Patent Application
20150252533
Holes in asphalt and concrete road beds, or as commonly known “potholes”, have become a national problem faced by a considerable number of drivers every day, especially in dense urban areas with large seasonal weather changes. For example, the City of New York patched 418,000 potholes city wide in 2011 and another 164,000 in the first three months of 2012. Poor road conditions are a large and growing financial liability for states. Between 2004 and 2008, states spent $16.3 billion annually on repair of roads and highways. In addition, roads in poor condition can negatively impact interstate trade and travel, the effect of which can be felt across large regions and across state lines. Therefore, road defects, such as holes in asphalt and concrete road beds, should be repaired quickly and effectively as possible.
Holes in asphalt and concrete road beds are usually caused by raveling, base failure, poorly compacted material, poor drainage, cracking, and/or aging of the pavement. Potholes are common after rain when water penetrates the surface layers of the pavement, softening the underlying pavement layers, which increases deflections. These holes are also common during thaws when pavements are weaker. Moisture seeps into the pavement, freezes, expands and then thaws, weakening the pavement. Fine material from the underlying pavement layers is lost, which reduces the overall structural strength and support for the pavement surface; thus, cracking the pavement surface. Traffic loosens the pavement even more, eventually creating a hole in the road bed.
As asphalt and concrete road beds age and deteriorate, the need for corrective measures to restore safety and rideability increases. Funding for rehabilitation and overlay of these pavements is not likely to keep up with the demand, requiring more government agencies to use the most cost-effective methods when patching distressed areas. These patches also need to survive longer and carry more traffic.
Patching of holes in asphalt and concrete road beds has been traditionally done by hot patching. Before hot patching a pothole, the hole in the asphalt or concrete road bed needs to be prepared. The pothole is prepared by removing loose material, drying the area to be patched, heating tar-based patching material, delivering the heated hot tar-based patching material to the hole in the road bed, and compacting the delivered patching material into the prepared hole in the road bed. As such, hot patching is a time consuming and expensive process. In addition, hot patching is heavily regulated because of the workplace risks.
It has been previously proposed to cold-patch holes in asphalt and concrete road beds by the system and method described in U.S. Pat. No. 7,939,154 (“the '154 Patent). The system and method described in the '154 Patent eliminates the need to heat the tar-based patching material, reduces workplace risks, and reduces the costs of heating the patching material. However, this patching system and method requires the presence of at least 55% magnetite (Fe3O4) as a reactive iron concentration, which does not include other forms of iron such as hematite (Fe2O3), wüstite (FeO) and elemental iron (Fe). In addition, the patching material disclosed in the '154 Patent has limited application to geographic areas of the country where magnetite is available and to related areas where the preparing patching material can be shipped at reasonable cost.
Some previously known or proposed methods for patching potholes in asphalt and concrete road beds may have the disadvantage of requiring removal of water or moisture from the pothole before patching. These methods require cleaning and drying the pothole, applying liquid asphalt to the edges of the pothole, placing the patching material, compacting the patching material, and cleaning up, resulting in an extremely long and expensive process. When conditions are cold or wet, the material used to patch holes does not stick well to the surrounding pavement causing the pavement to crack again, causing the pothole to recur. Therefore, if the pothole was not properly dried before patching, the pothole might reappear only after few days of patching.
Other patching methods may require removing the excess asphalt, applying an adhesive, adding the asphalt in layers, leveling it off, and compacting with a pavement roller, which also results in a long and costly process. See Virginia Department of Transportation. Furthermore, previously known or proposed methods may require the use of different types of patching materials depending on the weather or time of the year. For example, hot mix asphalt is used in the summer; whereas, a cold mix asphalt is used in the winter when hot asphalt plants are not working. See Utah Department of Transportation Maintenance Division.
As such, there is still a need for a method that provides a durable and cost-effective patching material that is not geographically limited and that is available in all parts of the country. Moreover, the method for patching potholes in asphalt and concrete road beds should also provide a patching material that is not sensitive to the presence of water, moisture, and oily materials in forming and maintaining the road bed patch. Furthermore, the method should also provide a patching material that can be easily put in place by road maintenance personnel with reduced workplace risks.
