Development of a Comprehensive Pavement Design System for Roads in Wind and Solar Farms

This paper briefly, illustrates the structure and contents of an ongoing research program aimed at developing a set of procedures and tools to be used for the design of pavements in renewable energy projects and mainly in wind and solar farms. Challenges related to this topic derive from the non-standard nature of several factors that affect the structural and functional performance of such pavements, with the consequent need of employing purposely defined prediction methods, design criteria and specifications. Further crucial aspects to be taken in account in the research program are related to the life cycle cost analysis of pavements, to be carried out in a multinational context by considering alternative scenarios according to an OPEX (operating expense) versus CAPEX (capital expenditure) philosophy. It is envisioned that results and deliverables of the project will contribute to the enhancement of the effectiveness of operations in wind and solar farms, optimizing investments and leading to the selection of more sustainable pavement solutions

Performance-based assessment of rutting resistance of asphalt mixes designed for hot climate regions

In hot climate regions asphalt mixes can be designed using the classical volumetric approach supplemented by the evaluation of basic mechanical parameters. To minimize the risk of permanent deformation, composition of the mixes can be defined by selecting densely packed aggregates and low binder contents. Despite the effectiveness of such an approach, mix design systems need to be improved by including performance-based tests that focus on the evaluation of the true rutting potential of asphalt mixes. The investigation described in this paper addressed these issues by considering twelve rut-resistant asphalt mixes designed as per the requirements set in the State of Qatar. These mixes, containing neat and polymer-modified binders (PMBs), were subjected to the Hamburg Wheel-Track Test (HWTT), dynamic modulus test and flow number test. Analysis of experimental data led to tentative requirements set on the results of dry HWTTs that can be introduced in the mix design framework currently adopted in the State of Qatar. Calculation of rank correlation coefficients showed that the various tests can be employed in different conditions for the assessment of the true rutting potential of asphalt mixes

Relationship between bailey and dominant aggregate size range methods for optimum aggregate packing and permeability limitation

The Bailey method and the Dominant Aggregate Size Range (DASR) method were developed to optimize aggregate skeleton packing for enhancement of structural strength designs of Hot/Warm Mix Asphalt (HMA/WMA). These design support methods are not always properly correlated with each other. They aroften perceived as giving conflicting or confusing descriptions of the same aspects of the HMA/WMA. To help clarify and improve the correlation, the aggregate skeleton is broken into macro, midi and micro level aggregate subset skeletons to evaluate the contributions of various aggregate fraction ranges to structural strength of the mix. Rut resistance and fatigue cracking limitation are traditional design objectives of any HMA mix design. Permeability of HMA is linked with durability effects such as stripping. Permeability is however not directly controlled via the aggregate skeleton packing efficiency methods. The Bailey method, and more so the DASR method, show promise to understand this link or help to control permeability. The Bailey method is discussed as a reference by looking at new ratios and attempting to verify the aggregate skeleton packing in a logical fashion. The DASR principles of porosity are used to explain the impact of the numerator and denominator, particularly the new or rational Bailey ratios, in terms of porosity as separate and combined contiguous aggregate fraction ranges. The logical filling of voids of the macro, midi and micro aggregate skeleton subsets can thus be traced as well. These aggregate skeleton subsets combined or infilled, constitute the overall matrix of the aggregate mix. Data sets of published papers on this subject were reworked / re-analysed to help illustrate the concepts and trends observable for improved aggregate packing as well as limiting permeability. New improved criteria for permeability control are also presented in DASR and rational Bailey ratio terms to help optimize the design outcome.Papers presented at the 36th Southern African Transport Conference, CSIR International Convention Centre, Pretoria, South Africa on 10-13 July 2017.Transportation research board of the national academie

Evaluation and calibration of dynamic modulus prediction models of asphalt mixtures for hot climates : Qatar as a case study

DATA AVAILABILITY : No data was used for the research described in the article.Please read abstract in the article.Qatar University and Texas A&M University at Qatar (International Research Collaboration Co-Fund). Qatar National Library funded the open-access publication of this article.https://www.elsevier.com/locate/cscmhj2023Civil Engineerin

Use of Crumb Rubber Modified Binders and Asphalt Mixtures in Public Works Authority Road Projects - State of Qatar

This paper illustrates the approach adopted by the Public Works Authority (Ashghal) of the State of Qatar for the widespread implementation in road projects of paving technologies related to the use of crumb rubber modified binders (CRMBs). Such an approach has entailed the monitoring of a full-scale preliminary trial, the definition of a prequalification system for crumb rubber and CRMB producers, and the development of mix design and quality control guidelines applicable to CRMB asphalt mixtures. Experimental results obtained in the preparatory phases of work and during the approval process of materials and mixtures are critically presented

Preliminary Study on the Use of Reclaimed Asphalt in Public Works Authority Road Projects in the State of Qatar

This paper describes the outcomes of a preliminary study focused on the evaluation of four full-scale pavement sections in which reclaimed asphalt (RAP) was used in partial substitution of virgin aggregates during the production of asphalt mixes. Considered mixes were produced with different RAP percentages and were thereafter laid on site for the formation of asphalt base course layers of pavements in local roads of the State of Qatar. For comparative purposes, two trials included asphalt mixes containing no RAP, and in one case use was made of a rejuvenating agent. Activities carried out for the monitoring of field trials included analysis of component materials, critical observation of production and laying operations, assessment of the most relevant characteristics of produced asphalt mixes, and evaluation of the degree of compaction achieved during construction. Experimental results were of crucial importance for the introduction of RAP-related paving technologies in the State of Qatar, providing a meaningful background to the preparation of the "Ashghal Recycling Manual" issued by Ashghal and of the draft updated version of Qatar Construction Specifications

