Effect of self-cementing properties on the mechanical behaviour of recycled concrete aggregates in unbound pavement layers

Recycled concrete aggregates (RCA) are increasingly being used in unbound pavement base and subbase layers, while the influence of their self-cementing properties on the mechanical behaviour has not been thoroughly studied. In this paper, the self-cementing properties, permanent deformation and resilient deformation behaviour of two RCA, NRCA (New RCA, crushed recently) and ORCA (Old RCA, crushed long time ago), showing significantly different self-cementing properties, after curing for different times (1, 180, 360 and 720 days), were investigated by pH value measurements, calorimeter tests and repeated load triaxial tests (RLTT). The results show that the self-cementing properties can significantly improve the mechanical behaviour of RCA, which is comparable to that of lightly treated materials. The permanent strains of NRCA, showing strong self-cementing properties, decrease to a very low value quickly after curing for 180 days, and then stabilize. While the resilient modulus of NRCA increases continuously with curing time, up to the studied curing time (720 days), 4.3 times larger than that curing for 1 day. It was also found that the traffic loads can damage the bonds between particles formed due to the self-cementing properties. On the contrary, for ORCA, showing negligible self-cementing properties, curing has no influence on the mechanical behaviour.

Automated summary

In this study, the self-cementing properties, permanent deformation, and resilient deformation behavior of two recycled concrete aggregates (RCA) with different self-cementing properties were investigated after different curing times. The results showed that the self-cementing properties significantly improved the mechanical behavior of RCA, comparable to lightly treated materials. The permanent strains of RCA with strong self-cementing properties decreased quickly after 180 days of curing and then stabilized. On the other hand, curing had no influence on the mechanical behavior of RCA with negligible self-cementing properties.