Additionally, potholes occur on asphalt and concrete road beds subjected to a broad spectrum of traffic levels, from two-lane rural routes to multi-lane interstate highways. Pothole patching may be generally performed either as an emergency repair under harsh conditions, or as routine maintenance scheduled for warmer and drier periods of the year. Patching of holes in asphalt and concrete road beds is done during weather conditions ranging from clear warm days to harsh cold storms, with temperatures generally ranging anywhere from 38° C. to −18° C. As a result, there remains a need for an economical method for patching asphalt and concrete road beds that may be used in any type of weather conditions.
Currently disclosed is a practical and economical way of patching asphalt and concrete road beds using iron metallurgical material. A method of patching asphalt and concrete road beds is disclosed, comprising the steps of:
(a) removing debris from a hole in the road bed;
The disclosed method of patching asphalt and concrete road beds involves a patching material comprising in part of iron metallurgical material. In the making of steel, iron metallurgical material dust and sludge is created and collected from various sources. A common iron metallurgical material is mill scale, which is ubiquitous in steelmaking. Mill scale includes various forms of iron oxides consisting of iron (II, III), typically comprising between 10% and 58% FeO, and between 38% and 85% Fe2O3. Mill scale is formed at the surface of steel by oxidation of the surrounding atmosphere. See The Making, Shaping and Treating of Steel, at 946-947 (9th Ed. 1971).
Mill scale is formed during heating, hot working and cooling of steel slabs, steel strip, blooms, and billets, as well as most other types of intermediate and finished steel products. The presence of such mill scale is particularly objectionable on the intermediate product to be further processed. For example, such scale typically must be removed and a clean steel surface provided if satisfactory results are to be obtained from the hot rolling of sheet or strip involving reduction or deformation of the steel. Similarly, if the steel sheet is for hot or cold drawing applications, the mill scale is removed as its presence on the steel surface tends to shorten die life, cause irregular and defective drawing conditions, and cause surface defects on the finish product. Mill scale is also removed if the sheet or strip is to be processed with a hot dip coating to permit proper alloying and adherence of the metallic coating, and satisfactory adherence when non-metallic coatings or paints are to be applied.
Additionally, other sources of iron-containing materials are available. In certain regions, iron-containing mine waste, such as wash-ore tailings and red ore tailings may be available for recovery of iron.
Even where not a hazardous waste, mill scale such as Basic Oxygen Furnace (BOF) dust and sludge and other iron metallurgical materials have been typically disposed of in landfills at considerable cost. The need for a commercially practical way of using iron metallurgical material has been emphasized by the public awareness of environmental issues in solid waste, by the decreasing availability of landfill areas, and by the continuing awareness of the depletion earth's mineral resources. Further, federal and state regulations regarding the use of the earth's natural resources and the disposal of waste materials have become more encompassing and more restrictive. As a result, there remains a need for a method for turning readily available iron metallurgical material into something useful, such as a patching material for asphalt and concrete road beds.
Mill scale and other iron metallurgical materials are readily available to provide road patching material since steel making facilities are not limited to a specific area, but are located throughout the country. The disclosed method of patching asphalt and concrete road beds may additionally include adding recycled material selected from the group consisting of asphalt, concrete and a mixture of asphalt and concrete. The recycled material may be oily. This provides for broad usage of locally available recycled asphalt, concrete and mixtures thereof from old road beds. The iron metallurgical material also may be available or processed to a material particle size of at least 20% between −14 and +28 mesh.
The patching material may comprise of at least 40% iron metallurgical material and a dilute acidic activator comprised of phosphate anions. In one embodiment, the patching material may comprise between 50-80% iron metallurgical material. In another embodiment, the patching material may comprise 95% iron metallurgical material. The dilute acidic activator may comprised phosphate anions between 30% and 75%. In one embodiment, the phosphate anions are formed from dilute phosphoric acid.
The iron metallurgical material is combined with the dilute acidic activator to form iron ceramic material, which may provide a compressive strength of at least 900 psi with a 2 inch by 4 inch test cylinder. In another embodiment, the iron metallurgical material combined with the dilute acidic activator forming iron ceramic material may provide a compressive strength of at least 1000 psi with a 2 inch by 4 inch test cylinder.
The method of patching asphalt and concrete road beds may include a patching material comprising in addition an antifreeze material. An antifreeze material is a chemical additive which lowers the freezing point of a water-based liquid. An antifreeze material is used to achieve freezing-point depression for cold environments and also achieves boiling-point elevation (“anti-boil”) to allow higher coolant temperature. In one embodiment, the antifreeze material may be ethylene glycol. The patching material may include 1-10% wt of antifreeze material. In another embodiment, the patching material may include 1-2% wt of antifreeze material.
