GB2249975A

GB2249975A - Reclaiming aggregate from waste concrete

Info

Publication number: GB2249975A
Application number: GB9025651A
Authority: GB
Inventors: Colin Kingsley Dymott
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-11-26
Filing date: 1990-11-26
Publication date: 1992-05-27
Also published as: GB9025651D0; EP0558582A1; AU9030091A; WO1992009369A1

Abstract

Aggregate is reclaimed from waste plastic concrete in apparatus which comprises a container (1) hinged (17) to a base (16). The container is divided by partitions (2, 3) into a washing tank (4), a settling tank (5) and a drain tank (6). The upper edge of each partition defines a weir (7, 8). Waste concrete is deposited into the washing tank (4) and subjected to the jetting action of water, together with entrained air, from pipes (9). Cement and fine aggregate are carried over the first weir (7) into the settling tank (5), coarse aggregate remaining in the washing tank (4). Cement and some aggregate fines are carried over the second weir (8), whilst the major proportion of the fine aggregate settles in the second tank (5). An oscillating paddle (13) assists the separation in that tank. A slurry of cement and aggregate fines is discharged from the third tank (6) via drain outlets (12) for further treatment in a settlement tank/pit or hydrocyclone. The separated aggregates are removed by tipping the container (1) about the hinge (17) to a discharging position.

Description

APPARATUS FOR THE RECLAMATION OF AGGREGATE FROM WASTE CONCRETE.

This invention relates to apparatus for the reclamation of aggregate from waste plastic concrete.

A certain amount of waste plastic concrete is generated at ready mixed and precast concrete plants due to plastic concrete being returned by customers, breakdowns etc. Disposing of this waste to tip is expensive and is becoming increasingly difficult due to environmental pressures. In addition the cost of aggregates is increasing and in some parts of the U.K are in short supply.

The object of this invention is to provide apparatus for removing cement and some aggregate fines from waste plastic concrete and to return the coarse aggregate (stone) and a large proportion of the fine aggregate (sand) to stock for reuse.

According to the present invention, there is provided apparatus for reclaiming aggregate from waste plastic concrete comprising a first tank separated from a second tank by a weir, means being provided for introducing water under pressure, optionally together with air, into the first tank so that in use waste plastic concrete present in the first tank is subjected to the action of the water introducing means so as to cause cement and fine aggregate to be washed out of the concrete and to be separated from the coarse aggregate by being carried over the weir for collection in the second tank.

The apparatus may include a third tank which is separated from the second tank by a further weir so that in use cement and aggregate fines are carried over the further weir into the third tank to be separated from the fine aggregate (sand) which settles to the bottom of the second tank.

Means are provided for discharging a slurry of cement and fines from the third tank. A separator e.g. a hydrocyclone or a settling tank/pit may be provided to subject the slurry to further separation.

The apparatus conveniently comprises a container provided with one or more substantially vertical partitions for forming the tanks, the upper edge or region of each partition defining the weir(s).

The means for introducing water under pressure into the first tank may comprise one or more downwardly extending pipes, preferably arranged in one or more series extending above the first tank, with each series being connected to a pressurised common water supply line. The pipes may be oscillated across the first tank to provide uniform washing. The pipes may be vertical or offset from the vertical.

Each pipe may comprise an inner tube and an outer tube, the outer tube being provided with one or more air inlets, and the inner tube being connected to the water supply line. In this way the water flowing through the inner tube draws in air through the inlets so that the washing action is a combination of water and air treatment. Whilst not intended to be limiting, the means for introducing water under pressure into the first tank is considered to take the form of a jet action.

The container may be pivotally mounted so that the contents of the tank(s) can be discharged by tipping up the container.

Means may be provided for preventing the separated fine and coarse aggregate from mixing during discharge from the container. The discharge end of the container may include a water stop. The container is preferably provided with a hopper for loading the waste concrete into the washing tank and may include load cell(s).

The weir between the first and second tanks may be formed by a horizontally-extending surface so as to discharge the overflow into the centre region of the second tank.

A specific embodiment of the apparatus will now be described by way of example with reference to the accompanying drawings in which: Fig.1 shows a perspective view of the apparatus Fig.2 shows a plan view of the apparatus Fig.3 shows a cross-sectional view taken along the line I - I in Fig.2 Fig.4 shows the apparatus in its loaded condition Fig.5 shows the apparatus in its unloading condition Fig.6 shows a cross section of a pipe ; and Fig.7 shows a perspective view of the first weir.

Referring to Figs.1,2 and 3, the apparatus comprises a container 1 provided with vertical partitions 2,3 which divide the container into a washing (first) tank 4, a settling (second) tank 5, and a drain (third) tank 6. The upper edge or region of each partition 2,3 forms a weir 7,8. Pipes 9 extend downwardly into the washing tank 4, the pipes being supplied with water under pressure from a common supply line 10. A loading hopper 11 is arranged in a position above the washing tank 4. Load cell(s) (not shown) are provided between the container 1 and its support frame to control loading of waste concrete into the washing tank 4. Drain outlets 12, are provided in the drain tank 6.

