Comparison of methods for measuring porosity of porous paving mixtures

The porosity of porous paving mixtures is critical to their performance and is a commonly measured parameter. However, as there are a number of methods to measure the porosity of a specimen, this research addressed how these different methods compared to one another and identified where differences in measurements arose. The four methods tested were the Corelok, Montes et al., vacuum, and image analysis methods (listed in order of increasing porosity measurements for the same specimens). All four methods, as well as variations of methods, were found to be statistically different except for the vacuum and image analysis methods. The Corelok method measured lower porosity values than the soak/tap and vacuum methods due to how the total specimen volume was measured, though once the difference in volume was accounted for, it fell between those two methods. The soak/tap and vacuum methods measured similar porosities for higher porosity samples (>25%), but due to the efficiency of the vacuum at removing entrapped air pockets from smaller voids, the vacuum method recorded higher porosity values for specimens that had lower porosity (<25%).