METHOD OF MANUFACTURING A HOLLOW SELF-SUPPORTING CONCRETE STRUCTURE, MEANS FOR PERFORMING SAID METHOD AND STRUCTURES OBTAINED BY MEANS OF THE METHOD

Abstract: The invention relates to a method and means for manufacturing freely supported dome or tunnel-shaped structures by means of spraying a particular mortar with micro silica onto an inflated bladder (2) or sheet with or without a primarily applied layer (15) of foam and with or without reinforcing means (23, 24, 28) in particular for manufacturing a tunnel-shaped span (21) for a highway or railway portion.

Description: Method of manufacturing a hollow self supporting concrete structure, means for performing said method and structures obtained by means of the method. The present relates in the first place to a method of manufacturing a tridimensional hollow self supporting concrete structure by inflating an airtight space formed by an airtight sheet having its edges secured to a foundation or base, which sheet after having obtained its proper inflated shape is stiffened by spraying onto it a hardening material, such as mortar or concrete. Such a method is well known from a number of publications for the manufacturing of dome-shaped structures. According to one known method (US-A-3,277,219) it is known to spray concrete on the outerside of the inflated sheet or on the innerside. To obtain initial stiffness and good adherence of the spray mortar a foam layer, e.g. a polyurathene layer, is first sprayed upon the sheet after which anchors for reinforcing rods are placed upon the foam layer, a further foam layer is applied and subsequently reinforcing rods are mounted and the structure is finished by spraying, layer by layer, a mortar against the foam layer and around the reinforcing rods. From US-A-4,155,967 a method is known in which the foam layer is first completed, anchors for reinforcings rods are subsequently placed as well as the reinforcing rods after which the mortar layer is applied. From EP-A-0 357,151 a method is known in which the foam layer is completed first, anchors are placed in the foam layer, a first concrete layer is applied over the anchors to keep them in place after which the reinforcing rods are mounted and the concrete or mortar layer is completed. All known methods are relatively complicated because spraying the mortar with known spraying devices and mortar compositions requires high forces and considerable know-how in applying the mortar layers one by one and from bottom to top to avoid that the sprayed upon mortar loosens. Purpose of the invention in the first place is to simplify the manufacturing of the abovementioned structures. A further object of the present invention to provide a method by means of which long tunnel-shaped objects can be made which e.g. can serve as sound-walls spanning traffic areas. The first object is achieved according to the invention in that a sprayable mortar is used having a micro-silica content which is such that the freshly sprayed mortar in its still plastic stage has form stability. Such a mortar composition and method and device for spraying it, i disclosed in the not yet published German patent application P 39 41 152.4. By using this particular mortar, which has to fulfil DIN 1045 it is possible t spray mortar against vertical walls and even against the underside of horizontal area which before hardening maintain their form. This facilitates the manufacturing of dome-shaped structures and the like b spraying mortar, be it on the outerside or on the innerside of the inflated sheet, i particular " if spraying takes place on the innerside as no particular know-how i necessary any more. Moreover this mortar surprisingly covers and adheres in an excellent manner behind and around reinforcing rods. Apart from the micro-silica said mortar can have any type of additional materials added to the cement such as hardening accelerators, fly ash, synthetic porcelain, quartz, sand, quartzite, tress, bauxite and acceptable synthetic materials as well as all kinds of fibre reinforcements made from resins, glass, steel, carbon or aramide. Said fibre reinforcements are of particular use if spraying takes place without the use of reinforcing rods as will be the case with spraying on the outerside of the sheet or in the manufacturing of structures of relatively small size. If the sprayable mortar is applied against the innerside of the inflated sheet, in particular where required, a synthetic foam layer which is sprayed first and in which the mortar is reinforced, the invention provides for a method by means of which structures with a large span can be manufactured by first spraying spaced apart ribs against the underside of the inflated sheet and after hardening of said ribs filling at least part of the areas between the ribs by spraying mortar. In this case the mortar can be the particular sprayable mortar having the said micro-silica content, but it can be as well an ordinary mortar or a mortar having other accelerators and or stabilizers. The adherence of the spray mortar upon the