US3919372A

US3919372A - Process for the production of building elements from porous concrete

Info

Publication number: US3919372A
Authority: US
Inventors: Josef Voegele
Original assignee: Hebel Gasbetonwerk GmbH
Current assignee: Hebel Gasbetonwerk GmbH
Priority date: 1971-02-20
Filing date: 1974-03-25
Publication date: 1975-11-11
Anticipated expiration: 1992-11-11

Abstract

A process for the production of porous concrete building elements in which a large block is cast in a mould, the block while still plastic is cut up by means of tensioned cutting wires into plates or bricks by cuts made in planes parallel to the narrow edges of the block, the cut block is turned onto one of its broad faces so that the lines of division are in vertical planes, thus preventing deformation and sticking together of the cut elements, and while in this position the elements are steamhardened in an autoclave.

Description

United States Patent Vogele 1 1 Nov. 11, 1975 1 PROCESS FOR THE PRODUCTION OF BUILDING ELEMENTS FROM POROUS 6] R f ren Cited CONCRETE UNITED STATES PATENTS [75] Inventor: Josef Viigele, Furstenfeldbruck, 2.2391473 4/1941 Uline 83/35} Germany l-l 11/1962 JilkObSSOD 3641 37 3.407.457 10/1968 Blom 425/307 X Asslgnee: Hebel Gasbetonwerk m 3.474.917 10/1969 Pearne 425/316 x Emmering-Furstenfeldbruck, 3.664.219 5/1972 Vrijma 425/315 X Germany 3.805.651 4/1974 Smorenburg 425/315 X [22} Filed: 1974 Prinmry Exmniner-Robert F. White [21] Appl. No.: 454,229 Assistant E.\'(m1iuerThomas P1 Pavelko Attorney, Agent, or FirmWoodhams, Blanchard and [63] C t' Relted z i e s i b 17 197" Flynn Ol'l ll'lUZlUOl'l 0 er, 0.

abandoned, A process for the production of porous concrete 30 F f Apphcauon Pnomy Data 1 building elements in which a large block is cast in u German) 08300 mould, the block while still plastic is cut up by means H of tensioned cutting wires into plates or bricks by cuts [52] made in planes parallel to the narrow edges of the 6 block. the cut block is turned onto one of its broad 5] I Cl C048 B B 4 faces so that the lines of division are in vertical planes. 'P' 4 59 thus preventing deformation and sticking together of 1 0 are 26 lg l the cut elements, and while in this position the elements are steam-hardened in an autoclave.

5 Claims. 23 Drawing Figures US. Patent Nov. 11, 1975 Sheet 1 015 3,919,372

U.S. Patent Nov. 11, 1975 Sheet 2 of5 3,919,372

U.S. Patent Nov. 11, 1975 Sheet 3 of5 3,919,372

US. Patent Nov. 11,1975 Sheet40f5 3,919,372

U.S. Patent N0v.11, 1975 Sheet50f5 3,919,372

PROCESS FOR THE PRODUCTION OF BUILDING ELEMENTS FROM POROUS CONCRETE This is a continuation of application Ser. No. 227,065, filed Feb. 17, 1972, now abandoned.

The invention relates to a process for the production of building elements from porous concrete, in which a larger block of porous concrete is cast, this is divided into plates or bricks and then these cut parts are brought into an autoclave.

In a known process a larger block of porous concrete is cast in the usual way lying on one broad face in a mould, then by tilting the mould through 90 the porous concrete block is placed on edge and then in this position is divided with cutting wires into plates which with the block standing on edge rest one on top of another to a great height. In this standing on edge position these cut parts are then transported to an autoclave and in the latter are steam hardened in this on edge position.

