Application of Cyclic Uniaxial Compression Testing to Investigate the Effects of Preload and other Factors on the Structural Properties of Concrete Affected by Alkali Silica Reaction

Jamal  M. SALAM

 The thesis is concerned with giving a quantitative assessment of the amount ofmicrostructural damage within concrete affected by Alkali Silica Reaction (ASR) and the particular influence of applied load on this damage.

 Literature relevant on the nature and mechanism of ASR is reviewed. This review provides the basis for the analysis and interpretation of the results obtained throughout the experimental investigations.

 Experiments were carried out on cores taken from large concrete blocks manufactured using mixes known to exhibit ASR within a few weeks of casting. They were aimed at studying the effects of ASR on certain engineering properties obtained from the Stiffness Damage Test (SDT) and to determine the extent and magnitude of the change in such properties while the ASR progressed. The SDT analyzes the stress‑strain curves produced from specimens subjected to low cyclic uniaxial loading. In parallel with the stiffness damage properties, changes in core compressive strength(fc), Ultrasonic Pulse Velocity (UPV) and dimensional changes were also determined. Another investigation was also made to study the development of crack patterns and expansions in ASR concrete blocks subjected to different levels of uniaxial compressive stress and to examine the mechanical properties of cores taken in the three principal planes of these pre-loaded blocks, once cracking had occurred.

 An investigation was also made to study the effects of saturation condition on the mechanical properties of ASR concrete.

 The work clearly demonstrates:

 (1) -The changes in the mechanical properties that occur over time as ASRprogresses within concrete.

 (2) -The importance of the intensity and direction of applied pre-load stress on the amount of damage suffered by ASR concrete.

 (3) -The variations in the mechanical properties that result from changes in the saturation state of ASR cores.