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Sustainable use of available aggregate sources in highway pavements - Best value engineering

Description:

In many metropolitan areas, aggregate supply is becoming expensive and less sustainable. Quarry owners will not get permission to open new pits near construction sites while existing quarries close to urban centers are closing or restricted in hours and land take. Limits may be imposed on visual and noise intrusion, further hindering the use of geographically convenient locations. The land that is accessible may not contain rock that is most suited for aggregate production or it may contain lower quality bands of rock that need to be expensively removed.

At the same time, aggregates derived from industrial by-products may be available at close-by locations and most urban areas will, or could, have secondary aggregate production from construction and demolition wastes. Pavement reconstruction, produces further aggregate of variable quality. These aggregates will seldom meet specifications drawn up to regulate supplies from rock quarries. Given that there is a general drive to improve both the economy and sustainability of pavement construction and rehabilitation, these aggregates from secondary sources need to be exploited more so as to consume waste materials beneficially, yet it is essential that they deliver adequate performance. Furthermore, it is desirable that conventional, lower quality natural as well as secondary aggregates are used as much as feasible in pavements so as to reduce consumption of Portland and asphalt cements with their high embodied energies and large carbon footprints.

Objective:

The overall aim of this study is to investigate and define strategies, assessment methods and performance requirements that will enable pavements to be constructed or rehabilitated with available aggregates used in such a way as to best take advantage of their potential, irrespective of their origin and quality. This will be achieved by:

·

Detailed literature survey, including review of states’ specifications.

·

Definition of performance-related characteristics that are generically applicable.

· Pavement design alternatives to demonstrate how aggregates of different qualities, potentially larger top sizes, and unconventional sources may be used more efficiently and more sustainably.

· Drafting of guidelines to show how design can be based on performance-based characterization of aggregates (MEPDG based testing such as gradation, moisture content, acceptable morphological limits and mechanistic response and performance)

· Review of barriers to implementation of the proposals and definition of practical, technical and scientific strategies to overcome them.

  • Case studies to demonstrate the applicability of the proposed methodologies.
Benefits:

Approximately 2 billion tons of aggregate are used in US roads every year. Most of this comes from natural sources, often supplied over considerable distances from the jobsite. Given that the cost of supply is a significant proportion of the purchase price of aggregate, any possibility of supply from local sources will have considerable economic benefits in addition to environmental benefits due to the lower haulage needs. Use of both secondary-sourced aggregates and lower quality natural aggregates would, in many locales, allow for more local materials to be used, reducing transportation costs and associated greenhouse gas emissions.

In addition, an estimated 360 million tons of hot and warm mix asphalt is used in the US annually, whereas Portland cement concrete production is around 200 million tons per annum into road pavements. Both asphalt hot mix and Portland cement concrete consume large amounts of energy in their production such that any replacement by unbound aggregate, even in thicker layers, will reduce greenhouse gas emissions significantly as well as generating considerable cost savings. Better quality aggregates could be used to partially replace bound materials, while larger top sizes, e.g. primary crusher run and recycled crushed concrete, and lower quality aggregates often have potential to be used as soil improvement (capping), subbase and lower base layers.

Where aggregates from secondary sources such as industrial by-product streams (ash, slag, etc.) or construction and demolition waste are available, determination of their mechanical potential may allow them to be used in upper base layers as many of these materials exhibit a degree of self-cementation thereby reducing problems of waste disposal and delivering a renewable benefit in place of primary extraction.

The principal beneficiaries would be highway agencies, but society at large would also benefit due to more sustainable resource utilization.

Related Research:

"Existing research” (see references at the end) has considerably advanced our understanding of the behavior of unbound granular materials whether in- or out of-specification and whether formed of stones derived from geological or anthropogenic sources. However the missing understanding is:

  • how to place this knowledge into a pavement design framework;

  • how to select the use of a particular candidate in an appropriate design so that it can, indeed, result in a sensible and economical option for achieving end performance and sustainability; and

  • how to have workable means of assessing the wide variety of candidate materials in a timely, efficient and reliable manner.

