Determination of the Properties of Natural Rubber Crumb –Modified Bitumen Blends (NRCMB)

Abstract

Bitumen is a complex mixture of organic molecules comprising mainly of hydrocarbons and it is use as a binder in constructions and in tarring of roads. This study was conducted to investigate some of the physical and mechanical properties of bitumen modified with natural rubber crumb (NRC) when cured and when left uncured. Five different blend ratios (2%, 6%, 10%, 14% and 18%) NRC by mass of the bitumen were used as modifiers. Penetration, softening point, Viscosity and Ductility tests were conducted on the ordinary bitumen and the blends. These basic property tests were used to explain the effect of natural rubber crumb and vulcanization on the binder (bitumen). Tests conducted gave a penetration value for ordinary bitumen 60/70 grade as 50.0mm and the value decreased to 32.5mm, 20.5mm, 19.8mm, 18.0mm and 17.4mm as the blend ratio increased from 2% to 18% respectively for the vulcanized mix and 46.0mm, 40.0mm, 36.0mm, 38.0mm and w41.0mm for the un-vulcanized blends as the blend ratio also increased from 25 to 18%. For softening point, 40⁰C was enough to soften ordinary Bitumen but as the blend ratio increased from 2% to 18%, the temperature increased to 53.0⁰C, 56.0⁰C, 59.0⁰C, 62.0⁰C and 66.0⁰C respectively for the vulcanized mix and for the uncured, 50.0⁰C, 52.0⁰C, 48.0⁰C and 46.0⁰C respectively. As the blending ratio increased, Viscosity also increased from 8seconds for the ordinary bitumen to 12sec, 23sec 50sec, 72sec and 84sec for the vulcanized mix and 10sec, 15sec, 27sec, 39sec and 48sec for the un-vulcanized mix respectively. Similarly, ductility also increased from 105cm for the ordinary bitumen to 124.0cm, 136.0cm, 151.0cm, 178.0cm and 200cm for the vulcanized blends and 115.0cm, 120.0cm, 129.0cm, 139.0cm and 152.0cm for the un-vulcanized mix respectively. These findings shows that NRC can be used to influence the chemical and physical properties of bitumen binder.