ANALYSIS OF CHANGES IN THE ELASTIC-STRENGTH CHARACTERISTICS OF MODIFIED AND UNMODIFIED FINE-GRAINED CONCRETES DEPENDING ON THEIR WET STATE AND TEST TEMPERATURE

Abstract

Using the example of unmodified and modified cement composites, the effect of temperature and humidity operating factors on the strength characteristics of fine grained concretes was studied. It was revealed that for unmodified concrete, varying the test temperature leads to a significant change in the strength characteristics of cement composites, increasing (taking into account their moisture content) during bending and compression tests in the region of negative temperatures. The greatest increase in the elastic strength characteristics is observed in moisture saturated samples. For samples in the dry state, the change in the strength characteristics under compression with a decrease in temperature from + 40 to -40 ° C is 17 %, and 22 % for bending stretching. According to the research results, it has been established that for modified highstrength and dispersion reinforced concrete there is a significant increase in tensile strength in bending throughout the entire range of temperatures studied for water saturated samples compared to samples in a dry and equilibrium moisture state. These differences in the nature of the influence of the test temperature and the moisture content of the samples on the change in the physicomechanical characteristics of the modified and unmodified concretes are explained by the difference in the structure and the type of moisture contained in them. In particular, the structure of modified composites is dominated by adsorption and crystallization related water, characterized by high binding energy, and in the structure of “traditional” concrete there is a large amount of capillary saturated and free water, which is weakly associated with the solid phase of unmodified composites.