The Effects of Biogeotextiles on the Stabilization of Roadside Slopes in Lithuania.

Soil erosion, Water erosion, Soil conservation, Geotextiles, Geotextile mats, Roadside slopes, Vegetation cover, Biogeotextiles , Palm mat geotextiles - Borassus aethiopum - Mauritia flexuosa - Buriti mats - BORASSUS Project - LithuaniaBiogeotextiles constructed from the leaves of Borassus aethiopum and Mauritia flexuosa are investigated at the Kaltinėnai Research Station of the Lithuanian Institute of Agriculture, which is participating in the EU-funded BORASSUS Project. Biogeotextiles are potentially excellent biodegradable and environmentally-friendly materials useful for soil conservation. Field studies on a steep (21–25°) roadside slope in Lithuania suggest biogeotextile mats are an effective and sustainable soil conservation technique. Biogeotextiles have a potential as a biotechnical soil conservation method for slope stabilization and protection from water erosion on steep industrial slopes and may be integrated with the use of perennial grasses to optimize protection from water erosion. The investigations demonstrated that a cover of Borassus and Buriti mats improved the germination and growth of sown perennial grasses. The biomass of perennial grasses increased by 52.0–63.4% under cover of Borassus mats and by 18.6–28.2% under cover of Buriti mats. Over 2 years, the biogeotextiles (Borassus and Buruti, respectively) decreased soil losses from bare fallow soil by 90.8% and 81.5% and from plots covered by perennial grasses by 87.9% and 79.0%, respectively

Characterization of Asphalt Treated Base Course Material

INE/AUTC 11.0

Characterization of Alaskan HMA Mixtures with the Simple Performance Tester

INE/AUTC 12.2

Material Thermal Inputs of Iowa Materials for MEPDG, 2011

The thermal properties of concrete materials, such as coeffi cient of thermal expansion (CTE), thermal conductivity, and heat capacity, are required by the MEPDG program as the material inputs for pavement design. However, a limited amount of test data is available on the thermal properties of concrete in Iowa. The default values provided by the MEPDG program may not be suitable for Iowa concrete, since aggregate characteristics have signifi cant infl uence on concrete thermal properties

Evaluation of Poisson’s Ratio of Asphalt Concrete

Poisson´s ratio can be defined as the negative ratio of strains perpendicular to the load direction to the strains parallel to the loading direction. If elastic or viscoelastic models are used, Poisson´s ratio, together with elastic modulus, is a main input used to predict distresses in flexible pavement structures such as rutting and cracking. In asphalt concrete, Poisson’s ratio is commonly measured using two different testing configurations: indirect tension (IDT) and uniaxial. However, results from these two testing configuration can potentially have differences. Design methodologies such as the Mechanistic Empirical Design Guide (MEPDG, now PavementME) have been shown to be very sensitive to variations of Poisson’s ratio. The objective of this research is to determine whether or not there are significant differences between the values of Poisson’s ratio measured in indirect tension configuration and uniaxial configuration. This work also aims to investigate the potential variations of values of Poisson’s ratio among a number of asphalt mixture treated with different types of asphalt modifiers: poplyphosphoric acid (PPA) alone and in combination with liquid anti-stripping agent (LAA). Cylindrical shaped samples specified in AASHTO T 342 were used to measure Poisson’s ratio in uniaxial configuration, and disc shaped samples specified in AASHTO T 322 were used to measure Poisson’s ratio in an IDT configuration. Samples were tested at each combination at the following temperatures, -10 C, 4 C, 21 C, 37 C, and 54 C, and frequencies, 25 Hz, 10 Hz, 5 Hz, 1 Hz, 0.5 Hz, and 0.1 Hz. No statistical difference was found in values of Poisson’s ratio measured within each testing configuration. IDT Poisson’s ratio were significantly different to those of uniaxial configuration (3:1). This reduction of Poisson’s ratio by about 60% could lead to an increment of predicted distresses, such as longitudinal cracking, using PavementME by more than 400% of its design limit

Effect of Concrete Strength and Stiffness Characterization on Predictions of Mechanistic–Empirical Performance for Rigid Pavements

The hierarchical approach for specifying design inputs is a key feature of the new Mechanistic–Empirical Pavement Design Guide (MEPDG). The three levels of design input for the strength and stiffness characterization of portland cement concrete (PCC) range from a Level 1 laboratory measurement of modulus of elasticity and modulus of rupture at 7, 14, 28, and 90 days to a Level 3 estimation of the 28-day unconfined compressive strength. This paper evaluates the effect of design input level for PCC strength and stiffness properties on MEPDG performance predictions for jointed plain concrete pavements (JPCPs). The effects of the different PCC stiffness and strength design input levels on predicted faulting, transverse cracking, and international roughness index (IRI) are evaluated for eight PCC mixtures in several JPCP design scenarios. Faulting was found to be insensitive to the MEPDG PCC input level, transverse cracking was extremely sensitive, and IRI was only moderately sensitive. In particular, the results showed that the Level 3 input combination of a measured 28-day modulus of rupture and a measured 28-day modulus of elasticity yielded predicted distresses that were consistently in closest agreement with predictions that used Level 1 inputs. Reliable and accurate 28-day modulus of rupture and modulus of elasticity values can therefore be used as less-expensive and more-practical alternatives to full Level 1 stiffness and strength characterization in JPCP analysis and design. When full Level 1 characterization is performed, high-quality testing is mandatory for avoiding small anomalies in measured values that can cause physically unrealistic predictions by the MEPDG of stiffness and strength gains over time

