An analysis of the design and assembly of the AAR tri-axial machine

Abstract

The following work is an analysis of the design and reassembly of a tri-axial machine in the laboratory at UPC designed to test the expansive alkali-silica reactions that can occur in concrete under various conditions.

The expansive reactions between alkalis and alkali-reactive aggregates within concrete structures are a problem which has been known about since the mid 20th century. This slow-evolving concrete damage causes a huge amount of damage to susceptible concrete structures worldwide. This damage is serious because it leads to a degradation of the material properties of the concrete, leading to a less safe structure. This phenomenon is the leading cause of dam concrete deterioration.

Much research has been carried out in this field in attempting to understand the causes; however the engineering community is far from fully understanding and being able to predict expansions caused by this reaction as it can vary greatly with environmental conditions. This thesis presents a summary of the main factors which affect this reaction, which are the temperature, humidity and confinement stresses. This is given with a view to explaining the design of the experimental testing machine.

The aim of the experimental results the machine will provide is to further refine and understand the processes behind the alkali-silica expansion, which will help in the refinement of current expansion-prediction models and in the creation of new models. A brief analysis of some of the main expansion prediction models is given as background to the design of the machine.

The main body of work carried out this year has been the assembly of the experimental machine, with all of the work required to set up a one of a kind machine such as this in a new environment. The final parts of this thesis provide detailed information on the workings and setup of each of the systems the machine relies on for the benefit of the next users, as well as information on its current status and a guide to future operation.