SYSTEM FOR PROCESSING UNHARDENED CONCRETE

Abstract

A system and associated methods for processing unhardened concrete are disclosed. It at least one embodiment, the system for processing unhardened concrete includes a means to estimate a quantity of returned concrete; a foam adder to add foam to the quantity of returned concrete; a mixer to mix the added foam and returned concrete together to create treated concrete; a discharger to discharge the treated concrete; a discharge area configured in which to allow the treated concrete to set and harden; a converter to convert the hardened treated concrete into a particulate or aggregate form; and a user to determine the specific utilization of the particulate or aggregate form loose material.

Claims

1. A system for processing unhardened concrete, that increases the porosity of the unhardened returned concrete, which decreases its strength by greater than 80 percent when compared to the strength of the original returned concrete, after which it can be easily broken up into loose particulate material for sale or reuse, the system comprising: a means to estimate a quantity of returned concrete, the returned concrete comprising original course aggregate, a mixture of fine aggregate, and partially hydrated cement; an adder to add a chemical admixture or a combination of chemical admixtures to the quantity of returned concrete to increase the porosity of the concrete; a mixer to mix the added chemical admixture or the combination of chemical admixtures and returned concrete together to create treated concrete; a discharger to discharge the treated concrete; a discharge area configured in which to allow the treated concrete to set and harden; a converter to convert the hardened treated concrete into a particulate or aggregate form loose material that substantially comprises the original coarse aggregate and a mixture of fine aggregate, partially hydrated cement, and chemical admixture or a combination of chemical admixtures; and a user to determine the specific utilization of the particulate or aggregate form loose material; wherein the hardened form treated concrete has a strength that is decreased by greater than 80 percent when compared to the strength of the original returned concrete.

2. The system of claim 1, further comprising: a device to add an expansive agent to the returned concrete to create bubbles in the returned concrete and to significantly reduce the strength of the returned concrete.

3. The system of claim 1, further comprising: a device to apply an anti-foaming agent to the particulate or aggregate form to counteract the foaming agent residue and to reduce the air content of the concrete made from the recycled particulate or aggregate form loose material.

4. The system of claim 1, further comprising: a means to determine a quantity of foam to use to add to the returned concrete based upon the foaming agent selected, the concentration of the foaming agent when mixed with water, and the foam generator selected with which to add the foam.

5. The system of claim 1, wherein the adder to add a chemical admixture or combination of chemical admixtures to the quantity of returned concrete further comprises: a foaming machine with compressed air; a foaming agent disposed in the foaming machine; and a means to add the foaming agent to water with an appropriate water-to-foaming agent ratio.

6. The system of claim 1, further comprising: a crusher device to convert the hardened treated concrete into a particulate or aggregate form loose material that substantially comprises the original coarse aggregate and a mixture of fine aggregate, partially hydrated cement, and foaming agent residue.

7. The system of claim 1, further comprising: a collector to gather and recycle the particulate or aggregate form loose material after conversion for use as coarse or fine aggregate and with which to produce new concrete.

8. The system of claim 1, wherein the adder is a foam adder configured to add a foam to the quantity of returned concrete to increase the porosity of the concrete.

9. The system of claim 1, wherein the chemical admixture comprises a foam.

10. The system of claim 1, wherein the chemical admixture is an expansive agent either used individually or in combination with other chemical admixtures

11. The system of claim 1, wherein the chemical admixture is a foaming agent either used individually or in combination with other chemical admixtures

12. The system of claim 2, wherein the expansive agent is aluminum powder.

13. The system of claim 2, wherein the expansive agent is hydrogen peroxide.

14. The system of claim 2, wherein the expansive agent is expandable micro spheres.

15. The system of claim 3, wherein the foaming agent is foam liquid concentrate.

16. The system of claim 3, wherein the foaming agent is a synthetic foam liquid concentrate.

17. The system of claim 3, wherein the foaming agent is a protein-based foam liquid concentrate.

18. The system of claim 3, wherein the foaming agent is an air-generating admixture.

19. The system of claim 3, wherein the foaming agent is a surfactant.

20. The system of claim 1, wherein the specific utilization comprises recycling the particulate or aggregate form loose material after conversion in one or more of these applications: embankment fill, trench backfill, void filling, and base or sub-base material for pavements, and wherein the particulate or aggregate form loose material after conversion further comprises a plurality of cementitious particles that continue to hydrate and contribute to strength gain in the one or more applications over time.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0087] The technology described herein is illustrated with reference to the various drawings, in which like reference numbers denote like device components and/or method steps, respectively, and in which:

