Laurence Bridgemohan, BSc., MSc. R.Eng

A Chat with Engineer Laurence Bridgemohan, a young research engineer pursuing engineering excellence in transforming Asphalt with Foamed Bitumen Technology

APETT ATC2024 Technical Conference held on 14-15 May 2024, HYATT Regency Hotel, Port of Spain, Trinidad, saw the emergence of a number of young engineer-researchers making presentations of their impressive and valuable research work. Laurence Bridgemohan was one such presenter and one who is actively engaged in asphalt pavement design, construction and testing. Laurence is a PhD candidate pursuing on-going pavement material research into foamed bitumen stabilization materials technologies. His projects experience includes pavement stabilization technology transfer activities in the Caribbean and Latin/Central America working alongside global industry pioneers in the field.    

Engineer Bridgemohan in 2017 gained local recognition for his engineering specialization when he became the first Engineer to be registered by the Board of Engineering of Trinidad and Tobago (BOETT) in the specialist Category of Road/Asphalt Engineer, thereby cementing his achievement as a local subject matter expert in the field of asphalt

Q1. Can you tell us a bit about your background and what inspired you to pursue the specific research topic you presented at APETT’s ATC2024 technical conference?

Entering the industry as a graduate civil engineer in the year 2010, I was fortunate to benefit from early mentoring in the pavement engineering field, by the late Eng. Raymond Charles and current industry stalwart Eng. Cecil Chin. My exposure at an early age to asphalt mix design, manufacturing processes, asphalt pavement equipment and construction, paved the way for specialization in a field which I quickly became fascinated in.  

I am now actively involved in stabilised pavement research, design, and construction, and currently engaged in stabilized technology transfer activities throughout the region.  After past academic research projects at both undergraduate and postgraduate levels, my interest in the field further inspired my ongoing PhD research in foamed bitumen stabilized materials.

Notably, the stabilized pavement technology was introduced in TT in the year 2006. The APETT’s ATC 2024 technical conference however allowed an opportunity to feature recent advancements in the technology, material research developments and the benefits of new in-plant stabilization to improve pavement layer materials for road building.

Q2. Could you give us an overview of the key points of your presentation?

The presentation includes an introduction into the key aspects of foamed bitumen stabilized pavement technology, examining recent advancements in the globally referenced South African, TG2 2020 foamed bitumen stabilized material design procedures and construction guidelines. The presentation further identifies successful applications of the technology in TT, the enhancement of reclaimed and locally available aggregate materials, for road bases and subbases. An overview of the advantages of cost-effective, balanced stabilized pavement systems as alternatives to conventional thick layered granular layered pavement systems are also included as potential benefits to applications in other small island developing states (SIDS).

Q3. What was the most challenging aspect of your research and how did you overcome it?

Notably, updated stabilized material research design methods incorporate the use of advanced laboratory equipment and the cost of acquiring these posed an immense challenge. Fortunately, I was able to partner with a local road building contracting entity, Dannys Enterprises, duly interested in research and development, and willing to invest in updating to state-of-the-art stabilized material laboratory equipment. These laboratory machines were imported directly from Germany and South Africa at a significant cost. They were however recognized by Mr. Danny Gokool, principal at Dannys, as critical to successful stabilized design and construction and necessary for moving the local road building industry forward.

Q4. How did you decide on the methods and techniques you used in your research?

The research was aimed at investigating stabilization technology as an effective pavement engineering solution for road building in TT. The methodology for the laboratory investigation followed the processes outlined in the revised South Africa TG2 2020 bitumen stabilization guidelines. The TG2 2020 serves as a complete reference for treatment selection, material classification, design and construction requirements, for projects utilizing BSMs. These processes outlined significant steps inclusive of determining parent material suitability, stabilized specimen strength testing and subsequent stabilized material classification. Strength data and material classification information were then utilized in structural design procedures, also adopted from the TG2 2020. This approach was then incorporated in stabilized pavement construction and rehabilitation design proposals for various construction applications in TT.

Q5. What were some unexpected findings or results that emerged during your study?

From the study, it was discovered that both reclaimed pavement materials and available quarried aggregates could be enhanced and incorporated in pavement structural layers. Significantly, quarried crushed stone aggregates are conventionally utilized for bases and subbase layers in local flexible pavement structures.

Although these quarried crushed aggregates may meet current strength and durability requirements and considered as quality road building materials, this research highlighted that these aggregates could be further improved for the construction of durable, thinner layered pavement structures. The result includes opportunities for significant cost savings, particularly derived from the use of thinner layers in the costly upper pavement structure. In addition to improved strength characteristics, stabilized materials displayed improved resistance to moisture damage, reflected in favorable retained strength results.

Q6. Can you discuss any potential real-world applications of your findings?

