RESEARCH OF DEFORMATIVE PROPERTIES OF CONCRETE CLASS C50/60 TAKING INTO ACCOUNT THE DESCENDING BRANCH OF DEFORMATION

Abstract

Hundreds of experimental works have been known to determine the compressive strength limit, but they were all executed with incremental load increments. Our own experiment claims to be a novelty approach, namely, the use of a ‘hard’ machine and load by means of a stepwise increase in the displacement of a press plate. This method of loading provides much less information for analyzing the process of working concrete in compression. There is no descending branch in the ‘load-displacement’ diagram, and the sample itself collapses instantaneously at the maximum point of displacement. The maximum stress obtained by increasing the load is almost the same as the one obtained in the hard loading mode.  In addition, on samples that were tested in National University of Water and Environmental Engineering laboratory. Additional indicators were installed to determine the movements between the press plates. Thus, the movements determined were similar to those identified in the INSTRON 8806 press. It is clear that it is extremely difficult to determine the true deformation of the sample due to the friction on the edges of the sample. Deformation is essentially overestimated. According to the most approximate estimates the displacement spent on clutter is about 60% of the total reduction in the distance between the press plates. Almost all of the first plot in the diagram consists of deformations of the friction on the edges of the sample. However, we will try to determine the real diagram of deformation of concrete, taking into account the diagram obtained on the press PG-250. The deformation of the concrete in the prisms tested in the INSTRON 8806 press was by dividing the movements found between the press plates on the distance between the plates of the press. Since, as was noted above, the true deformation of the sample due to the stiffening at the edges of the sample differs from those obtained in this way. To correlate these deformations, use the true deformation diagram found in the PG-250 press. This can be done taking into account the identity of the results obtained on both presses. Comparison of the received data with the normative which confirms the adequacy of the data was conducted.