Also disclosed is a method for patching asphalt and concrete road beds using iron (II) oxide (FeO) comprising the steps of: (a) removing debris from a hole to be patched in the road bed; (b) filling the hole with a patching material comprised of at least 40% FeO having a size of at least 50% between −6 and +100 mesh, and a dilute acidic activator comprised of phosphate anions between 30% and 75%; and (c) combining the FeO with the dilute acidic activator to form iron ceramic material. The dilute acidic activator may be phosphoric acid.
Referring now to
As shown in block 12 of
With reference to block 14 of
In one alternative, the iron metallurgical material may be mill scale. Mill scale is a by-product of iron and steel formed during the hot rolling of sheets. Benchiheub et al., Elaboration of iron powder from mill scale, J. Mater. Environ. Sci. 1 (4), 2010, pgs. 267-276. Mill scale is a flaky surface of hot rolled steel, iron oxides consisting of iron (II, III). Dry mill scale particles are generally in the size range of between 0.5 mm to 2 mm in diameter. As such, when the iron metallurgical material comprises of mill scale, the iron metallurgical material does not need to be finely-ground or otherwise physically reduced in particle size. Also, the mill scale may be used even if it contains some oil.
In another alternative, the iron metallurgical material may comprise a mixture of mill scale with other similar iron metallurgical material, as described below, and the mixture may contain more than 55% by weight FeO and FeO equivalent. FeO equivalent is formed from metallic Fe)(Fe°). FeO equivalent is defined as the lesser of:
metallic Fe×3×72/56, or
(total Fe−metallic Fe−(FeO×56/72))×3/2×72/56.
For example, the similar metallurgical material for mixing with mill scale may include recyclable iron-bearing material, pellet plant wastes and pellet screened fines. Such pellet plant wastes and pellet screened fines may include a substantial quantity of hematite. In one alternative, the iron-bearing metallurgical material may include a mixture of mill scale and at least one selected from the group consisting of processed electric arc furnace (EAF) dust, basic oxygen furnace (BOF) sludge, blast furnace dust, and mixtures thereof. Alternatively, or in addition, iron bearing material metallurgical material for mixing with mill scale may include iron ore concentrate, taconite pellets, hematite, magnetite concentrates, oxidized iron ores, and red ore tailings.
With reference to blocks 16 and 18 of
The iron metallurgical material and the dilute acidic activator are combined to form iron ceramic material. The iron ceramic material is formed by the reaction of the metal cation with the phosphate anions. The reaction is attained by mixing a cation donor, generally an oxide such as iron oxide, with a acidic activator, such as phosphoric acid or an acid phosphate such as ammonium phosphate solution.
The reaction between the dilute acidic activator and the iron metallurgical material results in a rapid-setting iron ceramic material. The setting time may be increase by further diluting the acidic activator. The iron ceramic material cures rapidly because of an exothermic reaction with the phosphate. The result is a durable and resistant iron ceramic material that may be use as a patching material in a method for patching asphalt and concrete road beds even at temperatures below freezing.
Compressive strengths for the iron ceramic material were determined following U.S. DOT Standard Compression Tests for both concrete cylinders and asphalt cylinders. The compressive strengths of cylindrical concrete specimens were determined using the ASTM C39 and AASHTO-T22 test methods. These methods consist of applying a compressive axial load to molded cylinders or cores at a rate which is within a prescribed range until failure occurs. The compressive strength of the specimen is calculated by dividing the maximum load attained during the test by the cross-sectional area of the specimen. The compressive strengths of compacted asphalt mixtures were determined using the AASHTO-T167 test method. The iron metallurgical material combined with the dilute acidic activator forming iron ceramic material may provide a compressive strength of at least 900 psi with a 2 inch by 4 inch test cylinder. In another embodiment, the iron metallurgical material combined with the dilute acidic activator forming iron ceramic material may provide a compressive strength of at least 1000 psi with a 2 inch by 4 inch test cylinder.
The following examples are offered to further illustrate various specific embodiments and techniques of the present invention. It should be understood, however, that many variations and modifications understood by those of ordinary skill in the art may be made while remaining within the scope of the present invention. Therefore, the scope of the invention is not intended to be limited by the following examples.