inflated sheet is insufficient in itself so that there where the sheet deviates from the substantially vertical extent a foam layer is applied first, as is well known, upon which foam layer the mortar adheres perfectly well. In the substantially vertical parts this is not always necessary so that according to the invention a low wall first may be formed upon the base and against the lower side wall of the inflated sheet, preferably before the said ribs are made. Said ribs can be made in parallel vertical planes or in vertical planes of which at least two planes intersect at an angle. in case reinforcing bars are used the reinforcing bars for the ribs, prior to the spraying of the ribs, are placed between temporary mounted side casing plates delimiting the sides of the ribs, which plates are removed prior to the spraying of the final layer or layers of the ribs. Said plates are desirable but not always necessary, because they limit the sideward extent of the spray and prevent that non-coherent fine particles of the spray, the spray mist, coat areas of already provided reinforcing bars outside the area of the ribs. According to a preferred embodiment of the method according to the invention the sheet is composed of a plurality of parallel webs having their parallel side edges secured to each other and having their outer end edges secured to the said base whereas the outermost webs having their edges detachably secured to end sheets which are connected to the base as well such that in the inflated condition the length of the sheet is larger than its width so as to form a tunnel-shaped structure in which the spraying of the mortar only takes place against the webs and not against the end sheets and that after having finished an inflated length, the pressure is relieved and the downstream end sheet is removed and a new series of webs is connected to the already finished part and closed with an end sheet after which a further length of the structure is manufactured by spraying. In this way a great length can be made stepwise. The removable end sheet at the downstream end can be used again and only serves to make inflation possible. With the known methods it is known to make use of an airlock allowing to enter or leave the inflated area without considerably affecting the inside pressure. According to the preferred embodiment the means for performing the method of manufacturing longitudinally extending tunnel-shaped structures has an inflatable sheet with two air locks one at each end of the longitudinal axis of the sheet, preferably at the end sheets, each air lock having a size such that it can take up a truck or the like device such as the spraying apparatuses and/or road making devices. In this way concrete can be supplied by means of a truck at one end which truck leaves the structure under manufacturing at the other end. Preferably the end sheets in inflated condition have the shape of one quarter of a sphere, preferably each with an air lock added to it. With the method according to the invention a great variety of structures by means of inflation and spraying can be made. The areas between the ribs may be completely filled but of course it is possible to leave part of the areas between said ribs uncovered so that openings remain in which the sheet more or less allows the entrance of light or at which the sheet is removed for ventilation purposes. A preferred application is the manufacturing of a tunnel-shaped structure which spans a highway or railway track portion. This may be of importance in densely populated areas where the so called "sound-walls" are insufficient to keep traffic sound away from the living quarters of the population. Said structures may even be covered afterwards with earth. The present invention is, however, not limited to this form of application. The tunnel-shaped structures manufactured according to the invention can also be used as inner coating of a tunnel drilled through rock. The invention now will be further elucidated with reference to the drawings. Figure 1 is a side view of an inflated sheet to be used in the method according to the invention. Figure 2 is a cross section according to the line ll-ll of figure 1. Figure 3 is a cross section according to the line Ill-Ill of figure 1. Figure 4 shows in a perspective view a section of the structure to be manufactured according to the invention. Figures 5a to 5f incl. disclose a number of subsequent phrases in the manufacturing of the structure as shown in figure 4 or 8. Figure 6 is a cross section through a rib at a level adjacent to the base, e.g. at the level of the arrow VI in figure 5d. Figure 7 is a cross section through a rib, e.g. at the level of the arrow VII in figure 5e. Figure 8 discloses schematically the supply and discharge of material during the manufacturing process. Figure 9 is a top view of one embodiment of the structure obtained by applying the method according to the invention. Figure 10 is another top view of the structure obtained by obtaining the method according to the