A total solution to a hard problem
Increasing pressure on finite natural resources, coupled with the problems associated with traffic disruption during structural repairs has enticed the Highways Agency to look at the use of EME-type materials in base and binder courses.
EME has been successfully used in France for a number of years and combines strict protocols of aggregate-specific mix design, use of high-modulus bitumens and careful optimization of those bitumen contents to product thin structural layers with long-life performance.
The Modulotal range of binders from Total Bitumen exhibit high-modulus characteristics that contribute to the indirect tensile stiffness modulus (ITSM) of the mixture in a very different way to the ‘normal’ paving-grade binders. The elastic components of the bitumen positively contribute to the stiffness of the mixture, adding to the stiffness contribution of the aggregate interlock in the dense mixture design. At the relative extremes of binder richness moduli, the ITSM of the mixture remains at around 10Gpa. This ensures the more binder-rich mixtures still contribute adequate stiffness to perform as an effective ‘load spreader’, thus reducing strain levels at the bottom of the base layer, while retaining adequate fatigue resistance to ensure durability.
Standard EN 12591 paving-grade bitumens do not show this level of stiffness contribution, and as a consequence the ITSM stiffness tends to drop as the binder richness increases, so requiring a compromise between stiffness and durability in this range of binder richness moduli.
Total Bitumen, Chain Caul Way, Riversway, Preston, Lancs PR2 2TZ; tel: (01772) 729302; fax: (01772) 724713.
EME has been successfully used in France for a number of years and combines strict protocols of aggregate-specific mix design, use of high-modulus bitumens and careful optimization of those bitumen contents to product thin structural layers with long-life performance.
The Modulotal range of binders from Total Bitumen exhibit high-modulus characteristics that contribute to the indirect tensile stiffness modulus (ITSM) of the mixture in a very different way to the ‘normal’ paving-grade binders. The elastic components of the bitumen positively contribute to the stiffness of the mixture, adding to the stiffness contribution of the aggregate interlock in the dense mixture design. At the relative extremes of binder richness moduli, the ITSM of the mixture remains at around 10Gpa. This ensures the more binder-rich mixtures still contribute adequate stiffness to perform as an effective ‘load spreader’, thus reducing strain levels at the bottom of the base layer, while retaining adequate fatigue resistance to ensure durability.
Standard EN 12591 paving-grade bitumens do not show this level of stiffness contribution, and as a consequence the ITSM stiffness tends to drop as the binder richness increases, so requiring a compromise between stiffness and durability in this range of binder richness moduli.
Total Bitumen, Chain Caul Way, Riversway, Preston, Lancs PR2 2TZ; tel: (01772) 729302; fax: (01772) 724713.
