CONCRETE STRUCTURES INTERACTING WITH SUBSOIL DEPENDING ON THE USE OF SLIDING JOINT

Abstract

Article describes the interaction of concrete structure (usually foundation structure or industrial
floor) with subsoil, where unwanted friction occurs. Friction can be reduced with sliding joint. This generally
known assumption is followed by research described in the article, which determines the effectiveness of
sliding joints with respect to concrete volume changes on large-dimensional specimens. Large-dimensional
specimens with dimension of 150 x 500 x 6000 mm were placed in the laboratory and outdoor environment,
defining different boundary conditions. The research included various concretes in the same strength class and
various sliding joints that respect the requirements of construction practice. The paper also describes the
comparison of measured results with calculation models from technical standards and regulations, which allow
calculation of volume changes on concrete structures. Regarding the subsoil and the sliding joint, this is one of
the main long-term goals of the research, since the calculation models do not take these two parameters into
account. Deformations from volume changes then deviate significantly from theoretical calculations, as friction
in the sliding joint area affects the magnitude and course of volume changes. Practical results show that the
steel fibres mixed into concrete have a positive effect on reducing volume changes in early stages of setting
and hardening of concrete. Regarding the use of the sliding joint, the most important finding is that there are
no significant differences from the selected sliding joints in the experimental part. In connection with friction,
the use of the sliding joint itself has a significant effect.