Polymer modified asphalt emulsions for treatment of road surfaces

Abstract

A composition for rejuvenating asphalt pavement according to the present invention comprises an asphalt binder, water, a cationic surfactant, a recycling agent, and a cationic, co-agglomerated styrene butadiene rubber latex, which includes sulfur and a vulcanizing agent. The composition is also useful as a scrub seal, fog seal, sand seal as well as for crack filling and the prevention of reflective cracking. The inventive composition may be used in emulsions with different setup times. The invention also includes a method for treatment of aged and cracked asphalt by application of the disclosed compositions.

Description

[0001] The present invention relates to asphalt emulsions for treatment of road surfaces. More specifically, the present invention relates to improvements in methods for treatment of aged, cracked or otherwise deteriorated road surfaces paved with asphalt. The improvements provide stronger, more stable and less costly emulsions than those previously available.[0002] The annual worldwide consumption of asphalt for road surfacing applications exceeds 90,000,000 tons. Europe and North America are responsible for approximately two thirds of this consumption. In the United States more than four million miles of roads are paved with asphalt. Asphalt pavement deteriorates with use, due to oxidation of asphalt binder, high loads and varying climatic conditions. A recent study demonstrates a statistically significant relationship between a country's economic development and its road infrastructure.sup.1. Accordingly, maintenance and rejuvenation of asphalt surfaced roads is a matter of some ...

AI Technical Summary

Benefits of technology

[0007] Although the invention of the '428 patent continues to be a substantial commercial success, there continues to be a need for asphalt modifiers with performance that is superior to PASS, yet that can be manufactured at a lower cost. Accordingly it is an object of the invention to provide a modifier for asphalt paving that provides improved flexibility, faster setup time, and superior performance at low temperatures. These and other advantages of the present invention are described in detail below.

[0029] When polymerization is terminated, butadiene and styrene mononers removed, the solids content is below 50%, and also latex particle size is below 100nm, typically 50-70 nm. For these small particles and very narrow size distribution, the latex viscosity becomes above 1000 cP (1 Pas) at above 50% solids content. This latex is then agglomerated to produce larger particles, with a distribution of particle size ranging from 1 00nm to between 2 and 3 microns. The result is to substantially decrease the viscosity of the latex, to about 50 mPas or less at about 50%. Even after removal of water, leaving the solids content at 70-72%, the viscosity of the SBR latex is below 2000 cP (2 Pas).

[0035] Asphalt emulsions used in road construction and maintenance are either anionic or cationic, based on the electrical charge of the asphalt particles, which is determined by the type of the emulsifying agent used. The asphalt contents of these emulsions are, in most cases, from 55 to 75% and prepared using a high shear mechanical device Such as a colloid mill. The colloid mill has a high-speed rotor that revolves at 1,000-6,000 rpm with mill-clearance settings in the range of 0.2 to 0.5 mm. A typical asphalt emulsion has a mean particle size of 2-5 micrometer in diameter with distribution from 0.3 to 20 micrometer. U.S. Pat. No. 5,180,428 refers to a non-ionic surfactant for ease of emulsion preparation with non-ionic chloroprene latex. This invention employs a cationic emulsifier-cationic latex, or non-ionic emulsifier-cationic latex combination for better asphalt adhesion to aggregate, which results in enhanced asphalt antistripping capability.

Problems solved by technology

Asphalt pavement deteriorates with use, due to oxidation of asphalt binder, high loads and varying climatic conditions.

Oxidation of asphalt binder during its service time, climate conditions and use of road surfaces, particularly by heavy loads, result in deterioration of the road surfaces over time.

For example, repeated contraction of the road surface during the cold winter nights due to temperature changes results in formation of perpendicular cracks in pavement, known as cold fractures.

The asphalt binder becomes too soft during the hot summer days, resulting in a permanent deformation of the road surface under repeated heavy loads, termed "rutting".

In addition, as a result of continuous mechanical stress, road surfaces become fatigued, resulting in formation of alligator skin-like cracks, known as fatigue fracture.

However, removal and replacement is expensive and wasteful.sup.3.