Paving compositions and methods for their use

Details Paving compositions and methods for their use Paving compositions and methods for their use

2002-06-27

2004-09-07

Klemanski, Helene (Department: 1755)

Compositions: coating or plastic

Coating or plastic compositions

Bituminous material or tarry residue

C106S284400, C427S138000

Reexamination Certificate

active

06786963

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a paving composition for use in road construction and related applications. In particular, the invention relates to an asphalt-based paving composition with an anti-stripping agent to improve the adhesion of the asphalt to mineral aggregate.
BACKGROUND OF THE INVENTION
Bituminous materials, such as asphalt, have been used in the building of roadways, driveways, and the like. In addition to asphalt, mineral aggregates are also used to increase the strength and to prolong the life of such surfaces. In road construction, bitumen-aggregate mixtures are applied to the road surface. These bitumen-aggregate mixtures generally can be obtained by mixing anionic or cationic asphalt emulsions with a mineral aggregate, such as stone chips, gravel or sand, or by mixing free flowing heated asphalt (asphalt cement) with a pre-dried mineral aggregate, by a hot mix process. The pre-dried aggregate can also be mixed with asphalt diluted in a hydrocarbon solvent, known as cutback asphalt.
The quality of the road surface is generally dependent upon the strength of the bonds between the asphalt and aggregate after setting of the composition. Poor service performance is, in part, due to poor adhesion between the asphalt and aggregate, resulting in the stripping off of the asphalt from the aggregate surface.
Asphalt compositions have relatively poor adhesion to mineral aggregates in the presence of water. Since the aggregate is preferentially wetted by water, even if the aggregate is dry at the time it is blended with the asphalt, the eventual penetration of water into the composition reaches the aggregate and interferes with the bond between the aggregate and the asphalt. The result of this stripping is flaked pavement and pot holes. Stripping problems also generally occur if the aggregate is poorly dried, if sandy carbonate aggregate containing a large amount of quartz particles is used, if carbonate aggregate is covered with dust, or if igneous (silicate) aggregates, such as granite, diorite, gabbro, diabase, or basalt, that strip in the presence of external water are used. To avoid such failures, adhesion improving agents known as “anti-stripping agents” are commonly added to the asphalt. Before the mixing operation, these agents are added to the bituminous binder to reduce its surface tension and to induce on the binder an electrical charge opposite to that of the aggregate surface. Lower surface tension gives improved wettability of the aggregate, and charge reversal enhances bond strength by increasing Coulomb's attractive forces.
Cationic substances, particularly amines, have been traditionally used as anti-stripping agents. The cationic substances increase the hydrophobicity of the aggregate, making the aggregate resistant to the penetration of water so that water seeping into the asphalt does not tend to destroy the bond between the asphalt and the aggregate. The addition of the cationic substances tends to make the aggregate sufficiently water resistant that a good bond with the asphalt is formed. Among the cationic materials which have been used as adhesion promoters with asphalt are primary alkyl amines (such as lauryl amine and stearyl amine) and alkylene diamines (such as the fatty alkyl substituted alkylene diamines). Because these amines may rapidly lose their activity when combined with asphalt and stored at elevated temperatures for an extended period, it has therefore been necessary to combine the amine with the asphalt at the work site when the asphalt is combined with the aggregate, which in practice presents difficulties in obtaining a homogeneous mixture. It is also noted that these amines are generally corrosive and may have an unpleasant smell.
Various asphalt formulations have been reported in attempts to enhance the properties of paving compositions while avoiding the above-described difficulties. U.S. Pat. No. 4,447,269 offers cationic oil in water type bituminous aggregate slurries. The emulsion comprises bitumen and a reaction product of a polyamine and a polycarboxylic acid, and water. Lime or cement can be added to reduce the setting time of the mixture.
U.S. Pat. No. 4,721,529 suggests the preparation and use of asphalt admixtures with the reaction product of an amine antistrip and an acid salt. The acid salt is a divalent or trivalent metal salt of an inorganic acid.
U.S. Pat. No. 5,443,632 suggests cationic aqueous bituminous emulsion-aggregate paving slurry seal mixtures. The emulsifier is the product of reaction of polyamines with fatty acids and rosing, and a quaternizing agent.
U.S. Pat. No. 4,806,166 proposes preparation of an aggregate comprising asphalt and an adhesion improving amount of an anti-stripping agent comprising the aminoester reaction product of a tall oil fatty acid and triethanolamine. The reaction product is of low viscosity, has good coating performance, and is inexpensive.
U.S. Pat. No. 5,019,610 offers an asphalt composition comprising a blend of a thermoplastic rubber polymer and a fatty dialkyl amide, and asphalt cement. The preparation method requires only gentle stirring. The amide has a C
6
-C
22
alkyl group attached to the carbonyl, and two C
1
-C
8
alkyl groups attached to the amide nitrogen. The compositions offer good viscosities at relatively low residue percentages. The compositions are offered for use in road paving, asphalt roofing cements, mastics, moisture barriers, joint and crack fillers, and sheeting.
U.S. Pat. No. 4,430,127 suggests preparation of a bitumen and epoxylated polyamine composition. The compositions provide improved adhesion between aggregate materials and the bitumen material. At least two of the amino nitrogen atoms are separated by six carbon atoms.
U.S. Pat. No. 4,462,840 proposes use of a cation-active emulsifier which is the product of a polyamine and polycarboxylic acids. The emulsifier is useful in producing aqueous bituminous emulsion-aggregate slurries.
Although significant effort has been spent on improving the adhesion between mineral aggregates and asphalt, there continues to exist a need for paving compositions with improved adhesion between mineral aggregate and asphalt. Preferably, the paving compositions should not have an unpleasant odor or smell.
SUMMARY OF THE INVENTION
Paving compositions comprising a bituminous material such as asphalt and an amide compound are disclosed. The amide is preferably a diamide. The compositions can further comprise mineral aggregates or other materials suitable for use in paving applications. The compositions can be used in new road construction, or in road repair applications.
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the invention provide a paving composition and methods for making and using the composition. The paving composition comprises a bituminous material, such as asphalt, and a reaction product of at least one polycarboxylic acid reacted with at least one polyamine or amine. Preferably, the composition is substantially free of water. The composition is preferably not an emulsion. The paving composition can further include mineral aggregate mixed with the bituminous material and the reaction product. Preferably, the reaction product of the polycarboxylic acid and the polyamine or amine is an amide compound. The amide compound includes one or more amide functional groups:
Preferably, the amide compound is a diamide or a compound including multiple amide functional groups (i.e., three or more amide functional groups). The term “multiamide compound” used herein refers to an amide compound with two, three, four, five, six, seven, or more amide groups per molecule. In some embodiments, polymeric amide or polyamide is used as an anti-stripping agent; in other embodiments, polymeric amide or polyamide is substantially absent in a paving composition.
It is found that an amide compound, such as a diamide compound, can be used to enhance the adhesion between a bituminous material and mineral aggregate without using water. Thus, it functions as an anti-stripping agent. To make a paving composit

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