Design and construction of a new Mechanised Cement Bound Macadam (MCBM)

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

“…Some test samples also showed Phase 3 can develop a "steady state" phase, whereby the strength is sustained for an extended loading time before the unconfined test sample loses strength and "collapses" during breakdown in Phase 4. The same strength behaviour, whereby a unique secondary strength gain follows the peak load, was also observed from in-situ field samples tested under four-point beam tensile and indirect tensile "splitting" strength (van Blerk, 2023).…”

“…In order to illustrate the strength phases, a representative unconfined cube compression strength versus time plot from a MCBM65 field sample saw cut from constructed pavements is included as Figure 1. This illustrates the strength behaviour transitioning through multiple phases, highlighting the unique strength properties obtained from the MCBM interlocked stone structure (van Blerk et al, 2023). The plot shows Phase 1 (bound phase) is an almost linear strength increase to the point of peak load followed by strength loss defined as Phase 2.…”

“…1827). For further information on the MCBM materials specifications, gradation and construction technique, readers are referred to van Blerk et al (2022) which provides insight on the background and the principles of the design and construction technique.…”

“…The readers are also referred to van Blerk et al (2023) which describes the MCBM performance testing of in-situ field samples. Field core and beam samples were extracted from constructed MCBM pavements.…”

“…In particular, a threshold fatigue life criteria was proposed in order for the pavement to be considered perpetual. Specifically, if the threshold stress level is maintained below 30% of the fatigue strength (beam breakage strength) the layer should not fatigue and can be defined as perpetual (van Blerk et al, 2023 andNZTA, 2023).…”