In some countries, particularly where surface properties are high priorities for a wearing course, in addition to other parameters, requirements for macrotexture are also laid down. The British requirements (HA MCHW, 2008) for mixtures with an upper (D) aggregate size of 14 mm or less, stipulate a minimum 1.3-mm macrotexture depth[64] (measured using the volumetric patch method described in EN 13036-1) for high speed roads at the moment of opening the road to traffic. In some other countries the requirement for the macrotexture depth is a minimum of 1.0-1.2 mm, but this requirement usually does not apply to fine graded SMA 0/7 or 0/8 mm.
10.6.2 Nuclear Gauge Density Measurements
In many countries, nuclear gauges are used for field testing compacted asphalt layers. If well-calibrated with core samples, nuclear gauges are convenient tools for rapid testing of field density.
In a report by Brown and Cooley (1999), they pointed out that the application of leveling sand and dynamic correction factors improve the accuracy of the density tests.
British guidelines (BS 594987:2007) provide a protocol for calibrating and operating indirect density gauges, including gauge operations, initial calibrations, and consistency of calibration.