invention. Rgure 11 is a cross section through a finished structure. Figure 12 is a cross section through another embodiment of the finished structure. Figures 1 and 4 show a base structure 1 made from concrete either prefabricated or manufactured at the site. A plastic sheet having the general reference 2 is secured to said base in an airtight manner. Said plastic sheet 2 is composed of a plurality of parallel webs 3, which as shown in figure 3 overlap each other and are welded with their overlapping edges upon each other by means of high frequency to form welding seam 4. The connection at said overlapping edges is a permanent connection. At the outer ends end sheets 6 and 7 respectively are connected in a detachably manner to the outermost edges 8 and 9 respectively of the innerconnected webs 3 by clamping said outermost edges between strips 10 and 11 respectively which extend in planes parallel to the surface of the webs. Said connection, by means of bolts and nuts 12 and 13 respectively is detachable so that said end sheets 6 end 7 respectively can be removed. This removal is necessary when the required length of the tunnel-shaped structure is finished and/or an extension in one or the other direction is desirable. The end sheets 6 and 7 are also connected to a base part 14 and 15 respectively which are removably connected with the base 1. Preferably said parts 6 and 7 have the shape of one quarter of a sphere in the inflated condition. After inflation in a well known manner the coating of mortar can be applied. In most cases a foam layer will be applied first. Figure 5a shows in cross section the inflated sheet. Figure 5b shows the situation after the application of a foam layer 15. Figure 5c shows as well as figure 4 that primarily lower wall portions 16 and 17 respectively are made by spraying or by pouring concrete between the inner side of the sheet with or without coating with foam and a temporary casing (not shown). After the manufacturing of said wall portions 16 and 17 ribs 18,19,20 and so one are manufactured as shown in figure 5d. As next step reinforcing rods 19 are placed between the ribs as shown in figure 5e and finally mortar is sprayed in the areas remaining between the ribs so that the final shape shown in figure 5f is obtained in which the self supporting is substantially formed by mortar or concrete 21. Figure 4 discloses in perspective the lower wall portions 16 and 17, the ribs 18 to 20 etc. and the reinforcing network 22 between said ribs. The reinforcing network between the ribs is substantially the same as the reinforcing network used in accordance with the above cited prior art. In the manufacturing of the ribs 18-20, which ribs give initial strength to the structure, allowing wide spans, it may be desirable to use reinforcements as well. Although the mortar may contain any kind of reinforcing fibre the traditional reinforcing rods are preferred to take up the loads in particular bending loads to which the entire structure is and will be subjected. Figure 6 discloses that reinforcing rods 23 are placed parallel to the contour of the rib to be manufactured in a space which is delimited by temporarily casing plates 22 and 25 respectively. After the mounting of said rods 25 and the casing plates 24 and 25 mortar is sprayed in the space limited in a lateral direction by said plates 24 and 25 until the reinforcing rods are covered. Thereafter the plates 24 and 25 are removed and a final layer 26 is applied either on the ribs separately or together with the spraying of the areas such as 27 between the ribs. Figure 7 discloses the same situation but now after the application of a foam layer 15 upon the outer sheet 2. Prior to the application of the final layer 26 additional reinforcing rods like 28 can be applied. Figure 8 discloses one way of manufacturing the tunnel-shaped structure shown in the preceding figures by using an inflatable sheet 2 having air locks 29 and 30 respectively of a size such that a truck 31 can enter it. Said truck can enter at one end, deliver its material inside the inflated part and leave it through the other air lock 30. Since an extension of the structure shown in figure 1 easily can be made as indicated with the interrupted lines 31 large lengths can be manufactured. Figure 9 discloses an embodiment which may have the cross section shown in figure 11 or 12 and which in the upper part of the tunnel-shaped structure has uncoated areas 32 between the ribs 18, 19 etc. and at which the sheet 2 may have been removed. As shown in figure 11 a highway shielded in this way from its environment can have light and ventilation openings provided by said uncoated areas 32 and it can be or not be incorporated in the landscape by the additional application of earth 33. Instead of placing the ribs parallel to each other and perpendicular to the longitudinal axis said ribs can be placed at angles as shown in figure 10 in which each pair of ribs 34, 35 intersects at the top at a shaφ angle. Also here open spaces 36 and 37 respectively can be created.

