Salah E. Zoorob

A study of crumb rubber modified bitumen used in South Africa

In South Africa, an empirical characterisation of crumb rubber modified (CRM) bituminous binders has historically been the only means of predicting their performance in pavement layers, short of constructing pavement test sections. An improved characterisation is provided by means of rheological analysis using a dynamic shear rheometer (DSR). However, the heterogeneous morphology of CRM bitumen makes it a challenge to test using current methods and equipment. DSR testing of CRM bitumen requires a plate gap adjustment to avoid any influence by the rubber particles. This has been done by monitoring the effect of changing the DSR plate gap setting on the measured linear visco-elastic properties of the binder. An adjusted gap was adopted for rheological measurements so as to characterise CRM bitumen properties with ageing. But, the incomplete recovery of CRM binder from asphalt/seals makes it impossible to monitor the rheological properties of the in situ binder within a pavement layer. This has led to indirect methods of investigating relationships between tested properties of the pure CRM bitumen to those of the in situ binder.

The Use of Bitumen Linear Viscoelastic Properties to Assess Rutting Sensitivity

The use of viscosity temperature relationships to predict creep performance of road bitumens have been shown to be inadequate in particular with respect to the analysis of polymer modified binders. In this paper we explore the origins of the US Strategic Highway Research Programmebinder performance grading system and detail two examples of more recent developments towards improved creep characterisation.Starting from first principles, an equation to analyse the ratio of dissipated to stored energy during sinusoidal loading of viscoelastic bitumen was derived. The energy equation was contrasted with an empirical relationship proposed by Anderson D.A., and with a second more theoretical derivation proposed by Shenoy A.Using frequency sweep data from a conventional 40/50 pen grade bitumen and a proprietary SBS modified binder, the applicability of the energy equation was subsequently compared to the two aforementioned post-SHRP creep relations. Recommendations are made regarding the suitability of the proposed relations in ranking bitumen creep performance.

Sustainable and Eco-Friendly Vege Roofing Tiles: An Innovative Bio-Composite

This paper presents a research study conducted on the usage of vegetable oil for the production of eco-friendly Vege roofing tiles. Conventional roofing tiles which constitute of concrete and clay are considered as environmentally unfriendly because of the significant amount of greenhouse gas emission during their production. An entirely novel methodology of utilizing catalyzed vegetable oil is proposed which can totally replace the use of traditional binders like cement and clay. Limited trails conducted on prototypes samples revealed that when catalyzed vegetable oil mixed with aggregates, properly compacted and heat cured at 190oC for 24 hours, have shown flexural strength up to 9.5 MPa. The superior strength gain of these prototype samples was considered due to the use of the catalyst with vegetable oil, which resulted in the initiation of catalytic oxy-polymerization set of reactions during heat curing, converting vegetable oil to solid, hard polymer which is considered responsible for strength achievement factor for these novel Vege roofing tiles. All prototypes samples were tested for performance indicators like water absorption, permeability, and flexural strength according to ASTM standards. Moreover, the susceptibility of oil leachate from the tiles oil, when tested using electrical conductivity method showed a negligible amount of the electrical conductivity. Moreover, the estimated embodied energy requirements for these tiles were found quite less when compared to conventional tiles.