With this process the division of the block can certainly be effected with relatively short, tensioned cutting wires, so that the cut parts or plates have greater accuracy in their dimensions. This accuracy is, however, considerably impaired through the subsequent transport to and into the autoclave, since during this transport, as a result of the large weight of plates lying one above the other, which are still in the plastic condition, deformation easily occurs, while moreover through this weight the plates are pressed against one another at the cut places and the gaps produced by cutting disappear. In the autoclave therefore the steam cannot enter into these cut gaps so that as a result not only is the hardening time prolonged but also uneven hardening occurs. Through the pressure of the still plastic plates lying one above the other, a connection between the plates is also produced which during the hardening process becomes a firm connection. This baking together of the plates is further strengthened in that during the steam hardening a chemical reaction occurs which effects this firm connection. The result is that after the hardening the firmly stuck together plates must be forcibly separated from one another, either by hand or machine, during which it is, however, difficult to avoid damaging the hardened porous concrete plates. In order to separate the stack of hardened porous concrete plates, not only is a special operation necessary but also a relatively complex separating process which is unsatisfactory in its operation.

The problem underlying the present invention is to achieve a new process avoiding the foregoing disadvantages which not only makes possible the production of plastic building elements with high accuracy during the division of the porous concrete block, but also during the subsequent handling, that is to say during transport to and into the autoclave, avoids any deformation and the pressing against one another and baking together of these building elements during hardening. Steamhardened porous concrete elements should thereby be produced with the greatest accuracy and uniform quality.

This problem is solved according to the invention in that the porous concrete block after stripping is divided first in the longitudinal direction and then in the transverse direction of the block by means of short cutting wires which extend parallel to a narrow edge of the block, whereupon the block, which at least for the transverse cutting is positioned on edge, is turned through onto a broad face and is introduced into the autoclave in this position.

Through the division of the plastic porous concrete block both in the longitudinal direction and in the transverse direction by means of short cutting wires, still plastic building elements (plates or bricks) are produced with great accuracy. The block thus cut up standing on edge is then tipped through 90 onto one broad face, so that the block in this position has only a small height and the cut gaps all lie vertically. The cut building elements thus lie side by side and not as formerly one on top of another. During transport to and into the autoclave, therefore, no deformation can occur. Since the cut building elements then lie freely side by side in the autoclave, on the one hand the steam can enter the cut gaps and on the other hand the abovementioned baking together of the porous concrete elements cannot occur. The additional separation of the building elements, which is damaging to the latter, can thus be omitted, as can the additional grading or trimming of the building elements after the separation. This process also offers larger scope for varying the mixing of the porous concrete mass as regards the binding medium, moisture content and temperature, as well as greater tolerance in the hardening operation in regard to temperature, steam pres sure, moistness or saturation of the steam, and heating up time. The standing time, i.e., the time from the cutting to the introduction into the autoclave, does not have a disadvantageous influence. A further advantage of the new process consists is that the cutting of the plastic porous concrete elements can take place in a relatively soft condition of the latter, thus the porous concrete block can be removed from the mould earlier and thus a valuable saving of time results.

In the following the new process is explained with examples shown in the drawings.

FIGS. 1 and la show a plan and perspective view of a cast porous concrete block;

FIGS. 2 and 20 show a plan and perspective view of an apparatus during longitudinal cutting of this block;

FIG. 3 shows a tilting device for the block in perspective view;

FIG. 3a shows a block raised with this tilting device and standing on edge;

FIGS. 4 and 4a show a plan and perspective view of an apparatus for vertical cutting of this block;

FIG. 5 shows the divided block tipped from this onedge position onto a broad face;

FIGS. 6 and 6a show in plan and perspective a block first lying on a broad face and then tipped up on edge;

FIGS. 7 and 7a show in plan and perspective view an apparatus during cutting in the longitudinal direction of this block as it stands on edge,

FIG. 8 shows the plan view of a cutting apparatus (according to FIG. 4a) for vertical cutting of the block;

FIG. 9 shows the divided block tipped from this onedge position onto a broad face;

FIG. 10 shows an installation for carrying out the process in accordance with the invention;

FIG. 11 shows an elevation of a cutting machine in the direction XI of FIG. 10;

FIG. 12 and 13 show different working positions of the cutting table of this cutting machine;

FIG. 14 shows an elevation of a loading carriage in the direction XIV of FIG. 10;

FIG. l shows another installation for carrying out the process in accordance with the invention;

FIG. 16 shows an elevation of part of a cutting machine in the direction XVI of FIG. I5, and

FIG. 17 shows an elevation in the direction XVII of FIG. of a tilting frame.

