Using a magnesia binder to improve the airproof performance of molded composites

Introduction. Water resistance is one of durability criteria of building materials. As a rule, the value of the liquefaction ratio is applied to assess the water resistance. However, even water resistant materials are not always able to withstand cyclical weather impacts that cause linear deformations, reduced strength and cause destruction of building products. Therefore, it is necessary to take into account the resistance of building materials, namely, their resistance to alternating humidification and drying (airproof performance). The purpose of this research is to study the producibility of molded composites containing a modified magnesium binder that features higher resistance to weather impacts. Materials and methods. The magnesium binder was modified by the silica fume and high pressure molding to increase the water resistance and airproof performance of the composites. The influence produced by the modifier on the change in the compressive strength of dried and water-saturated molded composites, liquefaction and airproof performance ratios, as well as linear deformations of the reference specimens were studied following a pre-set number of cycles of alternating wetting and drying. Results. The water resistance and airproof performance of construction products, containing magnesia binders, may be improved by the micro-silica, added to pressed mixtures, and their compaction by press molding. Compositions of molded composites, containing a modified magnesia binder, were developed for the manufacture of products used to make enclosing structures and for the flooring of rooms having the indoor humidity of over 60 %. Conclusions. It is established that molded composites containing a modified magnesia binder feature high resistance to alternating wetting and drying. The proposed method of modifying magnesia binders prevents the destruction of molded stone-like materials containing these binders in case of exposure to alternating stresses; it reduces linear deformations and, as a result, decelerates the fatigue failure. The use of a recyclable material as a mineral additive must contribute to the reduction of the cost of products and allow to consider the method of their production as one of the best technologies available.