METHOD AND DEVICE FOR PRODUCING A DRAINABLE MORTAR FILLING OF A VOCATION

Description

[0001] The invention relates to a method for producing a drainage-capable mortar filling of a cavity, in particular an annular gap between a subsoil and the segments of a tunnel structure.

[0002] A method for filling an annular space between the outer surface of a tunnel segment ring and the surrounding subsoil of a tunnel structure by introducing a construction material mixture is known from EP 3 048 243 A1. A low-viscosity base component of the construction material mixture, conveyed via a pipe, is mixed with an activator component at the point of injection into the annular space. The base component, containing only fine-grained particles, comprises either a bentonite-cement mixture or a mixture of bentonite with ground granulated blast furnace slag, or a combination of both, as well as water, and may contain further fillers and / or additives. The base component either does not set spontaneously at all or exhibits a setting time delayed by more than 24 hours. The proposed activator component preferably contains water glass, but may also contain an alkaline earth oxide or hydroxide, or an aluminate.Additionally, a surfactant component is added to the transported base component. The mixture of base component, activator component, and surfactant component is guided through a tubular flow chamber of a foam generator, preferably with a cylindrical cross-section, which serves as an aeration section. The outer wall of the flow chamber is formed by a porous material and surrounded by a pressure chamber to which compressed air of a predetermined pressure is supplied. The pressure is set such that a predetermined quantity per unit of time penetrates the porous wall into the flow chamber, forming air bubbles of a predetermined size and distribution. The process described in the publication is based on the idea of ​​adding air to the building material mixture used to fill the annular space, i.e., introducing a building material foam, in order to achieve high compressibility.The air should only be mixed in at the point of introduction into the annular gap to improve the delivery, since a foam-free base component is easier to pump over longer distances.

[0003] From WO 2016 / 179612 A1, a method for producing a water-permeable annular gap mortar is known, in which a foamed mortar intermediate is first formed, wherein the mortar intermediate comprises aggregates, water and binder, wherein the aggregates have an aggregate granulation with a void content between 30% and 50%, wherein the aggregate granulation, the water and the binder together have a void content of 10% to 25%, then the foamed mortar intermediate is conveyed through a conveying line into an annular gap and immediately after leaving the conveying line has an air void content which is absolutely 10% to 25% greater than the void content of the aggregate granulation, the water and the binder together.Then, in the area of ​​the end of the conveying line, a fresh mortar is formed from the mortar intermediate product by adding a defoamer, and finally the foam is at least partially destroyed by the defoamer before the fresh mortar hardens into the annular gap mortar.

[0004] In the known method for producing a water-permeable annular gap mortar, the water permeability or drainage capacity is achieved through the properties of the aggregates, in particular the void content between the aggregate particles. Good water permeability is achieved through high void content between the aggregate particles due to a suitable selection of particle sizes and shapes.

[0005] German patent application DE 10 2009 008451 B3 describes a water-permeable mortar for annular space filling, which, among other things, exhibits good pumpability and guarantees sufficient strength. The proposed mortar mixture consists of 10–25% by mass of cement as a hydraulic binder, 25–40% by mass of water, 40–60% by mass of an amorphous granulate, preferably spherical expanded glass granulate, as an aggregate, 0.5–5% by mass of at least one substance based on synthetic surfactants as an air and / or foaming agent, and 0.05–2% by mass of an active ingredient based on polyethylene oxide in combination with a cellulose ether as a stabilizer to achieve increased viscosity. The patent application does not disclose the specific air content or method of incorporation into the mortar.

[0006] WO 93 / 02783 discloses a foam generator with a tubular aeration section having a porous wall. A medium to be foamed, for example a mortar, is passed through the interior of the tubular aeration section, with compressed air from a pressure air chamber being forced through the porous wall of the aeration section into the interior.

[0007] From DE 10 2010 062762 A1, a method for producing foamed concrete is known, in which a cement paste and a foam are first formed, and then the cement paste is mixed with the foam, and the resulting foamed concrete is dried. The formation of the foam, with a density of 10–160 g / l, preferably 80 g / l, from water, foaming agent, and air is carried out using a foam generator. The mixing of the foam thus formed with the cement paste takes place in a truck mixer.

[0008] Based on this state of the art, the object of the invention is to provide a way to produce a drainage-capable mortar filling of an annular gap that combines good pumpability of the components to be supplied with high water permeability and strength of the annular gap filling in the hardened state.

