Title of Invention	AN ASPHALT CONCRETE ADDITIVE AND A PROCESS FOR PREPARING ASPHALT CONCRETE USING THE SAME
Abstract	The present invention relates to an asphalt concrete additive, comprising 40 t0 50 parts by weight of waste tire rubber powder, 49 to 50 parts by weight of petroleum resin powder and 0.01 to 1 part by weight of polyethylene as packing paper, based on 100 parts by weight of total asphalt concrete additive.

Full Text

ASPHALT CONCRETE ADDITIVE AND PROCESS FOR PREPARING ASPHALT CONCRETE USING THE SAME BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an asphalt concrete additive and a process for preparing asphalt concrete using the same, and more particularly to an asphalt concrete additive that is added in preparing asphalt concrete as a modifying agent and a process for preparing asphalt concrete using the same. Description of the Related Art Recently, as quality of daily life improves, increase of traffic volume due to rapid increase of the number of cars, and a trend toward heavier cars raises the importance of pavement of roads, runways, and the like. In paving the roads and runways, asphalt concrete is largely used. The asphalt concrete is prepared by mixing asphalt and aggregate, and more specifically by blending asphalt and crushed stone aggregate, sand and mineral powder in a predetermined blending ratio and subjecting them to mechanically forced mixing at a temperature of 150 to 170°C, and the asphalt concrete thus prepared is transported by transporting vehicles such as dump trucks to paving sites for use thereof. Typically/ a field construction process is performed with pavement of the asphalt concrete at a temperature of above 125^^0 by a finisher, a roller pavior, or the like, following by compacting "hereof. The asphalt used in preparing the asphalt concrete exhibits great variation in physical properties thereof according to fluctuations in a temperature and environment of surroundings, and in turn, the asphalt concrete, which is prepared by mixing the asphalt and aggregate, also exhibits significant deformations according to fluctuations in an environment and pressure of surroundings, after being paved. In particular, as the asphalt shows brittleness at a low temperature, paved roads may give rise to cracks, and as it also changes in morphology thereof at high temperatures, problems associated with r^jtting occur. Due ' to these disadvantages, there have occurred cracks or potholes, peeling off and releasing of aggregate ■ in the pavement, thereby lowering durability of pavement, and therefore re-paving and repairing should be repeatedly performed every 4 to 5 years on average. In order to solve these problems, a number of technological studies have been actively performed so as to modify characteristics of the asphalt concrete and as a result, a variety of modification methods have been developed. Among them, a technique of preparing asphalt concrete using waste tire rubber powder is known in the related art. More specifically, a pavement process is accomplished by mixing the asphalt, aggregate, and waste tire rxibber powder as an additive in a predetermined ratio at a high temperature to prepare the asphalt concrete and then transferring the mixture to paving sites followed by casting. However, during preparation of the asphalt concrete by blending raw materials in accordance with this method, an amount of a modifying agent such as waste tire rubber powder should be individually weighed and added, thus presenting inconvenience in preparing the asphalt concrete, and further there is a disadvantage that a blending ratio of raw materials m.ay be slightly varied whenever blending thereof is performed. SUMMARY OF THE I^^/ENTION Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide an asphalt concrete additive, capable of preparing asphalt concrete by easy addition of a proper amount of the additives without individual weighing of the respective modifying additives in a process of preparing asphalt concrete, and in particular, capable of enhancing durability of the asphalt concrete by increasing binding capacity thereof. It is another object of the present invention to provide a process for preparing asphalt concrete capable of reducing defects associated with low temperature brittleness and rutting by using the above additive. It is yet another object of the present invention to provide a process for implementing pavement using the asphalt concrete prepared by the above-mentioned method. In accordance with the present invention, the above and other objects can be accomplished by the