Evaluation of Nevada's HMA Mixtures Manufactured with Terminal Blend Rubber Modified Binders

The objective of this research effort is to compare the laboratory performance of Nevada’s HMA mixtures made with rubber modified asphalt binders with HMA mixtures made with polymer modified binders. Two Nevada HMA mixtures are used in the study: one mix from the south and one mix from the north. Each mix was designed with the two types of binders which resulted in a total of four HMA mixtures that were evaluated in the study. The laboratory performances of the mixtures are evaluated in terms of the following properties: Moisture sensitivity Dynamic modulus Resistance to rutting Resistance to fatigue cracking Resistance to thermal crackin

Optimizing asphalt mix design process using artificial neural network and genetic algorithm

Selection of aggregate gradation and binder content for asphalt mix design, which comply with specification requirements, is a lengthy trial and error procedure. Success in performing mix design rely largely on experience of the designer. This paper presents development of an automatic mix design process with the ability to both predict and optimize asphalt mix constituents to obtain desired mix properties. A successful automatic process requires the use of local past experience translated into a design aid tool, which then predicts properties of asphalt mix without actually testing the mix in laboratory. In the proposed approach, simple multilayer perceptron structure Artificial Neural Network (ANN) models were developed using 444 Marshall mix design data. The ANN models were able to predict both air voids and theoretical maximum specific gravity of asphalt mix to within ±0.5% and ±0.025, respectively, for 99.6% of the time. After that, the ANN models were called by a non-linear constrained genetic algorithm to optimize asphalt mix, while satisfying the Marshall requirements defined in the formulation as constraints. Durability of the optimized mix is ensured by introducing a constraint on adequacy of asphalt film thickness. The developed mix design aid tool is compiled into a computer software called Asphalt Mix Optimization (AMO) that can be used by road agencies as a mix design tool. A case study is presented to demonstrate the ability of the model to optimize aggregate gradation and minimize binder content in asphalt mix. The computed ANN outputs and the optimized gradation were found to compare well with laboratory measured values. Although, Marshall compacted mixes were used in demonstrating the approach, this method is general and can be applied to any mix design procedure.Doha Technical Laboratories (DTL) and the National Research Foundation (NRF) in South Africa.http://www.elsevier.com/locate/conbuildmat2019-04-20hj2018Civil Engineerin

Monitoring permeability potential of hot mix asphalt via binary aggregate packing principles correlated with Bailey ratios and porosity principles

Asphalt mix designs tend to optimise the load transfer via aggregate skeletons as main mechanism to provide rut resistance, often to the detriment of durability. Permeability, as a significant durability indicator, is more difficult to measure in the field than in the laboratory. Voids in the asphalt mix have a critical zone where an increase in voids is exponentially linked to permeability. This zone is where voids start to become increasingly interconnected. The aggregate grading envelope characteristics can provide an indication of the interconnectedness of the voids to enhance quality control. New rational Bailey Method Ratios (BMRs) were defined with contiguous aggregate fractions in the numerator and denominator. This allows also for porosity calculation using the Dominant Aggregate Size Range (DASR) method. The Binary Aggregate Packing (BAP) triangle porosity diagrams provide insight into the link between porosity and interconnected voids. The wall and the loosening effects create additional porosity (voids) with increased probability of interconnectedness. Clear threshold zones of interconnected voids can be determined with BAP coarse/fine mass ratios. The latter is the inverse of the rational BMRs. It allows for simple spreadsheet calculations of porosity and coarse/fine mass ratio as a screening tool for probable permeability via benchmark analysis. Reworked data sets demonstrated how the inverse of BMRs could show potential for interconnectedness of voids and, therefore, permeability propensity.http://www.journals.co.za/ej/ejour_civileng.htmlam2019Civil Engineerin

Rational bailey ratios and dominant aggregate size range porosity correlated with rutting and mixture strength parameters

A study done on the correlation of the Bailey method and the Dominant Aggregate Size Range (DASR) method managed to describe and develop new Bailey ratios that better describe the aggregate skeleton packing efficiency. DASR porosity was found to be linked to permeability as well. The aggregate skeleton is ‘deconstructed’ at macro, midi and micro level aggregate subset skeletons to evaluate the contributions of various aggregate fraction ranges. Bailey ratios were brought in line with the concept of nominator and denominator aggregate fractions that suit the DASR concept of contiguous fraction ranges and were described as the rational Bailey ratios. A data set which was based on Bailey method mix design was reworked to include the DASR porosities and the new correlated and rational Bailey ratios. This enabled the Bailey ratios and the DASR porosities to be related to rutting measured with Hamburg Wheel Tracking (HWT) tests. Other structural design parameters such as the Indirect Tensile Strength (ITS), Effective Film Thickness (EFT) of the binder mastic of these mixes were also correlated with various Bailey ratios and DASR fraction porosity ranges. The main purpose of this study was to confirm the viability of these new rational and correlated Bailey ratios and DASR porosities with rutting potential for further future detailed modelling via stepwise multiple regression analyses or via Neural Network Analysis (NNA) and modelling.Papers presented at the 36th Southern African Transport Conference, CSIR International Convention Centre, Pretoria, South Africa on 10-13 July 2017.Transportation research board of the national academie