[0088] FIG. 1 is a flowchart diagram depicting a method for processing unhardened concrete, according to an embodiment of the technology described herein;

[0089] FIG. 2 is a schematic diagram depicting a system for processing unhardened concrete, according to an embodiment of the technology described herein; and

[0090] FIG. 3 a flowchart diagram depicting additional method steps for processing unhardened concrete, according to various embodiments of the technology described herein.

DETAILED DESCRIPTION OF THE INVENTION

[0091] Before describing the disclosed embodiments of this technology in detail, it is to be understood that the technology is not limited in its application to the details of the particular arrangement shown here since the technology described is capable of other embodiments. Also, the terminology used herein is for the purpose of description and not of limitation.

[0092] In various exemplary embodiments, the technology described herein provides a system and associated methods for processing unhardened concrete by significantly increasing the porosity of the unhardened concrete to decrease its strength so much that it can be easily broken up for sale or reuse. In at least one embodiment this method includes: estimating the quantity of returned concrete; adding foam to the returned concrete; mixing the foam and returned concrete together; discharging the treated concrete; allowing the treated concrete to set; converting the hardened treated concrete into a particulate or aggregate form, and using the particulate or aggregate form loose material.

[0093] A new method and system to process returned concrete is disclosed herein. In at least one embodiment, the method includes adding a large volume of foam to the returned unhardened concrete in the ready-mixed concrete truck drum, other concrete mixers, or other concrete reclaiming devices. Through the mixing of foam with the returned concrete, the hydrated cement and aggregate particle are separated by large volumes of air voids, which dramatically reduce the strength of the resulting high porosity concrete. The treated concrete is discharged and allowed to solidify in this weakened state, after which it is easily broken into loose particulate material that can be sold or reused.

[0094] In at least one embodiment of this technology, it is also possible to add the foam to a ready-mixed concrete truck, for example, while at the jobsite or while the truck is driven on its way back to the batch plant. With this approach, the foam is mixed into the concrete while the truck is at the jobsite or returning to the batch plant. The treated concrete can then be discharged at any convenient location where it can be recycled. The addition of an expansive agent (such as aluminum powder, hydrogen peroxide, or expandable microspheres) or the mixing in of a foaming agent (such as foam liquid concentrate or an air-generating admixture) with the returned concrete to create bubbles in the returned concrete can also be used to dramatically reduce the strength of the returned concrete to allow it to be recycled. It is known in the art that through chemical reactions, gasses can be created that form a gas-bubble structure within the concrete. It is also known in the art that hollow microspheres can be used to increase the porosity of the concrete. It is also known in the art that large amounts of air voids can be created in concrete by mixing in foam liquid concentrates, air-generating admixtures, or surfactants.

[0095] In at least one embodiment, the method includes: (1) estimating the quantity of returned concrete; (2) adding foam to the returned concrete; (3) mixing the foam and returned concrete together; (4) discharging the treated concrete; (5) allowing the treated concrete to set; (6) converting the hardened treated concrete into a particulate or aggregate form; and (7) utilizing the particulate or aggregate form loose material.

[0096] It is preferred to mix the foam and unhardened returned concrete together in a ready-mixed concrete truck or some other mixing device. The treated concrete is then discharged onto the ground or into a holding bin to allow it to set and start hardening. The foam for use in this technology disclosed herein may be prepared by using any suitable foaming agent (air-bubble foam-making agent) that when mixed with water produces a foam that is stable enough to maintain its cell structure without significant collapsing when mixed with concrete. The quantity of foam needed will vary depending on the type of foaming agent, its concentration when mixed with water, and the foam generator. When using a foam generator with a solution of foaming agent in water, the volume can increase by 10 to 40 times. The addition of this large volume of foam to the returned concrete significantly increases the porosity and reduces the strength of the concrete.

