RMIT University
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A Sustainable Approach to the Utilisation of Non-Clinical Medical Waste and Food Waste in ConcreteApplications

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posted on 2024-06-20, 01:29 authored by Shannon Kilmartin-Lynch

In this research, the potential to utilise waste materials to improve the mechanical properties of concrete was explored. The two main sources of waste materials that are the key focus within this research stem from global issues that are currently being faced. These issues relate to the coronavirus pandemic and the global food loss issue. Firstly, the use of single-use plastic-based personal protective equipment (PPE) has been on a sharp incline since the onset of the Coronavirus pandemic in late 2019. This has led to a significant increase in the generation of PPE waste and various environmental strains from excess waste ending up in landfill that requires different recycling solutions to reduce its environmental impact from disposal or incineration. The coronavirus pandemic placed the world on hold in late 2019, and since then, health care waste management systems have been failing to keep the waste under control. Studies indicate that over 30% of healthcare facilities are not equipped to handle existing waste loads, let alone the additional waste introduced into the system due to the COVID-19 pandemic. This excess waste opened a unique opportunity to explore the potential opportunity for medical waste PPE to be utilised as fibre reinforcement in concrete.

Secondly, food waste is another stream experiencing economic loss with estimates showing global food loss is set to reach 2.1 billion tonnes, resulting in $1.5 trillion globally by 2030. Whereas the consumption of coffee has been on a steady trend, increasing between 1.7-2.5% annually, and it is currently the most consumed beverage globally. However, the consumption of coffee leads to an excessive amount of spent coffee grounds (SCG) ending up in the food waste cycle. Historically, coffee grounds have been tried and tested as an aggregate replacement in concrete with limited to no success. However, this thesis explores an innovative solution to transform spent coffee grounds into biochar to be utilised as a fine aggregate replacement within concrete applications. Therefore, having the ability to minimise the volume of SCG that are sent to landfills.

This thesis therefore aims to explore the utilisation of single-use waste PPE generated from the coronavirus pandemic in structural concrete to aid in scaling back the quantity of waste ending up in a landfill. Single-use nitrile gloves, isolation gowns and face masks were separately added to aggregates at varying percentages of the volume of concrete. The compressive strength, modulus of elasticity, indirect tensile strength and flexural strength tests of the concrete samples were undertaken as well as microstructural analysis to ascertain the effect of varying concentrations and materials on the mechanical properties and quality of concrete and the specific materials bond performance within the cement matrix. The results of this thesis demonstrate steady trend development across compressive strength, flexural strength and the modulus of elasticity with increases of 22%, 20% and 11%, respectively, across varying applications of waste PPE. At the same time, the results of the SEM-EDS analysis present an excellent bond formation between the materials utilised and the cement matrix.

Typically, SCG cannot act as a suitable aggregate replacement in concrete due to its high organic content. This thesis aims to explore the effect of turning SCG into biochar as a fine aggregate replacement in an attempt to scale back the current global food loss issue. The research explores SCG in its natural state and in the form of biochar created at varying temperatures to measure how the material interacts within the cement matrix. Biochar was produced from SCG at both 350 degrees and 500 degrees Celsius and incorporated into concrete samples between 5-20% by volume of fine aggregates. The effects of the different pyrolysing temperatures on the properties of biochar blended concrete were investigated through a series of compressive strength tests and an SEM analysis. The results demonstrate that the coffee biochar (CBC) increases the overall compressive strength of concrete by up to 29.3%.

In this research, two innovative solutions to current global trends have been explored to take a sustainable approach to concrete applications. The outcomes of this study will provide practical guidance on the application of both non-clinical medical waste and food waste in the applications of sustainable concrete. The research has the potential to benefit local governments, communities, and the construction industry as well as medical grade PPE manufacturers and waste management industries.


Degree Type

Doctorate by Research


© Shannon Kilmartin-Lynch 2023

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