Characterizing Asphalt Pavements for Performance

Abstract

Having fast computers with lots of memory makes it possible to make performance predictions using mechanics, which simply could not have been done even as recently as 3 or 4 years ago. This trend can be expected to continue. Pavement materials, whether asphalt concrete, base course, or subgrade, can now be characterized in realistic ways that were simply unavailable to pavement engineers. The dependence of these materials on stress state, moisture, temperature, strain rate, and damage is what has made their characterization difficult, if not impossible. This complexity has posed an almost insuperable problem for computational mechanics and for the linkage of these properties to construction specifications on the one hand and performance of in-service pavements on the other. Although these tasks will never be simple, the tools to work on them are becoming more adequate. Some examples are given of how one can proceed to simplicity through complexity in several areas that are important to pavement performance. In every case, one must be able to measure a property of the material that can be used as input to a computer program, principally a finite element program, that allows material properties to change from point to point. Several examples are given in the categories of material properties, material behavior, materials testing in the laboratory, nondestructive testing in the field, and performance prediction models. Laboratory testing, materials characterization and properties, nondestructive testing of pavements in service, construction specifications, pavement variability and reliability, field data collection, performance prediction modeling, and prediction of pavement response and distress with modern computer methods—taken individually, these subjects look complex. Combined with the glue of mechanics, they are simplicity itself. And they confirm Alfred North Whitehead’s principle, “The only simplicity that can be trusted is that which lies beyond complexity.”

Influence of waxes on adhesion properties of bituminous binders

“…The specific surface areas obtained from the octane, which is supposed to give more accurate values, were used for this calculation. The reason for the use of Octane is that it is a non-polar liquid and therefore the molecules orientation is not affected by different surface polarities of different aggregate surfaces [14]. Porphyry's low spreading pressure with Ethyl Acetate is the only noteworthy remark.…”

“…The adopted aggregates were sieved in order to obtain a 2.36-4.75 mm fraction, as requested in standard practice for DVS testing [14], and are:…”

“…Lytton utilized surface energies measured on bitumen and aggregate surfaces to calculate free energies of adhesion and cohesion by applying modern surface energy theories as discussed in the following paragraphs [15]. These concepts have played an important role in discoveries of the rules governing micro-fracture and healing in bitumen-aggregate mixtures and can be used to assess the adhesion characteristics [1,14]. The physico-chemical properties are directly related to the adhesion characteristics of the two materials and are responsible for adhesion or debonding between the materials [16].…”

Módulo complexo de compósitos asfálticos com argila calcinada sob flexão a quatro pontos

“…LYTTON [13] aborda as características gerais da rigidez do Concreto Asfáltico. Cita que em compósitos asfálticos, diante de seu comportamento viscoelástico, as deformações decorrentes da aplicação de uma carga são divididas em duas parcelas, uma oriunda da resposta elástica e outra devido à parcela viscosa do material.…”

Crack initiation in asphalt mixtures under external compressive loads

“…Cracks were experimentally observed in compressive tests [24] and micro-cracking was modeled as one of the components of rutting [25]. Lytton [26] emphasized that the tertiary creep of rutting is not a plastic flow but a growth of microcracks. Both Wang et al [27] and Freitas et al [28] reported that cracks were observed within the compressive stress zone in the wheel-tracking rutting tests on asphalt mixtures at relatively high temperatures and they interpreted this phenomenon as one of the reasons for top-down cracking.…”