Effect of Variation in Blending Variables on the Properties of CRMB
Authors: Memon N.A., Ansari K., Almani Z.A.
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The enhancement in the properties of the modified blends largely depends on the proper understanding of the interaction between CR (Crumb Rubber) and bitumen, where the CR particles swell after absorbing lighter fraction from the bitumen phase. However, the properties of CRMB (Crumb Rubber Modified Bitumen) blends at a wide range of temperatures are considered to be somewhat unclear due to the various interaction effects of CR and base bitumen. This largely depends on the interaction conditions such as blending time, temperature, speed and device, which may alter the properties of the blend to great extent. In this study, influence of the interaction condition was investigated by looking at the viscosity with a Brookfield viscometer. For this, CR and bitumen proportions along with other material characteristics were kept constant to understand the effect of interaction parameters of the properties of the CRMB blend. A total of 12 CRMB blends were produced with unvarying combinations of material constituents. However, selected variation in the blending parameters were; blending device, duration, speed and temperature. Observations from this laboratory study indicated: (1) blending performed with the high shear mixer resulted in higher viscosity values compared to the blends produced with the low shear mixer; (2) reduced blending time was required to achieve peak and ultimate stable viscosities, when blends were produced with the high shear mixer; (3) blending temperature of 180°C has resulted in the blends with consistent properties for longer blending durations compared to the blends produced at higher temperature. As a result, results with high shear mixer were always promising, which required comparatively lower interaction temperature, time and speed.