EP0385980B1

EP0385980B1 - Method and apparatus for constructing rammed earth walls with integral render

Info

Publication number: EP0385980B1
Application number: EP88901527A
Authority: EP
Inventors: Jan Novotny
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-02-02
Filing date: 1988-01-29
Publication date: 1993-03-03
Anticipated expiration: 2008-01-29
Also published as: DE3878917D1; LV5633A3; WO1988005849A1; HU206750B; UA19309A1; AU1241988A; EP0385980A4; DE3878917T2; EP0385980A1; RU1817809C; US5021202A; AU608810B2

Abstract

A method for constructing render jacketed, rammed earth walls for buildings which utilizes a rectangular container (10) which functions as a mould and also a hopper and skip, the container has an open top and a bottom closable by two half trapdoors (15a, 15b), maintained in inclined closed position up from the bottom by cam trapdoor-retaining bars (17, 18) releasable by hand pull rods (19, 20) attached to retainer chains (23, 24); the container (10) is removably carried with trapdoors (15a, 15b) closed upon a rubber-tyred, wheeled, ground level trolley (58) during level-filling with loose earth; two, three-sided trays (27, 28) of lateral dimensions substantially equal to those of the container (10) are level-filled with a powdered cement/sand render mix of low moisture content and stacked upon the container (10), each end (13, 14) of which is provided with a pair of pivot brackets (35, 36, 39, 40) of unequal length which respectively have a hole (37, 38) for detachable fixture of render trays (27, 28) to the container (10); the filled container (10) and trays (27, 28) are lifted by a hoist (55) and lowered into a wall mould formwork of plywood panels (62, 50), the external, lateral dimensions of the container (10) being sufficiently less than the internal dimensions of the formwork to create outer or veneer moulding cavities. When the container (10) rests upon a concrete footing (49), or previously rammed earth layer, the trays (27, 28) are tipped in mutually opposite directions in a vertical arc to put the loose render into the veneer mould cavities between formwork members (62, 50) and the container (10); the trapdoors (15a, 15b) are opened by undoing chains (23, 24), then freeing retainer rods (19, 20) to allow cam retainer bars (17, 18) to fall, the trapdoors (15a, 15b) opening under the weight of loose earth, the container (10) is lifted and loose earth pours out between outer render layers (68, 69) which are rammed simultaneously with the earth as a core (67) to obtain a rammed earth, render jacketed, integral mass.

Description

The invention relates to an apparatus and a method for forming rammed earth walls having a core of rammed earth and an integral jacket of rammed moist powdered sand and cement mix.
From DE-C-812 111 an apparatus is known comprising a formwork of two side and two stop end wood plank or board formwork members placed in parallel spaced relationship and clamped together to form a rectangular wall moulding cavity, wall spacer members provided at a distance from the inner surface of the formwork members to form an inner mould cavity for loose earth and outer cavities for a moist, powdered cement render, and a ram for ramming the loose earth and the render, wherein the wall spacer members are removable from the formwork moulding cavity after filling the inner mould cavity with earth and the outer cavities with render and prior to ramming. The wall spacer members are planks which are fixed to the end walls of the formwork moulding cavity. The cement render covers the inside and outside side plains of the walls but does not form a jacket around the stop ends of said walls. Between adjacent walls remain parts of the walls which are not sufficiently covered by a cement containing layer.
It is an object of the present invention to provide an apparatus to form walls having a core of rammed earth and an integral jacket of rammed moist powdered sand and cement mix which covers the site plains and also the stop end plains of said walls. It is another object of the invention to provide a method for constructing said walls without requirement for skilled labour.
The invention teaches an apparatus comprising the above features and characterized by

an earth hopper/skip for level filling with loose earth upon the ground while outside of the formwork members and the formwork moulding cavity, said earth hopper/skip having two side walls and two end walls and an openable and closeable bottom, wherein the side walls and the end walls form an open top and define the wall spacer members of inner mould cavity when the earth hopper/skip, level-filled with loose earth is lowered into the formwork moulding cavity, the width of the side walls and the end walls being substantially less than the width of the formwork moulding cavity so as to form on all sides of the earth hopper/skip jacket-forming outer cavities,
lifting means attached to the earth hopper/skip for lifting and lowering the earth hopper/skip into and out of the formwork moulding cavity,
a trapdoor in the bottom of the earth hopper/skip for selectively discharging the loose earth into the inner mould cavity,
two cement hoppers pivotally mounted upon the earth hopper/skip for level filling with a loose, moist powdered sand and cement mix, while the cement hoppers are outside of the formwork members and the formwork moulding cavity and for tiltably unloading the cement mix into the jacket-forming outer cavities,

