Abstract
The aim of the research was to determine how the admixture of nanosilica affects the structure and mechanical performance of cement concrete exposed to high temperatures (200, 400, 600, and 800 °C). The structural tests were carried out on the cement paste and concrete using the methods of thermogravimetric analysis, mercury porosimetry, and scanning electron microscopy. The results show that despite the growth of the cement matrix’s total porosity with an increasing amount of nanosilica, the resistance to high temperature improves. Such behavior is the result of not only the thermal characteristics of nanosilica itself but also of the porosity structure in the cement matrix and using the effective method of dispersing the nanostructures in concrete. The nanosilica densifies the structure of the concrete, limiting the number of the pores with diameters from 0.3 to 300 μm, which leads to limitation of the microcracks, particularly in the coarse aggregate-cement matrix contact zone. This phenomenon, in turn, diminishes the cracking of the specimens containing nanosilica at high temperatures and improves the mechanical strength.
Highlights
Concrete as a structural material is widely used in construction due to its low cost, good mechanical performance, and relatively high resistance to water and fire
The results are presented as the average value from these three specimens
Noof significant presents images of nanosilica used for modification cement paste difference and number of partial measurements was a consequence of the given test sample stabilization
Summary
Concrete as a structural material is widely used in construction due to its low cost, good mechanical performance, and relatively high resistance to water and fire. The development of modern engineering construction requires new properties of the materials used. Modern cement concrete has high compressive strength and other, never seen before properties, like antibacterial performance [2,3], self-cleaning ability [4,5,6], insulating properties, or self-repairing ability [7,8,9]. Obtaining such properties of concrete is possible, among others, by using various nanomaterials for cement and concrete production. The nanoparticles most often applied to the cement-based materials are nanometals (nanosilver, nanogold, nanocopper, nanoplatinum, nanopalladium), carbon nanostructures, like nanotubes or fullerenes, titanium dioxide (TiO2 ), silicon dioxide (SiO2 ), and zirconium dioxide [10,11]
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