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Development of a New Cold Binder Course Emulsion Asphalt

Dulaimi, AFD (2017) Development of a New Cold Binder Course Emulsion Asphalt. Doctoral thesis, Liverpool John Moores University.

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Abstract

Hot Mix Asphalt (HMA) is the most commonly used material in the construction of asphalt pavements. Approximately 650 million tonnes of asphalts for road pavements were produced, worldwide, in 2014. However, the HMA industry is responsible for a substantial consumption of energy, the creation of health and safety issues and has a negative impact on the environment. These shortcomings initiated substantial discussion within the industry with the aim to develop more environmental friendly, sustainable and economic pavement materials. These have resulted in the development of cold bitumen emulsion mixtures (CBEMs). However, to date, low early life stiffness, a slower rate of curing, the length of time necessary to achieve full strength, high air void contents and the presence of moisture in these mixtures have prevented them from being fully embraced by pavement authorities. This led to them being considered inferior to HMA because of a lack of essential mechanical properties. Currently, the use of CBEMs in pavement construction is limited to low traffic road surface course, reinstatement works and footways. Because of this, the development of CBEMs with high early strength and minimal time delay requirements before structural loading, would be considered as a breakthrough in CBEM research. This research aims to develop a novel, fast-curing and environmentally friendly, cold binder course emulsion asphalt (CBCEA) for heavily trafficked roads. The new CBCEA mixture comprises the same gradation as conventional dense bitumen macadam (DBM) mixtures which are normally used as a binder course and base in road pavements in the UK. The new CBCEA incorporates a new cementitious material, alkali activated binary blended cement filler (ABBCF), made from Paper Making Sludge Ash (PMSA) and a Fluid Catalytic Cracking Catalysts Residue (FC3R) activated by a waste NaOH solution (W-NaOH). Incorporation of the PMSA and FC3R was achieved through the replacement of conventional limestone filler (LF), while W-NaOH replaced the pre-water necessary to wet the aggregate in the CBCEA. It was found that the glass phases of the new filler particles were broken and reacted with Ca(OH)2 creating C-S-H gel through the hydration process. This results in a very high early strength and improved mechanical properties. Balanced oxide compositions, within the new filler, were identified as responsible for an enhanced hydration reaction. A laboratory programme of testing measured the stiffness modulus, conducted at 1, 3, 7, 14, 28, 90 and 180 days. Susceptibility to temperature, wheel track testing to establish rutting resistance, fatigue resistance measured by a four-point beam bending test, fracture resistance testing via semi-circular bending tests, moisture damage resistance and ageing tests were successfully performed. Advanced techniques for microstructure assessment, i.e. Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD), were used to provide scientific data to provide a deeper understanding of the microstructure and internal composition. An environmental investigation was performed using a Toxicity Characteristic Leaching Procedure (TCLP) test. The new ABBCF mixture offers a significant improvement in stiffness modulus compared to HMA and the reference cold binder course mixture containing conventional limestone filler (LF). Target stiffness, according to British and European standards, can be surpassed after less than one day of curing. The new ABBCF mixture offers a stiffness modulus which is 27 times better than the LF mixture after 3 days. This will overcome restrictions caused by the length of time required to achieve acceptable stiffness by traditional CBEMs. More remarkably, the new ABBCF mixture is 78% better than mixtures treated with Ordinary Portland Cement (OPC) in terms of ITSM after 3 days. Furthermore, the impact of a rise in temperature on stiffness modulus from 5 to 45°C, was much larger in LF and both HMA mixtures in comparison to ABBCF, revealing the potential to use these mixes in severe conditions, both hot and cold weathers. ABBCF mixtures displayed considerably reduced susceptibility to permanent deformation, demonstrating the potential advantage of using this material on heavily trafficked roads. Fatigue resistance was noticeably improved by the use of ABBCF in comparison to the reference LF and HMAs. Improved water sensitivity for progressive hydration with the new ABBCF was also established resulting in an enhanced long ageing performance meaning that these mixtures can be considered durable. SEM observation and XRD analysis confirmed the formation of hydration products at various curing times. The concentration of heavy metals in the samples incorporating ABBCF was observed to be less than the regulatory levels determined for hazardous materials. Microwave treatment has proven to be an effective technique to reduce the air void contents of the ABBCF mixture and achieve acceptable levels of porosity. Finally, achieving the aim of the current research will theoretically increase the application of such mixtures and allow them to be used as structural pavement materials. On a further positive note, the inclusion of waste and by-product materials in CBEMs results in more sustainable practice and eliminates disposal problems.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: Cold mix asphalt, waste materials
Subjects: T Technology > TE Highway engineering. Roads and pavements
Divisions: Civil Engineering
Date Deposited: 30 Jun 2017 08:49
Last Modified: 30 Jun 2017 08:49
Supervisors: Al Nageim, H and Ruddock, F and Seton, L
URI: http://researchonline.ljmu.ac.uk/id/eprint/6733

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