asphaltnews - sabita...bsms comprise a unique combination of the components of road building...
TRANSCRIPT
asphaltNEWS
Volume 31
Issue 1
April 2017
…….. Before
…….. After
In this issue
CEO Overview 3
TG2 Update: Bitumen Stabilisation 4-7
A National Champion of Best Practice 8-9
List of Sabita Manuals 11
Sabita Awards Ceremony & Strategy Session 12-13
Revised TRH21 14-16
Certification of Asphalt SurfaceRejuvenators 18-21
Labour-Based Surfacing 23-26
Gyratory Compacted Properties 28-30
Sabita Members 33-35
Asphalt News is published by the Southern African Bitumen Association (Sabita),
a non-profit organisation sponsored by its members to serve all stakeholders
through engineering, service and education.
No articles, extracts, photographs or other elements of this publication may
be reproduced in any form whatsoever without the written permission of the
Southern African Bitumen Association
Editor: Hazel Brown
3
CEO COMMENTS
With so many tumultuous changes in world politics and South Africa contributing its fair share of drama, the current economic climate is best described as very unpredictable. Due to the higher inherent risk most businesses face under these circumstances, a conservative investment approach would inevitable be adopted. This in turn counters the very need for economic growth which could lead to creating the employment opportunities so very much sought.
A simple formula one might think……….that is if leaders have the interest of the populace as their first priority. It would seem that leaders across the globe have forgotten that “to lead is to serve” and not the other way around.
Given this scenario, it behoves us as citizens of the world to not only listen to what is being promised by the politicians, but also demand the demonstration of values that are enshrined in integrity, honesty and trust.
Trust and good morals have over the eons gone hand in hand. In the world of commerce it has become so difficult to trust others that businesses have resorted to develop extremely cumbersome systems and processes to deal with what is inherently a human value. Very seldom does the question get asked – “how do we positively impact a human value like trust?”, as the default has in the main been to resort to the “system” for a remedy. Never will a business system or process be able to fully deal with something which the heart controls.
The legal term “contra bones mores” which loosely translated means, contrary to good morals, is so unclear these days, as the definition appears to be up for grabs with regular dilutions through arguments and actions by individuals who stand to gain materially or otherwise. A simple case in point is the non-adherence to traffic rules which ultimately has resulted in anarchy on the roads. The ultimate question is………who decides what is contrary to good morals?
A sad state of affairs……but what has this got to do with bitumen you might ask…Ah there’s the rub!
Bitumen does not display any of these dubious characteristics. It is honest in what it can and can’t do and continues to serve us extremely well. Hence we continue in efforts to better understand this forgiving construction material through ongoing research and the introduction of specifications based on performance criteria.
In this issue we say thank you to Kobus van De Walt for his stewardship of the Road Materials Committee, look at the revisions of TG2 and TRH21 amongst many other interesting topics.
Last, but by no means least, congratulations are extended to our two Sabita Award winners, featured on page 12: Ms Sharelle Burger from Naidu Consulting (Pty) Ltd in respect of the CEO Merit Award for Health and Safety and Mr George Basson from Dust-A-Side who was nominated the Sabita Outstanding Award for Achievement in the Sustainable Use of Bituminous Products.
Saied Solomons
4
Bitumen stabilised materials (BSMs) began their life in two separate camps i.e. Emulsion and foamed bitumen. Many will remember Sabita’s ETB and gems manuals that dealt with emulsion stabilisation. These manuals were the precursor to Technical Guideline 2: Bitumen Stabilised Materials, where, for the first time, emulsion and foamed bitumen were given an equal footing in terms of best practice guidelines and performance considerations. As BSM technology has developed, so TG2 has needed updates. The 2002 and 2009 versions bear testament to the evolution of this technology. Well, the time has come to recognise yet another version, capturing the latest developments. Key Areas of ImprovementBSMs comprise a unique combination of the components of road building materials i.e. bitumen, water, aggregate and active filler. The interactions between these components at the time of mixing, placement and compaction, require a special understanding in order to reliably evaluate the performanceof the mix. In addition, the evolution of strength and stiffness of BSM over time, with in-service traffic, is complex. It requires sound consideration in order to evaluate its structural contribution to the pavement accurately. The link between laboratory and field behaviour of BSM requires more attention in the design procedures. Research and development into BSMs has led to methods of improved laboratory performance conditioning and testing, as well as design limits.
In particular, TG2 (2017) aims to address significant developments that have been made in the following key areas:
· Investigation for Rehab Design: A new chapter is being included to cover specific aspects that must be considered when sampling and evaluating an existing pavement that requires rehabilitation and possibly cold recycling;
· Materials Assessment and Classification: Refinements in array of relevant test parameters, certainty factors and impact on overall class, are redressed;
· Mix Design: Improved specimen preparation, conditioning, methods of testing as well as the sequence of testing and number of tests is revised;
· Structural Design with BSMs: Further monitoring and data updates on in-service performance of pavements, has led to refinement of design models. This applies to the Pavement Number system, as well as a new Mechanistic Empirical design model;
· Application and Construction: Inclusion of more guidelines regarding BSM production using in-plant stabilisation and projects suited to this procedure. Originally, the focus was predominantly on in-place cold recycling applications.
Mix DesignThe aim of mix design is to optimise the composition of a material, in order to meet or surpass the specification requirements, whilst balancing cost against performance. In the case of BSMs, there has been a need to realign the laboratory specimen preparation, conditioning and testing with the in-field environment. To this end, several examples of improvements to mix design in TG2 (2017) are outlined overleaf.
TG2 Update: Bitumen StabilisationAuthored by: Professor K Jenkins (University of Stellenbosch)
Assisted by: Mr D Collins (UCD Technology cc) and Dr F John (Rubicon Solutions)
5
During construction, the primary compaction of BSMs is carried out using vibrating rollers fitted with either a ‘padfoot’ or smooth drum (with tandem). These rollers typically operate at an amplitude of 0.4mm to 2 mm. Laboratory compaction should aim to simulate this compaction technique as accurately and efficiently as possible. Various compaction methods have been adopted over the years, each of which has shortcomings. So, an improved method of laboratory compaction required identification.
It is clear that the vibratory hammer fits the bill, for compaction. However, certain issues required attention before implementation of the vibratory hammer compaction could be adopted:
• Vibratory Hammer Selection: Standardised type with sufficient point energy (>20 Joule) to enable compaction of materials normally stabilised with bitumen;
• Compaction Frame: Standardised frame-type required to limit significant variation in achievable density, as shown through research. Automated density control systems need to be incorporated, through height sensors and time switches; and
• Tamping Foot Design: Limiting the weight to 3.0 kg to avoid up to 3% loss in final relative compaction.
Research findings from Stellenbosch University and practical implementation at BSM Laboratories have led to final compaction package being developed commercially to meet the requirements of BSM specimens. A conceptual image of the compaction frame is provided alongside.
Historically, Indirect Tensile Strength (ITS) tests have been used for mix design and site Quality Control QC for BSMs. This allows numerous variables to be experimented with as well as several repeats to be tested, at the same time exercising resource economy. There are several drawbacks with ITS testing, however, including variability of results (COV > 15%, commonly), complexity of stress distribution in the test specimen and the vague link of ITS to field performance.
TG2 U
pdate: Bitumen Stabilisation
Compaction Issues for BSM in laboratory (compared to eld) specimens
Consideration Marshall Mod.AASHTO Gyratory Vibratory Hammer
Compaction technique
Not applicable (only asphalt)
Applicable but poor packing
Not applicable kneading action
Applicable
Amplitude 457mm 457mm - <5mm
Test specimen Poor packing Delaminates Low density Representative
Compaction Moisture
In ctive (pore pressure)
Representative In ctive Representative
Sp ion Variable 100%
Mod.AASHTO <100%
Mod.AASHTO 100%
Mod.AASHTO
Figure 1: Conceptual Frame andVibrating Hammer
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Triaxial testing provides the benefits of testing fundamental parameters (i.e. shear properties) of granular and BSM materials, reduced variability of results and a more direct link to field performance. Given the importance of a BSM base layer in a pavement intended to support substantial volumes of traffic, the performance evaluation must be reliable. Triaxial testing can provide significant and reliable performance parameters. It can also be carried out simply and efficiently, following developments at Stellenbosch University and BSM Laboratories. For these reasons, triaxial testing has been included in the new mix design method. However, in recognition of the need to simplify tests carried out in field laboratories, the ITS test has been retained for quality control on site.
The new developments in BSM mix design were driven by several imperatives including specimen representativeness to field conditions of compacted BSM layers, critical performance properties and their evaluation, as outlined in the conceptual figure below.
