Critical evaluation of air voids distribution in HMA performance bases: A case study on the eThekwini Go! Durban programme

Abstract

The importance of air voids in hot-mix and high modulus asphalt cannot be underestimated.  Mixtures exhibiting sub-optimal air voids can adversely affect pavement performance and subsequently its ability to perform suitably over its desired design life.

To ensure not only compliance and consistency of the mix, but also to work towards achieving the required performance in accordance with the design, lab voids and in-situ quality control are statistically assessed against the density requirements as set forth in the overarching project specification.  For the current paper, the eThekwini Go! Durban Project - C9 Corridor, Phase 2A - Phoenix Highway to Industrial Park, has been used as a case study with specific focus placed on the 150mm thick Bitumen Treated Base (BTB) and Enrobé à Module Élevé (EME) base courses used.

The main aim is to establish the potential relationship that exists between lab and field voids using the Vacuum Sealing (VS) voids.  The pavement structure under review may not attain the 100 MESA traffic design life it is set to if the as-constructed voids in the layer do not satisfy the required criteria.

The current paper further aims to obtain a risk-centred view of the project through statistical means of voids analysis.  The differences in outcome that may result between application of the current project specification in comparison to that which may be obtained when COTO DS is applied, will also be highlighted.

About the authors

Avi-Nash Sukuram - Nankhoo Engineers

Avi-Nash Sukuram likes to believe he is a geriatric millennial.  He is a qualified and registered professional civil engineering consultant who has 13 years of design and contract administration experience related to roads and civil infrastructure in the private sector.  In 2017 he won the national award for Young Professional Technologist of the Year.  Avi-Nash is an aspiring poet with recent publications in magazines spanning the African continent.  Recently he has been driven by the discovery and assimilation of knowledge pertaining to life, with a passion for discovering one’s true purpose.

Joanne Muller - AECI Much Asphalt

Joanne completed her Bachelor and Honours Degrees in Civil Engineering, followed in 2015 by her Master’s in Engineering Management, at the University of Johannesburg. She is an ECSA registered Candidate Engineer.

She began her career with AECI Much Asphalt in 2008 as a part-time Trainee, followed by two years as a Graduate Trainee in the company’s Gauteng Regional Laboratory. In 2013 Joanne was promoted to Quality Assurance Supervisor at the Benoni plant and in 2016 to Regional Laboratory Manager. In this role she strives to improve quality and cost metrics to meet strategic objectives and customer requirements.

Joanne’s experience in asphalt manufacturing, testing and design, together with her zest for problem solving, is also put to good use on working groups reviewing SANS standard test methods, Sabita manuals and protocols for industry.