In one example, 85 wt % of mill scale was mixed with 5 wt % of dilute phosphoric acid to mill scale for about 1-3 minutes and was set within 5-6 minutes. The cure time was approximately 30 minutes. The reaction resulted in a solid iron ceramic material with a compressive strength of at least 1000 psi. Complete hardening of the solid iron ceramic material was obtained between 8-12 hours. While the iron ceramic material was hardening, an exothermic reaction was observed. The exothermic reaction caused the patching material to heat up slightly to between 100-120° F. During this process, no smells were emitted from the reaction components or reaction products.
In another example, 90 wt % of mill scale was mixed with 10 wt % of dilute phosphoric acid for about 1-3 minutes and was set within 5-6 minutes. The cure time was approximately 30 minutes. The reaction resulted in a solid iron ceramic material with a compressive strength of at least 1000 psi. Same as above, complete hardening of the solid iron ceramic material was obtained between 8-12 hours. While the iron ceramic material was hardening, an exothermic reaction was observed. The exothermic reaction caused the patching material to heat up slightly to between 100-120° F. During this process, no smells were emitted from the reaction components or reaction products.
In another example, 95 wt % of mill scale was mixed with 15 wt % of dilute phosphoric acid for about 1-3 minutes and was set within 5-6 minutes. The cure time was approximately 30 minutes. The reaction resulted in a solid iron ceramic material with a compressive strength of at least 1000 psi. Similar to the examples above, complete hardening of the solid iron ceramic material was obtained between 8-12 hours. While the iron ceramic material was hardening, an exothermic reaction was observed. The exothermic reaction caused the patching material to heat up slightly to between 100-120° F. During this process, no smells were emitted from the reaction components or reaction products.
As mentioned above, presently used methods for patching asphalt and concrete roads require for the hole to be dried up first to remove any moisture before adding any patching material. If moisture is present, then the patching material does not bond well to the surrounding asphalt or concrete, which causes for the hole to reappear after a short period of time. The currently disclosed method does not require for moisture to be removed from the hole before adding the patching material. The currently disclosed patching material binds well to the surrounding road material because moisture is one of the components of the patching material (i.e. dilute acidic activator, e.g. dilute phosphoric acid). Therefore, contrary to presently known methods, even if the pothole is not dried and contains moisture, the patching material will absorb any surrounding moisture and will effectively bind to the surrounding asphalt or concrete.
The reaction between the patching material with the dilute acidic activator causes the patching material to expand slightly. This expansion occurs as the patch is setting and helps the patching material to get into the edges of the hole forming a durable contact between the patch and the asphalt or concrete edges of the hole as the patching material hardens. As such, contrary to previously known methods, the currently disclosed method does not require for holes to have four straight edges before adding the patching material.
When holes develop in the asphalt or concrete road beds, prompt action is required to correct the defect before the pothole increases in size and severity. The currently disclosed method provides an effective and fast way of fixing holes in asphalt and concrete road beds. Once the patching material comprising of iron metallurgical material and dilute acidic activator reacts in the pothole in the road bed to form iron ceramic material, the patching material starts to hardened within 5 to 6 minutes. The cure time is about 30 minutes. And complete hardening is achieved between approximately 8 to 12 hours.
With reference to block 20 of
One of the major problems that authorities face when fixing holes in asphalt and concrete road beds is that the currently available patching methods work best in warm weather, like spring and summer. The ideal time to patch holes in road beds is summer when things are fluid and sticky. In winter, presently known patching materials congeal and are not easy to work with. For example, hot patching does not bond well with dramatically colder pavement in cold winter weather, including above freezing temperatures. See City of Columbus, Ohio—Department of Public Service. The hot patch shrinks away from, and does not conform to, the surrounding asphalt and the contours inside the pothole. The problem with this is that potholes also occur in cold weather, like winter. Therefore, authorities use cold patch to fix potholes in the winter. The problem with cold patching is that it is a temporary fix designed to repair potholes until they can be hot patched during warmer weather in the spring and summer if the cold patched hole reopens. Consequently, even though they will have to fix the holes again in a short period of time after, authorities do not have a choice if they want to keep lanes safe for drivers. This practice results in millions of dollars being wasted. The currently disclosed method of patching asphalt and concrete road beds may be used in both cold weather and hot weather.
The method of patching asphalt and concrete road beds may include a patching material comprising in addition an antifreeze material. The antifreeze material may be ethylene glycol. The addition of an antifreeze material provides further assurance that the currently disclosed method may be performed regardless of the weather or climatic conditions and below the freezing point of water.
