WET CONCRETE CONDITIONING

Abstract

Method and equipment for conditioning wet concrete (703), the wet concrete (703) being agitated in a revolving-drum concrete mixer (702), thereby bringing changing portions of the wet concrete (703) to a free surface (706) of the wet concrete (703) inside the mixer (702), the agitated wet concrete (703) being cooled and partially carbonated in that liquid and/or solid carbon dioxide is supplied to the concrete mixer (702) simultaneously with liquid nitrogen so that both the supplied nitrogen and the supplied carbon dioxide contact the free surface (706) of the wet concrete (703).

Claims

1.-15. (canceled)

16. A method for conditioning wet concrete, comprising: (i) agitating wet concrete in a revolving-drum concrete mixer thereby bringing changing portions of the wet concrete to a free surface of the wet concrete inside the mixer, and (ii) cooling the agitated wet concrete in the concrete mixer by supplying nitrogen in liquid form to the mixer so that the supplied nitrogen contacts the wet concrete at the free surface and cools the wet concrete, wherein the agitated wet concrete is cooled and partially carbonated by supplying liquid and/or solid carbon dioxide to the concrete mixer simultaneously with the nitrogen so that both the supplied nitrogen and the supplied carbon dioxide contact the free surface of the wet concrete, the carbon dioxide comprising solid carbon dioxide.

17. The method according to claim 16, whereby the liquid and/or solid carbon dioxide is dispersed in the liquid nitrogen before the liquid nitrogen is supplied to the concrete mixer.

18. The method according to claim 16, whereby the nitrogen and the liquid and/or solid carbon dioxide are supplied to the concrete mixer separately.

19. The method according to claim 18, whereby the liquid nitrogen is supplied to a nitrogen injector, the nitrogen injector injecting said nitrogen into the concrete mixer in one or more nitrogen streams which contact the free surface and whereby the liquid and/or solid carbon dioxide is supplied to the mixer and dispersed in at least in at least one of the one or more injected nitrogen streams, the nitrogen being injected into the concrete mixer in a single nitrogen stream.

20. The method according to claim 19, whereby the one or more carbon-dioxide streams or at least one of the one or more carbon-dioxide streams are/is injected into the concrete mixer in contact with at least one of the one or more nitrogen streams.

21. The method according to claim 16, whereby the wet concrete is cooled and partially carbonated: before transport of the wet concrete, between two transport stages of the wet concrete, or at a location where the wet concrete is subsequently cast to form a set concrete product.

22. A process for conditioning wet concrete, whereby during part of the process the wet concrete is cooled and partially carbonated by means of the method according to claim 16 and whereby during a different part of the process the wet concrete is cooled by supplying nitrogen in liquid form to the concrete mixer without carbon dioxide being supplied to the concrete mixer.

23. An installation for conditioning wet concrete, comprising: a revolving-drum concrete mixer for agitating wet concrete, the concrete mixer having a revolution axis A-A and presenting a mouth at one end of the axis A-A, equipment for supplying a fluid to the concrete mixer through the mouth in a controlled amount and/or at a controlled flow-rate, said equipment including a source of the fluid to be supplied to the concrete mixer; wherein the source is a source of liquid nitrogen containing solid carbon dioxide dispersed therein.

24. The installation according to claim 23, the equipment comprising an injector for injecting the fluid in the controlled amount and/or at the controlled flow-rate into the concrete mixer in one or more streams, the injector being fluidly connected to the source by means of a conduit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0088] For a further understanding of the nature and objects for the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements are given the same or analogous reference numbers and wherein:

[0089] FIG. 1 is a schematic representation of a first installation for use in the present invention,

[0090] FIG. 2 is a schematic representation of an injector unit suitable for use in the installation of FIG. 1,

[0091] FIG. 3 is a schematic representation of an alternative installation for use in the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0092] FIG. 1 shows a concrete transport truck 704 having a revolving-drum concrete mixer 702 mounted thereon. While in the drum/mixer 702, the wet concrete 703 is agitated/stirred in that mixer 702 is rotated around inclined axis A-A, thereby continuously renewing the free surface 706 of said wet concrete 703, i.e. the surface of wet concrete 703 which is exposed to the atmosphere inside mixer 702. The interior of mixer 702 is fitted with a spiral blade (not shown) in a manner known in the art. The spiral blade improves the agitation/mixing of the wet concrete 703 inside mixer 702 when the latter is rotated and, acting as an Archimedes screw, assists with the charging and discharging of the wet concrete 703. Charging and discharging of the wet concrete takes place via the mixer mouth 705 located at the upper end of axis A-A.

[0093] The installation according to the invention comprises an upwardly extending support structure 108, which extends from ground level to above the level of mixer mouth 705.

[0094] An injector unit 104 is pivotally mounted near the top of the support structure 108 so as to enable the injector unit 104 to be directed towards and away from mixer mouth 705.

[0095] Injector unit 104 further comprises an extendable lance 102. When mixer truck 704 is positioned with its mixer mouth 705 towards injector unit 104, lance 102 may be extended to reach into mixer 702 via mixer mouth 705, or be retracted out of mixer 702 via mixer mouth 705. One or more injectors (not shown in FIG. 1) are provided at the far end 105 of lance 102, for the combined injection of liquid nitrogen and liquid and/or solid carbon dioxide into mixer 702 towards free surface 706 of wet concrete 703, preferably with the option of also injecting only liquid nitrogen for part of the injection process.

[0096] Thus, when a concrete truck 704 arrives and is placed in position near vertical support structure 108, injector unit 104 is pivoted towards mouth 705 of the mixer 702 of the truck 704 and lance 102 is extended to reach inside mixer 702.