The foamed bitumen stabilization technology has established itself globally as a sustainable, green, cost-effective pavement engineering solution. This research however highlighted an investigation into the enhancement of our locally available reclaimed and quarried aggregate materials. Locally sourced reclaimed and available aggregate materials could be blended, treated in-situ or in-plant and enhanced for construction of durable, cost-effective pavement structures. Additionally, for SIDS, the South African design approach of  “balanced” pavement system with a stiffer, durable stabilized base layer, allows for reduced reliance on costly thick layered asphalt pavement systems. Moreover, increased layer carrying capacity from stabilized layers reduces the need for thick asphalt layers to accommodate imposed repetitive vehicle loading. This translates to significant cost savings to the road building industry.

Q7. What feedback did you receive from the audience at the conference, and how has it influenced your work moving forward?

The presentation at the conference was well received, generating interest as a suitable solution for improving local road conditions. Value added to marginal materials through blending and treatment was also identified as a significant measure to addressing aggregate sourcing challenges facing the industry. Interestingly, post presentation discussions also focused on the use of stabilized material technology in improving current local utility repair and road restoration methods. Reclaimed pavement materials from utility trenching and excavation activities are valuable materials that may be enhanced for reuse in a durable stabilized pavement system. Harnessing stabilization technology to improve these materials can be further explored to improve current road restoration activities.

Q8. Did you collaborate with any other researchers or subject matter experts on this project? If so, who and how did these collaborations shape your research?

I am fortunate to be working alongside leading stabilized pavement consultants Loudon International, South Africa. The influence of Loudon’s Eng. Dave Collings and Eng. Andre Greyling, both co-authors on this ATC2024 paper, as well as Professor Kim Jenkins at the Stellenbosch University is invaluable. As global pioneers they possess a wealth of knowledge from decades of research, pavement monitoring and practical experiences worldwide, under variable conditions. These collaborations have afforded me opportunities for knowledge transfer, data sharing and valuable recommendations towards successful applications.

Q9. What are the next steps for your research following the conference presentation?

This presentation highlights the significance of pavement stabilization technology to an improved road building industry in TT. Similarly, there are many benefits to be derived from applications in other SIDS. It is proposed that this research be expanded to allow laboratory analysis of available aggregate materials within the wider region, for determining suitability for stabilized pavement applications.

Q10. Are there any new areas or questions you are eager to explore as a result of your findings?

This research provided valuable characterization of stabilized locally sourced aggregates.  My current academic research into foamed bitumen stabilized materials aims to expand on the existing theory of the influence of aggregate characteristics on stabilized material strength and performance. It is proposed that the data obtained from stabilizing locally sourced aggregates can be used to add to this existing body of knowledge. In addition, pavement monitoring and testing of in-service stabilized pavement applications can provide valuable information of field performance under local conditions.

Q11. What was the most rewarding part of presenting at the conference?

The opportunity to contribute at the conference using knowledge and experience gained during actual engineering practice was most rewarding. I have been involved in the early stabilized technology applications in TT since my introduction as a graduate engineering trainee. During this period, the technology has evolved with advancements in design, specialist machines and construction practices. I have also spent significant periods in the field to be able to compare laboratory material behavior and stabilized material behavior, under construction conditions. The conference provided a valuable opportunity to share my knowledge and experience attained over these years.

Q12. Who are some of your mentors or role models in the engineering field, and how have they influenced your career?

At a young age my fascination with pavement engineering started during summer engineering internships at Danny’s Enterprises Limited. At an early age I was fortunate to benefit from the knowledge of the late Eng. Raymond Charles, who served as a Consultant to Dannys and continue to have the advice and support of local engineering encyclopaedia, Eng. Cecil Chin, who boasts of 50+ years of local and regional practice. I must also recognize the contribution of Dr. Trevor Townsend to my academic pursuits, particularly his guidance on my PhD research journey to date. 

Q13. How do you stay current with ongoing developments and trends in your field of engineering research?

I am convinced that continuing education and skills training are key to professional development. I attend pavement training workshops, seminars and conferences annually to keep abreast with advancements in the field. Notwithstanding these, journal publications, research papers and even peer discussions are often undervalued educational sources. These are often easier accessed sources but are of immense value to a developing professional.

Q14. What are your long-term career goals, and how does your current research fit into these aspirations?

I am happy to be actively engaged in the specialist field of pavement engineering. As a pavement practitioner the pleasure of designing pavement engineering solutions and implementing these on site, through to completion is the most fulfilling experience. My primary long-term career goal is to be able to make a valuable contribution to the pavement engineering industry locally, regionally and internationally. Pavement engineers play a significant role in designing and constructing critical infrastructure for movement of people, goods and services. Through continuous research into sustainable, cost-effective and durable pavement engineering solutions, I aim to add to the existing body of knowledge in the field of pavement engineering. Additionally, just as I have benefited from valuable mentorship, I too aspire to acquire the knowledge, skills and experience to be able to contribute to the development of younger professionals in the field.