GB2256380A

GB2256380A - Device for plaster/mortar mix topping a prefabricated concrete slab.

Info

Publication number: GB2256380A
Application number: GB9112186A
Authority: GB
Inventors: John Anthony Douglas Br Durham; Zabiholah Asadolah Golmohamad
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-06-06
Filing date: 1991-06-06
Publication date: 1992-12-09
Also published as: GB9112186D0; EP0517505A1

Description

2 2 3 6-35,30 PLASTER MORTAR MIX "TOPPING" TO A PREFABRICATED CONCRETE

SLAB The present invention relates to a device whereby a plaster/mortar mix can be provided on a prefabricated concrete slab of indeterminate length.

Machines known as concrete hollow core production machines are used throughout the world to make an internationally recognised standard of precast concrete slab. A typical slab is usually cast in lengths of around 100 linear metres with a width of 1.2 metres. A series of hollow cores running the full length of the slab are formed in the cross section of a slab. Reinforcing wires or steel reinforcing bars are placed centrally between the hollow cores. An accurate mould or casting bed supports the hollow core casting machine. The machine, with 4 wheels, sits astride the casting bed on guide rails precisely aligned to the bed. Concrete is fed into the machine which moves down the bed as it slowly forces the concrete mix from one end into a precisely formed preset slab section. Whilst the soffit, or underside of the cast slab is generally very flat, the top surface of the slab tends to undulate and have a honeycombed surface.

If a high quality finish is required on the top of the slab a second independent machine is used to coat the slab top with I a smooth and flat mortar mix. This machine is generally used when the slab has set some 10-12 hours after the concrete slab has been made.

According to the present invention there is provided a plaster or mortar mix laying device for use with a concrete slab fabricator, of the type which moves relative to a stationary bed leaving a preformed slab behind it, the laying device comprising: a feed hopper for holding plaster mortar mix and adapted to be attached to the rear of said slab fabricator, said feed hopper being a throat for directing said plaster or mortar mix onto said preformed slab, and a smoothing member adapted to be attached to the slab fabricator behind the feed hopper relative to the direction of travel of the slab fabricator, for smoothing the plaster or mortar mix deposited onto said slab by said feed hopper into a topping layer.

The present invention also provides a concrete slab fabricator of the type which moves relative to a stationary bed leaving a preformed slab behind it; provided with a plaster or mortar mix laying device as described above.

The present invention further provides a method of fabricating a concrete slab, the method comprising the steps of; providing a stationary bed and a casting machine of the type which moves relative to a stationary bed leaving a preformed slab behind it; 5 operating the machine to fabricate a concrete slab; and as the machine moves, spreading a plaster or mortar mix on the slab close behind the machine, before the concrete cures, to form a topping layer.

Yet further, the present invention provides a concrete slab having a main part formed by vibrating and compacting a concrete mix on a molding bed and a topping layer of plaster or mortar mix bonded to one surface of said main part by the vibrations used to form said main part.

By the addition of a feed hopper and a smoothing plate attached to the hollow core casting machine the mortar mix can be introduced on to the cast slab immediately it is formed by the casting machine. By using a simple 4 wheeled trolley, free-wheeling behind the casting machine and resting on the same guide rails as the casting machine and moved, as necessary by machine operatives, masons with a hand or mechanically operated tamping and levelling device can accurately "float off" the plaster mix. This ensures a precise and consistent overall thickness of the completed 4 - 4 concrete slab with its mortar mix topping.

The plaster/mortar mix is introduced into a separate feed hopper set immediately behind the main concrete feed hopper. The base of the hopper is a narrow open uninterrupted throat across the full width of the casting machine. At the point where the casting machine moves away from the cast slab the plaster mix flows by gravity through the throat of the mortar feed hopper and falls onto the cast concrete. The residual vibration of the casting machine concrete mix vibrators serving to thoroughly bond the plaster mix onto the cast concrete below.

The cast concrete and the plaster mix set at the same time and can be cut up into small sections, as required, after approximately 8-12 hours of curing time.

In order that the invention may be more readily understood, the following description is given, merely by way of example, reference being made to the accompanying drawings, in which:-

Figure 1 is a cross section of a typical hollow core production machine with addition of the feed hopper and smoothing plate.

Figure 2 is a cross section of a typical slab produced by a hollow core casting machine.

Figure 3 is a cross section of a typical slab produced by a hollow core casting machine with the bonded plaster mix.

Figure 4 is perspective view of the 4 wheeled levelling trolley.

Referring now to Fig. 1 there is illustrated a typical cross section of a hollow core casting machine. The machine sits via 4 wheels (10) on a casting bed rail (11). A series of drive motors and gear boxes (12) rotate, via chains (13), a series of screws (14). The machine remains stationary whilst the concrete mix is fed into the hopper (15). The screws are then rotated mechanically and the vibrator motors (16) & (17) are started up. The mix is forced through the moulding chamber (18) and compacted, forming into the required slab section (19). Thereafter the machine screws itself out of the compacted mix and thus moves in the direction of the arrow (20), in other words away from the compacted and cast slab which remains stationary on the casting bed.