[0009] This problem is solved according to the invention by a method for producing a drainage-capable mortar filling of a cavity, in particular an annular gap between a subsoil and the segments of a tunnel structure, with the features of claim 1. In this method, in step a), a cement suspension with a water-binder ratio between 0.40 and 0.60 is first produced by mixing at least one cement binder with water and optionally aggregates, and a cement suspension volume flow is generated, wherein a surfactant is added to the cement suspension or the cement suspension volume flow.Then, in step b), the cement slurry flow is passed through a foam generator to create a foam flow, such that compressed air is added in a first predetermined volume fraction between 150% and 250% of the cement slurry flow, with a low dispersion of air void sizes, where the air void sizes of at least 70% of the compressed air volume fraction deviate from a mean air void size by no more than approximately 50%. In step c), a setting accelerator is added to the foam flow as it is introduced into the cavity. The setting accelerator is preferably a shotcrete accelerator."Compressed air" here refers to any air or similar gas mixtures or gases, such as nitrogen, that are "pressed" into the cement mixture to create foam bubbles or pores, regardless of the pressure applied and the exact composition of the gas mixture.

[0010] The invention is based on the fundamental idea of ​​achieving water permeability not—as in the known method—through high void content between aggregate particles, but by producing a predominantly open-pored, solidified foam. According to the invention, this is achieved by introducing a specific proportion of air voids with the most homogeneous air void distribution possible. This approach is based on the understanding that, on the one hand, if the air input is too low, resulting in a high density in the foam, an excessive proportion of the air voids are embedded in the cement slurry (particularly in the form of a spherical foam with spherical air bubbles, or even a polyhedral foam in which adjacent deformed air bubbles are separated by essentially flat liquid walls) in such a way that, upon setting, they form closed pores. dhThe foam solidifies into a closed-cell foam. Conversely, an excessively high air void content, resulting in a low density, leads to foam collapse. The desired outcome is a foam where the density and distribution of air voids have already caused the liquid (cement suspension with surfactant) to flow out of the lamellae between the touching air bubbles, causing them to rupture and coalesce, while still largely preserving the foam struts and nodes between the air voids. In this metastable state, where a largely open-cell foam exists for a short time, the foam should be stabilized ("frozen") by the onset of solidification and then fully harden.It was found that when an air void volume fraction of between 150% and 250%, preferably about 200%, is introduced, based on the cement suspension volume, and with an air void size distribution exhibiting low scatter in air void sizes, such a desired open-pore foam is formed. According to the invention, sufficiently low scatter exists when the air void sizes of at least 70% of the compressed air volume fraction deviate from a mean air void size by no more than about 50%. Preferably, the air void sizes of at least 85% of the compressed air volume fraction should deviate from a mean air void size by no more than about 30%. It is assumed that the low scatter in air void sizes sought here minimizes the effect observed in foams whereby large foam bubbles grow at the expense of neighboring smaller foam bubbles.The lower dispersion of air pore sizes leads to a more uniform disintegration of the foam and better adjustability of the optimal composition (especially the optimal air-cement suspension ratio) for the desired metastable foam state at the time of "freezing" due to the onset of solidification.

[0011] The high strength of the solidified, set foam mortar of at least 0.4 N / mm² (at 3 days old), which can also be achieved with sufficient water permeability, is achieved in particular by a water-binder ratio (water-cement ratio) of less than 0.60; the required flowability, pumpability and foamability of the cement suspension by a water-binder ratio (water-cement ratio) of more than 0.40.

[0012] In a preferred embodiment, in step a) a cement suspension volume flow with a density between 1500 kg / m³ and 2000 kg / m³, preferably between 1700 kg / m³ and 1900 kg / m³, is generated. In step b), compressed air is then added in the first predetermined volume fraction such that a foam volume flow with a density between 600 kg / m³ and 800 kg / m³, preferably between 650 kg / m³ and 750 kg / m³, is formed. Tests with cement suspensions in this density range, preferably with densities around 1800 kg / m³, have shown that sufficient water permeability is achieved within the aforementioned density interval. With a cement suspension having a density of approximately 1800 kg / m³ and an air addition of approximately 200%, an optimal foam density of approximately [value missing] was achieved with regard to the water permeability.700 kg / m³ < , whereby it must be taken into account that in practice not all of the compressed air supplied to the foam generator is actually incorporated into the foam, i.e., some of the compressed air escapes into the environment or leads to local defects in the annular gap filling. This proportion of air not incorporated into the foam can be minimized, among other things, by adding sufficient surfactant and is less than about 20% in the process according to the invention.

[0013] Preferably, in step b), the compressed air is added with an air void size distribution in which the mean air void size lies in the range between 200 µm and 1300 µm, preferably between 250 µm and 800 µm, and particularly between 300 µm and 500 µm. An optimal air void size is to be selected, especially with a view to achieving the metastable state mentioned above. Furthermore, smaller air voids increase the risk of clogging of the pore channels, and larger air voids reduce the strength.

