The dissertation topic of Structural Engineer, Nick Barnes has caught the eye of experts across the globe, and as a result, his dissertation is being presented at The 34th International Conference on Solid Waste Technology and Management conference in Annapolis, US later this year.

Nick recently graduated from his MSc at Nottingham Trent University, with a distinction in Structural Engineering with Materials, after writing his dissertation on:

Structural Performance of Concrete Elements Constructed using Recycled Concrete Aggregates and Recycled Tyre Steel Fibres’.

Dissertation overview

As the world begins to better understand the need to reduce carbon emissions, solutions are being sought for the waste materials produced by two of the biggest industries in the world; the construction and motor industries.

These waste materials consist of construction and demolition waste, most notably in the form of concrete elements from the demolition of structures, as well as waste tyres that cannot be re-used.

Concrete is being produced in quantities of 2 billion tonnes per year and it is estimated that during 2015, 55 million waste tyres were produced by the UK alone. Due to these astonishing figures, past research has been conducted to understand how these waste materials can be utilised in new construction projects with the aim to lower greenhouse gas and CO2 emissions.

Recycled Concrete Aggregates (RCA) and Recycled Tyre Steel Fibres (RTSF) have both been used previously in the construction industry in isolation, normally in areas where the properties of the materials are not as structurally important, such as in the construction of road bases and in ground bearing slabs. However, Nick could not find existing research to show these two materials being used combined together, or for structural purposes.

Nick’s dissertation set out to investigate existing research available around the use of RCA and RTSF, and to review if previous findings showed results that indicated these materials can be used more widely across the construction industry.


Nick created four different concrete mixes, testing for two different concrete strengths (C30 and C50). Two of the mixes contained Natural Aggregates (NA) with no additional fibres, the other two had 25% RCA materials and 1% RTSF per cement volume. Four beams were tested under 4-point bending with values of strain and deflection recorded along with cracking patterns and the ultimate failure load.


Nicks results indicated that the beams with 25% substitution of RCA failed at similar loads to those without. Other key findings showed that the compressive strength of the mixes with RTSF were lower and that the flexural strength for the mixes with RTSF and RCA were increased. Lastly the beams that contained RTSF experienced reduced cracking however the concrete mix when fresh had poor workability.


This insight into the properties and potential for using RCA and RTSF has opened up questions, opportunities and further avenues of research and investigation into the area. Further research pieces can expand on Nick’s research and find a mix of these aggregates that could potentially reduce the need for the use of virgin aggregates and specially produced fibres to allow the concrete industry to be more environmentally friendly.

Nick shared: “I was very happy that my dissertation was so well received and even more so that it was chosen to be presented at an international conference such as this, I’m thrilled that I could add some small piece of research into the development of more environmentally friendly building practices.”

Nick’s dissertation tutor, Dr. Hynda Aoun Klalib, added: “The research project provided new insight into incorporating construction waste and by-products into the production of new sustainable structural concrete.

“The presented primary results contribute to initial work done in the UK to find new use for the combination of recycled tyre steel fibres (RTSF) and recycled concrete aggregate (RCA) in concrete. A priori, RCA and RTSF are suitable for the production of structural concrete. The experimental observations and results confirmed that the use of RCA and RSTF would make an alternative to NA and manufactured steel fibres.”

Nick’s dissertation is soon to be published in ‘The Journal of Solid Waste Technology and Management’, to find out more about this topic, or to request a copy of this information, please contact Nick Barnes on 08450 990 285.