In FIGS. 1 and la a plastic porous concrete block produced by pouring in a mould is referenced l, which can have a length I of 6m., a breadth b of 2m. and a height h of 0.6m. This block is brought by means of an appropriate lifting apparatus (clamp tongs according to German Pat. No. l,208,67 l or suction lifting apparatus (according to German Pat. No. l,584,426) onto the fixed table I5 of a cutting machine according to FIGS. 2 and 2a and then this block is cut with a cutting device 2 which moves in the longitudinal direction A and has stretched cutting wires 3. This cutting in the longitudinal direction can advantageously be undertaken on a cutting machine (e.g., according to German Pat. No. l,087,960) in which a lattice grid consisting of longitudinal and transverse rods is arranged into the cutting table. The block divided into plates 4 can then be lifted from the cutting table 15 by this grid.

This block divided into plates 4 and lying on a broad face is then in accordance with FIGS. 3 and 3a turned into the on-edge position of FIG. 3 by means of a special device which has two

plates

5 and 6 firmly connected to one another and standing perpendicular to one another, so that it only rests on the narrow plate 6. For this tipping up on edge the abovementioned lattice grid is advantageously used as the plate 5. After removal of the plate 5, an illustrated in FIG. 4 and 4a, this block is then cut in the perpendicular direction with a cutting device 7. The division is carried out with straight wires 8, which are stretched between the shafts 9 and 10, whereby through a swinging movement of these shafts a reciprocating longitudinal movement B and the cutting wires can be effected for the achievement of a better cut. With these cutting wires 8 the plates 4 can either be cut to a predetermined length or by means of a plurality of wires 8 as shown divided into building bricks II.

During longitudinal cutting of the block according to FIGS. 2 and there are produced cut gaps between the plates. 4. These disappear after the tipping into the upright position of FIG. 3 by reason of the weight of the plates 4 lying one on top of the other. During transverse cutting according to FIGS. 4 and 4a, therefore, no breaking away of the plastic porous concrete can occur at the cut gaps. From FIGS. 2 and 2a and 4 and 40 it is apparent that both during the longitudinal and during the transverse cutting, the cutting wires 3 or 8 are arranged approximately parallel to a narrow edge 12 of the block, so that relatively short cutting wires can be used, which are not significantly longer than the height h and the block. With these short tensioned cutting wires, therefore, high accuracy can be produced during cutting, i.e., plates or bricks with very exact dimensions with a few tenths of a millimeter tolerance can be produced.

As illustrated in FIG. 5 the divided block is then tilted back again from its on-edge position (chain-dotted lines) onto its broad face (full lines), and this with the tipping device consisting ofthe above-mentioned

plates

5 and 6. The gaps between the new severed plates 4 reappear during this tipping process because the block has not yet been cured. On the plate 5, advantageously forming a lattice grid, the divided block lying on its broad sidc is then transported into the autoclave. During the steam hardening the plates 4 or the bricks 1] thus lie freely side by side so that no pressing arises across the cut gaps and the steam can enter these gaps. The access of steam is further faciltated by the lattice grid 5.

Since during the above-mentioned transport the plastic building elements do not lie one upon the other but one beside the other and moreover have only the relatively small height h, no deformation of the plastic elements can arise from vibration during transport. This will also be significantly hindered, especially with plates, if these are provided with a reinforcing assembly.

