Effect of Aggregate Gradation on Fatigue Life of Asphalt Concrete Mixes

Abstract

Four-point bending fatigue tests following the Strategic Highway Research Program (SHRP) M009 test protocol were executed to investigate to what extent gradation has an effect on fatigue performance of asphalt aggregate mixes. Gradations and mixes were selected that would satisfy all volumetric Superpave designs passing below the restricted zone. Other mixes were prepared with gradations passing through and above the restricted zone. The measured fatigue lives of 130 actual laboratory tests were compared with predictions by the Shell, Asphalt Institute, and SHRP-A003A fatigue-predictive equations.The fatigue life of an asphalt concrete mixture is influenced by several factors, such as bitumen type and content and air-void content. Others factors, such as temperature, frequency, and rest periods of applied loads, as well as other material properties, may also affect fatigue life. Although the influence of binder type and content has been studied extensively, the effect of some aggregate properties, such as the aggregate gradation, has not been widely presented.Superpave volumetric mix designs (previously referred to as Level I in the research documents) select a binder content and a gradation that are dictated by the behavior of the mix at compacting temperatures in the gyratory compactor. No performance-based tests are executed on the mix to evaluate its behavior at in-service temperatures.In the process of evaluating the possibility of adopting the Superpave volumetric mix design procedures in Portugal, the road administration (Junta Autónoma de Estradas) investigated to what extent mixes proposed by the Superpave volumetric procedure are superior in performance to other mixes. For that evaluation process, one of the tools used in comparing mixes was the determination of fatigue life using the Strategic Highway Research Program (SHRP) M009 four-point bending fatigue test. Fatigue performance needs to be evaluated to prevent dense-graded mixes from being too "dry," because that could lead to premature fatigue failures. Furthermore, criteria are needed to evaluate the performance of mixes to be placed on structural fatigue-resistant layers.The gradations proposed by the Superpave volumetric design procedures generally pass below the restricted zone. For comparison purposes, other gradations were selected that pass through and above the restricted zone. The other gradations were selected on the basis of standard specifications used by some highway agencies. As such, gradations were selected that would satisfy (or at least come

Avaliação da resistência ao trincamento de misturas asfálticas compostas por agregados miúdos com diferentes tamanhos máximos nominais

“…Estudos publicados na literatura relatam a importância das propriedades dos agregados minerais no comportamento mecânico de misturas asfálticas, tanto com relação à resistência à deformação permanente (Masad et al, 2003;Souza, 2009;Bessa, 2012), quanto com relação à resistência ao trincamento por fadiga (Monismith, 1970;Sousa et al, 1998;Vasconcelos, 2004;Masad et al, 2005). Esse comportamento está diretamente relacionado a propriedades de forma dos agregados minerais (forma, angularidade e textura) e a distribuição granulométri-ca da mistura asfáltica.…”

New phenomenological approach for modeling fatigue life of asphalt mixes

“…Simulating the fatigue behavior of hot mix asphalt (HMA) has been done using different test methods over the past 40 years, with varying success [3][4][5][6][7][8][9][10]. Tangella et al [11] listed the general categories of different test methodologies which included: simple flexure, supported flexure, diametral test, triaxial test, direct axial test, fracture test, and wheel tracking test.…”

Investigation of the Performance of Neat and Modified Asphalt Binders

“…Gradations passing above the restricted zone were concluded to be the least favorable. The HMA mixtures with gradations plotting above or through the restricted zone were reported to have better fatigue performance than gradations passing below the restricted zone (Sousa et al, 1998). Haddock et al (1999) concluded that both 9.5-and 19.5-mm (0.375-and 0.75-inch) NMAS mixtures with gradations passing above the restricted zone have higher strengths than those with gradations passing below the restricted zone.…”