A major cold mix development project (AUT) has just been completed in Norway; see previous abstract [IRRD E101745]. This article describes a device, developed as a result of AUT, for measuring the initial strength and hardening of a cold mix pavement. The initial strength needs to be measured immediately after compaction, to decide when the pavement can be opened to traffic; the AUT project also needed to compare the hardening process for various cold mixes. The device chosen for development is a torsion meter, consisting of a steel plate with a freely moving steel disc in the centre. The disc has four 30mm long studs, which penetrate the newly laid pavement. A momentum is applied to the disc while the plate is pressed against the pavement. The momentum required to move the periphery of the disc by 2cm is recorded. Because cold asphalt, like hot asphalt, is viscoelastic and its properties vary with temperature, a simple equation is used to apply the appropriate correction factor for the actual temperature during measurement. The torsion meter is easy to use, and its application was of great value to the AUT project, because it enables the hardening process to be followed during time, and decide the optimal number of passes by the compaction roller in laying the cold mix.
Abstract