News Item
Guidelines document for the assessment and certification of cold mix materials for patching and potholes
Release Date: 2010-06-24
Introduction
Cold-lay surfacing materials can be an attractive alternative to conventional hot-mix asphalt (HMA) in situations where the required quantity is small or the site is in a remote location.
A number of cold-lay products have been developed by the private sectors that contend to satisfy the functional and other requirements set by road authorities. Road authorities are faced with the problem that insufficient impartial information is available on the products to judge whether these products would be suitable for the intended purpose.
Stakeholders have proposed that proprietary products be assessed in terms of their ‘fitness-for-purpose’ and, if found to be compliant, a product certificate would be issued to the product owner. Certificated products are defined as products developed by industry for which no standard has yet been established (i.e. proprietary products), but which have gone through a formal evaluation phase (certification process). During the evaluation phase, the developer’s specifications for the product will have been validated, additional tests as requested by the certifying body conducted, their properties compared with those of standard products and/or specifications, and a certification statement issued by the certifying body in which the properties and application limits of the product are stated.
An industry task team was established and a workshop for stakeholders held to define the parameters against which products should be assessed for certification. The output of the industry workshop has been used as the point of departure for drafting the certification guidelines.
Proposed guideline document
It is intended that the guideline document will:
- define different categories of certification (e.g. traffic categories, temporary vs. permanent application)
- identify a range of parameters that, when combined, will provide a reliable view of the fitness-for-purpose of cold-lay surfacing material for a selected application
- set out an inspection protocol that will cover:
- the product that has been in service for some time
- the application of the product in the field
- the performance of the product from the date of assessment for a period of two
years
-
identify suitable test methods and protocols for each of the selected parameters
-
set minimum performance requirements, following a laboratory study, for each of the selected parameters
-
set minimum requirements regarding a quality management system that will cover the manufacture of the product and installation on site.
The draft guideline document describes the step-by-step certification procedure, from first application to the final issuing of the certificate, and also contain the related forms and protocols.
Proposed performance parameters and related test methods (an extract from the draft guideline currently being finalised –subject to change)
|
Parameter |
Test method |
Proposed performance |
|
Long-term voids |
Marshall compaction of long-term aged samples at 135ºC |
≥ 3,0% |
|
Rutting resistance |
Hamburg wheel tracking test (HWTT) at 30ºC on specimens compacted at 30ºC |
≥ 5 000 load repetitions to 20 mm deformation |
|
Moisture sensitivity |
Modified Lottman |
Sample not to disintegrate |
|
Permeability (optional) |
Constant head permeability test on long-term aged specimens |
≤ 500 l/m2/h |
|
Shelf life |
Compact specimens at sell-by date |
Mix should still meet above criteria |
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