2013 Session: 293

• Accelerated Method to Evaluate Performance of Slag Used as Unbound Material in Road Bases
  Abstract: Because of environmental reasons, secondary materials will be and are being used on a large scale in road construction. Using these materials however is becoming a challenge because little information is available about their future behaviors and their performance is therefore difficult to estimate. In this study, aging is proposed as a means of exploring the long-term mechanical and physical performance of secondary materials. A slag mixture which is routinely used in the Netherlands in road (sub-)bases was selected as a reference material. The A32 motorway in the Netherlands was used as a source of field aged granulated Blast Furnace Slag (BFS) materials. The base layer of this motorway suddenly experienced serious failure after 20 years. In order to prevent similar problems to occur an aging method is suggested to detect at an early stage potential poor material performance. Three aging approaches including freeze-thaw (FT) action, steam aging and normal aging were chosen and applied to fresh and the field aged materials. These treatments have affected material characteristics. The results show that there is a linkage between secondary material performance and temperature, moisture and time.Response behavior for the steam aged laboratory samples and the A32 base material are similar, suggesting that the steam aging method did a reasonable job of producing a material of similar distress. The microstructural analysis suggests that it is possible to trace the chemical components which may attribute to the failure process of slag materials.
  Authors: Akbarnejad, Sadegh; Houben, Lambert; Molenaar, André
  Authors: Akbarnejad, Sadegh; Houben, Lambert; Molenaar, André
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Materials; Pavements
  Session: 293
  Paper Number: 13-0804
• Application of Steam Aging Method for Evaluation of Slag System as a Granular Material
  Abstract: Long term performance of secondary materials is becoming a challenging aspect in road construction since due to their benefits they are being used on a large scale, but on the other hand their future behavior is difficult to estimate. Therefore, there is need for an accelerated test protocol that allows to estimate the potential loss of strength of such materials as well as their potential volumetric change. A research program was therefore carried out to investigate the effects of steam aging on the performance of slag mixtures.Different slag mixtures which are routinely used in the Netherlands in road (sub-)bases were selected. A motorway in the Netherlands was used as a source of field aged materials. The base layer of this motorway experienced serious failures. In order to prevent similar problems a steam aging method was suggested to detect at an early stage material with potential poor performance.The results showed that certain mixtures may expand during steam aging and the compressive strength of these mixtures increased during 7 days steam aging, afterwards it decreased. The microprobe technique was adopted to measure the corresponding chemical composition and monitor the micro-structural changes.It was found that the reactivity of slag materials is influenced by the chemical composition and the aging time. The measured data have indicated a relationship between some major chemical compositions and mechanical properties of the slags. Empirical equations were developed to estimate the influence of chemical composition on the compressive strength and volume expansion.
  Authors: Akbarnejad, Sadegh; Houben, Lambert; Molenaar, André
  Authors: Akbarnejad, Sadegh; Houben, Lambert; Molenaar, André
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Materials; Pavements
  Session: 293
  Paper Number: 13-0808
• Viscoelastic-Viscoplastic Characterization of Unbound Granular Materials
  Abstract: The mechanical behavior of unbound granular materials had proven to be extremely challenging. In the pavement field, as well as in other geotechnical disciplines, these materials are usually treated as elastic or elasto-plastic. The objective of this work is to explore the applicability and potential for a viscoelastic-viscoplastic constitutive theory to characterize unbound granular materials. Such a theory contains as special cases the commonly applied behavior types, it is capable of modeling time-dependence, and can be further compounded to simulate sophisticated effects such as: anisotropy, damage, stiffening in compression, thermal sensitivity, and aging. Laboratory investigation is presented, in which a compacted granular specimen was exposed to a sequence of unidirectional creep and recovery cycles while under constant confinement conditions. Such a testing protocol offers an almost ‘automatic’ separation of the behavior into resilient (viscoelastic) and permanent (viscoplastic) components. Related experimental issues and data preprocessing elements are described in detail. From the measurements it was observed that the material creeps under load and exhibits partial, time-dependent recovery upon unloading. A one-dimensional viscoelastic-viscoplastic constitutive theory was applied as a first attempt to reproduce this behavior. The model was able to simulate very well the observed data trends and magnitudes, and hence deemed potentially generalizable to more advanced conditions.
  Authors: Levenberg, Eyal
  Authors: Levenberg, Eyal
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Materials; Pavements
  Session: 293
  Paper Number: 13-0903
• Enhancement of Permanent Deformation Model for Unbound Materials Used by DARwin-ME
  Abstract: This study deals with the assessment and enhancement of the Mechanistic-Empirical Pavement Design Guide (MEPDG) permanent deformation model for unbound materials. A preliminary sensitivity study of the current model was conducted which yielded some limitations when typical soil properties were used for a variety of AASHTO Classification groups. Based on the results from the sensitivity analysis, an enhanced mechanistic model was developed and is the main goal of this paper. The proposed model was developed based on a database consisting of a total of nearly 4,000 laboratory data points obtained from experiments previously conducted at Arizona State University. The database contains results of static triaxial shear strength and repeated load triaxial tests conducted on four subgrade materials from the State of Arizona. The materials included gravelly and sandy materials with a wide range of fines content (1% to 32%). The proposed model predicts the permanent to resilient strain ratio (åp/år) and was found to be a function of the degree of saturation, shear stress/strength ratio, number of stress repetitions, plasticity index of the soil and percentage passing US Standard No. 200 sieve. The model was found to be rational, unbiased, and statistically sound. Interestingly, the shear stress/strength ratio proved to be a better predictor than the resilient modulus, provided degree of saturation and properties of the fine material were considered.
  Authors: Zapata, Claudia E.; Bani Hashem, Elham
  Authors: Zapata, Claudia E.; Bani Hashem, Elham
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Materials; Pavements
  Session: 293
  Paper Number: 13-3934
• Moisture-Sensitive and Stress-Dependent Behavior of Pavement Unbound Materials from In Situ Falling-Weight Deflectometer Tests
  Abstract: In an instrumented flexible pavement with subsurface drainage system, a field study was performed to investigate the influence of water on the response of the pavement structure. The drainage system of the structure was clogged during a three month period, allowing the water table to rise and the structure to undergo high moisture conditions. Thereafter the drainage was reopened allowing the structure to approach its previous hydrological equilibrium state. Along with subsurface groundwater level and moisture content monitoring, the structural response of the pavement was studied by conducting frequent Falling Weight Deflectometer measurements with multilevel loads. The stress sensitivity of the unbound layers and the influence of moisture on their stiffness were studied using the data with an effort to determine the unbound materials nonlinear parameters through a backcalculation algorithm. The study showed that the response of the pavement moisture content to changes in drainage system condition was very fast. The rise in the groundwater level significantly affected the overall stiffness of the pavement structure and the backcalculated stiffness of the unbound layers decreased as their moisture content increased. It was further observed that the unbound layers exhibited stress dependent behavior to multilevel loads. The granular layer showed stress hardening behavior but the subgrade showed stress softening response in unsaturated condition and stress independent behavior in saturated state. Backcalculation of the unbound nonlinear parameters according to the universal extended k ? model revealed that the k1 parameter decreased with increasing moisture content for both the unbound granular layer as well as unsaturated fine grained subgrade material.
  Authors: Salour, Farhad; Erlingsson, Sigurdur
  Authors: Salour, Farhad; Erlingsson, Sigurdur
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Materials; Pavements
  Session: 293
  Paper Number: 13-1936
  Practice-Ready: Yes
• Moisture-Sensitive and Stress-Dependent Behavior of Pavement Unbound Materials from In Situ Falling-Weight Deflectometer Tests
  Authors: Salour, Farhad
  Authors: Salour, Farhad
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Geotechnology; Materials; Pavements
  Session: 293
  Paper Number: 13-1936
• Enhancement of Permanent Deformation Model for Unbound Materials Used by DARwin-ME
  Authors: Bani Hashem, Elham
  Authors: Bani Hashem, Elham
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Geotechnology; Materials; Pavements
  Session: 293
  Paper Number: 13-3934
• Accelerated Method to Evaluate Performance of Slag Used as Unbound Material in Road Bases
  Authors: Akbarnejad, Sadegh
  Authors: Akbarnejad, Sadegh
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Geotechnology; Materials; Pavements
  Session: 293
  Paper Number: 13-0804
• Viscoelastic-Viscoplastic Characterization of Unbound Granular Materials
  Authors: Levenberg, Eyal
  Authors: Levenberg, Eyal
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Geotechnology; Materials; Pavements
  Session: 293
  Paper Number: 13-0903
• Microstructural Analysis for Mechanical Behavior of Granular Waste Materials
  Abstract:

