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Copyright of SDU Journal of Engineering Sciences & Design / Mühendislik Bilimleri ve Tasarım Dergisi is the property of Journal of Engineering Sciences & Design and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Currently in the UK, the mechanical properties of bituminous (asphalt) mixtures are determined by means of a suite of tests (stiffness modulus, resistance to permanent deformation and resistance to fatigue cracking) performed by means of a pneumatic apparatus known as the Nottingham Asphalt Tester (NAT). This paper presents a methodology for an alternative experimental characterisation and modelling procedure for bituminous (asphalt) mixtures using a dynamic plasticity based constitutive model. The paper briefly describes the material response model and details the monotonic, uniaxial compression and tension testing at various temperatures and strain rates that are necessary to determine the basic model parameters. Two standard UK wearing course mixtures have been included in the testing programme comprising a continuously graded, Dense Bitumen Macadam (DBM), and a gap graded, Hot Rolled Asphalt (HRA). The uniaxial test data has been used to determine mathematical functions for the compressive and tensile strengths of the asphalt mixtures as well as functions describing their hardening and softening behaviour. Plots of the flow surface (or yield surface) have been produced for both mixtures over a range of temperatures and strain rates and the model has been successfully used to simulate the compressive response of asphalt mixtures. Once implemented in a finite element code, the constitutive model has been able to simulate the damage occurring in a flexible bituminous pavement under traffic loading. [ABSTRACT FROM AUTHOR]

• Cost effective optimisation of modified bitumen with liquid rubber for pavements and roofing membranes is presented. • Design optimisation technique allowed producing superior bituminous binders. • LR improves the flexibility at low in-service temperatures (using up to 50% contents), while EBS improves stiffness at high in-service temperatures. • The Response Surface Methodology was successfully used to optimise the final blends also in terms of cost. • Analytical functions amongst the design parameters have been derived and here provided for future design exercises. • The final properties were comparable to Polymer Modified Binders. Polymer Modified Bitumens (PMBs) are largely used for pavement and roofing membranes applications with Styrene-Butadiene-Styrene Block copolymer (SBS) playing a major role in both markets despite its constantly increasing price due to the rising demand for quality bitumen modifiers. On the other hand, there is an increasing trend of recycling end of life tyres generating Recycled Tyre Rubber (RTR) at affordable price. This investigation aims at engineering a modified bitumen with a combination of Liquid Rubber (LR), a homogeneous blend of 50–70% RTR pre-processed in combination with heavy oils, and a wax denominated Ethylene Bis Stearamide (EBS). In the first phase, the effect of LR and EBS was independently characterised and compared to PMBs. Next, the Response Surface Methodology (RSM) was used to predict the response of different combinations of LR and EBS in terms of low and high temperature properties and cost, to then be optimised targeting conventional and rheological properties of PMBs currently used in asphalt mixtures and roofing membranes in UK. As a result, an optimum combination of LR and EBS was found leading to a cost-effective modified bitumen comparable to PMBs. The work provided also analytical functions that could be of use in further design exercises. [ABSTRACT FROM AUTHOR]