[0014] In a preferred method for producing a drainable mortar filling of a cavity, in step b) the cement suspension volume flow is passed through a tubular aeration section of the foam generator having a porous wall, wherein compressed air from a compressed air chamber is forced through the porous wall of the aeration section into an interior space carrying the cement suspension volume flow, the pore size of the porous wall being selected such that the desired air pore size distribution in the foam volume flow is achieved. A preferred pore size of the porous wall is between 30 µm and 100 µm, preferably between 50 µm and 60 µm.

[0015] Preferably, in the process for producing a drainable mortar filling, the cement slurry is prepared in step a) by mixing at least one cement of type CEM III or CEM IV, preferably type CEM III, with water. A blast furnace slag cement is preferred, in particular a blast furnace slag cement with a high strength class, high sulfate resistance, and low alkali content. Small amounts of an alumina layered silicate, preferably a bentonite, are preferably added to the cement slurry as a stabilizer and / or small amounts of a dispersant, each amount being less than 2 wt.% of the cement slurry. The use of a cement containing only small amounts of clinker or calcium compounds prevents the pores of the annular gap mortar filling from clogging (or growing over) due to sintering when the water to be drained acts on the calcium compounds.

[0016] In a preferred embodiment of the process, in step a) the cement suspension volume flow is first generated, and then the surfactant, in the form of a surfactant solution, is added to the cement suspension volume flow in a second predetermined volume fraction of a maximum of 20%, preferably between 5% and 15% of the cement suspension volume flow. The volume-controlled addition of the surfactant after mixing the cement suspension prevents uncontrolled pre-expansion of the cement suspension. The amount of surfactant used depends on the type and effectiveness of the surfactant and on economic considerations. The surfactant used and its quantity must be selected such that at least 80% of the air used is incorporated into the foam.

[0017] Preferably, a surfactant solution containing at least one anionic surfactant and / or at least one protein foaming agent is added. Examples of suitable surfactants include concrete additives known as foaming agents, which contain anionic surfactants or protein foaming agents. Synthetic surfactants based on alkali salts of alkyl ether sulfates, alkyl sulfonates, and / or alkylbenzenesulfonates are preferred.

[0018] In the inventive method for producing a drainable mortar filling of a cavity, a third volume fraction of between 4% and 16%, preferably between 7% and 10%, of the cement slurry volume fraction is preferably added to the foam volume stream in step c). The amount of the added setting accelerator depends on the type of accelerator, the homogeneity of its incorporation into the foam volume stream, and economic considerations. The homogeneity of the incorporation into the foam volume stream depends on the type of mixing device and the length and cross-section of the delivery line connected to the mixing device. If an annular nozzle is used, the third volume fraction is preferably between 7% and 10%.For example, if a so-called injection cap is used at the end of a pilaster, the accelerator concentration may need to be increased to up to 16% due to the poorer material mixing. The type of accelerator must be selected depending on the cement used. Furthermore, the type of setting accelerator must also be matched to the surfactant used and the other components of the foam to prevent foam disintegration and reduced compressive strength in the hardened state. For a cement suspension containing cement types CEM III or CEM IV, an alkali- and alkaline earth-free setting accelerator, for example, one containing aluminum hydroxide and / or aluminum sulfate, is preferably used. Preferably, in step c), an aqueous solution of at least 50 wt. is added to the foam flow as a setting accelerator.-% aluminum hydroxide and / or aluminum sulfate added.

[0019] In a preferred embodiment of the method for producing a drainable mortar filling of a cavity, in step c) the setting accelerator is added to the foam volume flow for a maximum of 20 seconds, preferably a maximum of 15 seconds, before it is introduced into the cavity. This time period should not be exceeded in order to reduce the risk of premature setting of the foam in the transport pipe, particularly in the piling.

[0020] The above-mentioned object of the invention, namely to provide a means of producing a drainage-capable mortar filling of an annular gap that combines good pumpability of the components to be supplied with high water permeability and strength of the annular gap filling in the hardened state, is also achieved according to the invention by a device with the features of claim 11.

