Influence of electrolytes on hardening of concrete with oxychloride magnesia cement at low temperatures

The specifics of performing construction and assembly works at negative ambient temperatures requires the use of special technologies. This is especially true of concrete works requiring the use of methods for intensifying the hardening of concrete in monolithic structures. The use of concrete based on magnesia binder can significantly reduce the cost and duration of work, because aqueous solutions of magnesium chlorideare used for its mixing, which are electrolyteswith a low freezing point. The article presents the main theoretical calculations on the formation of the structure of building composites during their hardening under negative temperatures. The factors of influence on the processes of structure formation and hardening of magnesian concrete are revealed. The technique of the experiment is given. The results obtained are described. An explanation is given to the nature of the curing of magnesian concrete aged for the first 7 days of hardening in the temperature range from -10 °C to -20 °C. A mathematical dependence of the strength of the magnesian solution on the density of the used aqueous solution of magnesium chloride with a consumption of binder from 50 to 25 % by weight of aggregate in the test temperature range under study is obtained. Studies have shown that magnesian concrete shut with an aqueous solution of magnesium chloride with a density of 1.15 ... 1.25 g/cm3 gains strength at holding temperatures from -10 °C to -20 ºС, and negative holding temperature decreases the hardening rate by 18 ... 62 % from R28.