Full-scale accelerated load testing of a new mechanised cement bound macadam (MCBM) pavement

The purpose of the research is to define and describe the performance behaviour during full-scale accelerated loading for a new heavy duty pavement type referred to as Mechanised Cement Bound Macadam (MCBM). MCBM is a cost-effective and reduced carbon footprint alternative to structural asphalt concrete and conventional concrete pavements. Four MCBM test sections were constructed with two key considerations in mind, the influence of layer thicknesses and maximum stone size within the gradation. In addition, defining the fundamental strength behaviour of the pavement, the failure mechanisms and their impact on perpetual pavement design were key objectives for the research. Dynamic and semi-static deflection measurements, strain measurements from strain gauges embedded in the pavement, crack mapping and transverse surface profile were collected at intervals throughout the accelerated loading. Performance testing showed that the stone interlocked structure is unique and undergoes multiple strength phases, enabling excellent shear and rut resistance by upholding vertical load bearing. The accelerated load testing also proved that significant structural strength remains post-bound phase. However, the MCBM design is based on a bound phase criterion and specifies a threshold fatigue stress value less than 30% of the flexural strength (breaking strength under four-point beam testing). Hence, the MCBM is perpetual by design and intended to function in the bound phase, requiring only intermittent resurfacing.