010008.