WO2003078068A1

WO2003078068A1 - A method of treating unset surplus concrete

Info

Publication number: WO2003078068A1
Application number: PCT/IE2002/000022
Authority: WO
Inventors: Dermot Eugene Mckeown; Martin Joseph Curran
Original assignee: Swainstown Stone Company Limited
Priority date: 2002-02-21
Filing date: 2002-02-21
Publication date: 2003-09-25
Also published as: AU2002234841A1

Abstract

Wet unset concrete is delivered to a concrete mixer drum and water is sprayed onto the concrete as is necessary. Then, the concrete is delivered into a scrubber drum (6) which is rotated and as it rotates, the concrete is mixed, agitated and washed by means of internal paddle blades. The concrete is then gradually delivered to a cylindrical rotary screen (8). As the wet concrete is delivered into the rotary screen (8), a spray bar delivers water to further wash the aggregate and to deliver the sand, fines, cement and most of the water into an outlet hopper (12). The washed aggregate is delivered onto a conveyor (13) and then to storage hoppers (14). The aggregate can be further screened, separated and sized. An outlet hopper associated with the rotary screen (8) delivers a slurry which is then further screened by a flat bed screen (9) such that the sand is delivered to the conveyor (13) and a slurry now of fines, cement and water is delivered to a settling tank assembly (20). Relatively clean water is then removed for recycling.

Description

"A method of treating unset surplus concrete"

Introduction

The present invention relates to a method and apparatus for the treating of unset surplus concrete and in particular to the recycling of most if not all of it.

One of the major problems of modern society is the amount of waste that requires disposal. Governments are now installing and enforcing vigorous and stringent recycling requirements, not alone on industry, but on the consumer. Landfill sites are becoming less available and people are becoming more concerned about the unfettered disposal of waste. One of the major problems is building waste. Concrete is a particular problem in that once concrete has set, it is effectively useless and the only way it can be recycled is by re-crushing which is relatively expensive.

A further problem is that most concrete is now being delivered by mixer trucks and these trucks require that they be fully cleaned out at the end of each shift or day and further, very often, when they come back to be replenished with concrete at a concrete mixer plant, any surplus concrete not delivered to the previous site has to then be disposed of. This is particularly the case where the mixes of successive deliveries might be different when it would require that the truck be fully cleaned out prior to accepting the next delivery.

What is required is a relatively simple and efficient way of treating unset surplus concrete to recycle some or all of it. Such concrete comprises aggregate, so-called sand, fines, cement and water. Essentially, aggregates are defined in most situations as being stones which are greater than +4mm and are usually not greater than 20mm. Then, sand, which can be ground stone or indeed can be sand reclaimed from sandpits, is usually defined as being less than 4mm, while fines and concrete are usually less than 75 micron. It should be noted that in various countries and in various situations, there may be variations in the sizes defined as used for defining the various materials, however, the former sizes are approximately correct for most countries. However, it is to be appreciated that while, in the present invention, fines are defined as those less than 75 micron in size, it does not mean that in every jurisdiction, this will be the definition. Thus, if the definition is different in other jurisdictions, it is to be taken as being approximately these figures.

Statements of Invention

According to the invention there is provided a method of treating unset surplus concrete, including aggregate, sand, fines, cement and water comprising:-

mixing and agitating the concrete in the presence of additional water to wash and separate the aggregate, sand, fines and cement;

initially screening the concrete while further washing it to remove the aggregate; and

further screening the sand, fines and cement to remove the sand and leave a slurry of fines, cement and water.

In one embodiment of the invention the sand and aggregate are removed to storage for re-use.

In another embodiment the slurry is allowed to settle and most of the water is removed therefrom to leave a concentrated slurry.

In a further embodiment the concentrated slurry is recycled by delivery to a concrete plant prior to hardening.

In another embodiment the concentrated slurry is agitated in a storage tank prior to delivery to the concrete plant.

in another embodiment water is added continuously to the concrete during the mixing and agitating.

Conveniently the further screening of the sand, fines and cement is carried out while washing them. In another embodiment the washing, during screening, comprises spraying water on the material through the screening.

