Abstract:
A modern, easily accessible, safe and resilient surfaced road network is the backbone of any country's economic growth. The high cost associated with road infrastructure makes continuous research in new construction technology and reduced operation and maintenance costs necessary. This research focuses on producing reliable laboratory testing methods for thin road surfacing layers that can provide repeatable and reproducible samples to Waka Kotahi (NZTA) field construction methods and specifications. Creating specimen at a scale verifiable with field samples will improve confidence in using the Cape seal as a road surfacing technique. Specimens from three distinct Cape seal slurry batching compositions were compacted by two functional methods in the Hydraulic Press (HP) and Roller Compactor (RC) and tested in the Overlay Tester (OT) for fatigue cracking. The improved Garcia (2017) method was applied to classify the Cape seal samples in a design interaction graph for crack resistance.
The crack progression rates of the specimens were statistically analysed using ANOVA and t-test. Results show that the Cape seal road surfacing technique can be constructed in the laboratory delivering repeatable and reproducible test samples. Repeatable results obtained from the OT fatigue tests confirmed consistent construction outcomes with meaningful differences resulting from variation in mixture composition. The study showed that polypropylene (PP) pellet improved Cape seal will enhance resistance to fatigue cracking and provide a solution to use in high-temperature areas prone to bleeding. PP pellets were added to the benchmark slurry mixture to measure changes in Cape seal's susceptibility to fatigue cracking. Adding 3% PP pellets to the slurry mixture provides improved resistance to fatigue cracking by 20% and 34%, for HP and RC compacted specimens, respectively.
This research provided the foundational work for further research into the performance of Cape seals using different bitumen additives and performance-enhancing material such as fibres. In addition, characterising the cracking fatigue using the OT also pave the way for comparative performance studies between chip seals and asphalt surfaces.
