Introduction
Polymer modification of bitumen has been commonly performed since the 1980s to decrease bitumen (and pavement) susceptibility to high and low temperatures, reducing common failure mechanisms such as rutting and cracking in bitumen concrete and bituminous roads.[1]
The addition of thermoplastic or elastomeric polymers has commonly performed bitumen modification.[1]
However, there are just a few studies on bitumen blends using multiple materials, seeking for specific advantages provided by the addition of these modifiers in applications such as bitumen waterproofing and bitumen driveways.[1]
This work describes the results obtained after the preparation of multicomponent polymer-bitumen blends (MC) based on an 80/100 penetration grade bitumen with varying amounts of (i) Polyethylene wax (PW); (ii) Styrene–Butadiene–Styrene copolymer (SBS); and (iii) crumb rubber (CR).[1]
Composition of Polymer Modified Bitumen
Polymer modified bitumen (PMB) is composed of base bitumen and polymer additives that enhance its properties. The composition may vary depending on the specific application and performance requirements. Here is a detailed description of the components:
1.Base Bitumen
Source: The bitumen derived from crude oil processing at ambient temperature is stable and poses no health hazard.[2]
Types: Penetration grade bitumen (e.g., 60/70, 80/100) or viscosity grade bitumen.
Function: It acts as the primary binder, providing basic adhesive properties and waterproof properties.
2. Polymer Modifiers
Polymer modifiers are added to the base bitumen to improve its performance characteristics. Commonly used polymers include:
Styrene-Butadiene-Styrene (SBS):
The styrene-butadiene-styrene (SBS) is a kind of thermoplastic elastomer which has the same elasticity with the rubber in normal temperature, and can be melt to flow at high temperature like plastics, called plastic material.[3]
Composition: A thermoplastic elastomer made from styrene and butadiene.
Properties: A copolymer like SBS has properties of both polymers of which it is composed. In the case of SBS, the polystyrene segments give the product strength and durability, while the polybutadiene segments provide flexibility. The substance acts like natural rubber at room temperature, but becomes soft and plastic when heated. The latter property means that products made of SBS can be formed into a variety of shapes.[4]
Applications: SBS is normally used in making not only waterproof membranes but also sealing material and waterproof paint.[3]
Ethylene Vinyl Acetate (EVA):
Ethylene-vinyl acetate (EVA) has been widely employed in the modification of asphalt binder due to the rigid three-dimensional network structure and special functional groups. EVA modified asphalt had excellent high-temperature performance while its low-temperature performance was poor due to its stiff characteristics. It was also found that under large strain conditions, the fatigue performance of EVA modified asphalt was rather poor. However, its fatigue performance was comparable to that of Styrene-Butadiene-Styrene (SBS) modified asphalt under small strain conditions.[5]
Composition: Ethylene-vinyl acetate (EVA) is the copolymer of ethylene and vinyl acetate. The weight percent vinyl acetate usually varies from 10 to 40%, with the remainder being ethylene.[6]
Properties: The material has good clarity and gloss, low-temperature toughness, stress-crack resistance, hot-melt adhesive waterproof properties, and resistance to UV radiation.[7]
Applications: In the construction industry, EVA is often used to seal cracks, crevices, or corners, such as when sealing between windows and door frames or incorporated into waterproof sealing materials.[8]
Polypropylene (PP) and Polyethylene (PE):
Composition: Thermoplastic polymer derived from propylene and ethylene.
Properties: Improved toughness and high temperature performance.
Applications: Used in areas requiring high temperature resistance.
Crumb Rubber:
Composition: Recycled rubber from used tires.
Properties: Increases flexibility and crack resistance.
Applications: It is often used in road construction to increase durability and reduce waste.
3. Additives and Stabilizers
To ensure the compatibility and stability of PMB, various additives and stabilizers are included:
Antioxidants:
Function: Prevent oxidative ageing of bitumen.
Common Types: Hindered phenol, amine.
UV Stabilizers:
Function: Protect bitumen from ultraviolet light degradation.
Common Types: Benzotriazoles, benzophenones.
Compatibilizers:
Function: Enhancing the interaction between bitumen and polymer modifiers.
Common Types: Maleic anhydride grafted polymers.
Plasticizers:
Function: Improve workability and flexibility.
Common Types: Phthalates, adipates.
4. Fillers and Extenders
Sometimes, fillers and extenders are added to modify the physical properties and reduce cost:
Mineral Fillers:
Examples: Limestone, fly ash, and silica.
Function: Improve stiffness and durability.