Volumetric analysis on asphalt mixtures using the computer program Prado in comparison with laboratory design tests

The volumetric analysis of asphalt mixtures mainly makes use of standard laboratory design tests. The Belgian Road Research Centre has developed an analytical computer programme (PRADO) that assists in desktop volumetric design. The University of Stellenbosch in co-operation with MUCH Asphalt has undertaken desktop volumetric analysis using PRADO on two asphalt mixes, a wearing course mix and an asphalt base mix. The analysis focussed on the determination of an optimal grading and optimal composition of the several aggregate fractions available. It was also used to predict volumetric properties such as voids in mineral aggregate (VMA), voids in mix (VIM) and voids filled with bitumen (VFB). This paper presents the results of these analyses and compares the predicted values with the actual volumetric properties as determined in standard laboratory design tests. 1. STUDY OBJECTIVES The University of Stellenbosch was approached by MUCH Asphalt to undertake a desktop mix evaluation of a wearing course asphalt mix and an asphalt base mix. The software used for this analysis is the PRADO program developed by the Belgian Road Research Centre. The objective of this analysis is to evaluate the proposed gradings, the composition of aggregate fractions and the volumetric properties of the two mixes. This paper reports on the results of the standard laboratory design as well as the results of the PRADO analysis. It will in some detail discuss the capabilities and possibilities of the PRADO software and evaluate resemblances and differences between the volumetric properties determined in the laboratory design (Marshall test method) and those calculated by PRADO. 2. STANDARD LABORATORY DESIGN (MARSHALL)