Structural DesignThere are currently two structural design methods used by industry for pavements incorporating BSMs. The way that theTG2 rewrite improves these methods includes:
• Pavement Number PN: Industry feedback on shortcomings of the current PN system have been recorded and addressed. In addition, nine more years of in-service performance data has been used in refining the PN method, which serves as a precursor to the advanced design procedure below;
• Mechanistic-Empirical analysis: Intended for the design of more heavily trafficked pavements and is based on the deviator stress ratio (DSR) transfer function, using stresses in the BSM layer as well as the tested shear properties of the BSM.
TG2
Upd
ate:
Bit
umen
Sta
bilis
atio
n
Figure 2: Evolution of BSM Mix Design Procedures
7
It is widely recognised that M-E analysis and design can yield variable design outcomes with small variation of the input variables. For this reason, guidelines are provided in the analysis procedure to take account of:• Stress dependency, by adopting sub-layering principles in granular and BSM layers, with controls
on layer thickness;• Selection of realistic resilient moduli for the layers in the pavement structure by implementing
realistic modular ratios based on material type; and • Equivalent long term resilient moduli of BSMs for use in the design, based on LTPP research.
The principle of using the Deviator (Shear) Stress Ratio (DSR) to design for an adequate pavement life is illustrated in the diagram below. The new M-E design procedure’s performance function that is currently been verified using LTPP data from in-service performance of pavements with BSM bases, takes account of four variables:
• Relative Density (% Mod. AASHTO) based on BSM class;• Retained Cohesion (%) based on shear properties from wet and dry triaxial testing;• Deviator (Shear) Stress Ratio = _d/_d,f ; and • Plastic Strain (%) to limit permanent deformation (rutting) of the BSM layer.
Way ForwardIn closing, the roads industry has long debated a worthy replacement test for CBR for the classification of granular materials. The TG (2017) rewrite is aimed at addressing similar challenges regarding the evaluation of BSMs. The implementation of the new BSM testing and design framework will take industry to the point where all of the equipment and protocols will be established for a smooth transition to triaxial testing of granular materials and a classification system based on shear parameters.
TG2 U
pdate: Bitumen Stabilisation
Figure 3: M-E Design Procedure for BSM layers, based on Deviator (Shear) Stress Ratio
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Last year Kobus van der Walt, Manager of SANRAL Western Region stood down as chairman of the COTO Road Materials Committee (RMC). Formed in 1966, this committee became dormant during 2007 to 2012 due, mainly, to the professional skills attrition in the roads authorities. Having taken the helm in 2012 Kobus rebuilt this committee, a subcommittee of the Roads Coordinating Body to perform a crucial role in the development of sound practice in the construction and maintenance of the country’s road networks. Today, it has regained its ground and is again stimulating public sector participation in the fields of pavement engineering and materials science, skills development, skills sharing, innovation and identification of research programmes.
According to Kobus, one of the first tasks undertaken was to make TRH and TMH documents freely available to practice through publishing all current issues of these documents on the SANRAL website, for easy access. During his term of office laboratory accreditation was supported aswas the standardisation of test methods (as SABS standards) to underpin the accreditation. In 2003 Dave Wright was appointed to this end. Kobus noted that “while the tangible contributions made by industry – notably Sabita – was underpinning this thrust, funding mechanisms were needed for the RMC to fulfil its function properly”.
Stable and representativeOne of the challenges faced by Kobus in the resurrection of the RMC was to develop stimulating meeting agendas to attract attendance and to disseminate a wealth of information. This aim was frequently tested by staff changes in the various road authorities. However, at present committee membership is reasonably stable and, with the inclusion of representation of the metropolitan authorities, the composition of the committee was considerably strengthened.
At present, giving impetus to the implementation of innovative technology e.g. the PG specifications for bituminous binders, prioritising the review of best practice TRH and TMH documents and linking with the construction sectors are priority focus areas. As Kobus says: “You can’t build a road without materials”. Proceedings at three to four meetings annually includes receiving reports from the RMC subcommittee on Materials Testing which cover career paths for materials technicians, test standards and ECSA registration of materials technicians. Additionally topics such as the status of TRH, TMH documents, quality management and environmental impact of road projects are frequently discussed.
After four years of leading the RMC, Kobus is handing over to Krishna Naidoo of eThekwini Metro Municipality, “who is the right man for the job”. He has no doubt that Krishna will sustain the goal of the RMC to promote best practice through communication and support for innovative practice.
A NATIONAL CHAMPION OF BEST PRACTICE IN ROADCONSTRUCTION & MAINTENANCE: Kobus van der Walt
Kobus van der Walt
9
SAPEM – a valuable referenceClosely related to his function as chair of the RMC, Kobus initiated the production of a South African Pavement Engineering Manual (SAPEM). Originally intended as an in-house SANRAL document, he had the foresight to realise that such a document was needed by the road engineering profession at large. Consequently, the document, under the leadership of Prof. Kim Jenkins, compiled by experts in the industry and edited by Dr Fenella Johns, was published by SANRAL – a real magnum opus of considerable value as a reference to the profession, especially new entrants. Not surprisingly positive comments and compliments have been forthcoming from road authorities and concessionaires, worldwide. “The intention is to keep the document live and up-to-date. No doubt a revision of the document, issued in January 2013, will be due shortly, but for obvious reasons will be held in abeyance pending the completion of the revision of the COTO national specifications for road works” Kobus says.
An up-to-date national specification for roadworksIt is common cause for some time now in the roads industry that the current COLTO specifications, the compilation of which commenced in 1996 under the Committee of State Road Authorities (CSRA) and which fairly reflect the best available knowledge at the time, was in urgent need of review. The RMC requested a revision in 2003 and Kobus, as Chairman, championed the cause to ensure that ultimately, road contracts nationally would be routinely based on cutting edge knowledge and practices. “This process is now nearing completion and is based on the concerted effort of expert practitioners who have given of their free time and working at reduced fees to bring this very necessary project to a conclusion. Their contribution is sincerely appreciated”, Kobus stated.
A feature of the new COTO specifications is that each chapter will, in addition to covering the scope, bill of quantities and guarantees, incorporate a part on labour enhancement / optimisation, which will provide the option of using hand labour selectively to replace mechanical equipment. Following approval by the RMC the document will be submitted to industry for comments within a 60 days period. Proposed revisions or amendments will be workshopped with industry, following which the document will be submitted to COTO for approval. The specification will be published and implemented as a “draft standard” for a period of two years. Any required reworking would be submitted to COTO for approval and publication.
Perhaps a less visible function that Kobus van der Walt has performed since the inception of SANRAL in 2000 is that of Chairperson of its Materials Cluster. This cluster, with focus groups covering materials and geotechnics, road maintenance and construction strives to coordinate activities, promote uniformity and develop guidelines and policy within SANRAL. “The idea is not to work in silos”, he said.
The industry salutes Kobus for his vision and leadership, foresight and energy in reviving the RMC and instilling it with a clear purpose to enhance best practice in road pavement engineering and, associated with this role, his drive to produce the SAPEM and up-to-date national specifications for road works.
Kobus has also participated actively in the compilation of the following national best practice guideline documents:M2 Procedure – construction quality controlM3-1 Visual assessment of concrete pavementsM10 Concrete pavement design and constructionTRH3 Design and construction of surfacing sealsTRH4 Structural design of urban and rural roadsTRH12 Flexible pavement rehabilitation designTRH15 Subsurface drainage for roadsTRH21 Hot mix recyclingTRH22 Pavement management systemsTMH9 Visual assessment manual for flexible pavementsUTG12 Assessment manual for flexible pavements in urban areasCOLTO Standard specifications (1998)
A N
ATION
AL CH
AM
PION
OF BEST PRA
CTICE IN RO
AD
CON
STRUCTIO
N &
MA
INTEN
AN
CE: Kobus van der Walt
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17 static plants • 5 mobile plants • extensive product range • stringent quality control • bitumen storage • industry training
Much Asphalt is southern Africa’s largest manufacturer of hot and cold asphalt products.
Our plants are designed and built for maximum output with minimum environmental impact. We can provide any asphalt mix, where and when you need it, with stringent testing and quality control on every site.
