Impact of cracks on chloride-induced corrosion and durability of reinforced concrete structures - a literature review

Structural EngineeringCivil Engineering and Geoscience

Application of acoustic emission measurements in the evaluation of prestressed cast in-between decks

A large number of concrete structures, that is built in the sixties and seventies of the twentieth century, need to be re-evaluated. It should be judged whether their capacity is still sufficient for the increased traffic loads. Acoustic emission (AE) is a non-destructive technique that can possibly be used to get a better insight in the structural state of these concrete structures. However, interpretation the AE measurements is challenging and is even more difficult when the concrete is cracked by for example alkali–silica reaction. Due to the existing cracks the wave attenuation affects the acoustic emission measurements. For an investigation into the capacity of pre-stressed cast in-between decks a 1:2 scale bridge was loaded in the Stevin laboratory of Delft University of Technology under two-way shear. In this preliminary research it was investigated whether AE-measurements can be used to get an idea about the structural condition of a structure, or more precise, to what extent the ultimate capacity is reached. For testing the concrete in-between decks a cyclic loading procedure is applied. It appeared that cyclic loading resulted in a lower capacity in comparison with the previously performed static loading experiments. There was no AE indication of early failure due to cyclic loading. Usually applied parameters, like ‘Kaiser Effect’ and ‘Calm Ratio’ are investigated. Furthermore, it was investigated whether the location of cracks could be determined by the emitted sound during the fracture process and applying a relatively large numbers of AE-sensors (so-called source location). In this article the performed AE measurements are reported and results discussed.Structural EngineeringCivil Engineering and Geoscience

Influence of particle packing density on the rheology of low cement content concrete

Optimizing concrete mixtures with regard to cement content is one of the most important solutions in sustainable concrete design. Workability o f these low cement content or ecological mixtures is very important. Eleven mortar mixtures are presented, which show how a higher packing density can be used to obtain mixtures that require less water. Higher packuig densities reduce the void volume between the particles and therefore decrease the amount of water necessary to fill this void volume. The reduced amount of water and lower water/cement ratio can be used to save a certain amount o f cement when concrete is designed for a fixed strength class.Structural EngineeringCivil Engineering and Geoscience