Analysis of hot mix asphalt compaction data by means of fuzzy clustering techniques Antonio Amadore, Gaetano Bosurgi, Orazio Pellegrino ⇑ University of Messina, Dept. of Civil Engineering, Contrada di Dio, Villaggio S. Agata, Messina I-98166, Italy highlights " The authors have recorded non only the density of the asphalt material, but also other important features of the context. " The proposed methodology, based on the application of some fuzzy clustering techniques, can help to prevent laying tests. " In fact it is not necessary to build and demolish relevant sections of pavement where the density is too low. " Again, costs are more contained because it is no longer necessary to use laboratory tests with the same frequency. " And, above all, it is possible to recognize, for that specific scenario, the most sensitive variables. article info Article history: Received 30 November 2011 Received in revised form 5 September 2012 Accepted 23 September 2012 Available online 13 December 2012 Keywords: Compaction Hot mix asphalt Density Fuzzy C-means abstract The analytical control of the compaction of an hot mix asphalt is difficult because of the complex relation- ship among uncertain features but it is fundamental to achieve the target established in the design respecting the estimated cost. For this reason it is necessary to use instruments that report the surveyed data in real time not only of the compaction but also of other parameters relative to the considered sce- nario, through evolved analytical procedures in order to extract useful information. The aim of this paper is the proposal of an expeditious procedure to be used during the execution of an asphalt layer that, based on a fuzzy clustering technique and starting from the knowledge of the informa- tion recorded by ordinary measuring instruments, predicts whether the material under certain conditions can reach the desired value of density. This result can be deduced with great rapidity during the paving operations on site without waiting for extraction time of cores and subsequent laboratory analysis. In this way it is possible to identify more precisely what aspects of the environmental context have to be corrected for performing the best compaction. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Compaction is the process by which action of rollers permits to thicken an asphalt material until an opportune value generally specified at the design stage [40,39,16,12,5,37]. If the execution is carried out properly, there is a considerable better answer regard to quality of the surface, strength to plastic deformation, fatigue, aging and cracking [20,27,35]. In the recent period, advances about analytical modeling of the phenomenon and modern measure instruments have highlighted a great complexity of the problem [24,14,23]. In fact, it is possible to record many features concerning the scenario [28] but the increase of the number of available data forces the analyst to use automated procedures in order to allow the execution of compaction operations in an optimal way and in accordance with the economic constraints [26,29]. At this regard, among the most important features that could influence the density [19], there are environmental factors (as ground and air temperature, wind speed, solar flux), mix properties (as aggregates and asphalt characteristics) and construction factors (as rollers type and speed, number of passes, lift thickness) but, maybe, the most analyzed has been the temperature of material [4,38]. In fact, when temperature is below a certain limit (called cessation temperature), in function of other conditions, it is almost impossible to reduce further air voids [22,20,37,43,3]. After this point, only the surface smoothness can be improved but without an increase of density. There is a need, therefore, to know the trend of the density va- lue during the execution in order to be able to make adjustments in a brief time. Traditional laboratory tests performed on core samples taken during rolling furnish certainly reliable results, but 0950-0618/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.conbuildmat.2012.09.082 ⇑ Corresponding author. E-mail addresses: aamadore@unime.it (A. Amadore), gbosurgi@unime.it (G. Bosurgi), opellegrino@unime.it (O. Pellegrino). Construction and Building Materials 40 (2013) 430–437 Contents lists available at SciVerse ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat