The investigation is focused on behavior and performance at both the micro and macro levels and the correlation between those performances and the observed behavior and performance of concrete joints in existing airfield pavements. The literature study involved examination of information from shear tests on rocks containing joints, from shear tests on joints between concrete blocks with and without reinforcement crossing the joint, and tests on slab systems. From that literature study several shortcomings in available information were identified as factors to be addressed in the laboratory bench top study. The bench top set-up developed for shear testing of concrete joints has been completed. Joints are made by casting stress concentrations into the midplane of concrete blocks and then tensioning those blocks so that cracking is induced on that midplane some several hours after casting.
Specimens are then moist cured before movement to the laboratory for storage and testing.
Prior to testing roughness data are obtained for each joint by carefully separating the joint on a level surface, making measurements and reclosing the crack and clamping. Tests are made in a special apparatus that holds the crack width constant while increasing and reversed shear displacements are applied along the joint. Measurements are made of the shear force, the shear displacement, the crack width and the stress induced normal to the joint. Results are described for fully reversed cyclic loading to failure where the crack widths are held constant at values varying between 0.03 and 0.10 inches and maximum shear stresses of 50 and 100 psi are applied as repeated loading cycle. Tests completed to date show a good reproducibility in the data from identical tests on identical joint systems, but that the results are significantly affected by minor changes in joint openings.