Asphalt institute deflection method

The Asphalt Institute deflection method for asphalt overlay design (Asphalt Institute MS-17 3rd Edition) requires surface deflection measurements for the determination of pavement structural condition. The method can be used for asphalt overlay design for either flexible or rigid pavements. 

The procedure for determination of the asphalt overlay thickness consists of the following steps  

The asphalt overlay consists of dense asphalt concrete, and before laying, any surface defects (potholes, minor cracking, surface depressions, etc.) should be repaired. 

More information about this overlay design method can be found in Asphalt Institute MS-17 3rd Edition. 

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The Asphalt Institute deflection procedure for asphalt overlay design over rigid pavements is considered as a supplement to the effective thickness design method. It is used to determine if corrective actions to minimise pavement deflection, particularly at the joints, should be initiated prior to overlay construction this is only in the case when rubblisation, or crack (brake) and seat, has not been selected. 

The effective depth method developed by the Asphalt Institute (Asphalt Institute MS-17 3rd Edition) is an alternative asphalt overlay design method to the deflection method. It is based on the concept that the pavement deteriorates and at any time there is a remaining life that could be utilised in designing the pavement for future conditions. This remaining life is provided by a pavement with a depth less than the original, called effective depth . 

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