[0097] Accelerating agents can also be added to shorten the set time and accelerate the hardening process of the treated concrete. Accelerating agents may also be used to shorten the processing time under cold weather conditions. Those skilled in the art are able to use accelerating admixtures to reduce the setting times and the time to reach a desired strength level.

[0098] The methods and systems disclosed herein utilize minimal water. The only water used is to rinse out any possible foam residue or paste remaining in the empty ready-mixed concrete truck mixer. Because of its very low strength, the solidified treated concrete is easily broken up with methods known in the art at an age of 5 to 72 hours or later. The dried and solidified treated concrete collapses into loose particulate material when stressed during the breaking up process. The loose particulate material may be stockpiled for sale or reuse.

[0099] Typical use of the recycled loose particulate material from this process includes use as embankment fill, trench backfill, void filling, base or sub-base material for pavements, or as aggregate in new concrete mixtures. The loose material after conversion may contain some cementitious particles that will continue to hydrate and contribute to strength gain in these applications with time.

[0100] If the recycled loose particulate material is used as aggregate in new concrete, the use of an anti-foaming agent may be needed due to the presence of foaming agent residue in the recycled material. These agents can be used to reduce the air content of concrete made with the recycled loose particulate material. There are various anti-foaming agents known in the art that will work for this purpose. An example of an antifoaming agent is tributyl phosphate, an odorless chemical available from most chemical manufactures. Another commonly available chemical, 2-ethyl hexanol, will reduce the air content in most concrete mixtures.

[0101] The technology disclosed herein does not produce wastes, substantially reduces the amount of water used, eliminates much of the maintenance expense on heavy machinery, allows the size of concrete plant sites to be reduced, and is environmentally friendly. With this method, natural resources are not exploited and multi-faceted economic benefit is accomplished. The ease of the process and the use of non-toxic substances make this method environmentally sustainable. Environmental, social, and economic benefits achievable by this new method provide important sustainability improvements for the concrete industry.

[0102] Referring now to the FIG. 1, a flowchart diagram 100 is shown, depicting a method for processing unhardened concrete. As will be apparent to one of ordinary skill in the art, upon reading this disclosure, some of the method steps may be implemented in varying order depending on the given circumstances. Additionally, one or more method steps may be omitted under the appropriate circumstances.

[0103] At step 102, the quantity of returned concrete is estimated. This step of estimating 102 can be carried out by a person in at least one embodiment. By way of example, the driver/operator of a truck containing returned concrete estimates the volume of unhardened returned concrete contained in the truck. This step of estimating 102 can be carried out by one or more generally-automated machines for such purpose in at least one embodiment. By way of example, a generally-automated machine can estimate the volume of returned concrete based on one or more factors such as weight or torque loading on the hydraulic drive which rotates the mixing drum.

[0104] At step 104, foam is added to the quantity of returned concrete to increase the porosity of the concrete. This step of adding foam 104 can be carried out by a person in at least one embodiment. By way of example, the driver/operator of a truck containing returned concrete can add foam into the returned concrete at the concrete plant, at the jobsite, or while in transit. This step of adding foam 104 can be carried out by one or more generally-automated machines for such purpose in at least one embodiment. By way of example, the foam can be added to returned concrete not only in the returned concrete truck, but also at another location such as at a processing facility for such purpose.

[0105] At step 106, added foam and returned concrete are mixed together to create treated concrete. Through the mixing of foam with the returned concrete, the hydrated cement and aggregate particle are separated by large volumes of air voids, which dramatically reduce the strength of the resulting high porosity concrete. In at least one embodiment, the mixing step 106 occurs in the truck containing the returned concrete. In at least one embodiment the mixing step 106 occurs at a location other than the return truck such as at a processing facility for such purpose.

[0106] At step 108, the treated concrete is discharged. The treated concrete is discharged and allowed to solidify in this weakened state, after which it is easily broken into loose particulate material that can be sold or reused. The treated concrete can be discharged onto the ground or in a discharge area for such purpose. The treated concrete also can be discharged into a fabricated area for such purposes.

[0107] At step 110, the treated concrete is allowed to set into a hardened form, thereby to significantly decrease the compressive strength relative to the strength of the original returned concrete. The time period in which the treated concrete is allowed to harden can vary, but as disclosed herein, time periods between 5 and 72 hours have been found to provide sufficient time to harden.