[0021] The device according to the invention for producing a mortar filling of a cavity serves to carry out the above-mentioned method and comprises a device for generating a cement suspension volume flow, a device for adding a surfactant to the cement suspension volume flow and a foam generator.The foam generator has a tubular aeration section with a porous wall, through which the cement suspension volume flow is passed, wherein a compressed air chamber is arranged on the outside of the porous wall such that compressed air from the compressed air chamber is forced through the porous wall of the aeration section into the cement suspension volume flow, so that a foam volume flow is generated, wherein the porous wall is designed such that the compressed air is mixed into the foam volume flow with an air void size distribution with a low scatter of air void sizes, in which the air void sizes of at least 70% of the compressed air volume fraction deviate from a mean air void size by no more than about 50%.The device further comprises a volume flow regulator connected to a compressed air inlet of the compressed air chamber for setting a compressed air volume flow; a control device coupled to the volume flow regulator, configured to set a compressed air volume flow approximately 1.5 to 2.5 times the cement slurry volume flow; and a device downstream of the foam generator for adding a setting accelerator to the foam volume flow, which is connected to a line for introducing the mixture formed in the device for adding the setting accelerator into the cavity. This is particularly due to the volume-controlled supply of compressed air in a predetermined ratio to the cement slurry volume by means of the foam generator and due to the design of the foam generator, which exhibits low variation in air void sizes. dhThe device, which enables a high degree of air pore homogeneity, allows a process that results in a water-permeable foam mortar that is largely open-pored.

[0022] In a preferred embodiment, the device for generating a cement suspension flow rate comprises a first pumping device and a first flow meter coupled to the control unit for detecting the cement suspension flow rate. This allows for a variable cement suspension flow rate (without a flow meter, a constant, predetermined flow rate would always have to be set).

[0023] Preferably, the device for adding a surfactant comprises a line for conveying the cement suspension flow, a mixer integrated into the line, and a branch line opening into the line upstream of the mixer for supplying a surfactant flow, wherein the branch line for supplying the surfactant flow includes a second pump and a second flow meter for detecting the surfactant flow, the second pump and the second flow meter being coupled to the control unit. This additionally enables volume-controlled, adjustable surfactant addition.

[0024] In a preferred embodiment of the foam generator, the tubular aeration section is a cylindrical pipe section surrounded by the porous wall, with an inner diameter between 10 mm and 20 mm and a length between 100 mm and 300 mm. etc.,wherein the pores of the porous wall have approximately the same diameter. Preferably, the diameter of the pores of the porous wall is between 30 µm and 100 µm, more preferably between 50 µm and 60 µm.

[0025] The device according to the invention is preferably characterized in that the device for adding a setting accelerator has a line for conveying the foam volume flow, a line branch opening into this line for supplying a setting accelerator volume flow, wherein the line branch for supplying the setting accelerator volume flow has a third pump device and a third flow measuring device, wherein the third pump device and the third flow measuring device are coupled to the control unit. This additionally enables a volume-controlled, adjustable supply of the setting accelerator.

[0026] The device for adding the setting accelerator preferably has an annular nozzle surrounding the line for conveying the foam flow, with the line branch for supplying the setting accelerator flow opening into the annular nozzle. The annular nozzle enables thorough mixing of the setting accelerator and cement foam, thereby reducing the amount of accelerator required and thus increasing its economic efficiency. Furthermore, the thorough mixing results in more uniform foam setting.

[0027] A preferred device serves to produce a mortar filling of an annular gap between a subsoil and the segments of a tunnel structure and is characterized in that the conduit for introducing the mixture formed in the mixing device into the cavity is a pilaster for introducing the mixture into the annular gap.

[0028] Advantageous and / or preferred embodiments of the invention are characterized in the dependent claims.

[0029] The invention will now be described in more detail with reference to a preferred embodiment shown in the drawing. The drawing shows: Figure 1 a schematic representation of a preferred embodiment of the device according to the invention for carrying out the method according to the invention and Figure 2 a schematic cross-sectional view of a device according to Figure 1 used foam generator.

[0030] The method according to the invention serves to produce a water-permeable and thus drainable mortar filling for a cavity, in particular an annular gap between a subsoil and the tunnel segments of a tunnel structure. The production of the drainage mortar to be introduced into the annular gap comprises several coordinated steps of producing and mixing components, which are based on the in Figure 1 The device shown will be explained. Figure 1 The device shows a series of containers in which pumpable components of the building material mixture are provided, connecting piping systems with pumping devices and flow measuring devices, and mixing devices for the stepwise mixing of the components. The device further includes a device for introducing the building material mixture. dh a mortar foam, into the annular gap of a tunnel structure.

[0031] To produce the building material mixture to be introduced into the annular gap, a cement suspension is first prepared in a container 10. The cement suspension consists of cement of type CEM III or CEM IV, preferably cement of type CEM III / A, in particular cement of type CEM III / A with strength class 52.5, and water. Preferably, a small amount of bentonite (less than 2 wt.%, in particular less than 1 wt.%) is added as a stabilizing additive. Furthermore, a small amount of a dispersing agent (less than 2 wt.%) is preferably included. Aggregates may also be added. egin the form of rock flour, the proportion of which should be less than 20 wt.%, preferably less than 10 wt.%, for reasons of achieving the desired strength. In a preferred embodiment, the following are used to produce one cubic meter of cement suspension: 1190 kg cement CEM III / A 52.2, for example "Dyckerhoff Variodur 40 (CEM III / A 52.5 R)" from Dyckerhoff GmbH, 595 kg water, and 4 kg activated sodium bentonite "IBECO CT" from Imerys Industrial Minerals Greece. SO and 8 kg of dispersing agent "MC Montan Drive CA 02" from MC-Bauchemie Müller GmbH & Co. KG Chemische Fabriken. The cement suspension provided in container 10 is preferably mixed using a colloidal or circulating mixer. The water-binder ratio or water-cement ratio (w / c ratio) is in the range of 0.4 to 0.6, ensuring a pumpable consistency while preventing excessive sedimentation.

