EXPERIMENTAL STUDY ON RHEOLOGICAL BEHAVIOUR OF OLD AND NEW CONCRETE

Abstract

Replacement of cement concrete slab is one of the important measures for its maintenance after being used for several years. Due to structural differences between old and new cement concrete pavement slab, it is found that the old cement concrete slab has the tendency of accelerated damage in use. In this work, rheological behaviour of old and new concrete specimens is evaluated by obtaining C30 old cement concrete specimens drilled from a four (6) years old used cement concrete pavement with similar fresh cement concrete prepared specimens. One-time loading and cyclic loading and unloading tests were carried out by control displacement method on the old and new concrete specimens at 0.1mm/min, 0.3mm/min and 0.5mm/min loading speeds respectively. Rheological behaviour of cement concrete is characterized by the stress-strain curve variation law at three different rates. The rheological characteristics of cement concrete materials are explored by combining the test phenomena and the damage degree of the specimens in each test process. The experimental results show that the stress-strain curves of new cement concrete specimens grow linearly in a certain range (80% of maximum stress). The maximum stress of new concrete specimens increase linearly with the intensification of loading speed which indicates that cement concrete has certain viscous properties at different loading speeds and the cement concrete can be considered as linear elastic material when the change in slope of stress-strain curves is undeviating. Therefore, experimental study on the rheological properties of cement concrete is of great theoretical and practical significance for understanding the mechanical properties of cement concrete materials