BS EN 14769:2012 pdf download – Bitumen and bituminous binders — Accelerated long-term ageing conditioning by a Pressure Ageing Vessel (PAV)
5.7Vacuum oven (optional), which shall be capable of maintaining a temperature up to 180 °C with anaccuracy of ± 5 °℃.
The vacuum system shall be capable of maintaining pressures below (15,0±2,5) kPa absolute. Alternatively,the pressure vessel itself may be used in lieu of the vacuum oven if it is capable of maintaining a temperatureof 180 °c and a vacuum of (15,0±2,5) kPa.
5.8Commercial bottled air, which is suitable for the purpose of providing a sufficient supply of pressurizedair to carry out the test. (Only bottled air is suitable.)
6 Procedure
SAFETY PRECAUTIONS — Use laboratory safety procedures when handling the hot bituminousbinders and preparing the specimens and when removing the residue from the pressure vessel. Takeparticular care when lifting the lid of the pressure vessel.
Pre-heat the PAV vessel or forced draft oven to the ageing temperature.The binder is firstly pre-conditionedas necessary, prior to the long-term ageing procedure.The procedure used shall be stated in the report.
lf it is necessary to prepare more than one set of samples in the short-term ageing/conditioning procedure(using either EN 12607 series or a stabilisation procedure) in order to obtain sufficient quantity for thisprocedure, sub-samples shall be combined and homogenised before the test. The stabilisation procedureshall be stated in the report.
NOTE1 The hot residue may be poured immediately into the container or allowed to cool for PAV ageing later. fallowed to cool, the container with the binder should be covered and stored at ambient temperature.When it is to be used,the sample should be re-heated in accordance withEN 12594 for the minimum possible time and stirred prior to pouringinto the container.
NOTE2 Pre-heating the vessel up to 15 “C above the conditioning temperature may be used to reduce the drop inPAV temperature during the loading process and minimise the time required for stabilisation of the set temperature afterloading. However,pressurising the vessel causes an increase in temperature and the vessel may cool slowly,making itdifficult to achieve the specified temperature at the start of the test.
Pre-heat the container to the PAV conditioning temperature.Place the heated container on a balance andpour(50,0±0.5) g into the container.Ensure that the binder is distributed over the entire base of the containerby tilting the filled container if necessary.
NOTE3 The binder flm thickness will be about 3,2 mm. The number of containers per binder will depend on theamount of binder required for subsequent testing. The heating of the container should be sufficient to enable the flow ofthe binder.
NOTE4 (50,0± 0.5) g refers to containers conforming to EN 12607-2.When using containers of a different diameter, therequirement is that sufficient binder shall be poured such that the flm thickness will be about 3,2 mm (see 5.5).
Place the pan holder inside the heated pressure vessel and set the ageing temperature to the specfiedtemperature.
NOTE5 Typical conditioning temperatures are 85 °C, 90 “C, 100 °C and 110 °℃.Typical ageing times found to besuitable are 20 h ± 10 min for the 9o °C, 100 °C and 110 ‘C temperature conditions, and 65 h ± 30 min for the 85 °ctemperature condition.
The chemistry of bituminous binder ageing is complex and the mechanism changes with increasingtemperature. For this reason,the conditioning temperature should be kept as low as possible.Hightemperatures may make this ageing procedure unrepresentative of field ageing.The 110 °C condition shouldbe limited to conditioning of binders for use in high ambient temperature (desert) areas.
Binders containing polymers could exhibit separation andlor degradation in a way that does not occur duringnatural ageing.
NOTE6 Several temperatures are currently used for the accelerated long-term ageing method. No correlation of aparticular temperature with performance has been established at this time.
Place the filled containers in the pan holder. Place the pan holder complete with containers into the pressurevessel.Close the pressure vessel, ensuring that all bolts, clamps etc are secure and tighten the pressurevessel lid according to the manufacturer’s instructions.
NOTE7 Containers containing binders from different sources may be used in the same ageing test. Less than the fullset of 10 containers may also be used.
NOTE 8 lf desired, the change in mass after the long-term ageing may be determined by following the procedure givenin EN 12607-2:2007,6.2, the only difference being the heating period is that which is described in this method.
The loading process into the pressure vessel shall be carried out as quickly as possible to minimisetemperature loss.