24/02/2017
2017 16th Annual International Conference on: Asphalt, Pavement Engineering and Infrastructure
Accelerated Durability Testing using the Immersion Ageing Test Chibuzor Ojum, Iswandaru Widyatmoko, Martin Heslop*, Arash Khojinian** Pavement Design and Asset Management, Centre of Excellence for Asset Consultancy, AECOM *Acland **Highways England 16th Annual International Conference on; Asphalt, Pavement Engineering and Infrastructure, 22-23 February 2017, Liverpool, UK
Acknowledgements This project was funded by Highways England under Highways England Framework for Transport Related Technical and Engineering Advice and Research Package Order: 451(4/45/12)ARPS.
Delivered by:
in collaboration with
Immersion Ageing Test
February 24, 2017
ACLAND
Page 2
1
24/02/2017
Brief for the Project The primary objective of this project is “to ensure that asphalt surfacings continue to deliver value for money on the strategic road network and to maximise the benefit from innovation” Task 1.
State of the art review of moisture susceptibility tests
2.
To develop a new approach to simulate and assess the effects of ageing and moisture on Thin Surface Course Systems (TSCS) under a laboratory accelerated durability test.
Immersion Ageing Test
February 24, 2017
Page 3
Factors Influencing Failure of Asphalt Internal material based mechanisms Traffic loading related forces
Factors Influencing Failure of Asphalt
Environmental influences Substrate strain loading Interface shear stress
Immersion Ageing Test
February 24, 2017
Page 4
2
24/02/2017
Factors affecting Durability
Source: Shell Bitumen Handbook
Immersion Ageing Test
February 24, 2017
Page 5
Key Requirements for Durable Surfacings
Source: J.C. Nicholls, “Permanent Potholes Repair”, Asphalt Professional No 60, 2014
Immersion Ageing Test
February 24, 2017
Page 6
3
24/02/2017
Immersion Ageing Test (IAT) The IAT incorporates improvements to EN 12697-45 to widen the scope and applicability for different types of asphalt materials to be tested in order to ascertain effects of moisture susceptibility and ageing.
Immersion Ageing Test
February 24, 2017
Page 7
IAT Test Protocol Stage 1: Pre-conditioning of Samples • Dry mass of samples determined. • Unconditioned ITSM at 20°C for all samples.
Stage 2: Conditioning of Samples • Samples are immersed in distilled water at 20°C and saturated using a residual pressure of 33 kPa for 30 minutes. • Percentage saturation is determined by weighing wet mass of each specimen - “Saturation before conditioning.” • Saturation before conditioning values ≥ 80% are rejected and replaced.
Stage 3: IAT Test • The Pressure Ageing Vessel (PAV) is partially filled with distilled water to completely immerse samples P3 – P5. • The PAV’s temperature and pressure are kept constant at 85°C temperature, 0.5 MPa pressure for 24 hours. • PAV temperature is reduced to 30°C for 24 hours to cool down.
Stage 4: Post- Conditioning of Samples • Each specimen is surface dried and weighed in air. • The saturation after IAT test is calculated and termed as “saturation after conditioning.” • Specimen’s temperature is brought down to 20°C and the conditioned final ITSM is established.
