ABSTRACT
Cracking is one of two key failure modes for chipseals in New Zealand, it can lead to water ingress which then damages the underlying pavement structure.
Understanding the rate of crack progression and its effects on the pavement is critical when determining the life-cycle cost implications for scheduling maintenance, and the potential effects of deferring any maintenance.
Data collected on the New Zealand Transport Agency Long-Term Pavement Performance (LTPP) study over the past fourteen years was analyzed with a view to clarify crack growth, to define crack progression and crack growth rate in terms of the number of cracks and total cracked area.
The LTPP study collects pavement condition data annually, a detailed visual inspection identifies and records all pavement distress including crack length and crack location, making it possible to track the growth of individual cracks from which crack growth rate can be ascertained.
The cracking data was extracted from the visual condition data files and analyzed to determine both the rate at which an individual crack grows and the rate of crack growth in terms of increased area as multiple cracks develop. Furthermore, climatic conditions, traffic volume, and drainage at each site was analyzed to determine which of these factors if any had a definable influence on crack growth.
The analysis was able to define crack growth rate for three different crack types (longitudinal, transverse, and alligator cracks) and showed the average annual increase in crack length is approximately half the observed crack length.
