GB2264491A

GB2264491A - Concrete block manufacturing process

Info

Publication number: GB2264491A
Application number: GB9301382A
Authority: GB
Inventors: John Blackburn; Philip John Ford
Original assignee: PHILBURN PRODUCTS Ltd
Current assignee: PHILBURN PRODUCTS Ltd
Priority date: 1992-02-27
Filing date: 1993-01-25
Publication date: 1993-09-01
Also published as: GB9204182D0; GB9301382D0; ZA925859B

Abstract

A method of manufacturing reinforced concrete blocks comprises mixing metal fibres together with aggregates, cement, water and a plasticizer in predetermined quantities, and subsequently compacting the resulting mixture in moulds to form a number of blocks.

Description

CONCRETE BLOCK MANUFACTURING PROCESS The invention relates to a process of manufacturing concrete blocks.

Concrete blocks of the type used, for instance, in mine roof supports, need to be capable of withstanding relatively high stresses. In such situations, unreinforced blocks are not suitable, but going to the expense of using known pre-stressing techniques to provide the extra strength required may result in an over-engineered, costly and heavy item.

It has surprisingly been found that blocks of satisfactory quality can be produced by a process more similar to the manufacture of the unreinforced blocks generally used in building. This allows a streamlining of operations, for the demand for reinforced blocks is much less than for unreinforced; both can be manufactured on the same production line, with a consequent saving of cost. One of the problems is to prevent the metal fibres forming themselves into a ball, and to ensure that they mix with the other materials.

Accordingly the invention provides a method of manufacturing concrete blocks comprising: feeding metal fibres, aggregates, cement, water and plasticizer to a mixer; mixing them together in the mixer; feeding the resulting mixture into moulds and compacting it to form into blocks; removing the blocks from the moulds.

Preferably, the metal fibres and aggregates are received by the mixer before the cement, water and plasticizer are added.

Once the metal fibres and aggregates have been received by the mixer in their required amounts mixing may be started and feeding of the cement to the mixer commenced, prior to adding the water and plasticizer.

Preferably, as the mixing continues, feeding of the water to the mixer is commenced and continues, at a controlled rate, until a required amount has been attained.

Preferably, subsequent to the commencement of the pouring of the water in to the mixer, the plasticizer is added in a measured amount.

Preferably, mixing is carried out for a controlled period and the resulting mixture is poured or emptied into a container.

Preferably, a measured amount of the resulting mixture is discharged from the container into a moving mould filler and thereafter deposited into the moulds.

The mixture may be vibrated during the compacting process.

Preferably, after the blocks have been removed from the moulds they are conveyed away and allowed to set.

The metal fibres are, preferably, of a crimped construction.

Preferably, the metal fibres are of high tensile steel.

The method may be computer controlled.

The invention includes concrete blocks produced according to the method of the invention.

By way of example, a specific embodiment of the invention will now be described, with refernece to the accompanying diagrammatic drawings, in which: Figure 1 is a schematic side view of a sequence of conveyors whereby materials can be fed to a mixer in a process according to a preferred embodiment of the invention; Figure 2 is similar, and illustrates the ensuing steps in the process; and Figure 3 shows the moulding part of the process.

In Figure 1, there are shown a vibratory feed hopper 1 from which metal fibres can be released onto a fibre feed conveyor 10, a limestone aggregate hopper 2 and a sand hopper 3 from which the contents can be released onto an aggregate conveyor 12. The materials are released onto their respective conveyors, and transported together, without mixing, to a batch hopper conveyor 14, and thence to a batch hopper 4.

In Figure 2, the batch hopper 4 is raised and tipped into a rotary mixer 22. Dry cement is added at 23, water at 24, and plasticizer at 25. The resulting mixture is discharged onto a feed conveyor 26, and thence into a hold hopper 27. The mixture is then dropped into a movable mould filler box 28 and then into a mould box 29.

In Figure 3, the mould box 29 is shown isometrically with a hydraulically powered head plate 31 above and a row of moulded blocks 33 on the pallet below.