In another aspect the invention provides an unset concrete treatment plant for carrying out the method previously described comprising:-

a cylindrical substantially horizontally arranged scrubber drum having a spaced-apart inlet and an outlet; and

combined agitating and transfer means mounted on the interior surface of the scrubber drum to agitate and mix the concrete in the drum while moving the concrete from the inlet to the outlet.

in another embodiment the combined agitating and transfer means comprises:-

a plurality of radially and longitudinally arranged lifter blades mounted on the interior surface of the scrubber drum; and

additional transfer blades mounted on the interior surface of the scrubber drum to move concrete from the inlet to the outlet.

In another embodiment the combined agitating and transfer means comprises angled blades mounted in the interior surface of the scrubber drum and projecting into the interior thereof.

In another embodiment the plant comprises :-

a cylindrical rotary screen mounted co-axially with the scrubber drum against the drum outlet for reception of the concrete therefrom; and

a spray bar mounted inside the screen. Conveniently the cylindrical rotary screen is integral with the scrubber drum forming the one assembly therewith. In another embodiment the scrubber drum includes perforations to provide additional screening of all except aggregates.

In a further embodiment the scrubber drum comprises a plurality of longitudinally arranged spaced-apart bars proud of the interior surface of the scrubber drum.

In another embodiment a spray bar is mounted in the scrubber drum.

in another embodiment a spray bar is mounted adjacent the inlet to the scrubber drum.

In a further embodiment the plant includes a settling pond assembly comprising:-

an inlet pond for reception of the slurry from the plant;

an intermediate pond;

a final pond;

a divider weir separating the inlet pond and the intermediate pond;

a further divider weir separating the intermediate pond and the final pond;

a water outlet in the final pond; and

means for removing the sediment from each pond.

in another embodiment the plant includes:-

a storage tank for reception of the slurry of fines, cement and water; and agitating means in the tank to maintain the slurry in suspension. Preferably the plant includes an additional settling tank for reception of the slurry to allow the slurry to settle prior to delivery to the storage tank. Preferably also the plant includes a plant water recycling tank connected to the settling tank to receive surplus water therefrom:

Detailed Description of the Invention

The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which:-

Fig. 1 is an outline layout of a treatment plant according to the invention,

Fig. 2 is a side view of a scrubber and screen assembly forming part of the invention,

Fig. 3 is an end view of the portion of the plant illustrated in Fig. 2,

Fig. 4 is a sectional view of portion of the plant of Figs. 2 and 3,

Fig. 5 is another cross sectional view of portion of the plant of Figs. 2 and 3,

Fig. 6 is a sectional view along the lines VI-VI of Fig. 1 ,

Fig. 7 is a sectional view, similar to Fig. 4, of an alternative construction of scrubber drum in accordance with the invention,

Fig. 8 is an end sectional view similar to Fig. 5 of a still further construction of scrubber drum according to the invention,

Fig. 9 is view similar to Fig. 8 of an alternative construction of scrubber drum according to the invention, Fig. 10 is a view similar to Fig. 5 of a still further construction of scrubber drum,

Fig. 11 is a perspective view of various tanks used in accordance with the invention, and

Fig. 12 is a view similar to Fig. 1 of another layout of treatment plant.

Referring to the drawings and initially to Figs. 1 to 6 and in particular to Fig. 1 , there is provided an unset concrete treatment plant, indicated generally by the reference numeral 1 , comprising a concrete inlet hopper 2 for reception of concrete from a concrete truck. A spray bar 3 is sited adjacent the hopper 2 which in turn feeds an inlet 5 to a scrubber drum 6 which then feeds, out an outlet 7, a cylindrical rotary screen 8, above a further flat bed screen 9 feeding, by a conveyor 10, sand storage hoppers 11. The cylindrical rotary screen 8 feeds, through an outlet hopper 12, a conveyor 13 which in turn feeds an aggregate storage hopper 14. The screen 8 feeds, through a pipe 15 by a pump 16, a settling pond assembly, indicated generally by the reference numeral 20, which comprises an inlet pond 21 , an intermediate pond 22 and a final pond 23. The inlet pond 21 is separated from the intermediate pond 22 by a weir 24 and the intermediate pond 22 is separated from the final pond 23 by a further lower weir 25.