Stage 5: IAT Stiffness Ratio • From the known values of unconditioned and conditioned stiffness modulus, the ‘IAT stiffness ratio’ is calculated as the ratio of conditioned to unconditioned stiffness modulus. • The average value of stiffness ratio for each sample set (e.g. immersed or above water) is calculated; this value is termed the “IAT Durability Index”. IAT durability index ≥ 80% is deemed to be satisfactory. Immersion Ageing Test
February 24, 2017
Page 8
4
24/02/2017
Experimental Plan IAT Test Matrix
SMA 10 Surf 40/60
Low Voids (7%)
Low Voids (7%)
• SMA samples produced in accordance with EN 13108-5. • IAT Testing at 0.5 MPa, 24 hours and 85°C. • ITSM at 20°C in accordance EN 12697-26
Immersion Ageing Test
February 24, 2017
Page 9
IAT Test Results: SMA 10 Surf 40/60 Core Reference
Air Voids (%)
Saturation Before Conditioning (%)
Saturation after Conditioning (%)
Average Saturation After Conditioning (%)
Unconditioned ITSM
Conditioned ITSM
Stiffness Ratios
IAT Durability Index
IAT (0.5 MPa, 24 hours, 85°C) – Low Voids (< 7%) 616-1
4.5
9.0
17.0
9400
11500
1.22
9400
10900
1.16
17.0 616-2
4.7
11.0
1.19
17.0
616-3
4.8
9.0
36.0
616-4
4.5
11.0
34.0
616-5
4.2
8.0
30.0
626-1
7.8
20.0
33.3
9400
10700
1.14
8600
11200
1.30
9900
12200
1.23
5300
4000
0.75
5600
4600
0.82
1.22
IAT (0.5 MPa, 24 hours, 85°C) – High Voids (>7%) 19.0 15.0 626-2
7.1
15.0
626-3
6.2
11.0
28.0
626-4
8.2
20.0
37.0
626-5
8.7
19.0
41.0
Immersion Ageing Test
0.79
11.0
February 24, 2017
35.3
5500
4900
0.89
4900
4100
0.84
5500
4600
0.84
0.85
Page 10
5
24/02/2017
IAT Test Results: Durability Index SMA 10 Surf 40/60
2.0 1.8 1.6 IAT Durability Index
1.4
1.22
1.19
1.2 1.0
0.85
0.79
0.8 0.6 0.4 0.2 0.0 Above Water
Fully Immersed Sample
Low Voids (7%) IAT
• The mixtures with high air voids (>7%) had reduced “Durability Index” in comparison with the mixtures with low air voids (7%) 626-4 Ref
n/a
SMA 10 Surf PMB Binder
Voids
Description
685-1
G* (Pa) at 0.4Hz & 25°C
Penetration (dmm) at 25°C
SMA 10 Surf PMB Above Water
8.99E+05
31
SMA 10 Surf PMB Immersed
1.13E+06
27
SMA 10 Surf PMB Above Water
2.17E+06
19
SMA 10 Surf PMB Immersed
8.95E+05
31
Unaged PMB
1.77E+05
76
Low Voids (7%) 686-4 Ref
Immersion Ageing Test
n/a
February 24, 2017
Page 16
8
24/02/2017
Key Findings All recovered binders indicated signs of ageing as shown by higher G* and lower penetration values in comparison to reference unaged binders.
It should be noted that this was achieved after 24 hours following IAT protocol.
For binder recovered from SMA 10 Surf 40/60 and from SMA 10 Surf PMB with high voids, the ageing of the sample above water is greater than those immersed in water
Immersion Ageing Test
February 24, 2017
Page 17
Conclusions • The IAT protocol has been used satisfactorily for a 10 mm SMA TSC mixture using paving grade bitumen (40/60) with fibres and Polymer Modified Bitumen (PMB) produced with high binder content at 6.5%. • IAT is able to differentiate samples with low and high air voids. • IAT provides consistent saturation levels, durability index and ageing results for three immersed samples in the pressure ageing vessel (EN 12697-45). • IAT demonstrates the improvement in moisture susceptibility when using PMB especially for samples produced at high voids (>7%). • IAT has the potential to improve designs for thin asphalt surface courses for enhanced durability using currently available apparatus. Immersion Ageing Test
February 24, 2017
Page 18
9
24/02/2017
Future Work
Test other asphalt materials with low air voids such as Marshall Asphalt and AC to assess the effects of ageing and moisture susceptibility.
The IAT protocol could be extended to include pressure pulsing to potentially simulate the combined effects of ageing, moisture and traffic damage in a single 24 hour test.
Immersion Ageing Test
February 24, 2017
Page 19
Thank You
[email protected] Immersion Ageing Test
February 24, 2017
01159077163
Page 20
10