YEARS
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COMMITMENT TO DELIVERY
DELIVERY
11
SABITA
MA
NU
ALS A
ND
DV
DS
SABI
TA M
AN
UA
LS A
ND
DV
DS
Manual 1 Technical guidelines: Construction of bitumen rubber seals 3rd edition, 1998
Manual 2 Bituminous binders for road construction and maintenance (CD) 6th edition, 2014
Manual 3 (Withdrawn)
Manual 4 (Withdrawn)
Manual 5 Guidelines for the manufacture and construction of hot mix asphalt 3rd edition, 2008
Manual 6 (Withdrawn)
Manual 7 SuperSurf – Economic warrants for surfacing roads 1st edition, 2005
Manual 8 Guidelines for the safe and responsible handling of bituminous products (CD) 3rd edition, 2011
Manual 9 (Withdrawn)
Manual 10 Bituminous surfacings for low volume roads and temporary deviations (CD) 2nd edition, 2012
Manual 11 (Withdrawn) 1st edition, 1993
Manual 12 Labour Absorptive methods in road construction using bituminous materials (CD) 4th edition, 2016
Manual 13 LAMBs – The design and use of large aggregate mixes for bases 2nd edition, 1997
Manual 14 (Superseded by TG2)
Manual 15 (Withdrawn)
Manual 16 (Withdrawn)
Manual 17 Porous asphalt mixes: Design and use (CD) 1st edition, 1995
Manual 18 Appropriate standards for the use of sand asphalt 1st edition, 1996
Manual 19 Guidelines for the design, manufacture and construction of bitumen rubber asphalt wearing courses (CD)
4th edition, 2016
Manual 20 Sealing of active cracks in road pavements 1st edition, 1998
Manual 21 (Superseded by TG2)
Manual 22 Hot mix paving in adverse weather 2nd edition, 2006
Manual 23 Code of practice: Loading bitumen at refineries (CD) 2nd edition, 2011
Manual 24 (Withdrawn) 1st edition, 2005
Manual 25 Code of practice: Transportation, off-loading and storage of bitumen and bituminous products (CD)
2nd edition, 2012
Manual 26 Interim guidelines for primes and stone pre-coating fluids (CD) 2nd edition, 2011
Manual 27 Guidelines for thin hot mix asphalt wearing courses on residential streets 1st edition, 2008
Manual 28 Best practice for the design and construction of slurry seals (CD) 1st edition, 2010
Manual 29 Guide to the safe use of solvents in a bituminous products laboratory (CD) 1st edition, 2010
Manual 30 A guide to the selection of bituminous binders for road construction (CD) 1st edition, 2011
Manual 31 Guidelines for calibrating a binder distributor to ensure satisfactory performance (CD) 1st edition, 2011
Manual 32 Best practice guideline and specification for warm mix asphalt (CD) 1st edition, 2011
Manual 33 Design procedure for high modulus asphalt (EME) (CD) 2nd edition, 2015
Manual 34 (A) Guidelines to the transportation of bitumen and (B) Bitumen spill protocol (CD and Booklets)
1st edition, 2013
Manual 35/TRH8
Design and use of Asphalt in Road Pavements (Pdf – complimentary) 1st edition, 2016
Technical guidelines
TG1 The use of modified binders in road construction 3rd edition, 2015
TG2 Bitumen stabilised materials (UNDER REVIEW) 2nd edition, 2009
TG3 Asphalt reinforcement for road condition 1st edition, 2008
DVDs
DVD100 Test methods for bituminous products
DVD200 Training guide for the construction and repair of bituminous surfacings by hand
DVD300 Manufacture, paving and compaction of hot mix asphalt
DVD410 The safe handling of bitumen
DVD420 Treatment of bitumen burns
DVD430 Working safely with bitumen
DVD440 Firefighting in the bituminous products industry
DVD450 Safe loading and off-loading of bitumen
SABITA MANUALS AND DVDS
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As is customary, all Sabita Member representatives are invited, at the end of each year to nominate individuals or groups for both the Health and Safety, and the Excellence Award in the use of Bituminous Products.The Sabita Award for Outstanding Achievement in the Sustainable Use of Bituminous Products was presented to Mr George Basson (Shareholder & Chairman) of Dust-A-Side.
With over thirty years in operation George can easily talk about a life time dedication to the dust suppression and maintenance of haul roads.This in the main has been through the use of bitumen emulsion in the mining industry with mines like Sishen Iron Ore (biggest Iron Ore mine in Africa). George Basson is the founding father and the driving force behind the technology of using diluted bitumen emulsion (i.e. up to 2.5% emulsion into 97.5% water) to treat haul roads on mine (open cast and underground) for dust suppression and road maintenance for the past 40 years.
The creation of this technology has enabled the mining industry to:• Provide a safer environment for its employees and contractors
• Improve the mine environmental footprint• Provide financial saving to the mine
In respect of the CEO Merit Award for Notable HSE Achievement for 2016, we are pleased to announce that this award went to Ms Sharelle Burger, the Safety Officer of Naidu Consulting (Pty) Ltd. Sharelle has been with Naidu Consulting for the past 6 years and got herself involved with health and safety on road construction and other projects. By her own admission, she started with limited knowledge of bitumen but continuously strives to update her knowledge on all things bituminous!
A very proud moment, was receiving certification first time around for the implementation of ISO 14001/18001. A project she was tasked to head.
In efforts to entrench a safety culture in the workplace she regularly present HSE talks to in-house staff with the view that safety applies to both site and office environment. Her dream is to one day own her own Safety Consulting company which would specialise in the ISO side of business.
SABITA AWARDS &
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At Sabita’s Strategy review meeting on the 3rd of April, the Bureau of Research presented on the global and local economic outlook.
In essence, the message was that the global economy is showing muted growth with the Euro zone finally showing signs of life, the Chinese economy becoming stable but slowing and concerns regarding Trumps ability to push through “growth enhancing reforms”.
The forecasts are for developed economies to grow at an aggregate around 1,9% with the 3 main players in the emerging economies aggregating around 4,5%.
With its low business confidence, RSA is pegged at a growth of 0,4% for 2016 increasing to 1,8% in the outer year 2018. Slower growth in government spending and higher taxes will probably keep the lid on consumer spending during 2017-18. Broad-based fall in fixed capital investment can be expected as a result of subdued business confidence.
On the positive side, there appears to be some relief from lower global food price inflation ahead and the current budget appears to be more optimistic regarding infrastructure than that of 2016/17. This is already showing up in Civil engineers’ confidence. Underspend however is still pronounced, particularly at municipal level with provinces showing a much better performance.
President Zuma's cabinet reshuffle, heightened political and institutional uncertainties resulted in S&P giving the country a sub-investment rating. Besides increased concern about fiscal and GDP growth outlook, S&P emphasised that contingent liabilities are on the rise. In particular that SOE’s will increasingly need to tap into government guarantees to fund its build programmes. With more elevated debt-service costs, this poses a big ask.
Following the presentation by Mr Lemboe, Sabita’s Strategy session was led by Mr Peter Thomas from Participlan Group Facilitation who initiated purposeful discussion between the groups of members present.
Apart from reviewing Sabita’s Vision and, in particular, the objectives that have been realised over the past three years since the previous strategic session, Mr Thomas led the group to highlight specific areas where Sabita could play a significant role going forward. Of these, the two areas that were highlighted were: Road Funding – getting to grips with the current situation and what the future may hold, and, SMME (Small, Medium & Micro Enterprises) – establishing a methodology for sustainable SMME development.
ECONOMIC OUTLOOK
Photo 1: Craig Lemboe (Bureaufor Economic Research)
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The updated, revised edition of TRH 21: Use of reclaimed asphalt in the production of asphalt was approved by the working group of the RPF task group on bituminous materials, on 19th January 2017, after assessment of final comments. These comments have been incorporated into the document which has been submitted to the COTO Road Materials Committee for consideration at its meeting on 22 February 2017.
This marked the culmination of a process that commenced in January 2016. Through conscientious efforts of the task group members it was possible to reach the target within a year – a truly remarkable performance, by all standards. Following endorsement by the RMC, this 2017 edition will replace the 2009 version, having taken into account developments in SA and elsewhere in the world, to render the new edition up-to-date, incorporating the latest thinking and techniques in asphalt recycling.
A durable and sustainable productIn the introduction of the document, the term reclaimed asphalt (RA) is defined as:
Reclaimed asphalt (RA) is obtained from milling or excavation of existing bituminous pavement layers or from stockpiles of asphalt production overruns and returned material. The material so obtained is crushed and screened to ensure an acceptable maximum size and grading. Following the crushing and fractionating process, RA is stockpiled and loaded in such a manner as will enhance the uniformity of the material.
It is important to note that the material obtained from pavement layers should always be processed before use to ensure uniformity. Stockpiling techniques of both unprocessed– and processed RA are described in the document.
Another tenet advocated right up front is that recycled asphalt, i.e. mixes containing RA should, with good cause, perform at least as well as mixes using all new materials. It is not an inferior product and is subject to the same quality and performance requirements as conventional asphalt.
RA binder replacementA significant deviation from previous issues of this document revolves around the terminology used to define the proportion of RA in a mix, particularly as it influences the processing of RA as well as design routines and testing compliance.