[0032] With the help of a pump system, which is located in Figure 1In the illustrated embodiment comprising a transfer pump 11 pressurized with compressed air 12 and a suspension pump 13, the cement suspension is conveyed from the container 10 via a flow meter 14 and line 15 to a first inlet opening of a Y-piece 16. The other inlet opening of the Y-piece 16 is connected to a line 23 through which a surfactant solution is supplied from a container 20. A pump 21 and a second flow meter 22 are integrated into the surfactant transport line 23. The combined volume flows of the cement suspension and the surfactant solution in the Y-piece 16 are passed through a static mixer or mixing vessel 17 to ensure thorough mixing. To prevent uncontrolled pre-expansion of the cement suspension, the surfactant solution is added in a volume-controlled manner only after the cement suspension has been mixed.In this process, the volume-controlled addition to the flow of the cement suspension is preferably carried out by means of a low-pulsation pump using a Y-piece 16 having a nozzle and check valve.

[0033] The surfactant solution is added in an amount of preferably 10% to 16% by volume, based on the cement suspension. Preferably, 100 ml of surfactant solution per cubic meter of cement suspension is added, for example, the surfactant solution "Centripor SK 150 Concentrate" from MC-Bauchemie Müller GmbH & Co. KG Chemische Fabriken can be used.

[0034] After mixing the surfactant solution and cement slurry, the mixture flows via line 18 to the inlet opening of a gassing section of a foam generator 33. Compressed air is supplied to the foam generator 33 via line 32. The volume flow rate of the compressed air supplied via connection 30 is adjusted by the compressed air regulator 31. A control device connected to the flow meter 14 and the flow meter 22, as well as to the compressed air regulator 31, ensures that a predetermined volume ratio of cement slurry, surfactant solution, and compressed air is maintained. In the preferred embodiment, the volume fractions of the cement slurry Z to the volume fractions of the surfactant solution T and the volume of the supplied compressed air L are in the ratio Z:T:L = 10:1:20. While the surfactant solution is supplied with a volume fraction of 10% of the cement slurry, the compressed air fraction is approximately twice the volume fraction of the cement slurry.A control device is used to adjust the volume flows, which is coupled to the flow meters 14 and 22 and to the pumps 11, 13 and 21, the pressure measuring device 34 and the compressed air regulator 31 in order to control the pump performance and compressed air supply depending on the measured flow values ​​or the pressure level.

[0035] Figure 2 Figure 3 schematically shows some details of the foam generator 33. The foam generator 33 contains a gassing section in the form of a hollow cylinder with a porous wall 55, through whose interior 56 the cement suspension is passed. In the Figure 2In the illustrated embodiment, the hollow cylinder is clamped between two housing halves 50A and 50B. The two housing halves 50A and 50B have sealing receptacles at their ends, which are pressed against the end faces of the hollow cylinder. A seal 51 is provided at the connecting surface of the two housing halves 50A and 50B. By connecting the two housing halves 50A and 50B with the screw connections 52, the connecting surface of the two housing halves and simultaneously the end faces of the hollow cylinder are sealed against the housing halves. Housing half 50B has an inlet opening 58 corresponding to the cylindrical interior 56 of the hollow cylinder, and housing half 50A has an outlet opening 59 corresponding to the cylindrical interior 56. Inside the housing, the hollow cylinder with its porous wall 55 is surrounded by a compressed air chamber 53, the compressed air being supplied by a Figure 2The cement suspension is supplied through the inlet opening 54, indicated by a dashed line and located behind the hollow cylinder in this view. The cement suspension enters the foam generator and the interior 56 of the hollow cylinder through the inlet opening 58. As it flows through the interior 56 to the outlet opening 59, the compressed air introduced into the compressed air chamber 53 enters the interior 56 through the pores of the porous wall 55. This is indicated by the arrows 57. The compressed air bubbles that continuously form on the inner wall of the hollow cylinder are torn off by the flow of the cement suspension and mix with it, forming a foam flow that then exits through the outlet opening 59.The porous wall 55 has a uniform pore structure along the entire length of the hollow cylinder and is subjected to approximately the same pressure along the entire length of the aeration section, so that a multitude of uniform air bubbles are generated on the inner wall of the hollow cylinder in the interior 56. This results in a foam with a uniform air pore distribution and low variation in air pore size. A sufficient aeration section is required to introduce the air into the flow of the cement slurry within the foam generator 33, allowing a uniform pore structure to develop. In a preferred embodiment, the hollow cylinder has an outer diameter of 40 millimeters, an inner diameter of 15 millimeters, and a length of 159 millimeters, with a pore size of 50 to 60 µm.

