INFLUENCE OF PROLONGED MOISTURE ON THE DESTRUCTIVE CHARACTERISTICS OF HEAVY CONCRETE

Abstract

The description of the occurrence of changes in the stress-strain state of concrete and its physico-mechanical properties under the action of short-term loading directly depends on the duration of its wetting with water, i.e. on the changes in the internal stress state caused by this phenomenon, along with the action of the absorption wedging action of water in the defects and pores of the concrete structure and the excess pressure in these pores. It was found that simultaneously with these processes, the destruction of some and the creation of other physico-mechanical and physico-chemical bonds between the solution and the aggregate, the solution and water. Only the chemical bonds remain unchanged. This leads to a change in the properties of the capillary-porous body of concrete.

       During this period of load application, continuous compaction of concrete occurs to the lower limit of longitudinal microcrack formation. Subsequently, with increasing compressive loads, the moistened concrete undergoes decompression, its volume begins to increase and at a certain level reaches the initial values. This level corresponds to the upper limit of longitudinal microcrack formation and development. With further increase in load, microcracks in concrete also grow and a critical level of microcrack development is reached, which, merging, create a macrocrack.

       It has been established that with prolonged moistening of heavy concrete for 2-4 days, the strength decreases to 27% of the initial one with subsequent recovery to 40-60 days of moistening, and subsequently exceeds the initial one.

Destructive coefficients , ,   showing physical and mechanical changes in the internal structural state of heavy concrete also change, repeating to one degree or another the change in the strength of concrete from the action of prolonged moistening.