Essay On Crumb Rubber

A detailed review of research works carried out related to the present study are described as below. The penetration is a measure of hardness or softness of bitumen binder which shows an effect by adding crumb rubber to bitumen binder; it decreases as rubber content is increased. The penetration shows lower values as rubber content increases at different mix conditions of rubberized bitumen binder, indicating that the binder becomes stiff and more viscous The softening point refers to the temperature at which the bitumen attains a particular degree of softening. The use of crumb rubber in bitumen modification leads to an increase in the softening point and viscosity as rubber crumb content increases (Mahrez, 1999; MAshaan et al , 20011a). Mahrez and Rehan

For blending of crumb rubber with bitumen, it was heated to a temperature of 160 °C and then crumb rubber was added. For each mixture sample 15% [3] of crumb rubber by weight of four different sizes is used, which are coarse (1 mm - 600 μm); medium size (600 μm - 300 μm); fine (300 μm-150 μm); and superfine (150 μm - 75 μm). The blend is mixed manually for about 3-4 minutes. The mixture is then heated to 160 °C and the whole mass was stirred using a mechanical stirrer for about 50 minutes. Care is taken to maintain the temperature between 160 °C to 170 °C. The contents are gradually stirred for about 55 minutes. The modified bitumen is cooled to room temperature and suitably stored for testing.

4.2 Common tests on the modified bitumen

Penetration test and Softening point tests on both the plain and modified CRMB are performed and the results are analyzed for further study.

4.3 Preparation of Bituminous mix

For the present study Bituminous concrete mix gradation was used following specifications stated by MORT & H table