Killian Ngong

Durability of concrete is defined as its ability to resist deterioration after exposure to the environment of its use. This work investigates the performance of Rice Husk Ash (RHA) concrete in sodium sulfate (Na2SO4), magnesium sulfate (MgSO4) and combined Na2SO4 and MgSO4 solutions. Concrete bar specimens and cubes were prepared for expansion and strength deterioration tests respectively using RHA replacement at the 7.5% replacement by volume, which had achieved the highest compressive strength, as well as at the 30% replacement by volume, which was the highest replacement for the study. Strength deterioration tests were performed on the 7.5% replacement by the weight of cement. From the expansion test findings, it was concluded that at the 7.5% replacement, RHA could be used with an advantage over 100% cement concrete in MgSO4 environments, whereas at the 30% replacement, RHA could be used with an advantage over 100% cement concrete in both the Na2SO4 and mixed sulfate environments. RHA was also found to be more effective in resisting surface deterioration in all the sulfate solutions. The RHA specimens also exhibited superior strength deterioration resistance in comparison to the 100% cement specimens.

The world generates over 2 billion tonnes of waste annually, whilst at the same time increasing traffic on roads and climate change are causing pavements to deteriorate faster than their nominal design life. A lot of the waste generated could find useful applications as replacements for current construction materials, whose extraction and use cause serious environmental issues. It was in view of the above dilemma that a novel optimisation technique has been developed to increase the amount of waste that could be recycled into pavement materials. The project has developed novel and sustainable asphalt pavement materials from optimising substitutions involving recycled aggregates (Reclaimed Asphalt Pavement, Incinerator Bottom Ash, polyethylene terephthalate) and recycled binders (Low Density Polyethylene (LDPE), Polyethylene Terephthalate (PET), and Polypropylene). These substitutes have been shown, through rigorous laboratory testing to successfully replace less-sustainable constituents whilst at the same time increasing pavement performance to deal with increasing loads from traffic and the environment. The results show that binary substitutions consisting of reclaimed asphalt pavement, municipal incinerator bottom ash and polyethylene fine aggregate substitution respectively in combination with natural aggregates are optimal at percentages of 35%, 40% and 6%. The optimal ternary aggregate with reclaimed asphalt pavement, municipal incinerator bottom ash and natural aggregate is one consisting of 20% reclaimed asphalt pavement, 20% municipal incinerator bottom ash and 60 % natural aggregates. This combination also produces an optimal quaternary mixture with the addition of 6% PET fine aggregate substitution. It has also been established when the aggregate systems above are further combined with optimised asphalt binders, further benefits are derived. This work opens up numerous possibilities to increase the amount of recycled materials in asphalt concrete mixtures through systematic incremental optimisation.

This research investigates the optimization of sustainable asphalt concrete (SAC) by incorporating Reclaimed Asphalt Pavement (RAP), Incinerator Bottom Ash (IBA), and polyethylene terephthalate (PET) as substitutes for virgin aggregates and bitumen. Previous studies on sustainable asphalt concrete have often focused on specific case studies or limited aspects of material substitution. This research aims to provide a comprehensive evaluation of the performance and environmental benefits of these materials in SAC mixtures.To achieve this objective, a series of laboratory experiments were conducted to assess the indirect tensile strength, Marshall stability, and other relevant properties of asphalt concrete mixtures containing varying proportions of RAP, IBA, and PET. The optimal substitution levels for each material were determined through a systematic analysis of the experimental data.The findings of this research demonstrate that RAP can be effectively used as an aggregate replacement at a substitution level of 45% by mass. IBA, on the other hand, can be incorporated as an aggregate replacement at a substitution level of 10% by mass. The use of PET as a binder substitute proved to be beneficial, with optimal substitution levels varying depending on the aggregate type. For IBA-based mixtures, a 10% PET replacement was found to be effective, while a 2% PET replacement was suitable for RAP-based mixtures.The combined use of RAP, IBA, and PET in asphalt concrete mixtures offers significant potential for reducing the environmental impact of road construction. By substituting virgin materials with recycled components, carbon emissions can be substantially decreased. This research provides valuable insights for policymakers, engineers, and industry professionals seeking to implement more sustainable practices in road construction.