GB2313072A - Separation of wet building mortar and concrete - Google Patents

Abstract

A supply of wet mortar or concrete to be treated is introduced into a receptacle (1), and water added to break up the mortar or concrete and form a slurry. The slurry is passed through a screen (2) which removes material and objects coarser than sand. The slurry which passes through the screen (2) is then introduced to sand filtering means (3) which removes sand from the slurry, which sand is collected for re-use. The remainder of the slurry which has passed through the sand filtering means (3) is collected. The sand filtering means (3) may remove the sand in different grades, and may comprise one or more vibratory screens (4,5).

Description

WET BUILDING MORTAR OR CONCRETE SEPARATION This invention relates to wet building mortar or concrete separation whereby mortar or concrete is broken down into constituent materials for re-use of at least some of the materials.

When a batch of mortar or concrete is mixed it may not all be used.

Also when mortar or concrete has been mixed and/or carried in a container, some of the mortar or concrete is always left adhering to the surface with which it has come into contact, after the container has been emptied. It is essential that the interiors of mortar or concrete mixers and transporters are thoroughly washed after use in order to remove any remaining mortar or concrete from them.

Unused mortar or concrete and mortar or concrete removed from containers after cleaning can provide a useful source of material for reuse, if the mortar or concrete can be at least partially separated out into its constituent materials.

According to a first aspect of the present invention there is provided a method of separating wet building mortar or concrete into constituent materials, comprising the steps of introducing a supply of wet mortar or concrete to be treated into a receptacle, adding water to break up the mortar or concrete and form a slurry, passing the slurry through a screen which removes material and objects coarser than sand, introducing the slurry that has passed through the screen to sand filtering means which removes sand from the slurry to be collected for re-use, and collecting the remainder of the slurry which has passed through the sand filtering means.

The screen may remove bricks, gravel, stones, pieces of metal, wood or other material coarser than sand. Some of this material may be re-usable. The screen may be vibrated or may comprise a static grid.

The sand filtering means may remove the sand in different grades.

For example, the sand may be separated out into sharp sand (typical particle size in the range 5.00mm - 0.600mm) and soft sand (typical particle size in the range 0.600mm - 0.075mm) which can be collected separately for re-use. Preferably the filtering means comprises one or more vibratory screens. The screen or screens may be inclined for the slurry which passes therethrough to do so at the lower part of the or each screen, and the sand which is filtered out of the slurry to accumulate on the screen or screens and be discharged at an upper part to a store or collection means.

Further water may be added to the slurry at the sand filtering means.

The remains of the slurry collected after passing through the sand filtering means may be filtered further to remove cement and other additives included in the mortar or concrete treated in the method.

Filtering at this stage may be done by settlement, for example, in a weir system.

After such further filtering the water remaining may be used again in the method. It may be supplied to the receptacle and/or the sand filtering means. This re-cycled water preferably forms the principal source of water used in the method. A fresh supply of water may be added to top up the re-cycled water as necessary. Adding a fresh supply of water assists in dissolving aerating agents present in the re-cycled water from the treated mortar or concrete. The fresh supply may be recycled water from a mortar or concrete production plant, or water from a town supply.

The filtering means may be cleaned after use. The screen or screens of the filtering means may be sprayed with water to clean them.

According to a second aspect of the present invention, apparatus is provided for use in the method of the first aspect of the invention herein set forth, comprising a receptacle to receive wet mortar or concrete to be treated, water supply means which supplies water to the receptacle to break down the mortar or concrete therein to form a slurry, a screen adapted to remove material and objects coarser than sand from the slurry, sand filtering means adapted to remove sand from the slurry which passes through the screen, and collection means adapted to receive the remains of the slurry allowed to pass through the sand filtering means after removal of sand.

The receptacle may conveniently comprise a feed hopper having a distribution box which receives water from the water supply means to break down the mortar or concrete into the slurry.

The water supply means preferably includes provision for recycling water from the collection means to the receptacle. When the receptacle comprises a feed hopper having a distribution box water may be recycled to the distribution box. Water may be sluiced into the feed hopper by the water supply means around the perimeter of the hopper. Means may be provided for supplying water to the sand filtering means to add to the slurry received by the sand filtering means from the receptacle. Water re cycled from the collection means preferably constitutes the principal source of water provided by the water supply means.

Preferably the sand filtering means comprises one or more vibratory screens, which may each comprise a filter deck. Preferably two or more screens are provided which separate sharp sand from soft sand for the two grades of sand to be collected separately, and which may also remove material coarser than sand. Such screen or screens may be of a proprietary type vibrated by out of balance motors. A polyurethane filter or filters may be embodied in the or each screen. It has been found that sand re-claimed from the mortar or concrete using such a screen or screens is of good quality, and may be cleaner than the sand originally used.