[0108] At step 112 the hardened treated concrete is converted into a particulate or aggregate form loose material. The conversion process can include use of a front-end loader or like device to break up the concrete and move to another location. The weakened bond of the hardened treated concrete is easily broken up by pushing and scooping with a front-end loader. When placed under stress by pushing on the material with a front-end loader, the dried and solidified treated concrete will collapse into loose particulate material that can be stockpiled for sale or reuse. Alternative devices are utilized to break or crush the concrete in various embodiments.

[0109] At step 114 the particulate form or aggregate form loose material is utilized. By way of example, the utilization is for embankment fill, trench backfill, void filling, and base or sub-base material for pavements in various embodiments. Also by way of example, the utilization is to produce new concrete.

[0110] Referring now to the FIG. 2, a schematic diagram 200, used generally through route 216, is shown, depicting a system for processing unhardened concrete. As will be apparent to one of ordinary skill in the art, upon reading this disclosure, some of the system components may be implemented in varying order depending on the given circumstances. Additionally, one or more system components may be omitted or added under the appropriate circumstances.

[0111] An estimator 202 is utilized to estimate the quantity of returned concrete. The estimator 202 can be a person in at least one embodiment. By way of example, the driver/operator of a truck containing returned concrete estimates the volume of unhardened returned concrete left in the drum. The estimator 202 can be one or more generally-automated machines for such purpose in at least one embodiment. By way of example, a generally-automated machine can estimate the volume of returned concrete based on one or more factors such as weight or torque loading on the hydraulic drive which rotates the mixing drum.

[0112] A foam adder 204 is utilized to add foam to the quantity of returned concrete to increase the porosity of the concrete. In at least one embodiment, the foam adder is a foaming machine. The foaming machine is configured for receipt of a foaming agent. The foaming agent is mixed with water at a predetermined water-to-foaming agent ratio and with compressed air dispersed through the foaming machine into the returned concrete.

[0113] A mixer 206 is utilized to mix the added foam and returned concrete together. Through the mixing of foam with the returned concrete, the hydrated cement and aggregate particle are separated by large volumes of air voids, which dramatically reduce the strength of the resulting high porosity concrete.

[0114] A discharger 208 is utilized to discharge the treated concrete. The treated concrete is discharged and allowed to solidify in this weakened state, after which it is easily broken into loose particulate material that can be sold or reused. The treated concrete can be discharged onto the ground in a discharge area for such purpose. The treated concrete also can be discharged into a fabricated area for such purposes.

[0115] A discharge area 210 is provided to allow the discharged treated concrete to set into a hardened form. This process serves to allow the treated concrete to continue to hydrate and harden with time. After hardening the treated concrete has a compressive strength significantly lower relative to the strength of the original returned concrete. The time period in which the treated concrete is allowed to remain in this discharge area can vary, but as disclosed herein, time periods between 5 and 72 hours have been found to provide sufficient time to harden.

[0116] A converter 212 is utilized to convert the hardened treated concrete into a particulate or aggregate form loose material. The conversion process can include use of a front-end loader or alternative device to break up the concrete and move to another location. The weakened bond of the hardened treated concrete is easily broken up by pushing and scooping with a front-end loader. When placed under stress by pushing on the material with a front-end loader, the dried and solidified treated concrete collapses into loose particulate material that was stockpiled for sale or reuse. Alternative devices are utilized to break or crush the concrete in various embodiments.

[0117] A user 214 can be introduced to determine a specific utilization. By way of example, the utilization is for embankment fill, trench backfill, void filling, and base or sub-base material for pavements in various embodiments. Also by way of example, the utilization is to produce new concrete.

[0118] Referring now to the FIG. 3, a flowchart diagram 300 is shown, depicting optional, user-selectable, method steps for processing unhardened concrete, which may be utilized independently or in addition to steps depicted in FIG. 1. As will be apparent to one of ordinary skill in the art, upon reading this disclosure, some of the method steps may be implemented in varying order depending on the given circumstances. Additionally, one or more method steps may be omitted under the appropriate circumstances.

[0119] At step 302, an expansive agent is added to the returned concrete to create bubbles in the returned concrete and to significantly reduce the strength of the returned concrete.

