Measurement of pavement permanent porosity and compaction factors

When laying new pavements in a northern climate, it is extremely important to make sure that the road surface is tight (compaction) and that the permanent porosity (air pore volume) of the road surface is sufficiently low. According to the traditional method, up to 12 boreholes per kilometer of road are drilled in the pavement to find out the permanent porosity, but this is time-consuming, damages the new pavement, and most importantly – describes the investigated pavement in steps of only approx. 500 m. With ground radar, e.g. on a two-way road, measurements are typically made on three measurement tracks – on the so-called outer wheel track of both driving directions and on the pavement joint on the road axis. Unlike traditional inspection with drills taken during quality control, radar measurement provides uninterrupted information on the permanent porosity values ​​of the inspected asphalt concrete pavement on the measuring track, which significantly reduces the large randomness component in the compaction factor and permanent porosity determinations and precisely defines problem areas. The area of ​​effect of deductions is reduced hundreds of times per sector of permanent porosity checked. To calibrate the measurement results, only 8 boreholes are taken from the inspected section, so the number of inspection boreholes that damage the new coating is reduced tens of times. A limitation of this method is that measurements cannot be taken when the coating is wet or frozen. It is also not possible to reliably measure permanent porosity in the case of coatings that have used sodium chloride or the like. anti-skid chemicals.

Evaluation of thicknesses of road surfaces and other layers

The thickness of the coating plays a decisive role in terms of the bearing capacity of the road structure. Being typically the most expensive component of a road structure, it is important to make sure that a high-quality and designed-thick coating is installed on top of the high-quality base layers. Traditionally, the thickness of the cover is determined by drilling, which is time-consuming and breaks the road surface, which is why they are done very rarely – in a couple of places per 1 km of road. With ground radar, on the other hand, measurements are made as a continuous profile and the results are typically reported for each meter. To obtain reliable results, the layer thickness must be at least 6 cm, therefore it is recommended to use the ground radar to determine the thickness if the cover thickness is at least 8 cm. By applying special measures, it is possible to determine the thickness even on thinner layers.