[0097] After completion of the cooling and partial carbonation of the wet concrete 703 in mixer 702, lance 102 is retracted from mixer 702 and injector unit 104 is pivoted away from mixer 702, so that truck 704 can leave without damaging either mixer 702 or injector unit 104,

[0098] As illustrated in FIG. 2, according to one embodiment, the injector unit 104 may have a separate liquid-nitrogen inlet 41 and carbon-dioxide inlet 42. Liquid-nitrogen inlet 41 is fluidly connected to a source of liquid nitrogen (not shown) and carbon-dioxide inlet 42 is fluidly connected to a source of liquid and/or solid carbon dioxide (not shown). When the installation is used to simultaneously supply liquid nitrogen and solid and/or liquid carbon dioxide to mixer 702, liquid nitrogen flows in a controlled manner form the liquid-nitrogen source to liquid-nitrogen inlet 41 via a nitrogen conduit (not shown) and from said inlet 41 along lance 102 to far end 105 from which the liquid nitrogen is injected into mixer 702 so as to contact the free surface 706 of wet concrete 703. At the same time liquid and/or solid carbon dioxide flow in a likewise controlled manner from the carbon-dioxide source to carbon-dioxide inlet 42 via a carbon dioxide conduit (not shown) and from said inlet 42 along lance 102 to the far end 105 of lance 102 before being injected into mixer 702 in such a way that the carbon dioxide contacts the wet concrete 703 at its free surface 706. For example, the injection installation may comprise carbon-dioxide and nitrogen injectors 44, 43 in surrounding arrangement to one another so that when liquid nitrogen from the nitrogen source is supplied to the nitrogen injector 43 for injection into mixer 702 and carbon dioxide from the carbon-dioxide source is supplied in liquid form to the carbon-dioxide injector 44 for injection into mixer 702, the carbon dioxide and nitrogen are injected in contact with one another so that the liquid carbon dioxide solidifies and is entrained by the injected nitrogen towards fee surface 706 in the form of a spray of carbon dioxide particles/snow in and entrained by nitrogen 45.

[0099] When, during part of the process, only cooling with nitrogen is desired, only liquid nitrogen is supplied to the injection unit to injector unit 104, so that only nitrogen is injected into mixer 702, for example by means of nitrogen injector 43.

[0100] FIG. 3 illustrates an installation for use in the present invention, whereby liquid carbon dioxide is mixed with the liquid nitrogen before the resulting mixture is supplied to concrete mixer 702, via mouth 705, where it contacts free surface 706 of wet concrete 703.

[0101] Liquid nitrogen is stored on-site in cryogenic reservoir 241 and liquid carbon dioxide is stored in pressurized cryogenic reservoir 242. Nitrogen reservoir 241 is fluidly connected to blender 250 by means of nitrogen conduit 251 whereas carbon-dioxide reservoir 242 is fluidly connected to said blender 250 by means of carbon-dioxide conduit 252. Control valve 261 controls the amount and/or flow rate of liquid nitrogen from reservoir 241 to blender 250 and control valve 262 controls the amount and/or flow rate of liquid carbon dioxide from reservoir 242 to blender 250. No-return valves 271 and 272 ensure that no backflow can occur from blender 250 to respectively nitrogen reservoir 241 and carbon-dioxide reservoir 242.

[0102] Inside blender 250, carbon dioxide from reservoir 242 is mixed with liquid nitrogen from reservoir 241, in such a way that a suspension of solid carbon-dioxide particles is formed in the liquid nitrogen.

[0103] From blender 250, said suspension flows, via conduit 255 and mouth 705, into mixer 702 and onto free wet-concrete surface 706 inside mixer 702, where partial carbonation and cooling of wet concrete 705 takes place. In other words, conduit 251 and conduit 255 together form a ‘nitrogen conduit’ transporting liquid nitrogen from reservoir 241 to concrete mixer 702 and blender 250 constitutes a connector fluidly connecting carbon-dioxide reservoir to said ‘nitrogen conduit’ via carbon-dioxide conduit 252 and permitting the controlled addition of carbon dioxide to the nitrogen flow in the ‘nitrogen conduit’.

[0104] Valves 251 and 252 are controlled by control unit 600.

[0105] When control unit 600 closes carbon-dioxide valve 262 while nitrogen valve 261 is open, a controlled amount/a controlled flow rate of liquid nitrogen is supplied to blender 250, without any carbon dioxide being supplied to said blender 250, only liquid nitrogen is supplied to mixer 702 and only cooling of wet concrete 705 takes place inside mixer 702.

[0106] Control unit 600 is itself preferably remotely controlled. For example, control unit 600 may be equipped with a data sensor 601 and concrete transport trucks 704 may be equipped with data emitters 602. Data emitters 602 transmit to data sensor 601 of control unit 600 information concerning the identification of truck 704, the nature and volume of wet concrete 705 contained in mixer 704, the degree of partial carbonation sought and information permitting to determine the degree of concrete cooling required. In addition, the installation may be equipped with a further sensor/emitter (not shown), in communication with data sensor 601 of control unit 600, said sensor/emitter being capable of detecting a positions of mixer 702 and mixer mouth 705 relative to the fluid supply equipment, in particular, in the case illustrated in FIG. 3, with respect to outlet opening of conduit 255, and, in the case illustrated in FIGS. 1 and 2, with respect to the outlet end 105 of lance 102. In this manner, it may be ensured that no flow of liquid nitrogen and solid and/or liquid carbon dioxide or of liquid nitrogen as such, as the case may be, is released until the corresponding outlets are correctly positioned inside mixer 702, and a safe working environment is assured around the installation and truck 704.

[0107] It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.