The invention, according to another broad concept, resides in a method for constructing rammed earth walls with integral rammed sand and cement mix jackets for buildings, homes and the like which comprises:

placing side and end formwork members in parallel spaced relationship to form a rectangular wall moulding cavity,
outside of the formwork, level filling with loose earth an earth hopper/skip of a rectangular container having side walls and end walls of lateral dimensions less than the wall moulding cavity and having a trapdoor in the bottom of said earth hopper/skip,
level filling with moist, powdered sand and cement jacketing mix, separate hoppers carried atop the earth hopper/skip,
lifting the filled hoppers up over the formwork members and then down into the wall moulding cavity onto a foundation, the hopper being laterally equispaced from the formwork members to define a central core cavity within the earth hopper/skip and a pair of jacket cavities between side walls of the hoppers and internal surfaces of the formwork members,
filling the jacket cavities with sand and cement mix from the jacketing mix hoppers and opening the trapdoor allowing the loose earth to fall into central core cavity,
raising the hoppers as unit out of the wall cavity and simultaneously ramming the loose earth and the sand and cement jacket mix and repeating the steps to obtain successive layers in a completed wall structure.

The features of claims 20 and 21 relate to preferred embodiments of the method according to the invention.
Advantages of the rammed earth walls with integral rammed render of the invention are that the render is easier and quicker to apply without requirement for skilled labour and the finished render surface is smooth enough to receive wall paper on internal walls, or paint directly without prior preparation and sealing and is also high enough in density to eliminate the need for sealing against the weather. Advantageously, it is possible to use a wide veriety of earth and soil types and since the render can be wedged into the wall earth structure, it is less likely to separate as with conventional render. The integral rammed render is applied in a semi-dry low moisture content state and is stronger and denser than conventional render which is applied. in a wet slurry and is weaker amd more porous after curing.
A non-limitative example of a practical arrangement of the invention will now be described with reference to the accompanying drawings in which:

Figure 1 is a perspective view of a rammed earth wall forming and render facing hopper/skip apparatus, constructed in accordance with the invention.
Figure 2 is an end elevation of the apparatus of Figure 1 in situ between formwork and on foundation footings for a rammed earth wall shown in vertical cross-section.
Figure 3 is a scrap perspective of hopper/skip, optional, variable width arrangement.
Figure 4 is a schematic end view, similar to Figure 2.
Figure 5 is a partial, typical, vertical cross-section through a wall constructed in accordance with the invention.
Figure 6 is a perspective view of apparatus of the invention on a building site.

