Performance of Polymer Modified Bitumen PDF

Performance of Polymer Modified Bitumen INTRODUCTION Bitumen has been used for thousands of years and its importance as a valued engineering material continues to increase. The interest in the modification of bitumen using polymers, whether virgin, scrap or polymer blends, is intense. Polymer mod...

Performance of Polymer Modified Bitumen INTRODUCTION Bitumen has been used for thousands of years and its importance as a valued engineering material continues to increase. The interest in the modification of bitumen using polymers, whether virgin, scrap or polymer blends, is intense. Polymer modified bitumen (PMB) is one of the specially designed and engineered bitumen grades that are used in making pavement, roads for heavy duty traffic and home roofing solutions to withstand extreme weather conditions. Polymer modified bitumen (PMB) Pavements designed and constructed for heavy-duty traffic and extreme weather conditions require specially designed engineered bitumen Grades. By changing the characteristics of normal bitumen with the addition of a polymer, either they are of elastomeric nature or elastomeric. We succeed to obtain bitumen that allows the mixture to be more cohesive, with much more strength and significant higher resistance to parameters like fatigue and permanent deformations for road pavements. Need for Bitumen Modification Need for Bitumen Modification When a polymer is added to regular bitumen, it becomes more elastomeric, which provides it with additional elasticity. The polymer that is added is styrene butadiene styrene (SBS), which acts as a binder modification agent. The primary objective of SBS polymer modified bitumen is to provide extra life to pavement, roads and construction designs. Some of the qualities exhibited by PMB are: Higher rigidity Increased resistance to deformation Increased resistance to cracks and stripping Better water resistance properties High durability Advantage of using polymer modified bitumen Stronger road with increased marshall stability value and greater Rigidity. Better resistant towards rainwater and water stagnation. No stripping and no potholes. Better resistance to permanent deformation Reduction in pores in aggregate and hence less rutting and raveling. Much higher durability Bitumen behaviour – visco-elastic Targets of modification – Temperature susceptibility Targets of modification – Increased failure envelope Elastomers ▪ Thermoplastic rubbers ▪ High elastic response ▪ Resist deformation by stretching with quick recovery ▪ Natural or synthetic rubbers ▪ Block copolymers, homopolymers & random copolymers ▪ Styrene butadiene styrene (SBS) Physical structure of SBS  Plastomers ▪ Thermoplastic polymers ▪ Tough, rigid, three-dimensional network ▪ Exhibit high strength under initial loading but may fracture with accumulated strain ▪ Polyethylene, polypropylene, polyvinyl ▪ chloride, polystyrene ▪ Ethylene vinyl acetate (EVA) UK PMB market Bitumen market - circa 2 million tonnes PMBs > 10% Types of Polymer Elastomeric – SBS, SB Plastomeric – EVA Mostly in surfacing (thin or SMA) Increase in base or binder courses Crumb Rubber Modifier There are two methods of blending reclaimed rubber with bitumen. A commonly used method is the wet process, in which reclaimed tire rubber powder of 10% to 30% by total weight is blended with bitumen at elevated temperature. The other method is referred to as the dry method, in which reclaimed tire rubber powder is added to the hot aggregate in quantities of 1% to 5%. Degree of Modification ▪ Polymer type ▪ Polymer concentration ▪ Degree of dispersion ▪ Bitumen / polymer compatibility ▪ Bitumen grade and chemistry Chemical cross-linking Crosslinking is the method by which one polymer chain is connected to another, typically by a covalent or ionic bond. Sulfur vulcanization as the cross-linking agent is most widely used to promote the chemical reaction between asphalt and SBS polymer and improve the performance of modified asphalt Morphology tests Morphology tests for polymer-modified bitumen (PMB) are essential to understand the distribution and interaction of polymers within the bitumen matrix. Morphology tests Fluorescent Microscopy: This technique is widely used to observe the dispersion of polymers in bitumen. Under UV light, the polymer-rich phase fluoresces, allowing for the visualization of the polymer distribution. Scanning Electron Microscopy (SEM): SEM provides detailed images of the surface morphology of PMB, helping to analyze the microstructure and the interaction between the polymer and bitumen. Dynamic Shear Rheometry (DSR): While primarily a rheological test, DSR can be used alongside morphological analysis to understand the viscoelastic properties of PMB and how they correlate with the polymer distribution. Differential Scanning Calorimetry (DSC): DSC measures the thermal properties of PMB, which can be related to the morphology and phase transitions of the polymer within the bitumen. Polymer modified morphology EVA polymer modification SBS polymer modification Storage Stability G* isochronal plot @ 0.02 Hz –SBS PMB isochronal plot @ 0.02 Hz – SBS PMB Polymer modification PMBs can improve deformation resistance Rutting Fatigue testing PMBs for fuel resistance