[0036] It will be reopened Figure 1Reference is made to the following. After the compressed air supplied to the foam generator 33 via line 32 is introduced into the mixture of cement suspension and surfactant solution supplied via line 18, a foam volume flow exits the outlet 59 of the foam generator 33 and passes through a pressure measuring device 34 and a line 35 to a shotcrete ring nozzle 36, which serves as a mixing device. A setting accelerator is supplied to this ring nozzle 36 from a storage container 40 via a pump 41, a flow meter 42, and a line 43. The flow meter 42 and the pump 41 are coupled to the control unit that is coupled to the pump 13 and the flow meter 14 for the cement suspension, the pump 21 and the flow meter 22 for the surfactant solution, and the compressed air regulator 31 with pressure measuring device. This allows for volume-controlled dosing of the setting accelerator.A shotcrete accelerator based on an aluminum hydroxide / aluminum sulfate solution is preferably used as a setting accelerator, for example, the shotcrete accelerator "Centrament Rapid 640" from MC-Bauchemie Müller GmbH & Co. KG Chemische Fabriken. In the preferred embodiment, the setting accelerator is added in an amount between 4% and 12% by volume, preferably between 7% and 9% by volume, and particularly in an amount of 8% by volume, based on the cement slurry. This equates to approximately 80 liters of setting accelerator being added per cubic meter of cement slurry. Instead of the ring nozzles used for mixing, an injection cap, which is commonly used for annular gap grouting in two-component systems, can alternatively be used. Due to the poorer material mixing with this mixing device, the accelerator content should be increased to up to 16% by volume.The mixture of cement suspension foam and accelerator is then fed into the cavity, especially the annular gap, via a pipeline, in particular a pilaster or several pilasters.

[0037] In a preferred embodiment of the Figure 1In the illustrated device, pumps 13, 21, and 41 are low-pulsation pumps, for example, progressive cavity pumps, peristaltic pumps, or rotary pumps. Flow meters 14, 22, and 42 are preferably electronic flow meters for measuring the respective volume flows. The compressed air in the compressed air regulator 31 is expediently metered by means of an electronic mass flow controller. It should be noted that the aforementioned mixing ratios (volume ratios) refer to standard conditions (temperature T = 20 °C, pressure p = 1013 mbar). Since the compression pressure in the annular gap is generally higher than the pressure under standard conditions, it may be necessary to adjust the compressed air quantity accordingly due to the compressibility of the gaseous phase.Therefore, the pressure is measured as close as possible to the point of insertion, preferably in the line 35, using the sensor 34, since pipe friction losses due to the yield point and viscosity within the conveying section as well as the pressure in the cavity to be filled have an influence on the pressure level.

[0038] As previously explained, the addition of the setting accelerator is intended to achieve a "freezing" of a predominantly open-pore foam state. To achieve this, in addition to the foam structure generated in the foam generator 33 (ratio of air volume to cement suspension volume, air void size, and low scatter in air void sizes), the temporal progression of the foam dissipation must also be considered. After the foam leaves the foam generator 33, it reaches the mixing unit, in the form of a ring nozzle, within a few seconds. The setting accelerator is added there. Subsequently, the mixture of setting accelerator and foam travels through the pipeline (the piling), which, for example, has a length of 3 m and a cross-section of 20 cm², to the point of application. This takes the foam between 10 and 20 seconds, for example, 15 seconds.During its passage through this section, the setting accelerator and foam are further mixed. Simultaneously, the setting reactions are initiated. These processes, which are still taking place within the pipelines, must be taken into account during the process. After the construction foam has been introduced into the cavity, i.e., the annular gap, setting begins simultaneously with the continued breakdown of the foam, including the increasing rupture of the walls between the air pores. Given the aforementioned process conditions, this results in a settled foam that is predominantly open-pored and therefore water-permeable and capable of drainage.

[0039] For example, the following components were provided and mixed:

[0040] A foam generator with a gassing section 159 mm long, an outer diameter of 40 mm, an inner diameter of 15 mm, and a pore size of 50-60 µm was used. The resulting foam had a bulk density of approximately 700 kg / m³.