In use waste plastic concrete with a collapsed slump is loaded into the washing tank 4 via the hopper 11. The concrete in the washing tank 4 is subjected to the action of water, combined with air, from the pipes 9. Cement and fine aggregate (sand) below about 5mm particle size is washed out of the concrete in the washing tank 4 and carried over the weir 7 into the settling tank 5 with the coarse aggregate being retained in the washing tank 4. Sand particles are retained in the settling tank 5 whilst cement and fines are carried over the weir 8 into drain tank 6. A slurry of cement and fines is discharged from drain tank 6, via the drain outlets 12, to a hydrocyclone or settlement pit/tank for eventual removal off site.

Referring to Figs.4 and 5, after completion of the washing process, the container 1 is tipped up to discharge aggregate retained in tanks 4 and 5 therefrom. For this purpose the container 1 is pivotally mounted at 13 and hydraulic actuators 14 are provided between the container and its support frame 15. In order to prevent the coarse and fine aggregates from mixing together whilst being discharged, the discharge end of the container includes further partitions 16 (Figs.1 and 2) extending from the end of partition 2, so that the fine and coarse aggregates are caused to discharge from the side end regions 17, 18 of the container. A water stop 19 (Figs.1 and 2) extends across the discharge end of the container.

The construction of the pipes 9 is shown in more detail in Fig.6. Each pipe comprises an inner tube 20 arranged within an outer tube 21. The inner tube connects with the water supply line 10, and the outer tube includes a number of air inlets 22. In use water under pressure is delivered from line 10 into the inner tube 20. This causes air to be drawn into the air inlets 22 so that a mixture of water and air is discharged from the end of the outer tube 21 into the washing tank 4.

The lower end of each pipe 9 extends below the level of weir 7, whilst the air inlets 22 are kept above the level of the weir, i.e above the level of the liquid in the washing tank 4. The pipes are preferably arranged to oscillate to and fro across the washing tank 4. More than one set of pipes may be used and the pipes may be vertical or offset from the vertical.

The weirs 7,8 may be formed by the upper edge of each partition 2,3. Alternatively as shown in Fig.7 the weir 7 may be formed by a horizontal surface 23 extending from the top of the partition 2. This provides a more accurate delivery of the overflowing medium into the next tank.

Claims

CLAIMS.

1. Apparatus for reclaiming aggregate from waste plastic concrete comprising a first tank separated from a second tank by a weir, means being provided for introducing water under pressure, optionally together with air, into the first tank so that in use waste plastic concrete present in the first tank is subjected to the action of the water introducing means so as to cause cement and fine aggregate to be washed out of the concrete and be separated from the coarse aggregate by being carried over the weir for collection in the second tank.

2. Apparatus as claimed in claim 1 wherein a third tank is provided which is separated from the second tank by a further weir so that in use cement particles and aggregate fines are carried over the further weir into the third tank to be further separated from the fine aggregate (sand) which settles in the bottom of the second tank.

3. Apparatus as claimed in claim 2 wherein means are provided for discharging a slurry of cement and fines from the third tank.

4. Apparatus as claimed in claim 3 wherein a separator, e.g.

a settling tank/pit or hydrocyclone, is provided to subject the slurry of cement and fines to further separation.

5. Apparatus as claimed in any preceding claim which comprises a container provided with one or more substantially vertical partitions for forming the tanks, the upper edge or region of each partition defining the weir(s).

6. Apparatus as claimed in any preceding claim wherein the means for introducing water into the washing tank comprises one or more downwardly extending pipes.

7. Apparatus as claimed in claim 6 wherein a series of pipes are provided above the first tank, the pipes being connected to a common supply line for water under pressure.

8. Apparatus as claimed in claim 7 wherein more than one series of pipes is provided.

9. Apparatus as claimed in any one of claims 6 - 8 wherein the pipe(s) are arranged to oscillate to and fro across the first tank.

10.Apparatus as claimed in any one of claims 6 - 9 wherein each pipe comprises an inner tube and an outer tube, the outer tube being provided with one or more air inlets and the inner tube being connected to the water supply line.

11.Apparatus as claimed in claim 5 or in any claim appended thereto wherein the container is pivotally mounted so that the contents of the tanks can be discharged by tipping up the container.

12.Apparatus as claimed in claim 11 wherein means are provided for preventing the separated fine and coarse aggregate from mixing during discharge from the container.

13.Apparatus as claimed in either claim 11 or 12 wherein the discharge end of the container includes a water stop.

14.Apparatus as claimed in any one of claims 5 - 13 wherein the container is provided with a hopper for loading waste concrete into the first tank.

15.Apparatus as claimed in any one of claims 5 -14 wherein the container is provided with load cell(s).

16.Apparatus as claimed in any preceding claim wherein the weir between the first and second tanks is formed by a horizontally-extending surface.

17.Apparatus for reclaiming aggregate from waste plastic concrete substantially as herein before described with reference to the accompanying drawings.

18.A method of reclaiming aggregate from waste plastic concrete using apparatus as claimed in any one of claims 1 - 17.