Referring now specifically to Figs. 2 to 5 inclusive, the scrubber drum 6 is a cylindrical barrel mounted by rollers 30 on a support structure 31. One of the rollers 30 is a driven roller, however, the drive, for simplicity, is not shown. The scrubber drum 6 mounts a plurality of straight radially and longitudinally arranged paddle or lifter blades 32 on its interior surface 33. Further additional transfer blades 35 are mounted on the interior surface 33 between the paddle blades 32. The transfer blades 35 are angled slightly to deliver concrete from the inlet 5 to the outlet 7. The lifter blades 32 and transfer blades 35 form a combined agitation and transfer means, identified generally by the reference numeral 36. The rotary cylindrical screen 8 is mounted on the scrubber drum 6 and projects out from the outlet 7. The rotary cylindrical screen 8 is of a conventional perforated screen mesh and mounts a spray bar 40. The rotary screen 8 has an outlet hopper 41 above the screen 9 which in turn is mounted over a further discharge hopper 42 connected to the pipe 15.

Referring now to Fig. 6, there is illustrated the final pond 23 which is identical in construction to the other ponds 21 and 22, having a floor 50 inclining upwardly to form a ramp 51 for cleaning. The weir 25 has a plurality of holes 52 to allow water be delivered from the intermediate pond 22 to the final pond 23. A water outlet 26 is provided for the final pond 23 and is connected to a pump (not shown).

In operation, and referring to the drawings, wet unset concrete is delivered to the concrete inlet hopper 2 from a concrete mixer drum and water is sprayed onto the concrete from the spray bar 3 as is necessary. Then, the concrete is delivered from the inlet 5 into the scrubber drum 6. The scrubber drum 6 is rotated and as it rotates, the paddle blades 32 lift the wet concrete up the sides of the drum where it then falls back down into the bottom of the drum. The concrete is agitated and washed because it is now relatively wet and further, any water will generally tend to settle and thus remain in the drum so that the aggregate tends to have the sand and cement washed therefrom. As the scrubber drum 6 is being rotated, the concrete is being gradually delivered by the transfer blades 35 towards the outlet 7 where it is delivered to the cylindrical rotary screen 8 which, because it is mounted directly on the scrubber drum 6, rotates therewith. As the wet concrete is delivered into the rotary screen 8, the spray bar 40 delivers water to further wash the aggregate and to deliver the sand, fines, cement and most of the water through the rotary screen 8 into the outlet hopper 41. The washed aggregate is delivered through the outlet hopper 12 onto the conveyor 13 and then to the storage hoppers 14. Needless to say, the aggregate, when it is delivered to the storage hopper 14, can be further screened, separated and sized, if desired.

The outlet hopper 41 delivers a slurry which is then further screened by the flat bed screen 9 having a screen cloth of 75 microns such that the sand is delivered to the conveyor 13 and a slurry now of fines, cement and water is delivered to the pipe 15 and then to the settling tank assembly 20 where is it first delivered to the inlet pond 21 where most of the sediment will rest and then delivered across the weir 24 into the intermediate tank 22 and then across the weir 25 to the final tank 23 where there is relatively clean water which is removed for recycling. The ramps allow loading shovels to be used to remove the sediment. Equally well, pumps could be used and the sediment could then be recycled in the concrete plant.

Referring to Figs. 7 and 8, there is illustrated another construction of rotary scrubber drum, again indicated by the reference numeral 6 , in which parts similar to those described with reference to the previous drawings, are identified by the same reference numerals. In this embodiment, the scrubber drum 6 has an extension portion of mesh 60 which effectively form the rotary screen 8. Thus, the rotary screen 8 is integral with the drum 6. The spray bar 40 may be arranged to project into the further drum 6 to deliver water into the portion of the drum which is mixing and agitating the wet concrete. There is provided four longitudinally arragend bars 61 which will facilitate further agitation of the concrete.

