Research Pays Off Webinar Series: Improve Material Inputs in Mechanistic Design Properties of Recovered HMA Pavements

The National Road Research Alliance (NRRA) welcomes “Improve material inputs into mechanistic design properties of salvaged HMA roads »December 21 at 10am CST, presented by Bora Cetin, Bora Cetin.

The NRRA’s monthly seminar highlights research topics that will impact the work being done here in the state of Minnesota and across the country.

Project summary

In the mechanical pavement design approach (AASHTO, 2008), pavement performance is assessed based on the critical stresses, strains, temperatures and mechanically determined humidity levels which in turn are the inputs to the pavements. empirical prediction models for specific pavement degradations such as rutting, fatigue cracking. , thermal cracking and roughness for flexible pavements and cracking, faults and roughness for rigid pavements. Accurate characterization of the input parameters of traffic, climate and materials is therefore important to ensure that the theoretical calculation of pavement stresses, strains, temperatures and humidity levels is accurate at critical system locations. Local calibration is desirable to improve the accuracy of empirical distress model predictions for a particular state or region. Depending on the desired level of precision of the input parameter, three input levels are provided from level 1 (highest level of precision) to level 3 (lowest level of precision). Depending on the criticality of the project and the resources available, the designer has the option of choosing one of the input levels for the design as well as using a combination of levels.

The material parameters required for pavement foundation materials, including unbound granular material, subbase and bedrock, can be classified into one of three main groups: (1) pavement response model, (2) enhanced integrated climate model (EICM) material inputs, and (3) other material inputs. The required pavement response model materials are resilient modulus, Mr, and Poisson’s ratio, used to quantify the stress-dependent stiffness of unbound materials under moving wheel loads. The material parameters associated with the EICM are the parameters required and used by the EICM models to predict the temperature and humidity conditions in a pavement system. These inputs include Atterberg limits, gradation, and saturated hydraulic conductivity. The “other” category of material properties are those associated with special properties required for the design solution. An example of this category is the coefficient of lateral pressure.

While there is a rich nationwide database of Mr and California rolling ratio (CBR) / unconfined compressive strength (UCS) of subgrade and conventional unbonded granular aggregate, there is no stiffness / strength / gradation / hydraulic conductivity database for reclaimed hot mix asphalt (HMA) recycled asphalt paving materials (RAP) and recycled concrete aggregate (RCA) used as a base / underlayment in pavement systems. The main objective of this project is to collect this data from the Member States of the National Road Research Alliance (NRRA) and from the literature. In addition, the list of field and laboratory tests that have been performed for use in the mechanistic design of the pavements as well as the construction specifications will be summarized. In addition, it will be determined whether there are data evaluating the impact of specific characteristics and / or the design of a RAP blend on the stiffness and strength of pavement systems in the short and long term. The research team will also perform preliminary sensitivity analyzes with AASHTOWare software using the collected data to determine the most sensitive parameter that may impact pavement performance predictions using RAP as the base / sub material. -lying down.

Visit the MnROAD website for webinar login information.

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