The method of patching asphalt and concrete road beds may additionally include adding recycled material selected from the group consisting of asphalt, concrete and a mixture of asphalt and concrete. The recycled material may be oily. As such, the recycled material does not need to be heated to remove the oil, which decreases the operational costs. This provides for broad usage of locally available recycled asphalt, concrete and mixtures thereof from old road beds. The recycled material is crushed and screened. In one embodiment, the recycled material may be have a size of at least −6 mesh. In another embodiment, the recycled material may be have a size of at least −10 mesh.
In one embodiment, the iron metallurgical material combined with dilute acidic activator forming iron ceramic material may provide a compressive strength of at least 1000 psi with a 2 inch by 4 inch test cylinder. In another embodiment, the iron metallurgical material combined with dilute acidic activator forming iron ceramic material may provide a compressive strength of at least 1200 psi with a 2 inch by 4 inch test cylinder.
The recycled material may be added to the iron metallurgical material to form a dry mixture. In one embodiment, the dry mixture may comprise of between 40-60% mill scale and 40-60% recycled material. The dry mixture is then combined with the dilute acidic activator comprised of phosphate anions forming iron ceramic material.
In one example, 10 wt % of dilute acidic activator was added to dry mixture of iron metallurgical material and recycled material. The resulting mixture was mixed for about 1-3 minutes and was set within 5-6 minutes. The cure time was approximately 30 minutes. The reaction resulted in a solid iron ceramic material with a compressive strength of at least 1000 psi. Complete hardening of the solid iron ceramic material was obtained between 8-12 hours. While the iron ceramic material was hardening, an exothermic reaction was observed. The exothermic reaction caused the patching material to heat up slightly to between 120-140° F. During this process, no smells were emitted from the reaction components or reaction products.
The recycled material provides a better bond to the surrounding edges of the hole in the road bed. Furthermore, the addition of recycled material to the iron metallurgical material and dilute acidic activator makes the formed iron ceramic material more flexible, which increases the patching material durability.
The recycled material may comprise of organic road binder, which are often oily. The mill scale may also comprise of oily material. The presence of these oily materials does not have a detrimental effect on the road patching material. The currently disclosed patching material binds well to all types of road material and sticks to the edges of the road bed hole. The method provides a patching material that is also unreceptive to water; thus, it may be used under any type of weather.
Referring now to
As shown in block 22 of
With reference to block 24 of
With reference to blocks 26 and 28 of
FeO combined with dilute acidic activator forming iron ceramic material may provide a compressive strength of at least 1000 psi with a 2 inch by 4 inch test cylinder. In another embodiment, FeO combined with dilute acidic activator forming iron ceramic material may provide a compressive strength of at least 1200 psi with a 2 inch by 4 inch test cylinder.
The method for patching asphalt and concrete road beds may further comprise adding recycled material selected from the group consisting of asphalt, concrete and a mixture of asphalt and concrete. The recycled material is crushed and screened. In one embodiment, the recycled material may be have a size of at least −6 mesh. In another embodiment, the recycled material may be have a size of at least −10 mesh.
The recycled material may be added to FeO to form a dry mixture. In one embodiment, the dry mixture may comprise of between 40-60% mill scale and 40-60% recycled material. The dry mixture is then mixed with the dilute acidic activator comprised of phosphate anions forming iron ceramic material. In one example, 10 wt % of dilute acidic activator was added to dry mixture. The resulting mixture was mixed for about 1-3 minutes and was set within 5-6 minutes. The cure time was approximately 30 minutes. The reaction resulted in a solid iron ceramic material with a compressive strength of at least 1000 psi. Complete hardening of the solid iron ceramic material was obtained between 8-12 hours. While the iron ceramic material was hardening, an exothermic reaction was observed. The exothermic reaction caused the patching material to heat up slightly to between 120-140° F. During this process, no smells were emitted from the reaction components or reaction products.
With reference to block 30 of
The method of patching asphalt and concrete road beds may further include the addition of an antifreeze material. The addition of an antifreeze material provides further assurance that the currently disclosed method may be performed regardless of the weather or climatic conditions and below the freezing point of water.
The currently disclosed method provides a patching material that binds well to all types of road material and sticks to the edges of the road bed hole. The patching material is also unreceptive to water; thus, it may be used under any type of weather.
Although the invention has been described in detail with reference to certain embodiments, it should be understood that the invention is not limited to the disclosed embodiments. Rather, the present invention covers variations, modifications and equivalent structures that exist within the scope and spirit of the invention and such are desired to be protected.