[0041] The hardened mortar had a water permeability coefficient according to DIN 18130 of kF = approx. 4 * 10 -4< m / s, a strength after 3 days of f_3d = approx. 0.4 MN / m 2< and a strength after 28 days of f_28d = approx. 2 MN / m 2<.

[0042] Within the scope of the invention, numerous alternative embodiments are conceivable. For example, the cement slurry can contain several different cements or binders and additional aggregates, provided these do not undesirably impair the strength of the hardened material, the pumpability of the cement slurry, or the desired partial breakdown of the foam. The term "compressed air" is intended to refer to any air or similar gas mixtures or gases, such as nitrogen, that are "forced" into the cement mixture to create foam bubbles or pores, regardless of the specific pressure applied and regardless of the exact composition of the air. The surfactant is preferably an aqueous solution that is added to the finished cement slurry.Naturally, it is also within the scope of the invention if the water content is altered simply by reducing the amount of water in the cement suspension by a certain proportion, which is then immediately added to the surfactant solution before the thus diluted surfactant solution is added to the thus thickened cement suspension, thereby reducing the water-binder ratio of the remaining surfactant-free cement suspension. A similar approach applies if above-average heavy or light aggregates are added to the cement suspension in quantities that, while not yet having a significant impact on the strength of the hardened mortar mixture or on the foaming behavior, would lead to considerably different densities of the cement suspension and thus also of the foam. Instead of adding a surfactant solution, it would also be conceivable to add the surfactant in solid form (powder, granules, etc.). o.ä.)to be added to the cement suspension, whereby in this case, instead of controlling the amount of surfactant supplied via its volumetric flow rate, dosing via its mass or amount of substance would be conceivable. Instead of adding a single surfactant, several surfactants or surfactant components that only form a surfactant after mixing can also be added without departing from the scope of the invention. The same applies to the addition of the setting accelerator.

Claims

1. A method for producing a drainable mortar filling of a cavity, in particular of an annular gap between a subsoil and tunnel lining segments of a tunnel structure, wherein: a) a cement suspension having a water-to-binder ratio between 0.40 and 0.60 is prepared by mixing at least one cement binder with water and optionally aggregates, and a cement suspension volume flow is generated, wherein a surfactant is admixed to the cement suspension or to the cement suspension volume flow, b) the cement suspension volume flow is passed through a foam generator (33) for forming a foam volume flow such that compressed air is admixed in a first predetermined volume proportion of between 150% and 250% of the cement suspension volume flow and leads to a foam having a homogeneous air pore distribution with a low dispersion of the air pore sizes, in which the air pore sizes of at least 70% of the compressed air volume proportion deviate from a mean air pore size by not more than approximately 50%, and c) a setting accelerator is admixed to the foam volume flow upon its introduction into the cavity.

2. The method for producing a drainable mortar filling of a cavity according to claim 1, characterised in that in step a) a cement suspension volume flow having a density between 1500 kg / m3 and 2000 kg / m3, preferably between 1700 kg / m3 and 1900 kg / m3, is generated, and the compressed air in step b) is admixed in the first predetermined volume proportion such that a foam volume flow having a density between 600 kg / m3 and 800 kg / m3, preferably between 650 kg / m3 and 750 kg / m3, is formed.

3. The method for producing a drainable mortar filling of a cavity according to claim 1 or 2, characterised in that in step b) the compressed air is admixed with an air pore size distribution in which the mean air pore size is in the range between 200 µm and 1300 µm, preferably between 250 µm and 800 µm, in particular between 300 µm and 500 µm.

4. The method for producing a drainable mortar filling of a cavity according to any one of claims 1 to 3, characterised in that in step b) the cement suspension volume flow is passed through a tubular gasification section of the foam generator (33) having a porous wall (55), wherein compressed air from a compressed air chamber (53) is pressed through the porous wall (55) of the gasification section into an interior space (56) conducting the cement suspension volume flow, wherein the pore size of the porous wall (55) is selected such that the desired air pore size distribution in the foam volume flow is achieved.

5. The method for producing a drainable mortar filling of a cavity according to any one of claims 1 to 4, characterised in that the cement suspension in step a) is prepared by mixing at least one cement of cement type CEM III or CEM IV, preferably of cement type CEM III, with water, wherein small amounts of a clay layer silicate, preferably a bentonite, as a stabiliser and / or small amounts of a dispersing agent are admixed, wherein the small amounts each constitute less than 2% by weight of the cement suspension.

6. The method for producing a drainable mortar filling of a cavity according to any one of claims 1 to 5, characterised in that in step a) first the cement suspension volume flow is generated and then the surfactant in the form of a surfactant solution is admixed to the cement suspension volume flow in a second predetermined volume proportion of at most 20%, preferably between 5 and 15%, of the cement suspension volume flow.

