ADDITIVE COMPOUND FOR WARM MIX ASPHALT AND PROCESS OF SYNTHESIS THEREOF

Abstract

The present invention provides additive compound for warm mix asphalt (WMA) for the paving of road surfaces, whereby the additive compounds facilitate the mixing, lay down and compaction of asphalt mixes at low temperatures while retaining the mechanical properties of the asphalt composition. Further, the present invention provides a process of synthesis of the additive compounds. Additionally, the present invention provides a warm mix asphalt formulation involving the additive compounds and a method of preparation thereof. The chemical additives of the present invention are liquid surfactants that ensure reduction of internal friction during manufacturing, and subsequently formulations comprising these chemical additives results in reduction of compaction temperature of the bituminous mixtures.

Claims

1. An additive compound for warm mix asphalt (WMA) for pavement of road surfaces, wherein the additive is a compound of Formula I: wherein ##STR00009## wherein R and R are same or independently selected from C.sub.12 to C.sub.24 alkyl groups.

2. The additive compound as claimed in claim 1, wherein R in Formula I is derived from stearic acid.

3. The additive compound as claimed in claim 1, wherein R in Formula I is a C.sub.18 alkyl chain.

4. A process for synthesis the additive compound as claimed in claim 1, wherein the process comprises: a) adding diethylene triamine to a solution of methyl stearate under stirring to obtain a reaction mixture; b) heating the reaction mixture for 4-8 hours to obtain a brown coloured solid; c) filtering the brown coloured solid with methanol to obtain a diamide derivative; d) neutralizing the diamide derivative with a fatty acid to obtain the additive compound; wherein the additive compound is represented by Formula I; wherein ##STR00010## wherein R and R are same or independently selected from C.sub.12 to C.sub.24 alkyl groups.

5. The process as claimed in claim 4, wherein the fatty acid is selected from long chain acids having carbon number ranging from 12 to 24.

6. The process as claimed in claim 5, wherein the fatty acid is stearic acid.

7. The process as claimed in claim 4, wherein in step (b) the reaction mixture is heated at a temperature of 80? C.-160? C.

8. A warm mix asphalt formulation for pavement of road surfaces, wherein the formulation comprises warm mix asphalt and an additive compound in amount ranging from 0.4 to 5% by weight of the warm mix asphalt.

9. The formulation as claimed in claim 8, wherein the additive compound is selected from a compound represented by Formula I, a diester derivative of oxalic acid and a long chain alcohol, a diester derivative of sebacic acid and a long chain alcohol, or a mixture thereof; wherein the long chain alcohol has carbon atoms ranging from 20 to 24; wherein ##STR00011## wherein R and R are same or independently selected from C.sub.12 to C.sub.24 alkyl groups.

10. The formulation as claimed in claim 8, wherein the formulation has a viscosity ranging from 50-10000 cP over a temperature ranging from 80-200? C.

11. The formulation as claimed in claim 8, wherein temperature required to compact the formulation is 20-40? C. lower than a conventional hot mix asphalt.

12. The formulation as claimed in claim 8, wherein the additive compound is blended into the warm mix asphalt in a hot-mix plant.

Description

DESCRIPTION OF THE INVENTION

[0023] For the purpose of promoting an understanding of the principles of the present disclosure, reference will now be made to the specific embodiments of the present invention further illustrated in specific language to describe the same. The foregoing general description and the following detailed description are explanatory of the present disclosure and are not intended to be restrictive thereof. It will nevertheless be understood that no limitation of the scope of the present disclosure is thereby intended, such alterations and further modifications in the illustrated composition, and such further applications of the principles of the present disclosure as illustrated herein being contemplated as would normally occur to one skilled in the art to which the present disclosure relates. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one ordinarily skilled in the art to which this present disclosure belongs. The products, methods, and examples provided herein are illustrative only and not intended to be limiting.

[0024] The present invention provides chemical additives, which are liquid surfactants that act at the microscopic aggregate/binder interface to reduce internal friction during manufacturing. Thus, formulation prepared by combining these chemical additives with warm mix asphalt results in reduced compaction temperature of the bituminous mixtures without reducing their mechanical behavior. Unlike other additives and techniques for warm-mix, the present invention does not involve an introduction of water into the mix and hence does not have any adverse effect on low temperature properties of asphalt. More specifically, the present inventors have found that a unique combination of chemical additives improves the rheological properties of the warm-mix asphalt and facilitate mixing, lay down and compaction of asphalt mixes by reducing the viscosity of the mix during the production and paving of the mix and thereby reduces the compactive effort required to attain the optimum design densities. The chemical additive of the present invention enhances the ability to compact the warm mix asphalt at a much lower temperature by the reduction of viscosity of the warm mix asphalt formulation and significantly improves the moisture resistance properties of the formulation by improving both the adhesion and cohesion properties.

[0025] Thus, the present invention provides an additive compound for warm mix asphalt (WMA) for pavement of road surfaces, wherein the additive is a compound of Formula I: [0026] wherein

##STR00003## wherein R and R are same or independently selected from C.sub.12 to C.sub.24 alkyl groups.

[0027] In a preferred embodiment, the present invention provides that R in Formula I is derived from stearic acid.

[0028] In a preferred embodiment, the present invention provides that R in Formula I is a C.sub.18 alkyl chain.

