Dynamic properties of large stone asphalt mixtures under different methods testing and loading
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International Journal of Pavement Research and Technology Journal homepage: www.springer.com/42947
Dynamic properties of large stone asphalt mixtures under different methods testing and loading Igor Amorim Beja*, Márcio Muniz de Farias, Lucas Yuri da Silva Barbosa, Luiz Guilherme Rodrigues de Mello Department of Civil and Environmental Engineering, Faculty of Technology, University of Brasília, Brasília, Brazil Received 14 May 2020; received in revised form 9 July 2020; accepted 22 July 2020
Abstract
Dynamic properties like complex modulus and phase angle are fundamental for the modern designs of flexible pavements based on mechanistic– empirical methods. Several studies have already obtained a good database for these properties in conventional asphalt mixtures with nominal maximum aggregate size of less than 19 mm; however, there is limited information for mixtures with large aggregates (≥ 25 mm) known as Large Stone Asphalt Mixture (LSAM). Moreover, there is no data on the most appropriate test protocol to obtain these properties since different stress states are imposed. To investigate the influence of these variables, prismatic and cylindrical samples of LSAM asphalt mixtures and conventional mixtures were prepared. The specimens were subjected to cyclic four-point bending flexural tests and cyclic uniaxial compression tests under different sinusoidal frequencies and test temperatures. The mean results of the complex modulus and phase angle master curves were statistically compared using multivariate analysis of variance (ANOVA). The results showed that the modulus values are statistically equal for the mixtures analysed but are different for the test protocols investigated. Keywords: Dynamic modulus; Phase angle; Uniaxial test; Four-point bending flexural test; Factorial ANOVA
1. Introduction Dynamic modulus |E*| is a mechanical property used to characterise the stiffness of asphalt mixtures under harmonic cyclic loads at different temperatures and loading frequencies. In US manuals for flexible pavement design, this property is commonly used in Mechanistic-Empirical models to predict the behaviour of asphalt concrete such as the Mechanistic–Empirical Pavement Design Guide (MEPDG) [1,2] and Simple Performance Test (SPT) protocols of Superpave [3]. Dynamic modulus is considered a fundamental property for calculating the stresses and strains in the mechanistic analysis of pavement structures [4]. Witczak et al. [3] proposed the |E*| values at 37.8°C and 54.4°C for predicting rutting performance. In France, the historic Laboratoire Central des Pontes et Chaussées (LCPC) established performance tests of asphalt mixtures that consider both the dynamic and resilient modulus under specific conditions for the certification of mixtures to be applied in the field [5]. * Corresponding author E-mail addresses: [email protected] (I. A. Beja); [email protected] (M. M. de Farias); [email protected] (L.Y. da Silva Barbosa); [email protected] (L. G. R. de Mello). Peer review under responsibility of Chinese Society of Pa
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