DEVELOPMENT OF A RATIONAL PROCEDURE FOR EVALUATION OF MOISTURE SUSCEPTIBILITY OF ASPHALT PAVING MIXES By

Proper testing and screening for moisture susceptibility is a crucial requirement for designing good performing asphalt pavements. The objective of this ongoing study is to develop a rational procedure for evaluation of moisture susceptibility of asphalt paving mixes. Theoretical considerations show that pore pressure generated under saturated undrained condition is significantly higher than that generated under drained condition. Some preliminary tests with a modified existing equipment indicated that conditioning process of applying cyclic pressure of 35-210 kPa at 5 Hz and 60 o C is able to induce moisture damage within one hour. A new standalone equipment was used for conditioning samples of two mixes – one with and another without moisture susceptibility problems. The equipment consists of a system to use a supply of compressed air to load and apply vacuum to force water out and in through a sample. Results were compared to results obtained from AASHTO T283 and rut testing under water. It was concluded that the new procedure has good potential for use as a method for evaluation of moisture susceptibility of mixes. It is capable of repetitive generation of pore pressure and suction, causing hydraulic scouring of mixes, and causing progressive moisture damage with increasing number of cycles. The process has good repeatability and is sensitive to temperature and mix types. It is recommended that further improvement of this equipment and refinement of the test procedure be carried out and research be conducted with different types of mixes, especially with aggregates/mixes susceptible to stripping.