Referring to the drawings, there is shown in Figure 1, apparatus for progressively applying a structurally strengthening, aesthetic and protective facing or rendering simultaneously on both inner or outer wall surfaces of a rammed earth building wall structure, the apparatus comprising a hopper/skip 10, adapted to be level-filled with moist earth preferably of 10% moisture content - an ideal soil being about 60% sand and 40% clay. Organic top soil matter is unsuitable and must not be used for rammed earth wall construction. The tray is preferably in the form of an elongate metal box with side walls 11, 12, end walls 13, 14 and with an open top having a grid 14a and a bottom which is openable and closable by a trapdoor 15, split into two longitudinal segments 15a, 15b, (shown in fully open, earth dropping, vertical position in Figure 1), the top or inner edges thereof being hingedly mounted along the trapdoor support bar 16 which in turn is mounted along the longitudinal centre line of the hopper/skip at a vertical distance above the bottom line.
In Figure 4, the trapdoor segments 15a, 15b, shown in an inclined, fully closed, earth-retaining position, the radial distance or width of the trapdoor segments being such as to allow the segments to partially drop down in contact with the top surface of a foundation layer or previously rammed layer to allow loose earth to fall and form starting side portions of earth. The trapdoor segments 15a, 15b are also designed to be retained in an inclined, fully closed position by means of tilting cam bars 17, 18, pivotally mounted upon and extending longitudinally along the inside of the side walls at a distance from the bottom edge thereof. The cam bars 17, 18 are retained in lifted up position underneath the outer edges of the trapdoors by means of the rods 19, 20, the lower ends of the rods being pivotally attached to the cam bars while the upper ends each have a bolt head adapted to be placed over the slotted retainer brackets 21, 22. The rods are movable both laterally and vertically, as shown by the arrows and each has a retaining chain 23, 24, the end link of each chain being adapted to be retained upon a retaining spike 25, 26. Two, three-sided, tiltable trays 27, 28 are adapted to be level-filled with moist (5% to 15% and preferably 10% water), powdered cement render mixture (1:5 cement/sand ratio) by placing the trays in juxtaposition upon the ground with open (non-walled) sides facing in abutment and then level-filling the trays which are then stacked upon the hopper/skip, each tray has two pivot pins 29, 30, 31, 32, protruding from each end thereof, the pins being adapted to be placed respectively into grooves 33, 34 of brackets 35, 36, or holes 37, 38 of brackets 39 40 at each end of the hopper/skip. The brackets of one side are of different height than those of the other side to enable the stacked trays to be tilted successively, each in a vertical arc in an opposite direction to transfer loose, moist powdered cement render from each tray into a separate render moulding cavity, approximately 30mm wide, as shown in Figure 4 of the drawings.
The hopper/skip has two vertical suspension bars 41, 42, upstanding therefrom with a strengthening spacer bar 43 extending therebetween. At the top of each suspension bar, there is provided a hole for attachment of hooks of the lifting chain (or cable) 44, for lifting by a hoist (or a block and tackle) _ described later with reference to Figure 6 of the drawings. There is provided on each end wall of the hopper/skip 10, two pairs of freely rotatable guide members or wheels, such as the two shown 45, 46 and these wheels are adapted to help guide and maintain the hopper/skip in a horizontal position within a cavity between already formed walls and formwork as shown in Figure 6.
Referring to Figure 3, there is shown an end wall structure of the hopper/skip which is 240mm in height, whereby the width may be varied from 240 to 290mm in accordance with different wall thickness requirements. In a similar manner, the length may also be varied from 1200mm to 1900 mm. In the arrangement shown in Figure 3, each side wall panel is turned at right angles to form overlapping end wall panels and inner and outer full height and width strengthening/joining panel 47, 48 are bolted over the turned-in end wall segments.
Refering to Figures 2, 4 and 5 which illustrate the method of constructing an integral rammed earth wall and render structure, there is shown in Figure 2, the hopper/skip 10 of the invention, level-filled with earth together with the two stacked trays 27, 28, thereupon level-filled with powdered cement render (cement/sand mix of 10% moisture content) are lowered into the wall cavity, placed upon concrete footings 49 (Fig. 2, or rammed earth Fig. 4) and between plywood formwork members 50, 51. Damp course 49a is preferably included as in Figure 4. Each tray is tilted in a single, mutually opposite direction to onload moist cement render powder into wall outer cavities 52, 53. At this stage with the render in position, the trapdoor segments are allowed to drop down by loosening the chains and also the cam rods 19, 20 by hand from the brackets into a partially inclined, initial unloading postion to allow some earth to fall downwards and initially outwards, towards the cement render cavity while still retained by the sidewalls.
Referring to Figure 6, the hopper/skip is then raised by the hoist chain or cable 54 by operating the hoist 55 (or block and tackle) whereupon the trapdoor segments drop to a vertical, fully-open position to release the remainder of the loose earth from the hopper/skip after which the hopper/skip carrying the trays is lowered to the ground outside of the formwork and onto the rubber-tyred, wheeled, hand trolley. Both the outer layers of cement render powder and the earth are compacted together by ramming either manually or mechanically to form an integral, continuous 350mm thick wall. Vertical wall conduit cavities comprising continuous cavity 59 and interrupted cavities 60 are formed in the end face 61 of wall sections by angle-iron inserts in formwork stop ends. These cavities can be used for keying adjacent panels. Anchorages can also be embedded in wall structures.
The formwork shown in Figure 6, comprises a full height rear panel 62 formed in two sections, the front being formed of stacked single layer sections for access, such as that designated 50.
It will be appreciated that, instead of using the trays, the cement render mix can be poured into the outer cavities by pumping with a hose, or by mechanical shovels or the like.
After each wall is completed, the whole gantry is moved to the next wall section to be constructed by by means of wheels 63 on tracks 64.
A preferred method of constructing the wall is shown in Figure 5 of the drawings which shows a section of rammed earth wall, including steel or wire mesh, such as chicken wire reinforcement and wall ties 65 , 66, placed between alternate layers of a rammed earth core 67 and outer integral rammed, moist, powdered cement render jacket or facings 68, 69. It will be noted that there are protrusions of render, such as those designated 70, 71 into the rammed earth. This effect creates improved bonding between render and earth and is achieved by having the height of the render above the height of the earth, when the render is poured from the trays into the cavity between formwork and the hopper/skip.

