Thursday, 6 February 2020
Austroads has published two updated test methods to safeguard people who handle polymer modified binders (PMBs) or use them in road construction. An updated PMB sample preparation protocol has also been published based on best laboratory practice.
The test methods support the recently published technical specification ATS 3110: Supply of Polymer Modified Binders that sets out the requirements for supplying polymer modified binders (PMBs) and crumb rubber modified binders for use in sprayed seals and asphalt.
“We specify minimum flash points for PMBs to minimise the risk of flammable vapours from PMBs accumulating in storage containers or while they’re being transported, and possibly catching on fire,” explains Robert Urquhart who developed the test methods in consultation with Austroads members and industry. “Test method AGPT-T112-20, Flash Point of Polymer Modified Binders, sets out the procedure for determining a flash point by slowly heating a PMB in an open metal cup until vapours on its surface are ignited or ‘flash’ when exposed to a test flame.
Another test method indicates the presence of volatile components in PMBs that could be emitted as fumes during pavement construction and maintenance, affecting air quality and human health. Test method AGPT-T103-20, Mass Change or Loss on Heating of Polymer Modified Binders after Rolling Thin Film Oven (RTFO) Treatment explains how to detect these components in a PMB by determining its change in mass after applying the RTFO treatment.”
PMBs are heat‑sensitive so test results can be significantly affected by the amount of exposure PMBs have to high temperatures and the length of time they are exposed. The modifier in some PMBs can also separate out while the binder is heated. Improper heating and mixing of samples can therefore produce test results which may not be representative of the original material.
As a result, AGPT-T102-20, Protocol for Handling Modified Binders in Preparation for Laboratory Testing, minimises the changes that occur in binder samples when they are heated before testing so the test results accurately reflect the product. This protocol has been developed to complement Australian and New Zealand Standard AS/NZS 2341.21:2015: Sample preparation which provides information about how bitumen, bitumen emulsion and cutback bitumen samples should be prepared for testing.
“The methods will enable more accurate test results to be obtained for PMBs and also provide safety information regarding protecting human health and the surrounding environment,” says Robert.