Utilisation of granulated scrap tyre in asphaltic concrete mixes: a study of Agbabu Plain Bitumen in Nigeria
Rubber produced from scrap tyres known as crump rubber, can be used in asphalt mixtures either as a binder modifier (wet process) or as a fine and /or coarse aggregate replacement (dry process). This study is aimed at assessing the viability of utilizing Granulated Scrap Tyre Rubber (GSTR) as a modifier in asphalt concrete mixes prepared with bitumen obtained from natural bitumen field in Agbabu, Ondo State, Nigeria. In order to ascertain the binder properties of this bitumen in comparison with the standard specification of Asphalt Institute, American Standards for Testing and Materials (ASTM) and Federal Ministry of Works and Housing (FMWH), specific gravity test, softening point test, penetration test and flash point test were carried out. Used tyres were shredded and granulated into fine particles, 1-3% of it was added to asphalt concrete mixes for both wearing and binder course. Marshall Test method was employed using dry method of rubberized asphalt concrete. The results obtained showed that the stability and bulk density of the compacted asphalt concrete specimen decreased with increase in dosage of GSTR while percentage air void together with percentage void mineral increased. It was concluded that utilizing GSTR for heavy traffic may be feasible if the bitumen sample is modified or wet method is used.