provision of an asphalt concrete additive comprising waste tire rubber powder and petroleum resin powder, and polyethylene as a packing paper. In accordance with another aspect of the present invention, there is provided a process for preparing asphalt concrete, comprising mixing 5 to 15% by weight of an asphalt concrete additive comprising waste tire rubber powder and petroleum resin powder, and polyethylene as a packing paper, 5 to 10% by weight of asphalt and 75 to 90% by weight of aggregate at a high temperature of 170 to 190°C. In accordance with yet another aspect of the present invention, there is provided a pavement process, comprising the steps of mixing 5 to 15% by weight of an asphalt concrete additive comprising waste tire rubber powder and petroleum resin powder, and polyethylene as a packing paper, 5 to 10% by weight of asphalt and 75 to 90% by weight of aggregate at a high temperature of 170 to 190°C to prepare asphalt concrete, and casting the asphalt concrete at a paving site while maintaining a temperature of above 150°C, followed by compacting. DESCRIPTION OF THE PREFERRED EMBODIMENTS Now, the present invention will be described in more detail as below. The present invention provides an asphalt concrete additive comprising waste tire rubber powder and petroleum resin powder, and polyethylene as a packing paper. That is, the asphalt concrete additive in accordance with the present invention is prepared by packaging the waste tire rubber powder and petroleum resin powder with polyethylene as a packing paper, and when it is injected as a package, it may provide the asphalt concrete having modified effects. In this connection, the waste tire rubber powder has high miscibility with asphalt and thus assists in early development of the modified effects. Particularly, it reduces brittleness, which is a disadvantage by asphalt, and alleviates a low temperature expansion/contraction effect, thus resulting in reduction of crack development. In addition, the waste tire rubber powder contains anti-UV agent, flow resistant agent, carbon, and the like, v/hich were added in preparing the tire, and thus improves durability of the asphalt concrete and makes the asphalt concrete withstand contraction in winter. Therefore, the waste tire rubber powder may prevent bumpiness due to rutting in summer, bleeding due to heavy loads, potholes, etc., which are problems of conventional asphalt concrete pavement. As the waste tire rubber powder, it is preferred to use fine powder having a particle size of 20 to 300 mesh in order to increase miscibility between the waste tire rubber powder and asphalt in preparing the asphalt concrete so as to develop modification effects early. Where the particle size of the waste tire rubber powder is less than 2 0 mesh, there is a disadvantage that modification effects by the waste tire rubber powder are not rapidly obtainable in the prepared asphalt concrete. Where the particle size of the waste tire rubber powder is above 300 mesh, miscibility with the asphalt increases in the course of preparation of the asphalt concrete, and thus provides an advantage of early modification effect, but disadvantages such as aggravation of the work conditions due to large bulk and scattering of the waste tire rubber powder and increase of production costs are also presented. The asphalt concrete additive in accordance with the present invention contains petroleum resin powder together with the waste tire rubber powder. This petroleum resin powder is added to offset a disadvantage possessed by the waste tire rubber powder, and particularly is included to obtain a good workability by alleviating an increase of viscosity due to addition of the waste tire rubber powder. As the petroleum resin pcv;der, it is preferred to use fine powder having a particle size of 20 to 3 00 mesh in order that miscibility with asphalt in preparing asphalt concrete increases so as to develop modification effects early. Where the particle size of the petroleum resin powder is less than 20 mesh, the miscibility with the prepared asphalt is lowered, thus there is a disadvantage that modification effects by the petroleum resin powder are not rapidly obtainable in the prepared asphalt concrete. Where the particle size of the petroleum resin powder is above 3 00 mesh, problems associated with deterioration of storability and work conditions and increase of production costs are presented. Considering ease of handling, a thermoplastic resin powder having a softening point of 95 to 160°C and a specific gravity of 1.05 to 1.1 is preferably used