Damage to the porous concrete block during cutting is also avoided by the above-described process because both the longitudinal and the transverse cutting are effected on a stationary block supported at the time over its whole length and breadth. If necessary, however, this porous concrete block can also be cut longitudinally into plates by a method in which the cutting device 2, 3 remains fixed and the block is driven through this cutting device in the longitudinal direction, e.g., according to German Pat. No. 1,274,947.

In the above-described processes in accordance with the invention the porous concrete block cut longitudinally into plates is tipped into the on-edge position with a grid. Instead of this the longitudinally cut porous concrete block can, however, also be tipped into the onedge position by means of the cutting table. An installation for carrying out this process is shown in FIGS. 10 to 14. It consists of a cutting machine 15 for longitudinal cutting of the block, having a laterally tiltable cutting table 16 which is swingably mounted about a horizontal axis 17 on an under frame 18, the latter being capable of travelling on longitudinal rails 19 to an intermediate station 20, a transverse cutting device 21 arranged parallel to this station, a carriage 23 capable of travelling between this cutting device and the station 20 on transverse rails 22 and having a tiltable carrying plate 24, and an unloading carriage 25 capable of travelling on the longitudinal rails 19 on which carriage a frame 26 for the reception of a hardening grid 27 is mounted in such a way as to be swingable to the side through The cutting machine 15 corresponds essentially in its construction with the cutting device according to German Pat. No. l,087,960. The porous concrete block to be cut is placed on the cutting table 16, which has longitudinal grooves 28 for the guide rods 29. At one end these guide rods are connected together by a transverse bar 30, while at the other ends of these guide rods the lower ends of the vertical cutting wires are fastened. The upper ends of these cutting wires are fastened to a portal 32, which forms a framework with the transverse bar 30. This can travel lengthwise on the rails 33 in the direction R. In this movement of the framework 29 to 32 the porous concrete block is cut into plates 35 by the wires 31.

Thereafter the cutting table 16 travels on the rails 19 in the direction V to the intermediate station 20, here this cutting table takes up the position 16' shown in chain-dotted lines. Then the carriage 23 with the carrying plate 24 according to FIG. 12 is brought up to the table 16', in such a way that the hinge axis 36 of the carrying plate is exactly coincident with the hinge axis l7 of the table 16'. The carrying plate 24 is mounted on tilting arms 37 swingablc about the axis 36. the carrying plate 24 being displaceable. according to FIG. I2, in the tilting arms 37 in the direction 0 by shafts 38, so that for example by hydraulic means this displacement can be effected and thereby the carrying plate 24 can be laid against the side of the block 34. Through a mechanical interlock a firm connection between the table 16 and the tilting arms 37 can be effected, so that then, e.g., with hydraulic cylinder 39 and piston 40 the tipping of the block 34 into the on-edge position according to FIG. 13 can be effected. The cutting table 16 is then swung back in the direction of the arrow into the horizontal position and travels back again on the rails 19 to its starting position according to FIG. I0, so that the cutting machine is again ready to receive and cut a block.

According to FIG. 13 the block 34 is carried by the carriage 23 on the rails 22 to the cutting machine 21 (see FIG. 14). This cutting machine has a vertically displaceable cutting frame 41 in which horizontal cutting wires 42 are stretched. By dropping of this cutting frame the plates 35 are cut to length. However with this cutting frame 41 and a corresponding number of eut ting wires it is also possible to cut the plates 35 into bricks. After the cutting the frame 41 is again raised and then the carriage 23 travels back again to the intermediate station 20. In the meantime the unloading carriage 25 with the hardening frame 27 has travelled to this station. this frame being brought into the vertical position shown in chain-dotted lines according to FIG. I4. The swinging axis 36 of the carriage 23 thus coincides exactly with the swinging axis 43 of the tilting frame 26. Then the carrying plate 24 and the swinging frame 26 are swung together in the direction of the arrow A so that as a result the cut block 34 lies with its broad face on the grid 27. The unloading carriage 23 then travels back from the intermediate station to the initial position of FIG. 10. The hardening grid 27 with the cut block can then be taken from the unloading carriage and transported into an autoclave.