A key element of the design of a mix containing RA is to ensure that the resultant binder, i.e. the blend of binder in the RA and new binder meets the quality standards required for the specific application. The proportion of binder in a particular RA fraction is related to the aggregate size (or surface area) of that fraction. To account for this phenomenon it was deemed appropriate to base designs on blends of binder and aggregate on RA binder replacement i.e. the amount of binder yielded by the RA as a proportion by mass of the total binder content of the mix to meet the target binder content. The RA binder replacement would therefore determine the procedures to be followed in terms of processing / fractionating of RA, testing of recovered binder and design procedures. Testing regimens for aggregates, however, are defined by the total RA content of the mix.
The term recycled asphalt is defined, for practical purposes, as asphalt in which the RA binder replacement exceeds 10%.
15
Table 1: Recommendations for the RA mix design procedure
Use of RA makes both economic and environmental senseIn addition to a comprehensive treatment of the technical aspects of RA procurement and assessment, reclaiming, processing, stockpiling, production and quality control of recycled asphalt, new sections have been included on the economic and environmental benefits of the use of RA.
Recycling asphalt pavements underpins sustainable practice; the process enables petroleum and aggregate resources to be conserved, and saves landfill space that would otherwise have been taken up with the discarded asphalt. With the increasingly strong worldwide trend towards environmental issues, such as lifecycle inventories and carbon credits, the whole process of hot mix asphalt recycling not only makes good sense; there is an obligation on the part of the roads industry to encourage its use routinely.
Environmental and economic benefits are already being realised on an international and national level. The use of RA upholds the first two principles of the National Environmental Management: Waste Act (Act 59 of 2008), reinforcing the waste hierarchy, as follows:
1. Minimising the consumption of natural resources; and2. Avoiding and minimising the generation of waste.
Hence, the use of RA in low value applications like black-aggregate or bulk material for backfill, subgrade formations and trench reinstatement is discouraged as wasteful practice.
RA Binder replacement
Minimum no. of processed RA fractions
Tests on processed RA fractions
Recommendations for achieving the end binder
speci�cation
Determine blended binder properties
≤ 15 % One Binder M binder content M contaminants
Aggregate M Grading M intrinsic properties
• None • Not required
15 – 30% Two Binder M binder content M contaminants M Softening point &
penetration M G*, δ, JNR, S & m
Aggregate M Grading M intrinsic properties M ACV, 10% FACT M Flakiness index
• Use softer binder grade; • Use rejuvenator
• Use blending charts to determine appropriate softer binder grade
• Use blending charts to determine appropriate rejuvenator dosage rate
• Report blended binder properties
30 – 60% Two • Use Rejuvenator • Use blending charts to determine appropriate rejuvenator dosage rate
• Report blended binder property tests
REVISED
TRH21 - RECYCLED
ASPH
ALT
16
Another aspect dealt with is compliance with Treasury regulations promulgated in terms of legislation covering the ownership and disposal of state assets – as is the case with asphalt layers in pavements. RA, by default, vests with the road owner, who is obliged to transfer such ownership to another organ of state, or to the contractor in terms of the conditions of con-tract. In the latter case a payment item must be included in the bill of quantities reflecting a cost saving to the contract.
Contract documentationIt is common cause that inappropriate, erroneous or incomplete tender information/ speci-fications invariably lead to contractual disputes, with resultant administrative burdens to all parties and overruns in the total contract value and time. Contractual arrangements regard-ing the use of RA are no exception. This new version of TRH 21 gives guidance on how to avert these pitfalls through fair practices during the management of contracts involving reclaiming and recycling asphalt layers. Comprehensive guidelines are given covering the whole gamut of relevant issues, e.g. mix proportions, availability of mixing plant types, pre-tender inves-tigations of material types and dissemination of related information and allowance for mix design duration, depending on the level of design and need for specialised testing.
Scope for use of RAIn 2014 it was estimated that the usage of RA in South Africa was in the region of 10% of the annual asphalt production i.e. in the region of 350 000 tons. It has been stated by industry that, should the specifications permit higher proportions of RA in asphalt mixes, 95% of reclaimed material available at the various fixed asphalt plants can be utilised to this end.
There would therefore appear to be considerable scope in South Africa, through the use of higher pro-portions of RA in asphalt, to effect significant financial savings through a decrease in virgin material input, as well as reducing the pressure on non-renewable resources and the carbon footprint of the asphalt industry. Since 2009 asphalt manufacturers have gained experience in the use of higher pro-portions (up to 40%) in asphalt mixes on major road contracts. With the expertise gained, the road industry is now in a position to exploit the benefits attached to the use of RA in new road layers. TRH 21, updated, will no doubt contribute to the achievement of this goal by providing a platform for sound engineering practice in the production and laying of recycled asphalt.
Acknowledgement for their contribution to the revision is extended to the Members of the RPF working group:
– Saied Solomons (Chairman) Sabita– Willem du Toit WSP– Christi Botha SMEC– Trevor Freestone Hillary Construction– Ockert Keyser Martin and East– Mahendren Manicum Naidu Consulting– Herman Marais Much Asphalt– Alex Marais SASOL– Estime Mukandila Worley Parsons– Piet Myburgh Specialist consultant– Krishna Naidoo eThekwini Municipality– Wynand Nortje National Asphalt– Sasheen Rajkumar SANRAL– Greg Reynolds Hillary construction– Dennis Rossmann SANRAL– Johan van Heerden RHDHV
REV
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SABITA’S RO
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REVIEW
: 2016Supplier of top quality
Bituminous proven products.We Supply:
Anionic and Cationic Emulsions, Bitumen PrimesPenetration Grade Bitumen, Modified Bitumen Binders,
Tosas Pothole Patch, Mining Dust Suppression, Bitumen Rubber
NEW CRUMB RUBBER TECHNOLOGY
Labour intensive road surfacing and repair solutions
Head Office: 12 Commercial Road, Wadeville, Germiston, 1422 Tel: 011 323 2000 / Fax: 011 902 1112 Web: www.tosas.co.zaEmail: [email protected]
Products are sold in drums or in bulk
Binding roads, linking people.
18
CERTIFICATION OF ASPHALT SURFACE REJUVENATORSRoads are the circulatory system for our economy, the lifeblood of our society.1 Roads represent a huge investment in our economy, neighbourhoods and in town house complexes (where we are part owners); and it is in our own best interest to preserve such assets. Timeous preservation measures to extend pavement life can prove to be very cost-effective, as illustrated in Figure 1. Typically, the first 40 percent drop in the quality of a road happens over 75 percent of its service life, after which, there is a rapid deterioration. The goal is to prevent the road condition deteriorating to that point where it falls to below that first 40 percent drop, as at that stage maintenance no longer suffices and expensive rehabilitation is required.
A major contributor to the deterioration of asphalt roads is oxidative ageing of the bituminous binder within the surfacing. One of the most cost-effective preservation techniques is the application of a surface rejuvenator.
Asphalt surface rejuvenators can be defined as proprietary products with suitable properties to extend the lifetime of an asphalt mix layer (or seal); by delaying the appearance of fatigue-related distresses such as cracking and potholing, without increasing the risk of skid-related accidents. The use of asphalt surface rejuvenators can be seen as an economically justified maintenance tool to extend the binder lifetime, thereby postponing eventual costly rehabilitation.
Authored by: Johan O’Connell, CSIR Built Environment
Figure 1: The effect of preservation measure on pavement life (courtesy Federal Highways Administration)
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Rejuvenators vary in nature, ranging from emulsions to solutions, making it very difficult to have a national specification for rejuvenators. As a result, rejuvenators have been supplied into the market, which have displayed varied and inconsistent performances. This class of materials are, therefore, ideal candidates for certification by Agrément South Africa in terms of “fit for purpose”.
Recently, a guideline for the evaluation of rejuvenators has been prepared for Agrément South Africa by CSIR Built Environment. The aim of the guideline is to evaluate asphalt surface rejuvenators under similar surface conditions (levelling the playing field so to speak), using performance-related properties. The performance parameters and their proposed limits are shown in Table 1. It is also crucial that any preservation be carried out in a timeous manner, on a pavement in relatively good condition, with no major fatigue or base distress.
CERTIFICATION
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Figure 2: Timeous preservation prevents the loss of an asset!
Criteria Test Proposed interim limits
Philosophy
Visual condition of pavement
TMH 9 Comparative visual appraisal: Treated vs untreated (1992)
Monitor only Improvement in the treated area may be followed or, alternatively, the rate of deterioration of both the treated and untreated areas may be compared.
Skid resistance
SCRIM or Griptester
Maximum 20% loss. May not
cause instability when car
turns 90° at 10km/hr
By de�nition in the guideline, a surface rejuvenator may not impair the skid resistance of a surfacing. A decrease in skid resistance of less than 20% will not be acceptable if such a decrease results in the skid resistance falling below the limit speci�ed by road authorities for that road.
