Polymer modified bitumen emulsions (PMBEs) are a special class of bituminous emulsions. There are several ways to prepare PMBEs. One possibility is to emulsify a PMB; another is to add a latex to a bitumen emulsion, either prior to the colloid mill or after. In all cases, the resulting PMBE shows improved rheological properties of the residue after breaking.
The properties of paving bitumen and bituminous mixes can be improved by the addition of certain polymers and additives. In order to expand the application of asphalt and to improve its properties, the bitumen it contains is modified. High-quality, polymer-modified bitumens (PMB) are special, high-performance binders. The polymers change the elasto viscous behavior of the bitumen produced and make the binder more suitable to handle high stress. They are characterized by their high strength and high-temperature stability. You will find them, for instance, in areas of airports and roads which are heavily used.
At room temperature, bitumen is an extremely tough, black mass. Only when it is heated does it begin to liquefy slowly. When PMB is produced, the polymer is added to the hot bitumen and stirred. This is usually done to date in a batch process (in a large vessel with a moderately efficient stirring mechanism). This process is very time-consuming due to the fact that clumping delays the mixing process.
The raw bitumen at 180 degrees centigrade is pumped at a controlled feed rate and pressure into a specially designed heavy duty high shear milling machine. High quality polymers are simultaneously dosed into the mill using a polymer dosing system. The formulation is controlled by a PLC to manufacture the required grade of PMB. On exiting the mill chamber the processed product is transferred to the finished product storage tank provided with a recirculation pumping arrangement.
By contrast, the production of polymer-modified bitumen in the inline process is efficient in every respect. In one step, the liquid bitumen and solid polymer are added, mixed together, and finely dispersed and homogenized at the same time. The latter takes place using the Hindu Engineers manufactured inline disperser, which accelerates the dissolving process and reduces the mixing time.
>> Better product quality due to consistent mixing technology.
>> Fewer process steps: The polymer/bitumen premix is completely eliminated.
>> Less time required: Up to 50% reduction compared to a standard batch process.
>> Less space required for machines and storage.
>> Higher flexibility in terms of the production quantity.
>> Lower energy costs.
Bituminous mix prepared with modified bitumen are quite suitable for renewal course and overlay material on surfaces which are badly cracked and subjected to heavy traffic. They perform better than ordinary bitumen in high rainfall areas and in situations where aggregates are prone to stripping. Due to better creep resistance they can be used at busy intersections, bridge decks and roundabouts etc for increased life of the surfacing.
PMBEs have been successfully used for several decades in the road industry. They represent a class of high performance binders whose preferred application is in the form of chip seals and as micro surfacing for heavily trafficked pavements (highways, airports etc).For open pored asphalt layers, for water proof coatings.