The longitudinal cutting according to FIG. I0 can if need be also be effected in such a way that the cutting framework 29 to 32 is fixed and the cutting table I6 with the porous concrete block is moved in the direction V. In this case the longitudinal cutting of the block and the transport of the latter with the cutting table I6 to the intermediate station takes place simultaneously.

FIGS. 15 to I7 show an advantageous installation. in which the longitudinally cut porous concrete block is brought into the on-edge position with the help of a grid and after the transverse cutting is again brought by this grid into the lying position. so that the cut block can then be delivered into the autoclave by this grid.

This installation consists of a machine. known in itself, for the longitudinal cutting of the block. having a cutting table 44 with a grid 45 arranged in a lower position. of a lifting apparatus 46 with transport rollers 47, on which the longitudinal beams 48 of the frame are mounted. of a tilting frame 50, arranged at one end of the cutting machine, serving for the reception of the grid 45 with the cut block 34 and possessing corresponding trnsport rollers 49, the frame 50 being tiltable about a fixed axis 50a, of a transverse cutting device 21 arranged parallel to this tilting frame, of a carriage 23 with tiltable carrying plate 24 travelling on rails 22 between this cutting device and the tilting frame 50. and a fixed unloading frame 5I adjacent the tilting frame 50, which is provided with corresponding transport rollers 52 for the reception of the grid 45. The machine for longitudinal cutting shown in FIGS. I5 and 16 corresponds in its construction with the German Pat. No. 1,087,960 and likewise has the cutting framework 29 to 32 described above. In contrast to FIG. 10, however, in the cutting machine of FIGS. I5 and I6 the grid consisting of longitudinal beams 48 and transverse rods 53 is arranged below the cutting table (FIG. [6). This grid has longitudinal rails 54 with which the grid is mounted on the transport rollers 47. After the longitudinal cutting of the block 34 into plates 35, the grid 45 is so lifted up by the, e.g., hydraulic. lifting device 46, that the block 34 then rests on the grid 45. By driving the rollers 47 and the rollers 49 the grid with the block is then advanced onto the tilting frame 50 (see FIG. 17). The carriage 23 with the tiltable carrying plate 24 is then moved up to the tilting frame so that it takes up the position of FIG. I2 relative to the block 34 as previously described. By tipping of the frame 50 into the vertieal position together with the carrying plate 24 the block is then stood on edge on the carriage 23 (see FIG. 13) and then as previously described is transversely cut with the cutting device 21 and finally moved back again to the grid 45 which is still standing on edge and then by simultaneous tipping of the frame 50 and the carrying plate 24 is again brought into the lying position of FIG. 17. By driving the transport rollers 49 and 52 the grid 45 is then brought onto the unloading frame 51. From the latter the grid with the block 34 can then be lifted and delivered to an autoclave.

In the process illustrated in FIGS. 6 to 9 the porous concrete block is also first cast lying on its broad face in a mould (FIG. 6). With the aid of the two mould walls 50, 6a the block is then brought into the on-edge position of FIG. 6a. In this position the block is then. according to FIGS. 7, 7a, cut in the longitudinal direction into the plates 4 with a fixed cutting device 13 which has cutting wires 14 at various heights. staggered in the longitudinal direction. the block being driven through the cutting device in the longitudinal direction A.

The block, thus divided into plates 4, is then. in the same on-edge position. cut vertically with a cutting device according to FIG. 8 (equivalent to FIGS. 4, 4a). The thus ready cut plates or building bricks II are then in the same way as described above (FIG. 5) brought from the one-edge position of the block (shown in broken lines in FIG. 9) into the position shown in FIG. 9 in which the block divided into plates or building bricks 1] lies with a broad face on a plate or a grid 5, by means of which it is then brought into the autoclave.