Tasks:
  1. Perform literature survey of previous research and of specification and guidance information

  2. Review range of material types and key characteristic differences in mechanical performance and characterization requirements (per state or source location)

  3. Assess suitability of available performance-related mechanical testing for material types previously identified. Propose and briefly investigate adaptions needed (if any) to ensure suitability.

  4. Investigate non-mechanical concerns that might act to prevent utilization (e.g. environmental concerns, health concerns, durability). Using simple tests or established protocols, determine those that are insurmountable and those that can be economically addressed.

  5. Draft characterization and assessment aspects of a new protocol for use of aggregates from secondary and marginal sources. Apply these aspects to exemplar materials.

  6. Use characterization to design pavement options using the exemplar materials.

  7. Perform sustainability and LCA evaluations on alternatives to show how design decisions affect out-turns.

  8. Work with cooperating authorities to build test sections of pavements using exemplar materials, developing application aspects of the new protocol on the basis of experience so gained (eventually test some mixes at FHWA using their full-scale facility or at another similar facility).

  9. Formulate information into guidelines and protocol for generic implementation.

  10. Test the new guidelines and protocol with one or more ‘blind’ applications, by collaborating authorities, revising these documents in the light of experience so gained.

  11. Final reporting.

Implementation:

The research findings will be publicized through the final project report and scholarly publications and presentations in nationwide conferences and venues to advocate successful transportation agency implementation practices for adopting and utilizing the developed permanent deformation test procedure.

A draft selection protocol will be provided for adoption by agencies.

Relevance:

Federal and State DOTs, Researchers, Aggregates Industry

Sponsoring Committee:AKM80, Aggregates
Research Period:24 - 36 months
Research Priority:High
RNS Developer:Andrew Dawson & Erol Tutumluer
Source Info:Byrne, R and O ’Regan, B, “Increasing the Potential for Reuse and Recycling of Construction and Demolition Waste - A Case Study From Ireland,” Environment and Natural Resources Research, 4 (4), 2014.
Stroup-Gardiner, M and Wattenberg-Komas, T, NCHRP Synthesis 435: “Recycled Materials and Byproducts in Highway Applications-Summary Report, Volume 1,” Transportation Research Board, 2013.
Tutumluer, E, NCHRP Synthesis 445: “Practices for Unbound Aggregate Pavement Layers,” Transportation Research Board, 2013.
Northern Ireland Environment Agency, “Quality Protocol Aggregates from Inert Waste - End of Waste Criteria for the Production of Aggregates from Inert Waste”, Waste and Recycling Action Program and Environment Agency, October 2013.
Xiao, Y and Tutumluer, E, “Best Value Granular Material for Road Foundations,” Final Report, MN/RC 2012-01, Minnesota Department of Transportation, January 2012.
Wang, L, Druta C, and Lane, S, “Methods for Assessing the Polishing Characteristics of Coarse Aggregates for Use in Pavement Surface Layers,” Final Report VTRC 10 CR-7, June 2010.
Foth, M, Guenther, D, Haichert, R, Berthelot, C, “City of Saskatoon's Green Streets Program - A Case Study for the Implementation of Sustainable Roadway Rehabilitation with the Reuse of Concrete and Asphalt Rubble Materials,” ASCE Green Streets and Highways Development Conference, Denver, Colorado. Paper No. 80, November 2010.
Meininger, RC, Stokowski, SJ, “Wherefore art thou aggregate resources for highways?” Public Roads 2011; 75(2):34–41.
Saeed, A, “Performance-Related Tests of Recycled Aggregates for Use in Unbound Pavement Layers, NCHRP Report 598, 2008, 53p.
SAMARIS (Sustainable and Advanced Materials for Road Infrastructure), Final Summary Report, Document SAM-D32, European Community, 2006.
Date Posted:03/21/2016
Date Modified:04/08/2016
Index Terms:Sustainable development, Aggregates, Paving, Value engineering, Greenhouse gases, Supply,
Cosponsoring Committees: 
Subjects    
Highways
Construction
Materials
Pavements
Environment

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