Degradation behaviour analysis of SMA aggregate and skeleton

Abstract

Based on laboratory tests and field materials evaluation, the inner frictional resistance of SMA skeleton was investigated and then the degradation behaviour of SMA skeleton was characterized for recycling purpose. Inner frictional resistance test was designed to investigate the skeleton characteristics of SMA aggregate mixture. The experimental results indicate that SMA skeleton has much stronger inner frictional resistance than AC skeleton, and coarse aggregates provide main contributions to the inner frictional resistance of SMA skeleton. Crushing test and superpave gyratory compactor (SGC) test were designed to reveal the degradation behaviour of SMA skeleton. To verify the laboratory characterization, field materials were also evaluated. The results indicate that the degradation of SMA skeleton is not random but has fixed internal trend, especially the 4.75mm aggregate plays a key role in the graded aggregates. Based on the testing results, it can be concluded that long-term repeated loading can cause degradation of SMA skeleton. However, the gradation does not keep deteriorating under repeated loading. When the inner frictional resistance is small enough, outside pressure will cause flow deformation of skeleton instead of degradation. Thus, well-designed SMA aggregate mixture is valuable for recycling after long-term in service. And it is important to restore the skeleton, especially the coarse aggregate part.