In the accompanying drawings various possibilities for carrying out the new process are shown. The latter is not limited to these examples of execution. For example a porous concrete block already standing on edge in the position of FIG. can be cast in a mould and then after stripping in this on-edge position as explained in FIGS. 7 and 8 divided into plates and then these plates can be cut to length or cut down into bricks.

The process is, of course, applicable to the production of cast building elements composed of other types of concrete and other mouldable materials.

The embodiments ol'thc invention in which an exclusivc property of privilege is claimed are defined as follows:

l. A process of manufacture of porous concrete building elements comprising the steps of:

casting and stripping a block of concrete having a height equal to the height of the concrete building elements thereby defining a plurality of narrow sides on said block of concrete and a longitudinal length and transverse width thereby defining a pair of oppositely facing broad sides greater in area than the area of each of said narrow sides;

dividing said block while said block is lying on one of said broad sides longitudinally into plates by means of cutting wires extending parallel to said narrow sides of said block;

engaging at least two mutually perpendicular sides of said block and tipping the entire block through 90 onto said narrow side;

cutting said block transversely by means of cutting wires extending parallel to said narrow sides of said block while said block stands on said narrow side, said longitudinal cuts in said block having closed while said block is standing on one of said narrow sides so that a breaking out of block material will be prevented by the adherence of said block material across said longitudinal cuts during said transverse cut;

engaging said at least two mutually perpendicular sides of said block and tilting the entire cut block back through 90 to lie on said one of its broad sides and effect a reopening of said longitudinal cuts; and

placing the cut block in an autoclave while lying on said broad side with both the longitudinal and transverse cut gaps open and extending vertically, and steam-hardening the cut block in the autoclave.

2. A process according to claim 1, comprising the additional step of supporting said block during the longitudinal cutting on a cutting table having a lattice grid recessed therein, and tipping the longitudinally cut block on said narrow side by tilting the said grid.

3. A process according to claim 2, wherein the step of tilting said block to lie on its broad side after cutting includes placing the said grid against the broad side and then tipping the grid to the horizontal position so that the cut block is supported on the grid in the autoclave. 4. A process according to claim I, wherein said block rests on a cutting table during the longitudinal cutting and is then tilted onto said narrow side with the cutting table.

5. A process of manufacture of porous concrete building elements comprising the steps of:

casting and stripping a block of concrete having a height equal to the height of the concrete building elements thereby defining a plurality of narrow sides on said block of concrete and a longitudinal length and transverse width thereby defining a pair of oppositely facing broad sides greater in area than the area of each of said narrow sides; dividing said block longitudinally into plates by means of cutting wires extending parallel to said narrow sides of said block; cutting said block transversely by means of cutting wires extending parallel to said narrow sides of said block while said block stands on said narrow side, said longitudinal cuts in said block having closed while said block is standing on one of said narrow sides so that a breaking out of block material will be prevented by the adherence of said block material across said longitudinal cuts during said transverse cut; thereafter engaging only said one narrow side on which said block is standing and only one of said broad sides of said block mutually perpendicular thereto and simultaneously tilting the entire cut block through to lie on one of its broad sides, said engagement being maintained during the entire tilting movement, said tilting effecting a reopening of said longitudinal cuts and resulting in a divided block having divided block portions lying only one beside the other; placing the cut block in an autoclave while lying on said broad side with both the longitudinal and transverse cut gaps remaining open and extending vertically, and steam-hardening the cut block in the autoclave.

