These guidelines provide practitioners with a description of the current materials and selection criteria for Polymer Modified Binders (PMBs) together with some details of procedures for handling, storage, application and safety.
The current usage of PMBs in sprayed seals, membranes, asphalts and crack and joint sealants is covered in this guide. PMBs are widely available and are used for a variety of applications including crack control, resistance to deformation under heavy loads, fatigue resistance, aggregate retention and waterproofing as well as sundry special purpose uses. It is anticipated that the variety of these materials and their demand will increase in the future.
These guidelines should be used in conjunction with specifications and existing guides to good practice for sprayed sealing, asphaltic works, slurry surfacing and crack sealing, together with proprietary information relating to particular products chosen.
The recommendations embodied in these guidelines are based on experience gained from full scale field trials, appropriate laboratory testing and routine works during recent years. Due to the variety of applications for PMBs, there are only limited data available correlating laboratory test results with field performance. These guidelines comprise the current views of experienced practitioners and specialist material suppliers.
Several types of polymer can be utilised in PMBs. Some polymers require additives to ensure satisfactory dispersion in the bitumen. Common polymeric materials used to date include:
* Styrene Butadiene Rubber latices (SBR)
* Styrene Butadiene Styrene (SBS) block copolymers
* Ethylene Vinyl Acetate (EVA) copolymers
* Natural Rubber
* Scrap Rubber (SR)
* Ethylene Methacrylate (EMA)
* Neoprene and Acrylic
PMBs may be supplied as factory blends ready for direct job application or as concentrates (liquid or slabs). Neat polymers are also available for plant or field blending and may be in the form of granules, pellets or powders. Polymers are also available in latex (water emulsion) form. Some PMBs are used as emulsions while others are used as hot binders. In each case there are usually manufacturer’s instructions pertaining to their usage, storage, handling and safe practice. According to the application e.g. sprayed seal, asphalt etc, a suitable grade of a particular PMB should be selected for the job.