Sustainable use of available aggregate sources in highway pavements - Best value engineering
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.
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
· 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
· 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.
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
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.
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
The principal beneficiaries would be highway
agencies, but society at large would also benefit due to more sustainable
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
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
to have workable means of assessing the wide variety of candidate materials in
a timely, efficient and reliable manner.
Perform literature survey of previous research and of specification and
Review range of material types and key characteristic differences in
mechanical performance and characterization requirements (per state or source
Assess suitability of available performance-related mechanical testing
for material types previously identified.
Propose and briefly investigate adaptions needed (if any) to ensure
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.
Draft characterization and assessment aspects of a new protocol for use
of aggregates from secondary and marginal sources. Apply these aspects to exemplar materials.
Use characterization to design pavement options using the exemplar
Perform sustainability and LCA evaluations on alternatives to show how
design decisions affect out-turns.
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).
Formulate information into guidelines and protocol for generic
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.
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.
Federal and State DOTs, Researchers, Aggregates Industry
|Sponsoring Committee:||AKM80, Aggregates
|Research Period:||24 - 36 months|
|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.
|Index Terms:||Sustainable development, Aggregates, Paving, Value engineering, Greenhouse gases, Supply, |