Use of Pavement Management Information System for Verification of Mechanistic-Empirical Pavement Design Guide Performance Predictions

The performance models used in the Mechanistic-Empirical Pavement Design Guide (MEPDG) are nationally calibrated with design inputs and performance data obtained primarily from the national Long-Term Pavement Performance database. It is necessary to verify and calibrate MEPDG performance models for local highway agencies\u27 implementation by taking into account local materials, traffic information, and environmental conditions. This paper discusses the existing pavement management information system (PMIS) with respect to the MEPDG and the accuracy of the nationally calibrated MEPDG prediction models for Iowa highway conditions. All the available PMIS data for Interstate and primary road systems in Iowa were retrieved from the Iowa Department of Transportation (DOT) PMIS. The retrieved databases were then compared and evaluated with respect to the input requirements and outputs for Version 1.0 of the MEPDG software. Using Iowa DOT\u27s comprehensive PMIS database, researchers selected 16 types of pavement sections across Iowa (not used for national calibration in the NCHRP 1-37A study). A database of MEPDG inputs and the actual pavement performance measures for the selected pavement sites were prepared for verification. The accuracy of the MEPDG performance models for Iowa conditions was statistically evaluated. The verification testing showed promising results in terms of MEPDG\u27s performance prediction accuracy for Iowa conditions. Recalibrating the MEPDG performance models for Iowa conditions is recommended to improve the accuracy of pavement performance predictions

Calibration of Pavement ME Design and Mechanistic-Empirical Pavement Design Guide Performance Prediction Models for Iowa Pavement Systems

The AASHTO Mechanistic-Empirical Pavement Design Guide (MEPDG) pavement performance models and the associated AASHTOWare® Pavement ME Design software are nationally calibrated using design inputs and distress data largely from the national Long-Term Pavement Performance (LTPP). Further calibration and validation studies are necessary for local highway agencies’ implementation by taking into account local materials, traffic information, and environmental conditions. This study aims to improve the accuracy of MEPDG/Pavement ME Design pavement performance predictions for Iowa pavement systems through local calibration of MEPDG prediction models. A total of 70 sites from Iowa representing both jointed plain concrete pavements (JPCPs) and Hot Mix Asphalt (HMA) pavements were selected. The accuracy of the nationally calibrated MEPDG prediction models for Iowa conditions was evaluated. The local calibration factors of MEPDG performance prediction models were identified using both linear and nonlinear optimization approaches. Local calibration of the MEPDG performance prediction models seems to have improved the accuracy of JPCP performance predictions and HMA rutting predictions. A comparison of MEPDG predictions with those from Pavement ME Design was also performed to assess if the local calibration coefficients determined from MEPDG version 1.1 software are acceptable with the use of Pavement ME Design version 1.1 software, which has not been addressed before. Few differences are observed between Pavement ME Design and MEPDG predictions with nationally and locally calibrated models for: (1) faulting and transverse cracking predictions for JPCP, and (2) rutting, alligator cracking and smoothness predictions for HMA. With the use of locally calibrated JPCP smoothness (IRI) prediction model for Iowa conditions, the prediction differences between Pavement ME Design and MEPDG are reduced. Finally, recommendations are presented on the use of identified local calibration coefficients with MEPDG/Pavement ME Design for Iowa pavement systems

Financial Impact of Fines in the Unbound Pavement Layers

INE/AUTC 14.1

Sensitivity analysis of rigid pavement systems using the mechanistic-empirical design guide software

Initiatives are underway to implement the new mechanistic-empirical pavement design guide (MEPDG) in Iowa. This paper focuses on the sensitivity study of jointed plain concrete pavements (JPCP) and continuously reinforced concrete pavements (CRCP) in Iowa using the MEPDG software. In this comprehensive study, the effect of MEPDG input parameters on the rigid pavement performance is evaluated using the different versions of the MEPDG software (0.7, 0.9, and 1.0) available to date. Representative JPCP and CRCP sections in Iowa were selected for analysis. Based on the sensitivity plots obtained from the MEPDG runs, the design input parameters were categorized as being most sensitive, moderately sensitive, or least sensitive in terms of their relative effect on distresses. In this study, the curl/warp effective temperature difference, the PCC coefficient of thermal expansion, and PCC thermal conductivity had the greatest impact on the JPCP and CRCP distresses. Compared to the original version of MEPDG software (Version 0.7), the updated versions (Versions 0.9 and 1.0) are more sensitive to inputs, which shows the evolution of engineering reasonableness