Technical specifications of many Agencies are quickly moving from prescriptive to performance based, that requires field compliance tests of the constructed pavement, such as in situ pavement stiffness measurements by the Falling-Weight Deflectometer (FWD). This creates a number of issues for material suppliers, constructors, consultants, designers and end users who are now required to rely on data produced from such devices for design and compliance checks in the field. Whilst there is wide experience on the use of such devices, issues remain such as optimisation of test methodology, data interpretation and use, comparison between laboratory and in situ measured moduli. The aim of this work is to define a data interpretation procedure and a framework for the analysis of results obtained by using such device to ensure high quality data and decision making, particularly for their role in performance based specifications. In a previous work, a particular testing and data interpretation procedure have been proposed in order to evaluate strains in pavement layers directly from FWD deflections and pavement layer thickness; here the values of elastic modulus back-calculated in the previous work are compared with those of resilient modulus MR evaluated by laboratory tests carried out on cores taken from pavement. Stiffness Master Curves (SMC) have been developed by using the resilient modulus data determined at various test temperatures and loading frequencies, and they have been used for shifting data to the in-situ asphalt pavement conditions. The frequency spectrum of FWD load has been calculated in order to assume a representative loading frequency for this device. For this loading frequency, the back-calculated asphalt modulus has shown excellent correlation with the corresponding values of the SMC. This illustrates that reasonable estimates of the in situ asphalt modulus can be provided by using the Indirect Tensile Test for Cylindrical Specimens (IT-CY) protocol to determine resilient modulus on cores or specimens compacted in laboratory; values obtained by this test must be shifted to in situ test conditions in order to be related to in situ asphalt modulus values, and to be used with elastic theory in pavement design.
A New Step Towards Performance Based Specifications for Asphalt Pavements
LOSA, MASSIMO;LEANDRI, PIETRO
2007-01-01
Abstract
Technical specifications of many Agencies are quickly moving from prescriptive to performance based, that requires field compliance tests of the constructed pavement, such as in situ pavement stiffness measurements by the Falling-Weight Deflectometer (FWD). This creates a number of issues for material suppliers, constructors, consultants, designers and end users who are now required to rely on data produced from such devices for design and compliance checks in the field. Whilst there is wide experience on the use of such devices, issues remain such as optimisation of test methodology, data interpretation and use, comparison between laboratory and in situ measured moduli. The aim of this work is to define a data interpretation procedure and a framework for the analysis of results obtained by using such device to ensure high quality data and decision making, particularly for their role in performance based specifications. In a previous work, a particular testing and data interpretation procedure have been proposed in order to evaluate strains in pavement layers directly from FWD deflections and pavement layer thickness; here the values of elastic modulus back-calculated in the previous work are compared with those of resilient modulus MR evaluated by laboratory tests carried out on cores taken from pavement. Stiffness Master Curves (SMC) have been developed by using the resilient modulus data determined at various test temperatures and loading frequencies, and they have been used for shifting data to the in-situ asphalt pavement conditions. The frequency spectrum of FWD load has been calculated in order to assume a representative loading frequency for this device. For this loading frequency, the back-calculated asphalt modulus has shown excellent correlation with the corresponding values of the SMC. This illustrates that reasonable estimates of the in situ asphalt modulus can be provided by using the Indirect Tensile Test for Cylindrical Specimens (IT-CY) protocol to determine resilient modulus on cores or specimens compacted in laboratory; values obtained by this test must be shifted to in situ test conditions in order to be related to in situ asphalt modulus values, and to be used with elastic theory in pavement design.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
