Effects of moisture on properties of asphalt mixes in a wet tropical climate: a laboratory study

Abstract

A moisture treatment designed to simulate the condition that pavements are exposed to in the wet tropical climate of Singapore is described. A weathering chamber was specially fabricated to introduce simultaneous wetting-drying and thermal cycles. The experimental program subjected four different asphalt mixtures - an open-graded, a gap-graded, and two dense-graded mixes - to the moisture treatment. Results indicate that the treatment was able to induce bleeding, stripping, and softening (loss of strength) in test specimens. The extent and severity of the resultant moisture damage varied with the mixture type and with the length of the treatment cycle period and the number of treatment cycles. On the basis of the test results, a procedure consisting of 150 4-hr cycles of simultaneous wetting-drying and thermal cycles was recommended. The treatment procedure shows significant potential as a research and development tool for studying the moisture damage resistance of new asphalt mixtures and the effect of modified binders in a wet tropical climate.