A conveyor or conveyors may be provided to receive sand separated from the slurry by the sand filtering means, and deliver the sand to a store.

The collection means may comprise a holding tank into which the remains of the slurry from the sand filtering means is received. A weir filter system may be included to separate cement and other further matter from water in the remains of the slurry by settlement. Water may be pumped from the holding tank back to the receptacle and/or sand filtering means. Matter filtered from the remains of the slurry at the collection means may be re-used.

Alternatively, the remains of the slurry may pass from the holding tank to a pit. Settlement of the remains of the slurry into water and sediment may take place in the pit. The water may be passed into a recycled water tank and from there back to the receptacle and/or sand filtering means. The sediment filtered from the remains of the slurry may be reused.

A cleaning system may be provided which may clean the filtering means. The cleaning system may comprise one or more spray nozzles which may spray water onto the or each screen of the filtering means.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawing which is a flow diagram of a plant for separating wet building mortar into constituent materials.

The plant comprises a feed hopper 1, a coarse screen 2 below the feed hopper, a two deck sand filtering unit 3 below the coarse screen having an upper screen 4 and a lower, finer, screen 5 supported over a holding tank 6.

Water is supplied to the feed hopper 1, the coarse screen 2 and the upper screen 4 from a clean water tank 22 by a pump 9. Water is also re-cycled from a recycled water tank 23 to the clean water tank 22 and thence to the feed hopper 1, the coarse screen 2 and the upper screen 4.

Wet mortar to be treated is fed into the feed hopper 1 and is broken up and converted into a slurry in a distribution box 7. The mortar may be, for example, the remains of a mixed batch and/or mortar washed out of mixers or containers in which mortar has been held.

The coarse screen 2 receives the slurry from the distribution box 7 and separates from the slurry, brick, stones, metal and other material of larger size than sand. The coarse screen 2 is vibrated by out of balance motors, not shown. Material collects on the grid until it discharges over the upper end of the grid onto a conveyor, not shown, to be taken to a store 20. The grid may be manually cleaned at intervals, or provision may be made for cleaning it automatically.

The slurry which passes through the coarse screen 2 is received onto the upper screen 4 of the sand filtering unit 3. The upper and lower screens 4, 5 are vibrated by the same out of balance motors as the coarse screen 2. Each screen comprises a framework 11, 12 in which an inclined filter deck 13, 14 is supported. The filter deck 13,14 may include in each case a polyurethane filter. Typically the filter deck 13 of the upper screen 4 has a mesh of 0.5 x 12.0mm slots to separate from the slurry sharp sand having a particle size of 5.00mm to 0.600mm. The filter deck 14 of the lower screen 5 typically has a mesh of 0.2 x 12.0mm slots to separate soft sand from the slurry having a particle size of 0.600mm to 0.075mm. Sharp sand collects on the filter deck 13 of the upper screen 4 until it discharges over the upper end of the deck onto a conveyor, not shown, to be taken to a store 15 for re-use. The slurry containing soft sand passes through the lower end of the filter deck 13 onto the filter deck 14 of the lower screen 5. At the lower screen soft sand similarly collects on the filter deck 14 until it discharges over the upper end of that deck onto a conveyor, not shown, to be taken to a store 16 for re-use.

The mass of sand which is collected on the filter decks of the upper and lower screens squeezes water out of the sand to pass from the screens to the holding tank.

Typically approximately 20% of the treated mortar is collected as sharp sand and 70% is collected as soft sand. The soft sand may have a water content of only about 16%.

The remains of the slurry passing through the lower screen 5 typically consists essentially of water, cement, colouring matter and possibly some chemical additives. This is received into the holding tank 6 and passes from there to a wedge pit 21. In the wedge pit, the remains of the slurry undergoes settlement, removing particles of material or sediment from the water. The water is pumped from the wedge pit to the recycled water tank 23. The sediment may be removed manually when the wedge pit has been drained, or it may be arranged to be removed automatically. The sediment may be re-used.

A large proportion of the water used in the treatment of the mortar is re-cycled through the plant. Recycled water is supplied to the clean water tank 22 from the re-cycled water tank 23. Fresh water may also be supplied to the clean water tank 22 and the recycled water tank 23 from, for example, a supply of town water. This tops up the water supply for the treatment. The fresh water also helps to dissolve aerating agents in the mortar to be treated.