as the petroleum resin powder. Preferably, the thermoplastic resin powder is selected from Ca-io hydrocarbon-based condensation polymer resin powder. As the hydrocarbon containing 8 to 10 carbon atoms, monomer(s) selected from styrene (CsHs), halogen-substituted styrene (CeHiX wherein X is CI or Br) , vinyltoluene (C9H10) , halogen-substituted vinyltoluene (C9H9X wherein X is CI or Br) , indene {C^He) , halogen-substituted indene (C9H7X wherein X is CI or Br) , 3-phenylpropene (C9H10) or hexylvinylether (CgHigO) maybe used; alone or in any combinations thereof. In the present invention, the waste tire rubber powder and petroleum resin powder are packaged in a polyethylene packing paper. As this package itself is added in preparing asphalt concrete, it is possible to prepare the asphalt concrete by conveniently adding a suitable amount of the waste tire rubber powder and petroleum resin powder without separately weighing them. Further, as polyethylene is added together with them, a binding capacity of the prepared asphalt concrete can be increased. At this time, a low-density polyethylene having a degree of polymerization of 1000 to 50000 is preferably used as the polyethylene. In connection with the asphalt concrete additive comprising the waste tire rubber powder and petroleum resin powder, and polyethylene, its composition may be appropriately varied if necessary. Preferably, the additive may comprise 40 to 50 parts by weight of the waste tire rubber powder, 49 to 59 parts by weight of the petroleum resin powder and 0.01 'to 1 part by weight of the polyethylene as a packing paper, based on 100 parts by weight of total asphalt concrete additive. At this time, if an amount of the waste tire rubber powder or petroleum resin powder and polyethylene exceeds the above-specified ranges, a sufficient modification effect thereby cannot be obtained. Therefore, the asphalt concrete additive comprising the waste tire rubber powder and petroleum resin powder, and polyethylene as a packing paper, is added in preparing the asphalt concrete as a package itself. The waste tire rubber powder and petroleum resin powder contained in the additive become miscible with the asphalt concrete while at the same time, the polyethylene packing paper is melted. Accordingly, the asphalt concrete is prepared by mixing 5 to 15% by weight of asphalt concrete additive, 5 to 10% by weight of asphalt and 75 to 90% by weight of aggregate at a high temperature of 170 to 190°C to obtain asphalt concrete. Known asphalts may be used in preparing asphalt concrete. The present invention uses the asphalt having a penetration degree of 43 to 72 mm, a softening point of above 47°C and an elongation of above 50 cm. Upon preparation of asphalt concrete using the asphalt having such physical properties, interaction between the asphalt and additive may maximize durability, stability and binding capacity of the asphalt concrete prepared. Aggregates selected from those having a suitable size may be used depending on use and object of the pavement. Preferably, where the aggregate has a particle size of up to 13 mm, a particle size distribution thereof has preferably 92 to 100% of 13 mm, 62 to 81% of 9.5 mm, 10 to 31% of 4.75 mm, 10 to 21% of 2.36 mm, 4 to 17% of 0.6 mm, 3 to 12% of 0,3 mm, 3 to 8% of 0.15 mm, and 2 to 7% of 0.75 mm, based on amounts passed through a sieve. Further, where the aggregate has a particle size of up to 19 mm, a particle size distribution thereof has preferably 95 to 100% of 19 mm, 53 to 78% of 13.2 mm, 35 to 62% of 9.5 mm, 10 to 31% of 4.75 mm, 10 to 21% of 2.36 mm, 4 to 17% of 0.6 mm, 3 to 12% of 0.3 mm, 3 to 8% of 0.15 mm and 2 to 7% of 0.75 m.m, based on amounts passed through the sieve. In order to increase an abrasion coefficient of the aggregate having the particle size distribution as described above, 5 to 10% by weight of the aggregate having an average particle size of 4.75 mm is preferably replaced with rigid steel-making slag having a surface wear rate of less than 2.8 and a hardness of more than 3. As such, when a portion of the aggregate having an average particle size of 4.75 mm is replaced with the rigid steel-making slag, there are provided advantages of excellent anti-slip effect and high impact resistance thereby the asphalt concrete pavement being strongly resistant to breakage. Upon preparing the asphalt concrete by mixing the additive, asphalt and aggregate in the blending ratio as described above, mixing of them is suitably carried out at a temperature of 175 to 195^C. Preferably, the asphalt concrete thus prepared is cast