Higher PSV and other aggregate properties

PSV is a standard laboratory measurement of skid resistance. Many years of testing has shown that certain types of aggregate give higher values in relation to others. There is a general ranking of rock types e.g. gritstone has better PSV than basalt which is better than limestone. In the UK this natural ranking has resulted in the majority of higher trafficked roads to be surfaced using gritstone sources. However, within each of these general rock type groupings there is a tremendous possible range in PSV. PSV has been a key aspect of quarrying, specifications, aggregate selection and asphalt surfacing mixes development in the UK. However, the standard PSV method has remained relatively unchanged in contrast to the tremendous change in expectation to perform from modern highway surfacing materials. It considers whether the standard 6 hour test using coarse and fine polishing cycles is still able to predict the in-service skid resistance performance of surfacing aggregate. The effect of variables such as extended polishing, sideways polishing, freeze thaw and bitumen coatings during testing are discussed. The research clearly shows that the standard PSV test is simply a tool to rank one aggregate with another under a given set of laboratory conditions. The paper shows that an aggregates skid resistance is dependant on test conditions that in turn may be related to expected in-service conditions. The authors have developed a suite of test methods using the basic PSV test apparatus that better improve skid resistance prediction. It compares the data obtained with other test properties for a range of rock types. The paper shows that PSV is gained at the other aggregate properties such as strength, abrasion and durability. This is particularly important for countries that either currently do not have higher PSV aggregate sources, who are looking for higher PSV sources, or who are interested in using or specifying higher PSV aggregates.