Claims

Apparatus for forming rammed earth walls having a core of rammed earth and an integral jacket of rammed moist powdered sand and cement mix, said apparatus comprising a formwork of two side and two stop end wood plank or board formwork members (62, 50) placed in parallel spaced relationship and clamped together to form a rectangular wall moulding cavity, wall spacer members (11 to 14) provided at a distance from the inner surface of the formwork members to form an inner mould cavity for loose earth and outer cavities (52, 53) for a moist, powdered cement render, and a ram for ramming the loose earth and the render, wherein the wall spacer members (11 to 14) are removeable from the formwork moulding cavity after filling the inner mould cavity with earth and the outer cavities (52, 53) with render and prior to ramming, charcterized by,
- an earth hopper/skip (10) for level filling with loose earth upon the ground while outside of the formwork members (62, 50) and the formwork moulding cavity, said earth hopper/skip (10) having two side walls (11, 12) and two end walls (13, 14) and an openable and closeable bottom, wherein the side walls (11, 12) and the end walls (13, 14) form an open top and define the wall spacer members of the inner mould cavity when the earth hopper/skip (10), level-filled with the loose earth is lowered into the formwork moulding cavity, the width of the side walls (11, 12) and the end walls (13, 14) being substantially less than the width of the formwork moulding cavity so as to form on all sides of the earth hopper/skip jacket-forming outer cavities (52, 53),

- lifting means (44) attached to the earth hopper/skip (10) for lifting and lowering the earth hopper/skip (10) into and out of the formwork moulding cavity,

- a trapdoor (15) in the bottom of the earth hopper/skip (10) for selectively discharging the loose earth into the inner mould cavity,

- two cement hoppers (27, 28) pivotally mounted upon the earth hopper/skip (10) for level filling with a loose, moist powdered sand and cement mix, while the cement hoppers (27, 28) are outside of the formwork members (62, 50) and the formwork moulding cavity and for tiltably unloading the cement mix into the jacket-forming outer cavities (52, 53),
wherein the earth hopper/skip (10) and the cement hoppers (27, 28) form a hopper unit for simultaneously carrying and then successively unloading first the loose cement mix into the jacket-forming outer cavities (52, 53) and next the loose earth into the inner mould cavity, the unloaded hopper unit (10, 27, 28) being removable from the formwork moulding cavity prior to ramming.
Apparatus according to claim 1, wherein the trapdoor (15) is formed into two, equally divided, rectangular plate segments (15a, 15b) each pivotally mounted at the top edges thereof to a common trapdoor support bar (16) mounted along the longitudinal centreline of the hopper/skip (10) and in a fully-closed, earth-retaining position, the radial distance or width of each trapdoor segment (15a, 15b) is such as to allow the segments to partially drop down in contact with the top surface of a foundation layer (49) or previously rammed earth/sand and cement mix jacket layer to allow earth to fall and form side-starting wall portions.
Apparatus according to claim 2, wherein the trapdoor segments (15a, 15b) are retained in a fully closed position inclined to the horizontal by means of tilting cam members (17, 18), mounted upon and extending longitudinally along the inside of the side walls (11, 12) of the hopper/skip (10) at a distance from the bottom edge thereof.
Apparatus according to claim 3, wherein the cam members (17, 18) are retained in the lifted-up, trapdoor-closed position by means of lift member rods (19, 20) having lower ends thereof pivotally attached to the cam members (17, 18) and upper ends with widened ends removably placed within slots of retainer brackets (21, 22).
Apparatus according to claim 4, wherein the rods (19, 20) are retained by chains (23, 24) releasable fastenable to pins (25, 26) fixed to a cross member on the hopper/skip.
Apparatus according to claim 1, wherein the cement hoppers comprise two, three-walled trays (27, 28) which are adapted to be tiltably stacked one above the other upon the earth hopper/skip (10) after it has been filled with loose earth.
Apparatus according to claim 5, wherein each tray has lateral dimensions substantially equal to the earth hopper/skip (10).
Apparatus according to claim 6 or 7, wherein the earth hopper/skip (10) has a pair of lift support bars (41, 42) fixed to the ends thereof and connected by a cross bar, the support bars (41, 42) extending vertically upwards for a distance sufficient to enable the comment hopper trays (27, 28) to be freely swung up and down with respect to the earth hopper/skip.
Apparatus according to any of claims 1 to 8 wherein the earth hopper/skip (10) is of extendible width, the end walls being formed as right-angled, sleeved, part sections.
Apparatus according to any one of claims 6 to 8, wherein each tray (27, 28) is pivotally attached to the earth hopper/skip (10) along a closed longitudinal side edge thereof and is tiltable in a vertical arc in mutually opposite directions to empty unrammed render material into outer wall cavities (52, 53) between the formwork members (62, 50) and the side walls (11, 12) of the earth hopper/skip (10).
Apparatus according to any preceding claim wherein the earth hopper/skip (10) incorporates a screening grid along the top thereof.
Apparatus according to any preceding claim and which also includes a wheeled hand trolley (58) of rectangular form for transporting the rectangular hopper/skip unit along the ground at a building site.
Apparatus according to any preceding claim and which includes a hiost gantry (54a) mounted on wheels adapted to run on ground tracks to move the earth hopper/skip unit along the ground at a building site.
Apparatus according to claim 13, wherein the gantry (54a) supports a wheeled hoist carriage (56) mounted upon tracks for moving the hopper/skip unit transverse to wall formwork.
Apparatus according to any preceding claim wherein the hopper/skip unit (10, 27, 28) includes at least one guide member (45 or 46) projecting from along the centreline of each end wall (13, 14) thereof, each guide member (45, 46) being adapted to be placed within a respective pair of vertical guide rail members (59, 60) fixed to the formwork moulding cavity side of each end stop member, the arrangement being such as to enable entering of the hopper/skip unit (10, 27, 28) within the formwork in all lateral directions.
Apparatus according to claim 15, wherein there are two guide members (45, 46) in mutual, vertical alignment in each end wall.
Apparatus according to claim 15 or claim 16, wherein the two guide members are each freely rotatable wheels (45, 46) which are adapted to be rolled up and down the formwork in a gap between angle iron guide rail members (59, 60) fixed to the stop end members (61, 61a).
Apparatus according to any one of claim 15 to 17, wherein when the stop end formwork members (61, 61a) are removed with the guide rails fixed thereto and after formation of the rammed earth, cement-jacketed wall, the guide rails form cavities for conduits, tie rods, or the like.
A method for constructing rammed earth walls with integral rammed sand and cement mix jackets for buildings, homes and the like which comprises:
- placing side and end formwork members (62, 50) in parallel spaced ralationship to form a rectangular wall moulding cavity,

