Air Void Characterisation in Porous Asphalt Using X-Ray Computed Tomography

Abstract:

This study presents the characterisation of the air voids distribution for porous asphalt mixtures compacted using gyratory compactor. The distribution of voids content and voids shape within the porous asphalt were characterised for different nominal maximum aggregate size (NMAS) and specimen height. This is to evaluate the effect of different aggregate size composition and lift thickness on the air voids characteristics of the compacted porous asphalt. Two types of gradations were adopted i.e. Grading A (with NMAS=10 mm) and Grading B (with NMAS=14 mm) and they were fabricated for two different heights (50 and 100 mm). The internal structure was captured using X-ray Computed Tomography and image analysis techniques were used to process and analyse the images. It was found that mixture with coarse aggregate gradation produced larger void size with an elongated shape, which indicates voids connectivity within the mixture compared to fine gradation with more circular and smaller void size.For lift thickness, itacts differentlyfor different aggregate gradations. The specimen produced greater voids connectivity when the fine and coarse gradations were compacted at 100 mm and 50 mm respectively. These show that NMAS and lift thickness influence the mobility of the aggregate particles during compaction which affect the voids formation and determine the effectiveness of the compaction.

• Periodical: Advanced Materials Research (Volume 911)
• Pages: 443-448
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.911.443
• Online since: March 2014
• Authors: Abdul Hassan Norhidayah, Mohd Zul Hanif Mahmud*, Putra Jaya Ramadhansyah
• Keywords: Air Voids, Imaging Technique, Lift Thickness, NMAS, Porous Asphalt, X-Ray CT

References

[1] N.A. Hassan, G.D. Airey, R. Khan and A.C. Collop. Nondestructive Characterisation of the Effect of Asphalt Mixture Compaction on Aggregate Orientation and Segregation Using X-ray Computed Tomography., International Journal of Pavement Research and Technology 5. 2 (2012).

[2] F. Phumlani, E. Van Thulani, & P. Masondo. Further development of Twinlay porous asphalt surfaces. Diss. University of Cape Town, South Africa, (2001).

[3] Malaysia, P.W.D. Standard specification for road works, section 4, flexible pavement., Jabatan. Kerja Raya Malaysia, Kuala Lumpur (2008).

[4] N.A. Hassan. Microstructural characterisation of rubber modified asphalt mixtures. Ph.D. Thesis. University of Nottingham. (2012).

[5] Ferreira, T. A., and W. Rasband. The ImageJ User Guide—Version 1. 43., Image Processing And Analysis In JAVA (2010). (Placeholder1).

[6] E. Masad, LaithTashman, Dallas Little, and Hussein Zbib. Viscoplastic modeling of asphalt mixes with the effects of anisotropy, damage and aggregate characteristics., Mechanics of Materials 37. 12 (2005): 1242-1256.

DOI: 10.1016/j.mechmat.2005.06.003

[7] Hunter, Alistair E., Gordon D. Airey, and Andrew C. Collop. Effect of asphalt mixture compaction on aggregate orientation and mechanical performance. "Proceedings of the 8th Conference on Asphalt Pavements for Southern Africa (CAPSA, 04). Vol. 12. (2004).

[8] L.F. Walubita, B. Jamison, A.E. Alvarez, X. Hu, and C. Mushota. Air void characterisation of HMA gyratory laboratory-moulded samples and field cores using X-ray computed tomography (X-ray CT)., Journal of the South African Institution of Civil Engineering 54. 1 (2012).