Reduction of moisture susceptibility of cold asphalt mixtures
A laboratory study investigated the effect of reducing moisture susceptibility of cutback asphalt mixture by adding Portland cement and bentonite, a nanoclay capable of absorbing water and sealing cracks through swelling.
Test results showed that adding cement and nanoclay significantly improved the initial strength and cracking resistance, and reduced moisture susceptibility.
Best performance with 20% cement content
The 20% cement content group generally had the best overall performance. The Marshall stability and indirect tensile strength were improved even after 24 h soaking or freeze-thaw cycling for the 20% cement content group. Excessive cement caused thinner asphalt film and therefore the improvement of strength was relatively lower and the cracking resistance at low temperature was compromised. SEM images showed after freeze-thaw cycling, the mixture surface changed from a smooth surface with a few wrinkles on edge of small particles to a rougher surface with gel structure. When the asphalt film was damaged during the freeze-thaw cycling, the infiltrated water reacted with cement and bentonite cluster and the C–S–H cement hydration product was formed, sealing cracks or air voids and compensating the strength loss.
The study is published in: Journal of Cleaner Production.