Immediately the machine moves away from the compacted slab (21) a standard mortar mix (22) eg 1 part cement to 3 parts sand with appropriate water content to allow the mix to flow, is poured in the feed hopper (23). The mix immediately flows gravitationally via a throat (24) directly on the top of the cast concrete slab (19). A smoothing trowel (25) levels and smooths the plaster mix (26) which flows continuously from the hopper (23) as the machine moves away from the compacted 5 slab (19) that it has 'screwed' itself out of.

The vibration produced by the vibrators (16) & (17) effectively bonds the plaster mix (26) onto the cast concrete slab (19).

Figure 2 shows a typical cast concrete slab section as it leaves the casting machine. In this instance 6 holes, or hollow cores, are shown (27). The cores can be round, square or oval to suit the required design. The top surface (28) can, if the manufacturing machine is in excellent working order, be flat; however depending on variations in the concrete mix consistency, wear of machine etc, the top is very often randomly undulating.

Figure 3 shows the same slab type section as Figure 2, with the complete topping mix (26) bonded onto the top of the cast concrete slab (19).

Figure 4 shows a typical freewheeling trolley resting via 4 wheels (29) onto casting bed rails (11). The rails in turn affixed to the continuous casting bed (30). Once the 7 - concrete mix (19) and the mortar mix (26) are bonded the levelling trolley is pushed by hand or mechanically moved to straddle the area requiring finishing, usually some 1-3m away from the continuously moving casting machine (1).

A tamping base (31) precisely defines the top finish level required for the topping mix (26). The base (31) is rigidly fixed but adjustable for height to the outer wheels (29). This enables the trolley to be adapted to finish off various heights of cast slab and mortar mixes. The inside face of the tamping base (32) is completely separated by an air gap (33) from the top edge of the mortar mix (34). This allows the whole levelling trolley to be freely moved up and down the casting bed (3) at any time without restrictions.

A straddle bar (35) holds the two tamping bases (31) each side of the casting bed rails (3).

A levelling bar (36), which can either be operated by hand or mechanically vibrated is slid manually or mechanically backwards and forwards across the two tamping bases (31) straddling the casting bed (30). At all times the levelling bar (36) is kept in constant contact with the base (31).

In this way the plaster mix (26) is precisely trowelled off to give an exact overall thickness of cast slab and mortar as shown in the cut away section of the completed slab (26). The final touch up of the trowelled mortar mix is effected by a mason with a hand trowel following behind the levelling trolley.

Claims

1. A plaster or mortar mix laying device for use with a concrete slab fabricator, of the type which moves relative to a stationary bed leaving a preformed slab behind it, the laying device comprising: a feed hopper for holding plaster mortar mix and adapted to be attached to the rear of said slab fabricator, said feed hopper being a throat for directing said plaster or mortar mix onto said preformed slab, and a smoothing member adapted to be attached to the slab fabricator behind the feed hopper relative to the direction of travel of the slab fabricator, for smoothing the plaster or mortar mix deposited onto said slab by said feed hopper into a topping layer.

2. A laying device according to claim 1, further comprising additional smoothing means for smoothing the top surface of said topping layer.

3. A laying device according to claim 2, wherein said additional smoothing means comprises a trolley, adapted to run on rails parallel to the base of said stationary bed, for providing a tamping base to define the desired top surface of said topping layer to permit tamping and levelling to smooth off said topping layer to said desired surface.

- 10

4. A laying device according to claim 3, including a mechanically operated tamping and levelling device.

5. A laying device according to claim 2, 3 or 4, wherein said additional smoothing means is connected to said laying device by coupling means that are non-transmissive of vibrations.

6. A plaster or mortar mix laying device constructed and arranged to operate substantially as hereinbefore described with reference to, and as illustrated in, the accompanying 10 drawings.

7. A concrete slab fabricator of the type which moves relative to a stationary bed leaving a preformed slab behind it provided with a plaster or mortar mix laying device according to any one of the preceding claims.

8. A combination according to claim 7, wherein said fabricator comprises a hollow core casting machine.

9. A combination according to claim 7 or 8, wherein said fabricator includes means for generating Vibrations to compact the concrete slab and bond said topping layer to the 20 slab.

10. A combination of a plaster or mortar mix laying device and a concrete slab fabricator constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying 5 drawings.

11. A method of fabricating a concrete slab, the method comprising the steps of; providing a stationary bed and a casting machine of the type which moves relative to a stationary bed leaving a preformed slab behind it; operating the machine to fabricate a concrete slab; and as the machine moves, spreading a plaster or mortar mix on the slab close behind the machine, before the concrete cures, to form a topping layer.

12. A method according to claim 11, further comprising the additional step of smoothing the plaster or mortar mix before it sets to provide a smooth upper surface to said topping layer.

13. A method according to claim 11 or 12, wherein said machine which is provided includes means for producing vibrations and wherein said operating step includes operating the means for producing vibrations to vibrate the concrete to compact it and to bond the topping layer to the concrete slab.

14. A method of manufacturing a concrete slab substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

15. A concrete slab having a main part formed by vibrating and compacting a concrete mix on a molding bed and a topping layer of plaster or mortar mix bonded to one surface of said main part by the vibrations used to form said main part.

16. A concrete slab fabricated by the combination of any one of claims 7 to 10, or according to the method of any of claims 11 to 14.

17. A concrete slab constructed substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.