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)