Failure modes and mechanisms of pavements in saline foundations

Abstract

Saline soil causes problems for the construction of airfield pavements and results in some pavement failure modes that are different from or more serious than failure modes in non-saline soil. Through an investigation of several typical airports in China, the failure modes of airfield pavements were determined in this study as mainly blow-ups, faulting, slab cracking and black spots. These failures are mainly attributed to the subgrade course, cement-stabilising aggregate base course (CSABC) and concrete surface course subjected to different levels of sulfate and chloride attack. Salt-heaving experiments were conducted for the subgrade and base courses, while salt corrosion experiments were performed for the surface course. The results indicate that the salt-heaving pressure of soils not only increases with an increase in dry density of the soil and the content of sodium sulfate, but also varies with water content and reaches a maximum value at the optimum soil moisture. The compressive strength of the CSABC was found to increase first and then decrease as the contents of sulfate and chloride salt reached threshold contents of 0·3% and 0·2%, respectively. In addition, the impacts of sulfates on the flexural strength, dynamic modulus of elasticity and mass loss of concrete were found to be proportional to sulfate content.