Claims: C L A I M S 1. Method of manufacturing a tridimensional hollow self supporting concrete structure (20) by inflating an airtight space formed by an airtight sheet (2) having its edges secured to a foundation or base (1), which sheet (2), after having obtained its proper inflated shape is stiffened by spraying onto it a hardening material (15,20) such as mortar or concrete, characterized in that a sprayable mortar is used having a micro- silica content which is such that the freshly sprayed mortar in its still plastic stage has form stability. 2. Method of manufacturing a tridimensional hollow self supporting concrete structure (20), in particular method according to claim 1 , in which the sprayable mortar (16,17,19,20,21) is applied against the inner side of the inflated sheet, in particular, where required, against a synthetic foam layer (15) which is sprayed first and in which the mortar is reinforced, characterized in that spaced apart ribs (18,19,20) are sprayed first and after hardening of said ribs (18,19,20) at least part of the areas between the ribs (18,19,20) are filled by spraying mortar (21). 3. Method according to claim 2, in which a lower wall (16,17) is first formed upon the base (1) and against the lower side wall of the inflated sheet (2) before the said ribs (18,19,20) are made. 4. Method according to claim 2 or 3, characterized in that the ribs (18,19,20) are made in parallel vertical planes. 5. Method according to claim 2 or 3, characterized in that the ribs (34,35) are made in vertical planes having at least two planes which intersect at an angle. 6. Method according to one of the preceding claims 2 to 5 incl. in which at least the mortar layer is reinforced by means of reinforcing bars, characterized in that prior to spraying of the ribs (18,19,20) reinforcing bars (23) for the ribs (18,19,20) are placed between temporarily mounted side casing plates (24,25), which plates (24,25) are removed prior to the spraying of the final layer or layers (26) of the ribs (18,19,20). 7. Method according to one of the preceding claims, characterized in that the sheet (2) is composed of a plurality of parallel webs (3) having their parallel side edges secured to each other and their outer end edges to the said base (1) and with the outermost webs having their edges (8,9) detachably secured to end sheets (6,7) which are connected to the base (1,14,15) as well such that in the inflated condition the length is larger than its width so as to form a tunnel-shaped structure in which the spraying of the mortar only takes place against the webs (3) and not against the end sheet (6,7) and that after having finished an inflated length, the pressure is relieved and the downstream end sheet (6) is removed and a new series of webs (31) is connected to the already finished part and closed with an end sheet (6). 8. Means for performing the method of claim 7 in which the inflatable sheet (2) has been provided with an air lock, characterized in that two air locks (29,30) are provided, one at each end of the longitudinal axis of the sheet (2) preferably at the end sheet (6,7), each air lock (29,30) having a size such that it can take up a truck (31) or the like device. 9. Sheet for performing the method of claim 7, characterized in that the end sheets (6,7) in inflated condition form one quarter of a sphere. 10. Structure obtained by means of one or more of the preceding claims 2 to 7 incl. characterized in that part of the areas (32,36,37) between ribs (18,19,20,34,35) are uncovered. 11. Structure as claimed in claim 10, characterized in that at the uncovered areas (32,36,37) the sheet (2) is removed. 12. Structure obtained by performing the method of one or more of the preceding claims, characterized in that the structure is a tunnel-shaped span of a highway- or railway track portion with or without afterwards supplied each covering (33).

Inventors: VAN EEDEN JOHANNES PETRUS, VAN EEDEN, JOHANNES, PETRUS
Applicants: INT DOME SYSTEMS, INTERNATIONAL DOME SYSTEMS
Application year: 1991
Main classification: E04G11
IPC codes: E01F8, E04G11, E04G21, E21D11