ABSTRACT
ABSTRACT The study investigates the influence of silicate salts (Na and K) and nano-particles as well as the influence of the curing environment on the mechanical and physical properties of cement pastes. Solution and dry form of potassium silicate and solution of potassium meta-silicate were added to the fresh cement matrix. In a second series of pastes containing the salts, 1,5% nanoSiO2 and nano-CaO were also added. The pastes were subjected to a stable force in their fresh state (after 24 hours of their production) in order to deliberately crack them. Curing variables included moist curing and cycles of moist -drying. The final specimens were tested for compression strength, porosity and microstructure at the age of 28 and 90 days. Scanning electron microscope (SEM) imaging analysis and stereoscopic observation assisted in verifying the results. The test results showed greater improvement in the mechanical properties of samples subjected to moist curing than those subjected to cyclic curing. The samples with sodium silicate salts were more effective in relation to potassium meta-silicate. The role of nanoparticles needs investigation as they seem to form dense structure and managed to fill empty spaces with excess of C-S-H phases. SEM imaging revealed a number of flake and needle-like crystals in the pastes which were likely the primary reason for the mechanical properties.
