3D Laser Based Measurement of Mineral Aggregate Surface Area for South African Hot-Mix Asphalt Mixtures

Over the past several years, engineers and researchers in pavement engineering and construction have made efforts, and continue to develop methods/procedures for accurate measurement of the surface area of mineral aggregates used in hot-mix asphalt design. The difficult part of the process has been the fact that aggregate particles have irregular and non-ideal shapes. This paper introduces the use of a three-dimensional (3D) laser scanning based approach to quantify the surface properties of mineral aggregates used in road pavements in South Africa. The laser device was successfully evaluated for precision and accuracy, and utilized to directly obtain the surface areas of mineral aggregates used in five typical South African asphalt mixtures. As an application of the laser-based measurements, the asphalt film thicknesses of the five asphalt mixtures were calculated and compared with the film thicknesses calculated from the current Hveem method. It was evident that the surface areas of aggregate particles can be determined precisely based on direct measurement from a laser scanning device, and that the methods used to compute aggregate particle surface area has significant impact on the film thickness of the asphalt mixture. Based on the 3D laser scanner results, new surface area factors were developed for coarse aggregates typically used in South African asphalt mixtures.