A cleaning system is provided for cleaning the filter unit 3 after use. This comprises spray nozzles 25 mounted above and below the upper and lower screens 4, 5. These spray water onto the upper and lower sides of the filter decks 13, 14 to remove material therefrom. Water is supplied to the nozzles from a supply 26 of, for example, town water. Water is also pumped by pump 9 from the clean water tank 22 onto the holding tank 6 to clean it.

The plant described is compact, can be readily assembled from proprietary pieces of apparatus and enables a good quality of sharp and soft sands to be recovered from the treated mortar for re-use.

Claims (31)

1. A method of separating wet building mortar or concrete into constituent materials, comprising the steps of introducing a supply of wet mortar or concrete to be treated into a receptacle, adding water to break up the mortar or concrete and form a slurry, passing the slurry through a screen which removes material and objects coarser than sand, introducing the slurry that has passed through the screen to sand filtering means which removes sand from the slurry to be collected for re-use, and collecting the remainder of the slurry which has passed through the sand filtering means.

2. A method according to claim 1, in which the sand filtering means removes the sand in different grades.

3. A method according to claim 2, in which the sand is separated out into sharp sand of typical particle size in the range 5.00mm - 0.600mm, and soft sand of typical particle size in the range 0.600mm - 0.075mm.

4. A method according to claim 2 or claim 3, in which the different grades of sand are collected separately for re-use.

5. A method according to any preceding claim, in which the filtering means comprises one or more vibratory screens.

6. A method according to claim 5, in which the screen or screens are inclined for the slurry which passes therethrough to do so at the lower part of the or each screen, and the sand which is filtered out of the slurry to accumulate on the screen or screens and be discharged at an upper part to a store or collection means.

7. A method according to any preceding claim, in which further water is added to the slurry at the sand filtering means.

8. A method according to any preceding claim, in which the remains of the slurry collected after passing through the sand filtering means is filtered further.

9. A method according to claim 8, in which the further filtering is done by settlement.

10. A method according to claim 8 or claim 9, in which water remaining after further filtering is re-cycled to be used again in the method.

11. A method according to claim 10, in which the re-cycled water is supplied to the receptacle and/or the sand filtering means.

12. A method according to claim 10 or claim 11, in which a fresh supply of water is added to the re-cycled water.

13. An apparatus for use in the method of claims 1 to 12, comprising a receptacle to receive wet mortar or concrete to be treated, water supply means which supplies water to the receptacle to break down the mortar or concrete therein to form a slurry, a screen adapted to remove material and objects coarser than sand from the slurry, sand filtering means adapted to remove sand from the slurry which passes through the screen, and collection means adapted to receive the remains of the slurry allowed to pass through the sand filtering means after removal of sand.

14. An apparatus according to claim 13, in which the receptacle comprises a feed hopper and a distribution box which receives water from the water supply means to break down the mortar or concrete into the slurry.

15. An apparatus according to claim 14, in which water is sluiced into the feed hopper by the water supply means around the perimeter of the hopper.

16. An apparatus according to any of claims 13 to 15, in which the water supply means includes provision for recycling water from the collection means to the receptacle.

17. An apparatus according to any of claims 13 to 16, in which the screen is vibrated.

18. An apparatus according to any of claims 13 to 17, in which means are provided for supplying water to the sand filtering means to add to the slurry received by the sand filtering means from the receptacle.

19. An apparatus according to any of claims 13 to 18, in which the sand filtering means comprises one or more vibratory screens.

20. An apparatus according to claim 19, in which the or each screen is vibrated by out of balance motors.

21. An apparatus according to claim 19 or claim 20, in which the or each screen embodies one or more polyurethane filters.

22. An apparatus according to any of claims 13 to 21, in which the collection means comprises a holding tank into which the remains of the slurry from the sand filtering means is received.

23. An apparatus according to claim 22, in which the holding tank includes a filter system to separate water from further matter in the remains of the slurry.

24. An apparatus according to claim 23, in which the water is pumped from the holding tank back to the receptacle and/or sand filtering means.

25. An apparatus according to claim 22, in which the remains of the slurry is passed from the holding tank into a pit, where it is separated into water and sediment.

26. An apparatus according to claim 25, in which the water is pumped from the pit back to the receptacle and/or sand filtering means.

27. An apparatus according to any of claims 13 to 26, in which a cleaning system is provided.

28. An apparatus according to claim 27, in which the cleaning system comprises one or more spray nozzles.

29. An apparatus according to claim 28, in which the or each spray nozzle sprays water onto the or each screen of the filtering means.

30. A method substantially as described herein with reference to the accompanying drawing.

31. An apparatus substantially as described herein with reference to the accompanying drawing.