Presence of volatile materials
Gas chromatography analysis
Monitor only
This is an attempt to see if the performance of the rejuvenator is linked to the presence of volatile components such as petrol, spirits, etc. A rapid dissipation of volatile material may indicate a temporary improvement in binder performance.
Resistance Comparative ≥ 15% Abrasion loss is a�ected by means of the Los Angeles
Table 1: Criteria limits and philosophy for rejuvenated surfaces
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CERT
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Cantabro test: Treated vs Untreated
di�erence Abrasion machine. The percent of weight loss (Cantabro loss) is an indication of durability and relates to an improvement in the quality of the asphalt binder, which is indicated by improved cohesion. This test method determines the abrasion loss of 150 mm cores which have been trimmed to a height of 10 mm.
Resistance to cracking (binder sti�ness)
Comparative G*.Sinδ @ 28°C: Treated vs Untreated
≥ 20% di�erence
G*.Sin δ, as determined by a dynamic shear rheometer (DSR), is used to control fatigue cracking in the SUPERPAVE speci�cations, and is based in part on the results of controlled-strain fatigue tests that were developed as a part of the SHRP research e�ort (Deacon et al, 1997). The lower the value of G*.Sin δ, the higher the resistance of the binder to fatigue cracking.
Binder viscous component
Comparative δ @ 28°C: Treated vs Untreated
Monitor only
The phase angle gives an indication of the ratio of the viscous component to the elastic component. As the phase angle increases, so the viscous component increases, resulting in improved resistance to cracking for the same value of G*.
Resistance to Cracking (Binder sti�ness)
G-R parameter Monitor
Only / < 180 kPa
The Glover-Rowe (G-R) parameter is postulated to give an indication of load fatigue-related cracking. Internationally, a limit of 180kPa has been proposed for binder after long term ageing in the pressure ageing vessel.
Many of the results are carried out on the recovered binder of the rejuvenated surface (top 10mm, Figure 3). It is crucial that the recovery process be carried out using a national standard; and the laboratory tasked with the recovery must ensure that the method is validated on a regular basis (and preferably accredited).
Due to the nature of the product, estimates were made regarding the proposed performance level limits, which were based on work reported in international literature as well as local engineering experience. However, only limited information is available, so it is the intention that these limits be refined towards specifications in time, as further product testing provides additional information.
Figure 3: 10 mm slices of the rejuvenates surface
21
CERTIFICATION
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It is hoped that this article will provide a platform for knowledge dissemination, which will stimulate further discussion and standardization in the surface rejuvenation industry of South Africa.
Figure 4: A hand applied trial section on Grand Central Airport, Midrand
1 Chris Evers, “Return on Investment from Pavement Preservation”, Florida Community Association Journal, January 2017
EVENTS
Local Events 2017 International Events 2017/8 Materials Tester Course: Module 6 – Asphalt 29 May – 1 June - Cape Town 22 – 25 August - Gauteng 24 – 27 October - Durban
4th Middle East Society of Technologist Conference 1 – 3 May 2017, Kish Island, Iran
33rd Road Pavements Forum 9 – 10 May, Umhlanga, KZN
8th Africa Transportation Tech. Conference 8 – 10 May 2017, Livingstone, Zambia
Society for Asphalt Technology: AGM 9 May, Umhlanga, KZN
IICTG Conference 26 – 28 September 2017, Minnesota, USA
36th Southern African Transport Conference 10 – 13 July, Pretoria
Rubberized Asphalt Rubber Conference 25 – 28 September 2018, Kruger Park, Skukuza
22
23
“If the burning issues of poverty, inequality and unemployment are to be truly addressed, a fresh, creative and innovative approach needs to be found which genuinely reaches out to disadvantaged communities at a grassroots level”, states Carmen Lawrence from Bergstan South Africa, who penned this article. This requires projects to be identified which maximize the labour component without compromising quality, using innovative technologies that result in the effective transfer of skills that can continue to be used after the completion of the project.
In 2015 a multi-phased project in Mooiwater, Franschhoek was launched in line with the Stellenbosch Mayor’s vision to establish Stellenbosch Municipality as the innovative capital of South Africa. “It is the way we are doing it that makes it so special” explains the Executive Mayor “we do it with our community who will get the benefit of jobs but they will also gain valuable skills that will stand them in good stead long after the project has been completed”.
Bergstan South Africa was appointed by the Stellenbosch Municipality to undertake the upgrading of the gravel roads in Mooiwater, Franchhoek. The scope of work of this MIG funded project has been the upgrading of internal roads in Mooiwater from gravel to a bituminous surface. It was important from the outset however that a surfacing technology be identified that would not only meet existing road standards but also comply with the brief to maximize the labour component. A product was required that would be suitable for implementation and inclusion in poverty relief or EPWP programmes where contractors and their labour force have little or no prior experience and skills.
In order for the asphalt technology to meet both the quality and socio-economic objectives of the project, six key fundamentals were identified:
JOB CREATIONThe technology needed to be very specifically designed as a labour intensive road surfacing system with a high labour requirement. The project to date has been able to achieve a labour component value of 20% which has had a marked impact in the local community and a deliberate focus was placed on the empowerment of women and youth. In fact this technology has proved to be capable of facilitating up to an 80% woman labour component.
QUALITYThe labour based surfacing technology has been designed to the required standards for continuously graded fine and medium asphalt mixes suitable for inclusion in low order roads where thin asphalt surface seals (20mm - 25mm) are applicable. The design follows normal engineering best practice and during construction, samples were taken and assessed in the laboratory using recognized tests for pertinent criteria such as ITS, Marshall Stability, Dynamic Creep and Binder Content etc.
A detailed feasibility study, commissioned by the Department of Transport & Public Works, Western Cape (EPWP) was completed on the technology in 2011 by the then Jeffares & Green consulting engineers (now known as JG Afrika (Pty) Ltd). The study confirms that the technology meets the design criteria for continuously graded asphalt as defined in both COLTO and TRH8. It is important to note however that the technology has been designed specifically for low order roads and is not recommended for high trafficked roads or highways.
PAVING THE ROAD TO REAL ECONOMIC TRANSFORMATION
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COST EFFECTIVENESSDue to the unique methodology of this labour based surfacing technology where the asphalt premix is manufactured on site, normal costs associated with transportation are minimized resulting in a substantial cost saving over traditionally bagged asphalt.
This is further supported by an economic analysis that was done as part of the feasibility study which included a life cycle cost and economic benefits analysis. The study concluded that of the different surfacing options including hot mix asphalt, paving blocks and Cape Seal, that “both the labour based surfacing technology and Cape Seal options can be considered the most economically feasible” over a 25 year period.
SIMPLICITYDue to the high level of unskilled labour that have been appointed on the Mooiwater project it was imperative that the entire surfacing process be applied as simplistically as possible. The success of the completed phases of the project can be largely attributed to the simplicity and ease of use of the labour based surfacing technology. All equipment required on site for the mixing of the asphalt components have deliberately been kept as basic as possible. All containers have been purposely cut out or marked to hold the correct volumes eliminating complicated measuring and ensuring the correct proportions are consistently mixed, enabling the system to be effectively implemented.
TRAINING & TECHNICAL SUPPORTThe key to the successful implementation of this project has been un- questionably the time and effort that has been dedicated to training and skills development which has ensured that all the necessary skills required for the project have been transferred. A 3- step training program introduced by the appointed skills development company has provided a fresh approach to SAQA accredited courses covering both technical and entrepreneurial training which has now created an important foundation for sustainable employment. The comprehensive training programme was designed to transfer the following skills:
1. Sustainable Skills for Life which is vitally important because it nurtures the core of individuals before tackling the hard skills. Modules include: Leadership, Personal Finance, Goal Setting and Eco-Construction Practices.
2. To manufacture 4 different eco-friendly cold asphalt or asphalt related products for road surfacing, repair and maintenance, to apply and surface the 4 different eco-friendly mixes and to maintain and repair potholes using CSIR technical guide.
3. As part of the exit strategy, labourers are capacitated to become small contractors where they will be taught to: establish a construction business, operate a construction business and execute construction projects.
The labour based surfacing technology has been modelled in accordance with the EPWP operational level guidelines so the inclusion of these accredited training courses will allow the municipality to benefit from the associated incentive grants.
PAVI
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Photo 1: First trial section undertaken with training
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SUSTAINABILITY (EXIT STRATEGY)What makes projects like the Mooiwater roads upgrade project absolutely unique is the fact that for the first time local communities can be taught to manufacture a quality cold asphalt which can then be supplied to the municipality for their on-going road repair and maintenance program. This service not only allows the municipality to become self- sufficient for their asphalt requirements but effectively addresses the issue of sustainability. These community-based asphalt plants & pothole repair teams can be incubated through a mentorship program and developed into structured business units or cooperatives.