Referring to Fig. 9, there is illustrated an alternative construction of scrubber drum, again identified generally by the reference numeral 6, in which parts similar to those described with reference to the previous drawings, are identified by the same reference numerals. In this embodiment, the transfer blades 35 are of the same construction as before, however, the lifter blades 32 are now angled so as to lift a certain amount of the material when travelling in the direction indicated by the arrow

A, namely, anti-clockwise. The lifter blades 32 being angled, will now lift more material so that the material will be carried further up the scrubber drum 6 as it rotates.

Referring to Fig. 10, there is illustrated an alternative construction of scrubber drum, again identified generally by the reference numeral 6 in which the combined agitating and transfer means, again identified by the reference numeral 36, comprises angled blades 65 which are mounted on the interior surface 33 of the scrubber drum 6 and project into the interior thereof. These angled blades allow for the tossing and agitation of the concrete within the scrubber drum 6 while gradually transferring the concrete from inlet to outlet. Further, the drum 6 of Fig. 10 includes additional perforations, namely, holes 66 on its outer surface for removal of a certain amount of water and fines or indeed, water, fines and sand. However, when water, fines and sand are removed, it will be necessary to provide some way of gathering this, most preferably, by a hopper beneath the scrubber drum 6 and delivering that slurry back into the plant 1 at some stage during the production process.

Referring to Fig. 11, there is illustrated various tanks that may be used in the invention, either alone or combination with the settling tanks, as already described. There is illustrated a storage tank 70 incorporating agitating means, indicated generally by the reference numeral 71. The agitating means comprises perforated paddle blades 72 mounted by a vertical shaft 73 and driven through a gearbox (not shown) and motor 74 which preferably has an independent power supply. The storage tank 70 has an output pipe 75 and pump 76 for delivering the slurry to the concrete plant. The storage tank 70 is fed by a feed pipe 76 and pump 77 from a settling tank 80 fed from the plant 1 by the pipe 15 and pump 16. The settling tank 80 in turn feeds through a further pipe 81 and pump 82, a water recycling tank 85 which in turn is connected by a pipe 86 and pump 87 to either the plant 1 or to the concrete plant.

It will be appreciated that not all of the water recycling tank 85 or the additional settling tank 80 are necessary. Further, in the event of a surplus slurry being removed by the treatment plant 1 , the surplus slurry can be delivered to the settling tanks if such are provided.

Referring to Fig. 12 there is illustrated a modification of the treatment plant of Fig. 1 again identified by the reference numeral 1 in which parts similar to those described with reference to Fig. 1 are identified by the same reference numerals. There is provided a further storage bank 90, having paddle blades 91 on a shaft 92 driven by a motor 93. The bank 90 is fed by a pipe 94 through a change over valve 95. The tank 90 has a pipe 96 and pump 97 connecting it to the settling pond assembly 20. The pipe 96 incorporates a diverter valve 98 connected feeding a pipe 99 for delivery to the concrete plant.

While in the embodiments described above, the concrete was shown as being additionally wetted at the inlet hopper, the wetting of the concrete may not always be necessary and indeed, the concrete can be wet just as it enters the scrubber drum. This will depend entirely on what is considered, in the particular circumstances, to be the most suitable.

It will be appreciated that cement particles will form part of the slurry and while additional water is added to the concrete to aid with the separation of the concrete particles, it also acts to delay the setting of the cement. It will be appreciated that the concentrated slurry is recycled and delivered to the concrete plant prior to the cement or concrete sediment hardening.

It will further be appreciated that due to the nature of the sediment containing cement and sediment particles from different mixes and in different concentrations, some of the cement may partially harden. Therefore it is envisaged that a grinding means may be provided intermediate the settling pond assembly and the concrete plant to grind any partially hardened cement or concrete sediment as it enters the concrete plant for reuse.

Further, it is envisaged that instead of discarding and dumping the sediment in the settling pond assembly, the slurry formed in each of the settling tanks may be pumped directly to a concrete plant for reuse. The plant of Fig. 10 facilitates this.

in the specification the terms "comprise, comprises, comprised and comprising" or any variation thereof and the terms "include, includes, included and including" or any variation thereof are considered to be totally interchangeable and they should all be afforded the widest possible interpretation.

