Roads form a key element for the expansion of economy and development of a country. As with most countries, Brunei Darussalam has been facing a rapid development to meet the economic growth that requires an efficient road network. Therefore, the scarcity of conventional road aggregates in Brunei Darussalam means that the country has a strong dependence on imported aggregates from overseas to construct quality roads. Further restrictions on local road specifications make it almost impossible to include low quality granular materials. The study reported in this thesis was undertaken on the basis that the dependence on overseas resources is not a viable long- term solution. The research task has been, therefore, to ascertain the quality of local sandstones for road construction and then to propose means to upgrade their performance quality for optimum utilisation in cost effective applications. This study focused on the road base layer since that is where most aggregate is used. The approach used for this study was to identify the common rock in Brunei Darussalam and review the candidate treatment methods. A weighted matrix for these candidate treatment methods was constructed to determine the overall ranking with selected key criteria on the basis of the local climatic condition, construction preferences and traditions. From the reviews, Foamed bitumen was selected as a feasible treatment method that can improve the sandstone characteristics under local conditions. Three curing conditions were adopted in this study, simulating extreme field conditions in Brunei Darussalam, to characterise the mechanical properties of foamed bitumen stabilised sandstone mixtures, termed 'foam mix'. The following tests were conducted: • The response of stiffness modulus behaviour in the foam mix produced at different levels of mixing moisture content and cement content under dry and wet conditions was measured to study the mixing moisture content (MMC) in foam mix design. • A humid curing study was performed to indicate the short term stiffness of foam mixes in order to aid in the prediction of the delay necessary before a road comprising these foam mixes could be opened to traffic, and to determine how curing time and moisture content affect the development of stiffness modulus with and without cement. • A preliminary investigation was carried out into the potential of coir fibres as a reinforcement agent in the foam mix, measuring its effect on stiffness modulus, tensile strength and permanent deformation. • Being sensitive to moisture, the climatic durability of foam mix was further assessed by studying the effect of dry/wet cycles on the stiffness modulus incorporating other additives such as hydrated lime and pre-blended bitumen with wet fix. • Microscopic analysis has been undertaken as a guide to characterise the microstructure of the foam mix incorporating additives such as cement and coir fibres in order to support the laboratory findings. The laboratory results confirmed that the stiffness behaviour of the foam mix could be influenced by the amount of MMC, cement content and humidity of the environment. It was found that the foam mix with 1% cement (by mass of dried aggregates) at MMC, 70% of OMC, produced a durable mixture with a high stiffness modulus value in both dry and wet conditions as well as when subjected to the effect of alternate dry and wet cycles. The investigation on the potential of coir fibre to reinforce the foam mix indicated that the fibre did help to prevent large cracks in the foam mixes but unfortunately the reinforced foam mixes were easily damaged under a wet environment.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:689725 |
| Date | January 2015 |
| Creators | Haji Abdul Karim, Roslinah |
| Publisher | University of Nottingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://eprints.nottingham.ac.uk/29060/ |
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