The conveyors 10, 12, 14 in Figure 1 are started, as is the vibration of the feed hopper 1. Measured quantities of metal fibres, limestone and sand are released from the corresponding hoppers 1, 2, 3 onto the conveyors 10, 12, and transported together to the batch hopper conveyor 14, and thence to the batch hopper 4. When the batch hopper 4 contains its measured quota of material, a signal is emitted which stops the conveyors.

On receipt of a mix-start signal, the batch hopper 4 is emptied into the rotary mixer 22 (Figure 2). As the mixing starts, dry cement is added, and as the mixing continues, water is added at a controlled rate up to the required amount. Plasticizer, is added in a measured amount, and mixing is continued for a controlled period. The mixed concrete is then emptied into the hold hopper 27. A measured amount of mixed concrete is discharged from the hold hopper 27 into the filler shuttle box 28. The shuttle box 28 is moved into a position over a mould box 29, and made to deposit mixed concrete into the moulds. The shuttle box 28 is then moved away from the mould box 29.

The mixed concrete is compacted by the head plate (Figure 3) assisted by vibration induced from under a steel pallet 34 on which the mould box 29 rests. The mould box 29 is lifted, leaving formed blocks on the pallet 34, the head plate 31 is released, and the blocks are conveyed away on the pallet by a conveyor 44. Pallets carrying the freshly made concrete blocks are conveyed and accumulated for storage in a curing room for 24 hours.

After this period, the hardened blocks are removed from the pallets, and formed into packs for transportation to the finished stock yard. The empty pallets are returned to the press plant ready to accept further blocks for the curing room.

The metal fibres are manufactured from high tensile steel and are typically 40 mm long, 0.9 mm diameter and crimped with a continuous wave.

Crimping of the fibres has been found to produce particularly good strength characteristics and resistance to stresses.

The block is manufactured from aggregates and binders as defined in BS 882 and BS 12 and steel fibres blended and mixed typically as follows: Crushed Limestone (10 - 4 mm) 1000 kg Concrete Sand (Medium) 717 kg Portland Cement 400 kg Steel Fibres 50 kg Water 78 litres The blocks are tested in accordance with the requirements of BS 6073 to establish compliance with the following requirements.

a) Dimension Length 440 mm Width 100 mm Height 215 mm b) Weight/Density Block Weight 20.5 to 21.5 kg Material Density 2150 to 2250 kg/m3 c) Strength To be not less than 40 N/mm2 The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A method of manufacturing concrete blocks comprising: feeding metal fibres, aggregates, cement, water and plasticizer to a mixer; mixing them together in the mixer; feeding the resulting mixture into moulds and compacting it to form blocks; removing the blocks from the moulds.

2. A method according to claim 1, wherein the metal fibres and aggregates are received by the mixer before the cement, water and plasticizer are added.

3. A method according to claim 1 or 2 wherein once the metal fibres and aggregates have been received by the mixer in their required amounts mixing is started and feeding of the cement to the mixer commenced prior to adding the water and plasticizer.

4. A method according to claim 3, wherein as mixing continues, feeding of the water to the mixer is commenced and continues, at a controlled rate, until a required amount has been attained.

5. A method according to claim 4 wherein subsequent to the commencement of the feeding of the water to the mixer, the plasticizer is added in a measured amount.

6. A method according to any of the preceding claims wherein mixing is carried out for a controlled period and the resulting mixture is poured or emptied into a container.

7. A method according to claim 6, wherein a measured amount of the resulting mixture is discharged from the container into a moving mould filler and thereafter deposited into the moulds.

8. A method according to any of the preceding claims wherein the mixture is vibrated during the compacting process.

9. A method according to any of the preceding claims wherein after the blocks have been removed from the moulds they are conveyed away and allowed to set.

10. A method according to any of the preceding claims wherein the metal fibres are of a crimped construction.

11. A method according to any of the preceding claims wherein the metal fibres are of high tensile steel.

12. A method according to any of the preceding claims wherein the method is computer controlled.

13. A method according to any of the preceding claims in which the aggregates comprise limestone and sand.

14. A method of manufacturing concrete blocks substantially as described herein with reference to the accompanying drawings.

15. A concrete block produced by a method according to any of the preceding claims.