Claims

1. A PROCESS OF MANUFACTURE OF POROUS CONCRETE BUILDING ELEMENTS COMPRISING THE STEPS OF: CASTING AND STRIPPING A BLOCK OF CONCRETE HAVING A HEIGHT EQUAL TO THE HEIGHT OF THE CONCRETE BUILDING ELEMENTS THEREBY DEFINING A PLURALITY OF NARROW SIDES ON SAID BLOCK OF CONCRETE AND A LONGITUDINAL LENGTH AND TRANSVERSE WIDTH THEREBY DEFINING A PAIR OF OPPOSITELY FACING BROAD SIDES GREATER IN AREA THAN THE AREA OF EACH OF SAID NARROW SIDES, DIVIDING SAID BLOCK WHILE SAID BLOCK IS LYING ON ONE OF SAID BROAD SIDES LONGITUDINALLY INTO PLATES BY MEANS OF CUTTING WIRES EXTENDING PARALLEL TO SAID NARROW SIDES OF SAID BLOCK, ENGAING AT LEAST TWO MUTUALLY PERPENDICULAR SIDES OF SAID BLOCK AND TIPPING THE ENTIRE BLOCK THROUGH 90* ONTO SAID NARROW SIDE, CUTTING SAID BLOCK TRANSVERSELY BY MEANS OF CUTTING WIRES EXTENDING PARALLEL TO SAID NARROW SIDES OF SAID BLOCK WHILE SAID BLOCK STANDS ON SAID NARROW SIDE, SAID LONGITUDINAL CUTS IN SAID BLOCK HAVING CLOSED WHILE SAID BLOCK IS STANDING ON ONE OF SAID NARROW SIDES SO THAT A BREAKING OUT OF BLOCK MATERIAL WILL BE PREVENTED BY THE ADHERENCE OF SAID BLOCK MATERIAL ACROSS SAID LONGITUDINAL CUTS DURING SAID TRANSVERSE CUT, ENGAING SAID AT LEAST TWO MUTUALLY PERPENDICULAR SIDES OF SAID BLOCK AND TILTING CUT BLOCK BACK THROUGH 90* TO LIE ON ONE OF ITS BROAD SIDES AND EFFECT A REOPENING OF SAID LONGITUDINAL CUTS, AND PLACING THE CUT BLOCK IN AN AUTOCLAVE WHILE LYING ON SAID BROAD SIDE WITH BOTH THE LONGITUDINAL AND TRANSVERSE CUT GAPS OPEN AND EXTENDING VERTICALLY, AND STREAM-HARDENING THE CUT BLOCK IN THE AUTOCLAVE.

3. A process according to claim 2, wherein the step of tilting said block to lie on its broad side after cutting includes placing the said grid against the broad side and then tipping the grid to the horizontal position so that the cut block is supported on the grid in the autoclave.

4. A process according to claim 1, wherein said block rests on a cutting table during the longitudinal cutting and is then tilted onto said narrow side with the cutting table.

5. A process of manufacture of porous concrete building elements comprising the steps of: casting and stripping a block of concrete having a height equal to the height of the concrete building elements thereby defining a plurality of narrow sides on said block of concrete and a longitudinal length and transverse width thereby defining a pair of oppositely facing broad sides greater in area than the area of each of said narrow sides; dividing said block longitudinally into plates by means of cutting wires extending parallel to said narrow sides of said block; cutting said block transversely by means of cutting wires extending parallel to said narrow sides of said block while said block stands on said narrow side, said longitudinal cuts in said block having closed while said block is standing on one of said narrow sides so that a breaking out of block material will be prevented by the adherence of said block material across said longitudinal cuts during said transverse cut; thereafter engaging only said one narrow side on which said block is standing and only one of said broad sides of said block mutually perpendicular thereto and simultaneously tilting the entire cut block through 90* to lie on one of its broad sides, said engagement being maintained during the entire tilting movement, said tilting effecting a reopening of said longitudinal cuts and resulting in a divided block having divided block portions lying only one beside the other; placing the cut block in an autoclave while lying on said broad side with both the longitudinal and transverse cut gaps remaining open and extending vertically, and steam-hardening the cut block in the autoclave.