The invention is not limited to the embodiments hereinbefore described but may be varied in both construction and detail within the scope of the claims.

Claims

1. A method of treating unset surplus concrete, including aggregate, sand, fines, cement and water comprising:-

2. A method as claimed in claim 1 , in which the sand and aggregate are removed to storage for re-use.

3. A method as claimed in claim 1or 2, in which the slurry is allowed to settle and most of the water is removed therefrom to leave a concentrated slurry.

4. A method as claimed in claim 3, in which the concentrated slurry is recycled by delivery to a concrete plant prior to hardening.

5. A method as claimed in claim 4, in which the concentrated slurry is agitated in a storage tank prior to delivery to the concrete plant.

6. A method as claimed in any preceding claim, in which water is added continuously to the concrete during the mixing and agitating.

7. A method as claimed in any preceding claim, in which the further screening of the sand, fines and cement is carried out while washing them.

8. A method as claimed in any preceding claim, in which the washing, during screening, comprises spraying water on the material through the screening.

An unset concrete treatment plant (1) for carrying out the method of any preceding claim comprising:-

a cylindrical substantially horizontally arranged scrubber drum (6) having a spaced-apart inlet (5) and an outlet (7); and

combined agitating and transfer means (36) mounted on the interior surface (33) of the scrubber drum (6) to agitate and mix the concrete in the drum while moving the concrete from the inlet (5) to the outlet (7).

10. A plant (1) as claimed in claim 9, in which the combined agitating and transfer means (36) comprises:-

a plurality of radially and longitudinally arranged lifter blades (32) mounted on the interior surface (33) of the scrubber drum (6); and

additional transfer blades (35) mounted on the interior surface (33) of the scrubber drum (6) to move concrete from the inlet (5) to the outlet (7).

11. A plant as claimed in claim 9, in which the combined agitating and transfer means (36) comprises angled blades (65) mounted in the interior surface (33) of the scrubber drum (6) and projecting into the interior thereof.

12. A plant (1 ) as claimed in any of claims 9 to 11 comprising:-

a cylindrical rotary screen (8) mounted co-axially with the scrubber drum (6) against the drum outlet (7) for reception of the concrete therefrom; and a spray bar (40) mounted inside the screen (8).

13. A plant (1) as claimed in claim 12 , in which the cylindrical rotary screen (8) is integral with the scrubber drum (6) forming the one assembly therewith.

14. A plant (1 ) as claimed in any of claims 9 to 13, in which the scrubber drum (6) includes perforations (72) to provide additional screening of all except aggregates.

15. A plant (1 ) as claimed in any of claims 9 to 14, in which the scrubber drum (6) comprises a plurality of longitudinally arranged spaced-apart bars (71 ) proud of the interior surface (33) of the scrubber drum (6).

16. A plant (1) as claimed in any of claims 9 to 15, in which a spray bar (40) is mounted in the scrubber drum (6).

17. A plant (1) as claimed in any of claims 9 to 16, in which a spray bar is mounted adjacent the inlet (5) to the scrubber drum (6).

18. A plant (1) as claimed in any of claims 9 to 17, comprising a settling pond assembly (2) comprising:-

an inlet pond (21 ) for reception of the slurry from the plant;

an intermediate pond (22);

a final pond (23);

a divider weir (24) separating the inlet pond (21) and the intermediate pond (22);

a further divider weir (25) separating the intermediate pond (22) and the final pond (23); a water outlet (26) in the final pond; and

means for removing the sediment from each pond (21 , 22, 23).

19. A plant (1) as claimed in any of claims 9 to 18 comprising:-

a storage tank (70) for reception of the slurry of fines, cement and water; and

agitating means (71) in the tank (70) to maintain the slurry in suspension.

20. A plant (1 ) as claimed in claim 19, comprising an additional settling tank (80) for reception of the slurry to allow the slurry to settle prior to delivery to the storage tank (70).

21. A plant (1) as claimed in claim 20, comprising a plant water recycling tank (85) connected to the settling tank (80) to receive surplus water therefrom.