while maintaining a temperature of above 150°C at a paving site, followed by compacting. In this connection, the asphalt concrete may be used in pavement of runways, express highways, factories, and other roads. After the asphalt concrete was paved at the paving site, a compacting process is performed using vibration, a tire roller, and the like. Where the load of the roller is excessive in a first compacting process, asphalt concrete may not be compacted and pushed out, or flatness may be impaired, and thus the first compacting process is rapidly performed with the roller having a weight of less than 5 tons, without vibration. A second compacting process is performed at a temperature of above 110°C with a vibration roller. Preferably, a third compacting process is rapidly performed to effect a flattening operation at a temperature of above 60°C by a rubber tire. In case of the paved road as described above, brittleness of the asphalt is reduced by the waste tire rubber powder and petroleum resin powder thus inhibiting production of cracks and preventing irutting therefrom, and thereby, decrease of durability of the pavement due to cracks, potholes, and peeling off and releasing of aggregate are prevented. Now, the present invention will be described in detail with reference to the following examples and experimental examples. These examples are provided only for illustrating the present invention and should not be construed as limiting the scope and spirit of the present invention. EXAMPLES Examples 1 through 5 Waste tire riibber powder, in which waste tire was ground to a size of 25 to 300 mesh, and petroleum resin powder having a size of 25 to 300 mesh were packaged with a low density polyethylene to prepare an asphalt concrete additive in the form of 10 kg unit. A blending ratio between them is as shoVvTi in Table 1. The petroleum resin was prepared by condensing halogen-substituted styrene, halogen-substituted vinyltoluene, halogen-substituted indene and 3-phenylpropene, and has a softening point of 120°C and a specific gravity of 1.05 to 1.1. 100 kg of the asphalt concrete additive thus prepared, 80 kg of the asphalt, and 820 kg of the aggregate (a maximum size of 13 mm) were dry mixed at a temperature of 180°C to prepare asphalt concrete, and physical properties of the asphalt concrete thus prepared were determined according to the following method. The results are shown Table 1. Marshal Stability A cylindrical specimen having a diameter of 100 nim was subjected to a load of 50 mm velocity per min, at a temperature of 60°C, according to a method specified in KSF 2337 (a test method for resistance to plastic flow of a bituminous mixture using a Marshal tester). The results thus obtained are shown in Table 1. Flowability Flowability represents a total vertical displacement at a maximum load obtained when a cylindrical specimen having a diameter of 100 mm was subjected to a load of 50 mm velocity per min, at a temperature of 60^C, according to the method specified in KSF 2337 (a test method for resistance to plastic flow of the bituminous mixture using the Marshal tester). Density Density is detennined according to the method specified in KSF 2446 (a method for measuring an apparent specific gravity and density of the compacted bituminous mixture using a specimen in a surface dry saturated condition). Dynamic Stability Ground contact pressure of 6.4 kg/cm^ was applied to a specimen having a size of 300 mm x 300 mm x 50 mm at a temperature of 60°C according to Wheel Tracking Test Method by wheel to measure reciprocating number per depth of a pothole (times/mm). The higher the numerical value of the result, the better the dynamic stability is, thus representing less deformation. Indirect Tensile Strength A cylindrical specimen having a diameter of 100 mm was subjected to a load of deformation velocity of 50 mm per min in the vertical direction relative to a cross-section thereof to measure a final deformation value at breaking in the horizontal direction, and also a maximum load at this time. Indirect tensile strength was calculated using the deformation value and maximum load in accordance with a conventional method. For the indirect tensile strength result thus obtained, the higher the value is, the higher the maximum load is, and the less deformation occurs. As can be seen from Table 1, Examples 2 through 4, in which the waste tire mbber powder and petroleum resin were packed with polyethylene in the preferred range in accordance with the present invention to prepare an asphalt concrete additive, exhibited good