MOOIWATER PROJECT DETAILSThe project involved the upgrading of 3.5km of gravel road to surface standards using the LBS medium continuously graded blend, consisting of the following material proportions:
PAVING
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Material % of total Mass (kg) LBS Filler 20 30 Crusher sand 50 75 6.7mm Roadstone 8 12 9.5mm Roadstone 12 18 Bitumen emulsion 9 15 Total: 100 150
Measuring wheel e.g. Rotowheel Pedestrian roller e.g. Bomag 60/75 50m tape measure 1000ℓ water tank (or open top drums) Pliers Drum stand – provided by LBS Supplier Hammers Drum tap – provided by LBS Supplier 1Kg bag 4” nails (concrete) Drum key – provided by LBS Supplier Fish Line Hand stamper Spirit level Bucket 25/30mm angle iron (5mm thick) Builders brush 4m levelling bar Trowel
Note: The final mix proportions may vary depending on the actual properties of the individual aggregate components from the typical mix proportions mentioned in the above table.
The following tools and equipment were used:
Photo 2: Team ‘Mooiwater’
26
The total labour utilized for the overall project averaged 40 local labourers.
A team of 14 people were used for the manufacturing of approximately 15 metric tons of asphalt pre-mix per day however the labour requirements will be determined by the production rate required and can be increased or decreased according to project needs.
To surface approximately 300m2 per day a team of 10 people were used, although labour requirements can be established and adjusted according to the production rate required.
The LBS Asphalt is manufactured on site and follows standard asphalt design.
During construction, samples were taken and tested for pertinent criteria such as ITS, Marshall Stability, Dynamic Creep and Binder Content.
With its high labour requirement, the technology has proved to be an excellent tool for job creation with a particular focus on the empowerment of women and the youth, and is capable of facilitating up to an 80% woman labour component.
Due to the product’s unique methodology, the LBS Asphalt system can be effectively applied wherever the road surfacing is required irrespective of the location, empowering even the remotest of communities with no prior skills.
These types of innovative labour based construction projects should be embraced by our Engineering communities. Appreciation is extended to the Head of Road and Stormwater, Engineering Services Directorate Mr. Johan Fullard for embracing this type of project and enabling things to be done differently.
PAVI
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Before...........
...........After
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Our Company is pleased to introduce Pavetest’s DTS-130 Dynamic Testing System, which is their Highest Capacity Testing Machine.
This Servo-Hydraulic testing machine uses digital control of a high performance servo valve to provide accurate loading wave shapes up to 100Hz. It can be operated in both tension & compression dynamic loading modes.
Features • Robust 2 Column Load Frame • Double Acting Servo Hydraulic,
equal area type with low friction, long life bearings & seals
• Portable Temperature Control Unit
• Fully Configurable, to suit a large range of Testing Applications
• Digital Servo-Hydraulic control • 4 Axis Control & 16 Channel
Data Acquisition as standard
The DTS-130 is well suited to testing a range of engineering materials &/or asphalt specimens at very cold temperatures, down to -50°C via a “two piece” temperature control unit.
The Control & Data Acquisition System (CDAS) provides excellent waveform fidelity, from integrated acquisition & control functions. Low level sampling occurs at speeds of up to 192,000 samples per sec., simultaneously on all channels. Features: Superior low noise performance & a resolution of 20 bit, over the full dynamic input signal range.
The Hydraulic Power Supply (HPS) uses a variable flow pump with a working pressure up to 210 Bar. There is a choice between water (heat exchanger) or air (electric fan) oil cooling. Features; low oil, over temperature & dirty filter indication, remote starting as well as user selectable working pressure (via software).
The TestLab Test & Control Software allows real time results graphing & real time configurable transducer levels display with unprecedented analytical power. This software caters for all levels of operator experience.
Contact us for more information, enquiries or technical specifications:
JHB: Tel: +27 (0)11 499 9400 ([email protected]) or Durban: Tel: +27 (0)31 700 2551/1875 ([email protected])
28
Since 2000 – 2001 studies performed by the USA FHWA showed that air voids of specimens compacted in the super pave gyratory compactors could differ by as much as 1.0% within a single laboratory / technician context and by as much as 1.8% in multi-laboratory situations. Such discrepancies in results readily lead to contractual disputes and uncertainty concerning the appropriate compactive effort for selecting design binder contents.
We are not aware of any replication studies performed in South Africa on the volumetric properties of gyratory compacted specimens and it may well be that we will find ourselves in a situation where testing uncertainty, both in respect of single laboratory / technician and multi-laboratory situations, is of such a scale as would lead to unacceptable discrepancies and questionable decisions.
As is the case with all materials testing, a significant source of variability in determining asphalt sample properties relates to sampling and testing. Clearly steps must be taken to ensure that all persons involved in asphalt sampling and specimen preparation adhere to best practices.
While a number of apparatus-related factors may contribute to difference in volumetric properties of SGC prepared specimens e.g. regular maintenance, cleanliness mould wear and machine frame compliance, a method of calibrating SGC units using an internal angle of gyration is discussed below.
Angle of GyrationClearly, discrepancies in void content mentioned above and those published in ASTM D 6925 Standard Test Method for Preparation and Determination of the Relative Density of Hot Mix Asphalt specimens by Means of the Superpave Gyratory Compactor based on an inter-laboratory study described in NCHRP Research Report 9-26 i.e. repeatability, r 0.9 to 1.4% and reproducibility, R 1.7% impede design and quality management processes.
It was speculated by researchers that calibrating SGCs using the ‘external’ angle of gyration did not sufficiently limit the parallelness of the top and bottom plates. A confounding factor was that manufacturers utilized different approaches to external measurements of the angle of gyration of the moulds.
Furthermore, differences in frame compliance and calibration technique would lead to bias in properties of compacted HMA samples. Independent appraisal using a single calibration technique of the critical parameters of the compaction process was therefore not feasible.
In 1998 a device was developed to measure the angle of gyration from inside the mould, initially referred to as the Angle Validation Kit (AVK) and now known as the Dynamic Angle Validator (DAV). Proof was needed that changing to an effective internal angle calibration procedure would remove or significantly reduce the bias between results from different SGCs. Eight laboratories participated in an experiment to assess the effectiveness of the proposed procedure.
The study was comprehensive in terms of the number and brands of SGCs as well as the wide range of mixture types. The results generally indicated that the DAV calibration procedure removed some of the bias between the SGCs – in some cases from 20 to 100%.
REPLICATION OF GYRATORY COMPACTED
SPECIMEN PROPERTIES – Where do we stand?
29
Measurement of Dynamic Internal Angle using Simulated LoadingAdvancements in the measurement of internal from 2003-2006 lead to the development of two devices to induce a load during compaction similar to that induced by asphalt– the Rapid Angle Measurement (RAM) and the Hot Mix Simulator (HMS). The HMS is used in conjunction with the DAV.
There are three primary methods for determining the internal angle of gyration – DAV with mix, DAV with the HMS, and the RAM. Two questions arise:
– How do the methods compare; and
– Are the methods interchangeable?
In 2007 a comprehensive study focused on establishing the precision and bias of the measurement of internal angle using a simulated load. This study also provided a comprehensive comparison of internal angle results generated by the two simulated load devices.
The study included:
– 28 SGCs (representing major models then in service);
– 9 Laboratories/agencies; and
– 12 Internal angle instruments (6 RAM devices 6 DAV/HMS devices)
The major findings were:
– The acceptable range of two internal angle measurements (d2s) for single operators is 0.03°
– The acceptable range of two internal angle measurements (d2s) for multiple operators is 0.04°
– There is no consistent, significant difference in angle measurements using the RAM and DAV/HMS instruments, across the major SGC brands/models typically in use in the USA
Relationship between Internal Angle and Air VoidsASTM D 6925 (which is specified for Level IB to Level III design in Sabita Manual 35 / TRH 8) now recommends that the internal angle of gyration of 1.16 ± 0.02 degrees be used, especially for machine calibration.
A study was carried out by the FHWA and the University of Arkansas in 2008 to determine the relationship between internal angle and air voids of compacted asphalt Two mixtures were examined including a fine-graded, 9.5 mm NMAS with unmodified binder and a coarse-graded, 12.5 mm NMAS with a polymer-modified binder. Five internal angles were selected, ranging from 0.86° to 1.46°.
While noting that the relationship between internal angle of gyration and air voids may be mixture-specific, in general terms it was found that a change in internal angle of 0.01 degrees results in an average change in air voids of 0.05 percent. (See Figure 1).
Based on this relationship and considering the improved r and R, emanating from the study mentioned above, it would seem feasible to deduce that the corresponding effect on voids would be r = 0.15% and R = 0.2%, a far cry from the earlier values of 1.0% and 1.8% for r and R respectively.