- outside of the formwork, level filling with loose earth an earth hopper/skip (10) of a rectangular container having side walls and end walls of lateral dimensions less than the wall moulding cavity and having a trapdoor (15) in the bottom of said earth hopper/skip,

- level filling with moist, powdered sand and cement jacketing mix, separate hoppers (22, 28) carried atop the earth hoppers/skip (10),

- lifting the filled hoppers (10, 27, 28) up over the formwork members (62, 50) and then down into the wall moulding cavity onto a foundation, the hopper (10, 27, 28) being laterally equispaced from the formwork members (62, 50) to define a central core cavity within the earth hopper/skip (10) and a pair of jackets cavities (52, 52) between side walls (11 to 14) of the hoppers (10, 27, 28) and internal surfaces of the formwork members (62, 50),

- filling the jacket cavities (52, 53) with sand and cement mix from the jacketing mix hoppers (27, 28) and opening the trapdoor (15) allowing the loose earth to fall into central core cavity,

- raising the hoppers (10, 27, 28) as unit out of the wall cavity and simultaneously ramming the loose earth and the sand and cement jacket mix and repeating the steps to obtain successive layers in a completed wall structure.
A method according to claim 19, wherein outside of the formwork members (62, 50), two sand and cement mix hoppers in the form of tiltable trays (27, 28) stacked one upon the other each being hingedly mounted atop the earth hopper/skip (10) are level filled with the sand and cement mix and transported as a unit with the earth hopper/skip (10) into the moulding cavity, are selectively tilted in opposite direction into the jacket cavities (52, 53) for filling the cavities with loose sand and cement mix and are lifted out of the moulding cavity with the earth hopper/skip (10) as a unit.
A method according to claim 19 or 20, wherein the loose moist, powdered sand and cement jacket mix is poured into the wall outer moulding cavites up to a height which is greater than the level of loose earth in central core cavity, so that the render is partially folded over onto the earth, when the earth is rammed.