physical properties, and in particular, excellent dynamic stability and indirect tensile strength. This represents that the asphalt concrete prepared in accordance with the present invention has a low deformation value, thus confirming a significant effect of enhanced durability of the pavement. Examples 6 through IQ 45 parts by weight of waste tire rubber powder, in which waste tire was ground to a size of 25 to 300 mesh, and 54.5 parts by weight of petroleum resin powder having a size of 25 to 300 mesh were packed with 0.5 part by weight of a low density polyethylene to prepare an asphalt concrete additive in the form of 10 kg unit. The asphalt concrete additive thus prepared, asphalt, and aggregate (maximum size of 13 mm) , in a blending ratio as shown in Table 1, were dry mixed at a temperature of 180°C to prepare asphalt concrete, and physical properties of the asphalt concrete thus prepared were determined. The results obtained are shown Table 2. As can be seen from Table 2, Examples 7 through 9, in which the asphalt concrete additive, asphalt and aggregate were mixed in the preferred range in accordance with the present invention to prepare asphalt concrete, exhibited excellent dynamic stability and indirect tensile strength. That is, the asphalt concrete prepared in accordance with the present invention has a low deformation value, thus confirming a significant effect of enhanced durability of the paved roads. Experimental Example 1 45 parts by weight of waste tire rubber powder, in which the waste tire was ground to a size of 25 to 300 mesh, and 54.5 parts by weight of petroleum resin powder having a size of 25 to 3 00 mesh were packed with 0.5 part by weight of a low density polyethylene to prepare an asphalt concrete additive in the foriTi of 10 kg unit. The asphalt concrete additive thus prepared was added in preparing a variety of asphalt concrete (dense gradation 13 mm, dense gradation 20 mm and 13 mm drainable 20% voids) , but 100 kg of the asphalt concrete additive, 80 kg of the asphalt, and 820 kg of the aggregate were dry mixed at a temperature of 180°C to prepare asphalt concrete. Physical properties of the asphalt concrete thus prepared are shown in Table 3. At this time, dense gradation 13 mm is a classification name of the asphalt concrete and represents that a maximum size of the aggregate is 13 mm and a proportion of fine aggregate ranges from 35 to 50%. Dense gradation 20 mm is a classification name of the asphalt concrete and represents that a maximum size of the aggregate is 20 mm and a proportion of the fine aggregate ranges from 35 to 50%. Drainable 13 mm ^20% voids) represents asphalt concrete having drainage and noise-reduction functions that has a void of 20% and a maximum size of 13 mm. As a control group, 80 kg of the asphalt and 82 0 kg of the aggregate were dry mixed, without addition of the asphalt concrete additive, at a temperature of 180=^C to prepare asphalt concrete (dense gradation 13 mm, dense gradation 20 mm and 13 mm drainable 20% voids). Physical properties of the asphalt concrete thus prepared are shown in Table 3. As can be seen from Table 3, the asphalt concrete additive prepared in accordance with the present invention exhibited markedly improved characteristics such as physical properties, dynamic stability, indirect tensile strength, etc., regardless of* kind of asphalt concrete to be prepared, as compared to the control groups in which no asphalt concrete additive was added. As apparent from the above description, the present invention provides an asphalt concrete additive comprising waste tire rubber powder and petroleum resin powder packed with polyethylene. Thereby, it is possible to prepare asphalt concrete by easy addition of an optimal amount of additives without individual weighing of the respective modifying additives in a process of preparing the asphalt concrete, and in particular, thus a binding capacity of asphalt concrete can be enhanced. Further, use of the asphalt concrete additive in the preparation of the asphalt concrete for road pavement may resolve disadvantages associated with low temperature brittleness and rutting and thereby significantly improve durability of the pavement. Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. WHAT IS CLAIMED IS: 1. An asphalt concrete additive comprising. waste tire rubber powder and petroleum resin powder, and polyethylene as a packing paper. 2. The asphalt concrete additive as set forth in claim 1, wherein it comprises 40 to 50 parts by weight of waste tire rubber powder, 49 to 59 parts by weight of petroleum resin powder and 0.01 to 1 part by weight of polyethylene as packing paper, based on 100 parts by weight of total asphalt concrete additive. 