7. The method for producing a drainable mortar filling of a cavity according to claim 6, characterised in that a surfactant solution containing at least one anionic surfactant and / or at least one protein foaming agent is admixed.

8. The method for producing a drainable mortar filling of a cavity according to any one of claims 1 to 7, characterised in that in step c) an alkali-free and alkaline earth-free setting accelerator is admixed to the foam volume flow in a third predetermined volume proportion of between 4% and 16%, preferably between 7% and 10%, of the cement suspension volume flow.

9. The method for producing a drainable mortar filling of a cavity according to any one of claims 1 to 8, characterised in that in step c) an aqueous solution of at least 50% by weight of aluminium hydroxide and / or aluminium sulphate is admixed to the foam volume flow as a setting accelerator.

10. The method for producing a drainable mortar filling of a cavity according to any one of claims 1 to 8, characterised in that in step c) the setting accelerator is admixed to the foam volume flow at most 20 seconds, preferably at most 15 seconds, before its introduction into the cavity.

11. An apparatus for producing a mortar filling of a cavity for carrying out a method according to any one of claims 1 to 10, comprising: a device (10 - 15) for generating a cement suspension volume flow, a device (16, 17, 20 - 23) for admixing a surfactant to the cement suspension volume flow, a foam generator (33) having a tubular aeration section with a porous wall (55) through which the cement suspension volume flow can be passed, wherein a compressed air chamber (53) is arranged on the outside of the porous wall (55) such that compressed air from the compressed air chamber (53) can be pressed through the porous wall (55) over the entire length of the gasification section at approximately the same pressure into the cement suspension volume flow, so that a foam volume flow can be generated, wherein the porous wall (55) has a uniform pore structure over the entire length of the gasification section, so that the admixture of the compressed air can lead to a foam having a homogeneous air pore distribution with a low dispersion of the air pore sizes, in which the air pore sizes of at least 70% of the compressed air volume proportion deviate from a mean air pore size by not more than approximately 50%, a volume flow regulator (31) connected to a compressed air inlet (32) of the compressed air chamber for adjusting a compressed air volume flow, a control device coupled to the volume flow regulator (31), configured such that a compressed air volume flow is set which corresponds to approximately 1.5 times to 2.5 times the cement suspension volume flow, and a device (36, 40 - 43) arranged downstream of the foam generator (33) for admixing a setting accelerator to the foam volume flow, the device being connected to a line for introducing the mixture formed in the device (36, 40 - 43) for admixing the setting accelerator into the cavity.

12. The apparatus according to claim 11, characterised in that the device (10 - 15) for generating a cement suspension volume flow comprises a first pumping device (13) and a first flow measurement device (14) coupled to the control device for detecting the cement suspension volume flow.

13. The apparatus according to claim 12, characterised in that the device (16, 17, 20 - 23) for admixing a surfactant comprises a line for forwarding the cement suspension volume flow, a mixer (17) integrated into the line, and a line branch (23) opening into the line upstream of the mixer for supplying a surfactant volume flow, wherein the line branch (23) for supplying the surfactant volume flow comprises a second pumping device (21) and a second flow measurement device (22) for detecting the surfactant volume flow, wherein the second pumping device (21) and the second flow measurement device (22) are coupled to the control device.

14. The apparatus according to any one of claims 11 to 13, characterised in that the tubular gasification section is a cylindrical pipe section surrounded by the porous wall (55) having an inner diameter between 10 mm and 20 mm and a length between 100 mm and 300 mm, wherein the pores of the porous wall (55) have an approximately equal diameter.

15. The apparatus according to claim 14, characterised in that the diameter of the pores of the porous wall (55) is between 30 µm and 100 µm, preferably between 50 µm and 60 µm.

16. The apparatus according to any one of claims 11 to 15, characterised in that the device (36, 40 - 43) for admixing a setting accelerator comprises a line for forwarding the foam volume flow, a line branch (43) opening into this line for supplying a setting accelerator volume flow, wherein the line branch (43) for supplying the setting accelerator volume flow comprises a third pumping device (41) and a third flow measurement device (42), wherein the third pumping device (41) and the third flow measurement device (42) are coupled to the control device.

17. The apparatus according to claim 16, characterised in that the device (36, 40 - 43) for admixing the setting accelerator comprises an annular nozzle surrounding the line for forwarding the foam volume flow, wherein the line branch (43) for supplying the setting accelerator volume flow opens into the annular nozzle.

18. The apparatus according to any one of claims 11 to 17, for producing a mortar filling of an annular gap between a subsoil and tunnel lining segments of a tunnel structure, characterised in that the line for introducing the mixture formed in the mixing device into the cavity is a grout tube for introducing the mixture into the annular gap.