Durability and performance of South African recycled granulates in unbound (sub)base pavement layers

Recycled granular materials such as Recycled Concrete Aggregate (RCA) and Recycled Crushed Masonry (RCM) are widely used in The Netherlands as base layers in asphalt pavements. The lack of natural resources and the growing amounts of demolition waste made that the Dutch industries in the early 1980s started to explore the possibilities to use construction debris in road construction. Recently, the application of recycled materials in pavement structures has also found traction in South Africa. Due to differences in pavement design, however, the mechanical and environmental exposure of these materials will be more severe than in the Netherlands. This results in different challenges with respect to (long term) performance and material durability. Understanding the potential durability issues and the way durability affects pavement performance is crucial to successfully implement these materials in South African pavements. This research, conducted at Stellenbosch University, South Africa, involves laboratory testing to investigate the performance and durability aspects of recycled aggregates. By means of triaxial testing before and after durability simulation, it is aimed to address the extent of potential material breakdown and the influence this has on performance. Tests are conducted on RCA, RCM, MG65 and MG30. The latter two refer to a mixture of RCA and RCM, with a mass percentage RCA of 65% and 35%, respectively. In addition to the recycled materials, a commonly used crushed rock of G2 quality is tested as well to serve as benchmark. Monotonic triaxial tests, to obtain the shear parameters, are performed on all materials except the pure RCM. Permanent deformation triaxial tests, to gain understanding of the long term response to cyclic loading, are performed on RCA and MG65. Specimens are tested under different confinement and deviator stress levels. For the durability simulation, the South African Durability Mill (DMI) is used. The DMI enables durability tes
Civil Engineering | Structural Engineering