This report details research carried out from 2012 to 2015 into chipseal flushing. The physical mechanisms causing flushing were investigated and a model was developed to predict the growth of flushing over the New Zealand state highway network.
Factors making a major contribution to flushing are:
Factors having no or making only a minor contribution to flushing are:
Further work is needed to quantify the significance of chip embedment into the basecourse.
A two-part model using parameters in the NZ Transport Agency Long-Term Pavement Performance database was developed. The first part uses a logistic model to predict the onset of flushing and an accuracy of 74% when used to predict the initiation of flushing on a separate data set.
The second part uses a linear model to predict the rate of flushing progression. First-coat seals, and second and higher generation seals were modelled separately.
The linear model was statistically strong (R2 of 0.445 for first-coat seals and 0.628 for second and higher generation seals).
Keywords: bitumen bleeding, chipseals, chipseal flushing, deterioration modelling, sprayed seals, surface dressings