Possibility of using Xenon arc chamber Weatherometer as an aging calibration tool for bitumen binder:
Estimé M MukandilaWSP Group Africa (Pty) Ltd
Acknowledgment
• SANRAL • CSIR• UP ( Prof Steyn)
Introduction
• Ageing simulation• Real ageing
Outline of Presentations
• Introduction• Bitumen ageing principles• Ageing by weatherometer• Analysis of binder ageing by Xenon arc chamber
compared to traditional method• Interpretation of ageing results and recommendation• Conclusion
Introduction• Evaluation of bitumen ageing is challenging due to
effect of : Temperature Time Pressure
• Difficulty to accurately simulate specific field conditions due to high number of variables microclimate play a major role in field condition.
Bitumen ageing principles• Bitumen is influenced by environment
factors during its lifetime Rain and humidity Temperature UV radiation
• Bitumen ageing is : Change in chemical characteristics
of materials reflecting in changes in physical properties of materials o Strength ( hardening)o deformability
• Ageing = hardening
+=
Ageing
Bitumen ageing principles• Two phases of bitumen ageing
In plant during mixing, storage and laying : Short –term (loss of volatiles)
In-service or filed-ageing: Long-term (oxidation→ hardening→ brittle condition )
• Ideal field-ageing simulation should represent long-term ageing in relative short testing time
• Short-term ageing test: Rolling Thin Film Oven (RTFO) Thin film oven and rotating flask
• Long-term ageing test Pressure Ageing Vessel (PAV) rotating cylinder ageing test long-term rotating flask test
Bitumen ageing principles• Focus on Long term ageing PAV test characteristics in SA
o Sample preconditioned with RTFOo Sample thickness: 3.2mmo Testing temperature: 100ºCo Testing pressure: 2.1MPao Testing time: 20 hours
In-service or filed-ageing: Long-term• Ideal field-ageing simulation should
represent long-term ageing in relative short testing time
Ageing by Xenon arc chamber Weatherometer
• Based on ageing method for bituminous roofing and waterproofing materials using Xenon-ARC method (ASTM D 4798-01)
• Specified to Accelerate weathering test of road bitumen Using UV and visible part of solar
radiation all factors of weathering in real life taken
into account Accelerate ageing by elevated
temperature Realistic condition of weathering function
of microclimate
Feature of Weatherometer
• Chamber fitted with different feature, functions and controls Operation in phases or cycles Rain and humidity functions Measurement and control of Chamber Air Temperature
(CHT) (max. 70 °C during light phase) Air-cooled Xenon lamps with adjustable power (range
between 1.7 and 2.1 kW) Measurement and control of UV irradiance,
o Broad band in the UV range (300 to 400 nm) in W/m2
o Narrow band at 340 nm or at 420 nm in W/(m2nm) Measure and control of Temperature (max. 100ºC during
light phase) sample spray system
Xenon arc chamber ageing testing parameters adopted
• Based on work done in Netherland TU Delft Temperature: 50°C UV light (340 nm): 0.35 W/m2
Testing time : 1 000 hours in the following hourly cycle: o 51 minutes of light exposureo 9 minutes of light and water spray
Used of PAV’s stainless steel pan as sample tray
Analysis of binder ageing by Xenon arc chamber compared to traditional method
• Bitumen aged by weatherometer and PAV were compared in terms of stiffness
• Bitumen used 70/100 pen Original unaged (“fresh-Unaged”) bitumen; PAV aged bitumen; Xenon arc chamber (Q-SUN) aged bitumen 28 sample recovered from field aged seal across
South Africa
Ageing model process
Original 70/100
Xenon aged (Q-SUN)
PAV aged (PAV)No action(Fresh-unaged)
Extraction CSIR protocol (Lab)
28 Seal samples70/100Field-aged
DSR Test (G*)
G* Master curve (Prony series)
Ageing model (G* vs time) based on 28 (lab sample) and 1(fresh-unaged ):𝑮𝑮∗ = 𝑮𝑮∗𝒕𝒕𝟎𝟎 + 𝒃𝒃𝒕𝒕𝒄𝒄
assessment of respective age of PAV aged bitumen and weatherometer aged bitumen base on the model
Ageing models
𝑮𝑮∗ = 𝑮𝑮∗𝒕𝒕𝟎𝟎 + 𝒃𝒃𝒕𝒕𝒄𝒄
Ageing model (G* vs time) based on 28 (lab sample) and 1(fresh-unaged ):
assessment age of PAV aged bitumen and weatherometer aged bitumen base on the model
𝑡𝑡: is the age (time) of the seal’s bitumen𝐺𝐺∗𝑡𝑡0: is the initial complex modulus of a seal’s bitumen (complex modulus of the fresh bitumen). In this case, 𝐺𝐺∗𝑡𝑡0= 183 106
𝐺𝐺∗: is the complex modulus of a seal’s bitumen at time 𝑡𝑡𝑏𝑏 and 𝑐𝑐 are constants. (𝑏𝑏 = 2.47 106 and 𝑐𝑐 = 0.711
Interpretation of ageing results
• PAV aged sample is just below 3 years (2.8 years)• Xenon arc chamber method is just over 5 years (5.3
years)• Literature report long term ageing to simulate 5 to 10
years• Traditional ageing method seems not to simulate long
term ageing• Xenon arc chamber s a potential tool, in the modelling of
bitumen ageing• But Xenon arc chamber operates in a relative long time
period (1 000 hours) compared to the standard long-term ageing
• Can be used as calibration tool for standard long-term ageing test.
Interpretation of ageing results
• calibration of ageing model: ageing model for PAV aged bitumen :
𝐺𝐺∗𝑃𝑃 = 𝐺𝐺∗𝑡𝑡0 + 𝑏𝑏𝑡𝑡𝑝𝑝𝑐𝑐
Ageing model for Xenon arc chamber aged bitumen:
𝐺𝐺∗𝑄𝑄 = 𝐺𝐺∗𝑡𝑡0 + 𝑏𝑏𝑡𝑡𝑄𝑄𝑐𝑐
Combination of the two equation𝐺𝐺∗𝑄𝑄 = 𝐺𝐺∗𝑃𝑃 + 𝑏𝑏(𝑡𝑡𝑄𝑄𝑐𝑐 − 𝑡𝑡𝑃𝑃𝑐𝑐)
𝑏𝑏 𝑡𝑡𝑄𝑄𝑐𝑐 − 𝑡𝑡𝑃𝑃𝑐𝑐 = A , calibration constant 𝐺𝐺∗𝑄𝑄 = 𝐺𝐺∗𝑃𝑃 + 𝐴𝐴
Recommendation
• Necessity of refining the protocol of Xenon arc chamber ageing method to optimise simulation of the long term ageing of bitumen Protocol appropriated to related microclimate
(testing time, light exposure time, water spray time refine some element of equipment (sample tray
type and position)
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