[0120] At step 304, a foaming agent is mixed with the returned concrete to create bubbles in the returned concrete and to significantly reduce the strength of the returned concrete.

[0121] At step 306, an anti-foaming agent is added to the particulate or aggregate form to counteract the foaming agent residue and to reduce the air content of a concrete made from the recycled particulate or aggregate form loose material.

[0122] At step 308, a quantity of foam is determined to add to the returned concrete based upon the foaming agent selected, the concentration of the foaming agent when mixed with water, and the foam generator selected with which to add the foam.

[0123] At step 310, the concrete is recycled in particulate or aggregate form loose material into a new aggregate in new concrete.

[0124] At step 312, the particulate or aggregate form loose material after conversion is recycled in one or more of these applications: embankment fill, trench backfill, void filling, and base or sub-base material for pavements.

[0125] At step 314, the recycled particulate or aggregate form loose material after conversion as coarse and/or fine aggregate is recycled to produce new concrete.

[0126] The technology described herein has been tested and shown to work effectively in multiple scenarios.

Example 1

[0127] In this example, foam was produced by using a foaming machine and a foaming agent (CMX foam concentrate or LD foam concentrate) supplied by Richway Industries Ltd. (Janesville, Iowa). Foam was added to various loads of returned ready-mixed concrete to determine the appropriate water-to-foaming agent ratio to treat each yard of returned concrete. Water-to-foaming agent ratios from 16 to 88 were evaluated, with the best ratio found to be approximately 40 to 50. High water-to-foaming agent ratios resulted in treated concrete that was too strong and difficult to break up. Low water-to-foaming agent ratios created a denser foam that sufficiently weakened the treated concrete to allow it to be broken up; however, this ratio used too much foaming agent.

Example 2

[0128] In this example, foam was produced by using a foaming machine and a foaming agent (CMX foam concentrate or LD foam concentrate) supplied by Richway Industries Ltd. (Janesville, Iowa). Foam was added to various loads of returned ready-mixed concrete to determine the amount of foam needed to process unhardened concrete. Water-to-foaming agent ratios of 40 to 50 were used. Trials with too little foam added to the returned concrete resulted in treated concrete that was too strong and difficult to break up. With large volumes of foam added, the treated concrete was very weak and easy to break up, but excess foam was clearly visible.

[0129] In this example trials were done with 15 to 48 cubic feet of foam per cubic yard of returned concrete added and mixed in within the truck drum. This volume of foam decreased the concrete unit weight from approximately 145 pounds per cubic foot to approximately 30 to 80 pounds per cubic foot. The 3-day compressive strength of the concrete decreased from greater than 3,000 psi to a value lower than what can be measured by a typical compression-testing machine. After setting, the very low-strength, foam-treated concrete was scooped up with a front-end loader at an age of 5 to 72 hours. The weaken bond of the hardened-treated concrete was very easily broken up by pushing and scooping with a front-end loader. Trials at a concrete age of 7 days and later were performed and even at this age, the treated concrete was very easily broken up with a front-end loader because of its very low strength. When placed under stress by pushing on the material with a front-end loader, the dried and solidified treated concrete collapsed into loose particulate material that was stockpiled for sale or reuse.

Example 3

[0130] This is an example where the recycled loose particulate material was collected and used as coarse and fine aggregate to produce new concrete. Returned concrete was treated as discussed in Example 2. After setting, the very low-strength, foam-treated concrete was scooped up with a front-end loader and stockpiled. Four cubic feet of the loose particulate material was collected for use as all the aggregate to produce a new concrete mixture. An anti-foaming agent (Air-Minus) supplied by FritzPak was added to reduce the total air content in the new concrete. After mixing, a total air content of 2.0 percent was obtained when tested in accordance with ASTM C231. Cylinders were made and tested in accordance with ASTM C39 and a 28-day strength of 4,500 psi obtained. These results indicate that concrete with acceptable properties can be made with the recycled loose particulate material obtained from recycling treated returned concrete.

[0131] Although this technology has been illustrated and described herein with reference to preferred embodiments and specific examples thereof, it will be readily apparent to those of ordinary skill in the art that other embodiments and examples can perform similar functions and/or achieve like results. All such equivalent embodiments and examples are within the spirit and scope of the technology disclosed herein and are intended to be covered by the following claims.