REPLICATION
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YRATORY CO
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30
REPL
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University of Arkansas
Average Internal Angle (deg)
9.5mm/64-22/N65
6.0
5.0
4.0
3.0
2.0
1.0
0.0
0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 0.8
9.5mm/64-22/N100y = -3.1528x + 5.9717y = -4.0769x + 7.8908
R2 = 0.9957 R2 = 0.9558 R2 = 0.9881
y = -5.6032x + 10.02112.5mm/76-22/N50
Air
Voi
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Determination of BiasOnce having examined the potential for variability generated by e.g. mould wear, lack of periodic maintenance and cleanliness, ongoing difficulties in producing consistent (bulk density) values among two or more gyratory compactors, would lead to a next step to determine whether bias exists. To this end comparison studies may need to be performed. An outline of a procedure for a comparative study is as follows.
Sampling of asphalt specimens
To compare two or more compactors, a consistent mixture is vital. Ideally, a mixture should be sampled at the asphalt plant and split into specimen sizes (generally 4500 to 5000 g) “on site” – without reheating the mix.
Number of Specimens/Mixes
Comparative studies may be performed for a particular mixture, or a variety of mixtures. A higher va-riety of mixtures provides a more comprehensive, complete outcome in terms of the relationship be-tween multiple compactors
(AASHTO PP 35 recommends a minimum of four mix types for each SGC validation. Also, a minimum of six asphalt specimens is required for each apparatus for each mix type.)
Compaction and testing
Clearly, according to this procedure the number of specimens ranges from a minimum of 12 to potentially a very large value. It is recommended that care must be taken to ensure that specimens are treated as consistently as possible.
Figure 1: Relationship between internal angle and air voids (University of Arkansas) Source: FHWA
31
Specimens should be selected and assigned to a particular compactor in a deliberately random way. Wherever possible, the same operator should perform all compaction and testing activities to avoid or limit inherent operator related variability.
Data AnalysisTwo values related to bulk density test results are used to compare compactors – the mean and standard deviation.
Comparison of mean values of the bulk densities obtained is the most basic procedure, for which purpose the t-test is proposed. Additionally the variance obtained can be assessed using the F-test. These form part of standard practice for comparing sets of results and it is proposed that these be considered.
To follow this recommendation the procedure currently adopted by the National Laboratory Association would have to be revised, in that the Z-score approach may not be adequate to assay results and locate sources of variation.
WHERE DO WE IN SOUTH AFRICA STAND ON THIS?
At the Sabita Technology Focal Point meeting on 21 February this year, the matter was discussed and a number of steps proposed on a way forward.
Firstly, the matter of laboratory proficiency in respect of the bulk density determination in accordancewith ASTM D 6925 should be pursued. The RPF Bituminous Materials Test Group will initiate the process. Clearly, the use of devices to determine the internal angle of gyration, such as the Dynamic Angle Validator (DAV) in conjunction with a Hot Mix Simulator (HMS) and the Rapid Angle Measurement (RAM) device should be investigated.
In addition laboratories should be encouraged to carry out regular apparatus maintenance programmes and periodically inspect apparatus, including moulds, for wear and setup cleanliness.
As mentioned already, a significant source of variability in determining e.g. the bulk density of a compacted asphalt sample relates to sampling and testing, particularly in respect of mixes that tend to segregate. For this purpose the review of TMH 5 Sampling Methods for Roads Construction Materials will go some way to mitigate variability stemming from poor sampling techniques. It should also be borne in mind that any test contains inherent variability, as is the case with determining bulk density of asphalt specimens and the volumetric parameters derived therefrom.
This article is based on FHWA TechBrief HIF-11-032 2011
Figure 2: Rapid Angle Measurement (RAM) Kit Source: Pine Test Equipment
REPLICATION
OF G
YRATORY CO
PACTED SPECIM
EN PRO
PERTIES – Where do w
e stand?
Call +27 86 146 6656 www.nationalasphalt.co.za
Call +27 12 562 9500 www.asphaltbotswana.com
National Cold Asphalt
Call +27 86 146 6656www.nationalcoldasphalt.co.za
Call +27 34 393 1259www.shisalanga.com
Leading Asphalt manufacturers and suppliers in Southern Africa
INNOVATION VALUE
PEOPLE
CONSERVATION
SUSTAINABILITY
GROWTH
ASPHALT IS OUR BUSINESS...
SUSTAINABILITY IS AT THE CORE OF OUR BUSINESS PRACTICES
33
SABITA BOARD MEMBERS
PRODUCER MEMBERS
Colas SA (Pty) LtdP.O. Box 82, Eppindust, 7475Tel: 021 531 6406 | Fax: 021 531 5514
Much Asphalt (Pty) LtdP.O. Box 49, Eerste Rivier, 7100Tel: 021 900 4400 | Fax: 021 900 4446
National Asphalt (Pty) LtdP.O. Box 1657, Hillcrest, 3650Tel: 031 736 2146 | Fax: 031 736 1938
Shell Downstream SA (Pty) Ltd6 Ipivi Road, Kloof, 3610Tel: 031 571 1000 | Fax: 031 764 6208
Rand Roads (a div. of Aveng Grinaker LTA)Private Bag X030, Kempton Park, 1620Tel: 011 923 5000 | Fax: 086 721 8513
Tosas (Pty) LtdP.O. Box 14159, Wadeville, 1422Tel: 011 323 2000 | Fax: 086 765 0890
Zebra Surfacing (a div. of Martin & East (Pty) Ltd)P.O. Box 14335, Kenwyn, 7790Tel: 021 761 3474 | Fax: 021 797 1151
Total SA (Pty) LtdP.O. Box 579, Saxonwold, 2132Tel: 011 778 2000 | Fax: 086 680 3283
SABITA MEMBERS
Leo Consulting (Pty) Ltd became an Associate member late last year and is a well-established companyconsisting of professional civil engineers and technical staff. They have a design office situated in Pretoria with various regional and field offices throughout South Africa.
Leo Consulting’s services include amongst others:
• Geotechnical Investigation;
• Providing environmental engineering solutions for the mining sector;
• Roads and Transportation: Feasibility studies and conceptual designs;
• Buildings and Structures: Design of sustainable infrastructure.
Prospective New MembersAs highlighted in our Membership Benefit document, Sabita has been pre-eminent in technology development and advancing the case for road provision and preservation. Direct involvement with road authorities is pursued to develop appropriate bituminous product solutions. Sabita’s other objectives for members includes, though is not limited to: providing education and training to develop skills and competencies that are sustainable and aligned to industry needs; advancing best practice in southern Africa with regards to worker health and safety; engaging stakeholders to promote the social and economic value of road provision and preservation. Please contact Hazel Brown via email: [email protected] for any membership queries you may have or to request a membership application form.