3. The asphalt concrete additive as set forth in claim 2, wherein the waste tire rubber powder has a particle size of 20 to 300 mesh. 4. The asphalt concrete additive as set forth in claim 2, wherein the petroleum resin powder is a thermoplastic resin powder having a softening point of 95 to 160°C and a specific gravity of 1.05 to 1.1. 5. The asphalt concrete additive as set forth in claim A, wherein the thermoplastic resin powder is selected from Cs-io hydrocarbon-based condensation polymer resin powder. 6. The asphalt concrete additive as set forth in claim 2, wherein the polyethylene is a low-density polyethylene having a degree of polymerization of 1000 to 50000. 7. A process for preparing asphalt concrete, comprising mixing 5 to 15% by weight of an asphalt concrete additive comprising waste tire rubber powder and petroleum resin powder, and polyethylene as a packing paper, 5 to 10% by weight of asphalt and 75 to 90% by weight of aggregate at a high temperature of 170 to 190°C. 8. The process as set forth in claim 7, wherein the asphalt concrete additive comprises 40 to 50 parts by weight of waste tire rubber powder, 49 to 59 parts by weight of petroleum resin powder and 0.01 to 1 part by weight of polyethylene as packing paper. 9. The process as set forth in claim 8, wherein the waste tire rubber powder has a particle size of 20 to 300 mesh. 10. The process as set forth in claim 8, wherein the petroleum resin powder is a theinnoplastic resin powder having a softening point of 95 to 160°C and a specific gravity of 1.05 to 1.1. 11. The process as set forth in claim 10, wherein the thermoplastic resin powder is selected from Ca-io hydrocarbon-based condensation polymer resin powder. 12. The process as set forth in claim 8, whereih the polyethylene is a low-density polyethylene having a degree of polymerization of 1000 to 50000. 13. The process as set forth in claim 7, wherein the asphalt has a penetration degree of 43 to 72 mm, a softening point of above 47°C and an elongation of 50 cm. 14. The process as set forth in claim 7, wherein when the aggregate has a particle size of up to 13 mm, a particle size distribution thereof has 92 to 100% of 13 mm, 62 to 81% of 9.5 mm, 10 to 31% of 4.75 mm, 10 to 21% of 2.36 mm, 4 to 17% of 0.6 mm, 3 to 12% of 0.3 mm, 3 to 8% of 0.15 mm, and 2 to 7% of 0.75 mm, based on amounts passed through a sieve. 15. The process as set forth in claim 7, wherein when the aggregate has a particle size of up to 19 mm, a particle size distribution thereof has 95 to 100% of 19 mm, 53 to 78% of 13.2 mm, 35 to 62% of 9.5 mm, 10 to 31% of 4.75 mm, 10 to 21% of 2.36 mm, 4 to 17% of 0.6 mm, 3 to 12% of 0.3 mm, 3 to 8% of 0.15 mm and 2 to 7% of 0.75 mm, based on amounts passed through the sieve. 16. The process as set forth in claim 14, wherein 5 to 10% by weight of the aggregate having an average particle size of 4.75 mm is replaced with rigid steel-making slag having a surface wear rate of less than 2.8 and a hardness of more than 3. 17. The process as set forth in claim 15, wherein 5 to 10% by weight of the aggregate having an average particle size of 4.75 mm is replaced with rigid steel-making slag having a surface wear rate of less than 2.8 and a hardness of more than 18. A process for paving asphalt concrete, comprising the steps of mixing 5 to 15% by weight of an asphalt concrete additive comprising waste tire rubber powder and petroleum resin powder, and polyethylene as a packing paper, 5 to 10% by weight of asphalt and 75 to 90% by weight of aggregate at a high temperature of 170 to 190°C to prepare the asphalt concrete, and casting the asphalt concrete at a paving site while maintaining a temperature of above 150°C followed by compacting. 19. The process as set forth in claim 18, wherein compacting is performed by first compacting with a roller without vibration, second compacting with a vibration roller at a temperature of above 110°C, and third compacting with a rubber tire at a temperature of above 60°C. 20. An asphalt concrete additive substantially as herein described and exemplified.

Documents:

735-che-2004-abstract.pdf

735-che-2004-claims filed.pdf

735-che-2004-claims grand.pdf

735-che-2004-correspondnece-others.pdf

735-che-2004-correspondnece-po.pdf

735-che-2004-description(complete) filed .pdf

735-che-2004-description(complete) grand.pdf

735-che-2004-form 1.pdf

735-che-2004-form 19.pdf

735-che-2004-form 26.pdf

735-che-2004-form 3.pdf