R. C. Elliott

Optimising the moisture durability SATS conditioning parameters for universal asphalt mixture application

The saturation ageing tensile stiffness (SATS) procedure is the first laboratory asphalt mixture durability protocol to combine moisture damage and oxidative ageing during the conditioning of asphalt mixtures prior to mechanical testing. However, the application of the SATS procedure has tended to be predominantly targeted at base materials with relatively ‘hard’ binders and overall high stiffness modulus requirements and is considered potentially too severe for more standard asphalt mixtures. This research study focused on understanding the effect of changes to the SATS conditioning parameters on the relative moisture damage assessment performance of asphalt mixtures, particularly ‘softer’ binder, high binder content and, finally, low air void content mixtures. Using four different aggregate types, together with ‘hard’ 10/20 pen and ‘softer’ 40/60 pen bitumen, the parameters of pressure, temperature and duration were altered, either one at a time or in combination, to arrive at a suitable combination for testing more commonly used 40/60 pen material. The optimum combination of parameters to allow the SATS procedure to be used for a wide range of typically used asphalt mixtures was found to be 0.5 MPa pressure, 85°C temperature and 24 h duration. The revised SATS durability conditioning protocol was still able to successfully discriminate between ‘poor’ moisture susceptible aggregate and ‘good’ material.

The Medialization of Regenerative Medicine: Frames and Metaphors in UK News Stories

Mass media interest in biomedicine and biotechnology is steadily growing and the communication strategies and rhetorical frames used by journalists are increasingly exploited by scientists in the promotion and legitimation of their research. This chapter explores the medialization of regenerative medicine through an investigation of the sources, metaphors and interacting scientific, political, commercial and patient discourses that frame this emerging field in UK newspaper coverage. It is argued that framing tends to reinforce and amplify the optimistic predictions of scientific and clinical experts and could ultimately prove detrimental to the social acceptance and uptake of cell and regenerative therapies.

Rheological and fracture characteristics of low penetration grade bitumen

ABSTRACT Interest in the rheological and fracture characteristics of low penetration grade bitumens has increased in recent times due to greater use of progressively stiffer base materials and the growing concern over the durability of these extremely hard, high stiffness modulus materials. This paper investigates the high and low temperature rheological characteristics, tensile fracture modes and cohesive properties of a series of semi-blown, polymer modified and straight-run (direct distillation) low (15) penetration grade bitumens using a Brookfield (rotational) viscometer, Dynamic Shear Rheometer (DSR), Bending Beam Rheometer (BBR), Direct Tension Tester (DTT) and Vialit Pendulum Cohesion apparatus. The binders have been tested in their virgin (unaged) condition and after short-term, Rolling Thin Film Oven Test (RTFOT) and long-term, High Pressure Ageing Test (HiPAT) ageing. The results show considerable differences in the high and low temperature rheological and fracture properties of the 15 penetration grade bitumens as a function of their production method especially after ageing, although only minor differences in terms of their cohesive properties. In general the semi-blown 15 pen bitumen showed a higher susceptibility to ageing than the polymer modified and direct distillation 15 pen bitumens and an increased elastic “brittle” response to loading in terms of DSR, BBR and DTT test data.

Development of the saturation ageing tensile stiffness (SATS) test

This paper describes the development of a combined ageing/moisture sensitivity laboratory test to evaluate the performance of coated macadam binder course and base mixtures with relatively low binder contents and relatively high air void contents. The test is known as the saturation ageing tensile stiffness (SATS) test, and consists of initial saturation prior to placing compacted asphalt core samples in a high-temperature and high-pressure environment in the presence of moisture for an extended period of time. The stiffness modulus measured after the test divided by the stiffness modulus measured before the test (retained stiffness modulus), and the specimen saturation after the test (retained saturation), are used as an indication of the sensitivity of the compacted mixture to combined ageing/moisture effects. The test was used to reproduce in the laboratory the loss of stiffness modulus observed on a trial site where high modulus base (HMB) had been used. Two different aggregate types (basic and acidic...