[0029] Further, the present invention provides a process for synthesis the additive compound for warm mix asphalt (WMA) for pavement of road surfaces, wherein the process comprises: [0030] a) adding diethylene triamine to a solution of methyl stearate under stirring to obtain a reaction mixture; [0031] b) heating the reaction mixture for 4-8 hours to obtain a brown coloured solid; [0032] c) filtering the brown coloured solid with methanol to obtain a diamide derivative; [0033] d) neutralizing the diamide derivative with a fatty acid to obtain the additive compound;
wherein the additive compound is represented by Formula I;
as

##STR00004##

wherein R and R are same or independently selected from C.sub.12 to C.sub.24 alkyl groups.

[0034] In another embodiment, the present invention provides that the fatty acid is selected from long chain acids having carbon number ranging from 12 to 24. Preferably, the fatty acid is a stearic acid.

[0035] In yet another embodiment, the reaction mixture in step (b) of the above disclosed process is heated at a temperature of 80? C.-160? C.

[0036] Further, the present invention provides a warm mix asphalt formulation for pavement of road surfaces, wherein the formulation comprises warm mix asphalt and an additive compound in amount ranging from 0.4 to 5% by weight of the warm mix asphalt.

[0037] In an embodiment, the present invention provides that the formulation comprises the additive compound selected from a compound represented by Formula I, a diester derivative of oxalic acid and a long chain alcohol, a diester derivative of sebacic acid and a long chain alcohol, or a mixture thereof; [0038] wherein the long chain alcohol has carbon atoms ranging from 20 to 24; [0039] wherein

##STR00005## wherein R and R are same or independently selected from C.sub.12 to C.sub.24 alkyl groups.

[0040] In yet another embodiment, the present invention provides that the formulation has a viscosity ranging from 50-10000 cP over a temperature ranging from 80-200? C. The viscosity of the warm mix asphalt containing the desired amount of the additive increases at lower temperature, while there is a decrease in the viscosity at higher temperatures.

[0041] In a further embodiment, the present invention provides that the temperature required to compact the formulation is 20-40? C. lower than a conventional hot mix asphalt. The use of the additives facilitates in lowering the compaction temperature of the warm mix asphalt.

[0042] In another embodiment, the present invention provides that the additive compound is blended into the warm mix asphalt in a hot-mix plant.

[0043] The present invention is further illustrated based on the disclosed embodiments through several non-limiting working examples.

Example 1: Synthesis of a Compound of Formula I

[0044] To a stirred solution of methyl stearate (2 equivalents), diethylene triamine (DETA, 1 equivalents) was added at room temperature. The reaction mixture was heated at 120? C. for 6 hours. After 6 hours, a brown color solid was obtained. The solid was filtered with methanol to obtain a diamide derivative. .sup.1H NMR data for the diamide derivative: 0.87 (t, 6H), 1.24-1.27 (60H), 1.61-1.79 (m, 8H), 2.15 (m, 4H), 2.71 (m, 4H), 3.32 (m, 4H), 6.1 (br s, 2H). The diamide was neutralized with the stearic acid (1 equivalents) to obtain the compound of Formula I (Compound 1). Yield: 92%.

##STR00006##

Example 2: Synthesis of a Diester Derivative of Oxalic Acid and a Long Chain Alcohol

[0045] C.sub.20 to C.sub.24 alcohol was reacted with diacid (oxalic acid) at 70? C. in the presence of sulphuric acid for 6 hours to obtain the diester derivative of oxalic acid and a long chain alcohol (Compound 2).

##STR00007##

Example 3: Synthesis of a Diester Derivative of Sebacic Acid a Long Chain Alcohol

[0046] C.sub.20 to C.sub.24 alcohol was reacted with diacid (sebacic acid) at 70? C. in the presence of sulphuric acid for 6 h to obtain the diester derivative of sebacic acid a long chain alcohol (Compound 3).

##STR00008##

Example 4: Viscosity Measurement for Additive Performance Evaluation

[0047] The warm mix additives increase the viscosity at lower temperature when blended with warm mix asphalt and decreases the viscosity at higher temperatures.

TABLE-US-00001 TABLE 1 Comparison of viscosity of the disclosed formulation Viscosity (cP) Base bitumen Base Base plus 0.5% Base Base bitumen bitumen compound 1 bitumen bitumen Temp Base plus 1% plus 1% and 0.5% plus 1% plus 0.1% (? C.) Bitumen compound 3 compound 2 compound 2 compound 1 compound 2 110 3634 5968 5390 5980 3627 120 2012 2278 2034 2974 2967 2056 130 1145 1178 1311 1385 1378 1185 140 722.4 689 577.9 920 911.3 742 150 466.8 444 334 548 544.6 440 160 344.5 256 233.4 279 283.4 320 170 233.4 155.6 155.6 182 178 220 180 155.6 77.79 77.79 94 92.13 77.79

[0048] From the above Table, it is inferred that warm mix asphalt formulation comprising the compound 1, 2 or 3 being mixed with the base bitumen in definite % amounts show a significant reduction in viscosity at higher temperatures. On the contrary, combination of the base bitumen with 0.1% compound 2 failed to impart the desired characteristics in the presently disclosed formulation.