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ORDINARY MEMBERS
Actophambili Roads (Pty) Ltd P O Box 16661 Atlasville 1465 Tel 011 3952293
AmandlaGCF Construction cc P O Box 6064 Welgemoed 7538 Tel 021 9817070
AJ Broom Road Products cc P O Box 16421 Dowerglen 1612 Tel 011 4543102
Aqua Transport & Plant Hire (Pty) Ltd Private Bag X11 Ashwood 3605 Tel 031 5336883
Astec – Asphalt Technology P O Box 589 Rothdene 1964 Tel 016 3621310
Bituguard Southern Africa P O Box 2523 Bethlehem 9700 Tel 058 3037272
Bitumen Supplies & Services (Pty) Ltd P O Box 1028 Sunninghill 2157 Tel 011 8039338
Bitumen World PVT P O Box AY20 Amby Harare Zimbabwe Tel +263 772417102
Cruze (Pty) Ltd P O Box 742 Gallo Manor 2052 Tel 011 0500705
Emergeco Trading (Pty) Ltd P O Box 635 Umhlanga Rocks 4320 Tel 031 4812450
Group Five Civil Engineering (Pty) Ltd P/net Suite 500 P/BagX26 Sunninghill 2157 Tel 010 0601555
Javseal (Pty) Ltd P O Box 26317 Isipingo Beach 4115 Tel 031 9025988
Milling Techniks (Pty) Ltd P O Box 779 Gillits 3603 Tel 031 7929580
More Asphalt (Pty) Ltd P O Box 2180 Durbanville 7550 Tel 021 9750784
Murray & Roberts Infrastructure P O Box 585 Bedfordview 2008 Tel 011 5905843
Nolans Earthworks & Plant cc P O Box 28617 Haymarket 3200 Tel 033 3866455
Polokwane Surfacing (Pty) Ltd P O Box 288 Ladanna 0704 Tel 015 2931221
Power Construction (Pty) Ltd P O Box 129 Blackheath 7581 Tel 021 9071300
Puma Energy Services SA (Pty) Ltd Postnet Suite 190 Private Bag X31 Saxonwold 2132 Tel 011 3436998
Raubex (Pty) Ltd P O Box 3722 Bloemfontein 9300 Tel 051 406 2000
Raubex KZN (Pty) Ltd P O Box 10302 Ashwood 3605 Tel 031 7006411
Road Material Stabilisers P O Box 84513 Greenside 2034 Tel 011 3903499
Spray Pave (Pty) Ltd P O Box 674 Alberton 1450 Tel 0118685451
Tau Pele Construction P O Box 13125 Noordstad 9302 Tel 0514360103
ASSOCIATE MEMBERS
Advanced Polymers (Pty) Ltd P O Box 9452 Edenglen 1613 Tel 011 3977979
AECOM SA (Pty) Ltd P O Box 3173 Pretoria 0001 Tel 012 4213500
Afrisam SA (Pty) Ltd P O Box 6367 Weltevreden Park 1715 Tel 011 6705500
Ammann Const. Machinery SA (Pty) Ltd Private Bag X43 Rynfield 1500 Tel 011 8493939
Anton Paar Southern Africa P O Box 50471 Randjiesfontein 1683 Tel 011 0215165
Aurecon SA (Pty) Ltd P O Box 494 Cape Town 8000 Tel 021 5269400
BSM Laboratories (Pty) Ltd P O Box 15318 Westmead 3608 Tel 031 7646537
BVi Consulting Eng. W Cape (Pty) Ltd P O Box 86 Century City 7446 Tel 021 5277000
Dick King Lab Supplies (Pty) Ltd P O Box 82138 Southdale 2135 Tel 011 4999400
DuPont de Nemours SA (Pty) Ltd P O Box 3332 Halfway House 1635 Tel 011 2188600
EFG Engineers (Pty) Ltd P O Box 3800 Durbanville 7551 Tel 021 9753880
Gibb (Pty) Ltd P O Box 3965 Cape Town 8000 Tel 021 4699172
Glad Africa Consulting Eng. (Pty) Ltd P O Box 3893 Cape Town 8000 Tel 021 4626047
GMH/Tswelo Consulting Engineers P O Box 2201 Randburg 2125 Tel 011 4620601
Hatch Goba (Pty) Ltd P O Box 180 Sunninghill 2157 Tel 011 2363331
HHO Africa P O Box 6503 Roggebaai 8012 Fax 021 4252870
iX Engineers (Pty) Ltd P O Box 22 Menlyn 0063 Tel 012 7452000
JG Afrika (Pty) Ltd P O Box 1109 Sunninghill 2157 Tel 011 8070660
Kantey & Templer (Pty) Ltd P O Box 3132 Cape Town 8000 Tel 021 4059600
MEM
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MEM
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ASSOCIATE MEMBERS (continued)
Kaymac (Pty) Ltd T/A Kaytech P O Box 116 Pinetown 3600 Tel 031 7172300
Lafarge Industries SA (Pty) Ltd Private Bag X26 Gallo Manor 2052 Tel 011 6571156
Leo Consulting (Pty) Ltd P O Box 32798 Totiusdal 0135 Tel 087 9805004
Mott MacDonald Africa (Pty) Ltd P O Box 7786 Roggebaai 8012 Tel 021 4405060
Nadeson Consulting Services (Pty) Ltd P O Box 51121 V&A Waterfront 8002 Tel 021 4184988
Naidu Consulting (Pty) Ltd P O Box 2796 Westway 3635 Tel 031 2656007
NAKO Iliso P O Box 686 Gillits 3603 Tel 031 2662600
Namibia Technical Services cc P O Box 30623 Windhoek Namibia Tel +264 61 215324
Rankin Engineering Consultants P O Box 50566 Lusaka Zambia Tel +260 1 290562
Royal HaskoningDHV P O Box 867 Gallo Manor 2146 Tel 011 7986051
Sasol Technology Fuels Research P O Box 1 Sasolburg 1947 Tel 016 9604068
Sasol Wax SA (A division of SCI) Chemcity 2 P O Box 1 Sasolburg 1947 Tel 016 9602126
SMEC SA (Pty) Ltd P O Box 72927 Lynnwood Ridge 0040 Tel 012 4813821
Specialised Road Tech. (Pty) Ltd P O Box 15324 Westmead 3608 Tel 031 7004510
TPA Consulting (Pty) Ltd P O Box 1575 Westville 3630 Tel 031 7651907
Tshepega Engineering (Pty) Ltd P O Box 33783 Glenstantia 0010 Tel 012 6652722
Worldwide Tanks on Hire cc P O Box 2250 Durban 4000 Tel 031 3620207
WSP Group Africa (Pty) Ltd P O Box 98867 Sloane Park 2152 Tel 011 3611402
Zimile Consulting Engineers P/ Suite 252 Private Bag X11 Halfway House 1685 Tel 011 4668576
AFFILIATE MEMBERS
Cape Pen. Univ. of Technology P O Box 652 Cape Town 8000 Tel 021 4603074
DMV Harrismith (Pty) Ltd P O Box 912 Harrismith 9880 Tel 058 6222676
Durban University of Technology P O Box 101112 Pietermaritzburg 3209 Tel 033 8458916
Fuge Rubber Holdings (Pty) Ltd P O Box 2000 Witkoppen 2068 Tel
Gavin R.Brown & Associates P O Box 51113 Musgrave 4062 Tel 031 2025703
GT Design & Technologies 137 Jan Hofmeyr Road Westville 3630 Tel 031 2660933
IMESA P O Box 2190 Westville 3630 Tel 031 2663263
Instant Tar Services P O Box 17219 Norkem Park 1631 Tel 011 3935194
Letaba Laboratory (Pty) Ltd P O Box 739 White River 1240 Tel 013 7527663
Mdubane Energy Services (Pty) Ltd 214 9th Ave. Morningside Durban 4001 Tel 031 3042470
Mmila Civils & Traffic Services P O Box 40158 Faerie Glen 0043 Tel 012 9933098
Nathoo Mbenyane Engineers P O Box 47595 Greyville 4023 Tel 031 3122097
Nelson Mandela Metro. University P O Box 77000 Port Elizabeth 6031 Tel 041 5043298
N3TC (Pty) Ltd P O Box 2063 Bedfordview 2008 Tel 011 4543596
Outeniqua Laboratory (Pty) Ltd P O Box 3186 George Industria 6536 Tel 044 8743274
Pride Lab Equipment (Pty) Ltd 3 Van Eyck Crescent De La Haye Bellville 7530 Tel 021 9462018
Reliance Laboratory Equipment P O Box 911-489 Rosslyn 0200 Tel 012 5498910
Salphalt (Pty) Ltd P O Box 234 Isando 1600 Tel 011 8232218
South African Road Federation P O Box 8379 Birchleigh 1621 Tel 011 3945634
Unique Trading and Outsourcing P O Box 5424 Benoni South 1502 Tel 011 7403452
Uni. of Pretoria Dept. Civil Eng. Lynnwood Road Hatfield 0002 Tel 012 4202171
Uni. of Stellenbosch Dept. Civil Eng. Private Bag X1 Matieland 7600 Tel 021 8084379
FOREIGN MEMBERS
Raetex Industries 550 Tiburon Blvd Suite B-1 TiburonCA 94920 United States of America Cell 072 0315266
Rettenmaier & Söhne GMBH Global (establishing a base in Johannesburg) Tel 011 5348619
Kraton Polymers Netherlands B.V 10 John M. Keynespein 1066 EP Amsterdam Netherlands Cell 082 4570210
LIESEN Bitumen (Pty) Ltd 107 Hope Street Cape Town 8001 Tel 021 3001631
Zydex Industries Gujaret India T+91 2653312000
Asphalt News is published by the Southern African Bitumen Asso-ciation (Sabita),a non-profit organisation sponsored by its mem-bers to serve all stakeholders through engineering, service and education.
Sabita and the associations listed below have founded a global strategic alliance of asphalt pavement associations (GAPA) and are working jointly towards a full, open and productive partnership:
Australian Asphalt Pavement Association (AAPA)European Asphalt Pavement Association (EAPA)Japanese Road Contractors Association (JRCA)Mexican Asphalt Association (AMAAC)National Asphalt Pavement Association (NAPA)Civil Contractors New Zealand
The contents of this publication may be reproduced without any changes and free of charge, providing the source is acknowledged.
Southern African Bitumen Association (Sabita)Postnet Suite 56, Private Bag X21 | Howard Place, 7450, South AfricaTel: +27 21 531 2718 | Fax: +27 21 531 2606 | Email: [email protected]
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