Peculiarities of hydration and frost resistance of cement with natural zeolite additive
The work is directed to the researches of composite binders, especially their strength properties in conditions of negative temperatures. Since the slowing down of concrete hardening with the addition of pozzolanic additives limits the possibility of using composite binders in regions with a short period of positive temperatures, a whole area of scientific works fails to find its application. The article presents the results on the determination of strength properties and hydration processes in cement stone with pozzolanic additive from natural zeolite during freezing and thawing. In determining the strength of the cement stone we chose the method of ultrasonic penetration. Graduation dependence of strength on the time of ultrasound propagation was revealed for its correct application. It allowed us to obtain dependences of cement stone strength with different amounts of additives on cycles of alternate freezing and thawing. The obtained results made it possible to get information on frost resistance of different compositions of the binders. It was shown that the addition of 30 wt. % and more of ground natural zeolite into Portland cement slows down the destructive effect of freezing-thawing due to unfinished hydration processes, which leads to an increase in the critical number of freezing-thawing cycles and the Portland cement frost-resistance grade from F300 to F400, respectively.