Volume changes of concrete in interaction with sliding joint

Abstract

The paper describes volume changes of cement plain concrete and steel fiber reinforced concrete with strength class C 30/37 in interaction with sliding joints. In the research experiment was performed large-dimensional specimens, on which volume changes were measured using string strain gauges. Below the large-dimensional specimens were designed sliding joints. The specimens were placed in a controlled laboratory environment and in an outdoor environment to simulate real conditions during construction and the measurements were carried out for several months. Volume changes of the concrete were compared to each other and significant influence of the sliding joints was observed. Significant influence on the development of volume changes also has dispersed reinforcement. Another part of the article is a comparison of experimental results with calculation models that allow to calculate the final shrinkage of concrete. Comparison results of volume changes with calculation models is important for demonstrating the effect of sliding joint, as currently valid calculation models do not consider the influence of subsoil and sliding joints, and the results are different as expected. For comparison model B4 (Bazant, 2015), model from technical standard EN 1992-1-1 (CSN EN 1992-1-1, 2006), model from fib model code 2010 (FIB, 2010) and model ACI (ACI, 2008) are used. The paper describes a unique experiment dealing with the influence of sliding joint on the development of volume changes of concrete from beginning of setting and hardening of concrete under precisely defined conditions, that allow comparison with calculation models and thus points to the shortcomings of the building practice.