  Many granular waste and recycling materials are being considered for use as substitutes for natural aggregates in construction applications. Incinerator bottom ash Waste (IBAW), a residue from burning household waste, was previously landfilled but now two-thirds of this ash is recycled mostly in road construction. In this study, IBAW was mixed with limestone to produce a blend with acceptable properties for use as a road foundation layer. Cement was added to the blends to improve their mechanical characteristics. Scanning Electron Microscopy (SEM) technique was used to study the physical and chemical features of untreated and cement-treated IBAW blends and to identify the nature of the materials and any secondary reaction elements, especially after mixing with water. The micromechanical behaviour of limestone-IBAW blends under uniaxial compression stresses was modelled based on the SEM images of the blends’ microstructures. The results of micro modelling in general matched the experimental data very well. Microstructure modelling proved the high stiffness of the cement-treated blends. The material behaviour in the plastic stage changed significantly with change in the geometry and stiffness of the inclusions. Experimental and modelling results also showed that IBAW material behaved like a conventional aggregate.

  Authors: Ahmed, Abdelkader T
  Authors: Ahmed, Abdelkader T
  Year: 2013
  Document Type: Paper
  Subject: Geotechnology; Materials; Pavements
  Session: 293
  Paper Number: 13-1432
  Practice-Ready: Yes