Improving the physical and mechanical properties of cement matrix using finely dispersed sulfur

The article discusses the possibility of improving the physical and mechanical properties of cement matrix using colloidal additives in the form of sulfur sol. This sol was obtained in various ways: by mixing the initial colloidal sulfur in the form of a 2 % solution in water, by the oxidation-reduction reaction method, and by the solvent replacement method. The hardening kinetics of the cement matrix with the addition of different amounts of sulfur sol is considered. The structure formation of the cement matrix modified with sulfur sol at the age of 3 and 28 days was studied.
When sulfur sol additives were introduced into Portland cement in microdoses — 0.002–0.02 % in terms of dry matter — a modified cement was obtained, the strength of which was on average 25-35 % higher than that of the original cement. It was established that the most rational compositions are those containing 0.8–1.0 % sulfur sol, providing an increase in 28-day strength by 19–36 % compared to the control composition. At the same time, the introduction of a colloidal additive in the form of sulfur sol increases the strength of the matrix in the early stages of hardening: at the age of 3–7 days it reaches 90–100 % of the strength after 28 days of hardening. The process of strengthening and compaction of cement matrix with sulfur sol additives is apparently due to the formation of hydrated calcium sulfoaluminates and complex sulfur-containing compounds in the early stages of hardening.