MTU CE 3401 - Asphalt Institute Method

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Lecture 22 Asphalt Institute MethodFlexible pavement design is based on the very simple idea that a stress applied at the surface of a road decreases with depth In the soil. Thus, it is necessary to have materials that have strengths greater then the applied stress. Usually the materials are the strongest at the surface and decrease in strength until the sub grade soil has adequate strength to resist the imposed stress. The result is a layered section with asphalt at the top followed by aggregate base and sub base.MaterialsEnvironmentFull depth asphalt-Fig 20.5Asphalt over aggregate base-Fig 20.9 to 20.14Additional information is available from the Asphalt Institute (Design Manual)..Minnesota Test Road on I94Lecture 22 Asphalt Institute Method Flexible pavement design is based on the very simple idea that a stress applied at the surface of a road decreases with depthIn the soil. Thus, it is necessary to have materials that have strengths greater then the applied stress. Usually the materials are the strongest at the surface and decrease in strength until the sub grade soil has adequate strength to resist the imposed stress. The result is a layered section with asphalt at the top followed by aggregate base and sub base.Typical of most pavement designs method the Asphalt Institute method requires information related to Traffic LoadMaterials EnvironmentTraffic loads by ESAL as discussed in a previous lecture. Table 20.3 provides the load factors.Materials Sub grade strength is defined by CBR CBR Test or resilient modulus test Resilient Modulus Test CBR = old test method that compares the sub grade strength to a standard aggregate when both are tested using standard compacted methodsResilient modulus test = a tri axial test that uses a repeated loading to obtain the modulus of elastic reboundEnvironmentCharts used to determine depth are different for different average annual temperatures at the design location.Thickness is determined from charts.Full depth asphalt-Fig 20.5Asphalt wearing course over bituminous treated base-Fig 20.6 to 20.8Asphalt over aggregate base-Fig 20.9 to 20.14Additional information is available from the Asphalt Institute (Design Manual).. Minnesota Test Road on


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MTU CE 3401 - Asphalt Institute Method

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