Pipe element or tank element and corresponding manufacturing method

Abstract

The invention relates to a pipe element or a tank element (10) comprising a first layer (20) that defines an inner side and an outer side, the first layer being made of cement mortar, the cement mortar comprising a filler (26) and a cement-based binder, and an end inner layer with a free inner surface arranged on the inner side of the first layer (20). The end inner layer comprises an additive having a Blaine specific surface area of at least twice the Blaine specific surface area of the cement, which additive is, by volume, the majority constituent of the end inner layer.

Description

[0001] TITLE: Pipe or tank element and corresponding manufacturing process

[0002] The present invention relates to a pipeline or reservoir element comprising:

[0003] - at least a first layer defining an inner side and an outer side, the first layer being made of cement mortar, the cement mortar comprising a filler and a cement-based binder, and

[0004] - an inner end layer with a free inner surface, arranged on the inner side of the first layer.

[0005] Raw pipe or tank elements made of ductile iron, steel or concrete are known, comprising an inner lining located on an inner wall of the raw pipe or tank element. The inner lining comprises at least a first layer of cement mortar. This cement mortar comprises a filler (sand) and a cement binder. In the case of installation by centrifugation, the inner lining may further comprise a second layer arranged on the first layer on the inner side, obtained by sedimentation and formed of a cement binder substantially free of filler.

[0006] For the transport and storage of water intended for human consumption, the use of materials based on cementitious binders, such as CEM I Portland cement or CEM III slag cement, is in most cases a satisfactory solution. This is due in particular to the safety of these materials in contact with drinking water.

[0007] The inorganic nature of these cement-based materials ensures their continued safety. However, due to the clinker manufacturing processes and some of the additives, such as blast furnace slag, steel slag, fly ash, silica fume, and metakaolin, the raw materials may contain trace metals such as antimony, arsenic, chromium, selenium, or vanadium.

[0008] Progress in knowledge about the presence, migration potential in water and toxicity of these substances has led regulations relating to the marketing of cement-based materials to impose migration limits on them. For example, the 4MS initiative within the European Union proposed in 2018 for cementitious products in contact with drinking water, Draft Sep 2018 - Assessment of Cementitious Products in Contact with Drinking Water - Table 4, a migration quota set at 10% of the tap limit set by Directive 98 / 83 / EC relating to the quality of water intended for human consumption. Controlling the release of these substances into stored or transported water is therefore a major obligation.

[0009] Consequently, the problem that the invention aims to solve is the uncontrolled migration of trace metal elements, in particular from a cement binder in contact with water intended for human consumption.

[0010] To this end, the invention relates to an element as indicated above, characterized in that the inner end layer comprises an addition having a Blaine specific surface area of ​​at least twice the Blaine specific surface area of ​​the cement and in that the addition is by volume the majority constituent of the inner end layer.

[0011] According to particular embodiments of the element, it may include one or more of the following characteristics:

[0012] - the Blaine specific surface area of ​​the addition is greater than 0.6 m 2 / g or greater than 0.8 m 2 / g or greater than 1.0 m 2 / g or greater than 1.2 m 2 / g, and is preferably less than 5.0 m 2 / g ;

[0013] - the addition consists of inorganic particles, in particular SiC>2, the inorganic particles being finer and / or less dense than the cement;

[0014] - the addition comprises or consists of one or more of the following mineral species: diatomite, moler, expanded perlite, andalusite, bentonite, chamotte, activated carbon, biochar, feldspar, graphite, graphene, halloysite, kaolin, mica, molochite, mullite, carbon black, talc and wollastonite;

[0015] - the addition constitutes, by volume, at least 50% of the inner end layer, more particularly at least 60% of the inner end layer;

[0016] - the pipeline or reservoir element comprises

[0017] . a second layer disposed on the first layer on the inner side, the second layer being based on a cementitious binder and being substantially free of filler, and

[0018] . a third layer disposed on the second layer on the inner side, the third layer being the inner end layer;

[0019] - the third layer is closed and continues on the second layer and this in particular over the entire extent of the second layer;

[0020] - the cement is based on Portland cement (CEM I) or slag cement (CEM III), in particular Portland cement or slag cement comprising one or more of the following additions: calcite, pozzolans such as blast furnace slag, steelworks slag, silica fume, fly ash, metakaolin; - the element comprises a support layer, which is made of metal, in particular gray cast iron or ductile cast iron or steel and which is an outer layer to the first layer; and

[0021] - the element has an axially symmetrical shape.

[0022] The invention also relates to a method of manufacturing an element as defined above, comprising the following successive steps: providing a mold, preparing a mortar mixture comprising the cement-based binder, the filler, the addition and water, introducing the cement mortar mixture in the non-solid state into the mold, the mold being in particular rotating,

[0023] - centrifuging the mold filled with the mortar mixture so as to separate the mortar mixture into an essentially liquid phase and an essentially solid phase, the essentially solid phase comprising a first layer of cement mortar, and an inner layer comprising the addition, in particular the essentially solid phase further comprising a second layer of cement paste arranged between the first layer and the inner layer comprising the addition, solidifying the mortar mixture by obtaining the element in which the first layer of cement mortar corresponds to the first layer of the element and the inner layer comprising the addition corresponds to the inner end layer of the element, in particular the second layer of cement paste corresponding to the second layer of the element and the inner end layer corresponding to the third layer of the element.

[0024] The invention will be better understood by reading the following description, given solely by way of example and with reference to the attached drawing.

[0025] [Fig 1] Figure 1 shows schematically and in cross-section a pipeline element according to the invention.

[0026] This figure describes a pipeline 2, advantageously buried, adapted to transport or store a liquid 6, for example drinking water. The pipeline 2 comprises a coated pipeline element 10, and other coated pipeline elements not shown.

[0027] Alternatively, the pipe element 10 is replaced by a reservoir or forms such a reservoir.

[0028] The coated pipeline element 10 comprises a support layer 12, which is for example a raw pipeline element, which is made of gray cast iron or ductile cast iron or steel or more generally metal. Alternatively, the support layer 12 is made of concrete. The support layer 12 defines an inner surface 14 and an outer surface 16.

[0029] The pipe element 10 has an axially symmetrical shape about a central axis XX and is, for example, a hollow cylinder with an annular cross-section. In the following, the terms "outer" and "inner" refer to the radial direction relative to the central axis XX.

[0030] The pipe element 10 comprises a first layer 20, disposed on the inner surface 14 of the support layer, defining an inner side 22 and an outer side 24 and which is made of cement mortar.

[0031] The cement mortar comprises a filler 26, in particular sand, and a cement-based binder 28.

[0032] The pipe element 10 comprises a second layer 30 disposed on the first layer 20 on the inner side 22 and forming an inner interface 32.

[0033] The second layer 30 is advantageously closed and continuous over the first layer 20 and this in particular over the entire extent of the first layer 20.

[0034] The second layer 30 is a cementitious binder-based layer and is substantially free of filler (sand or other aggregates).

[0035] The cement forming binder is characterized by its specific surface area. The Blaine specific surface area of ​​cement is, for example, between 0.3 and 0.4 m 2 / g. Furthermore, its density is for example between 2.95 and 3.20 g / cm 3 .

[0036] The channeling element 10 comprises a third layer 60 arranged on the second layer 30 on the inner side and forming an inner free surface 62. This inner free surface 62 is in contact with the liquid 6 or air. The inner interface 32 of the second layer forms the interface of the second layer 30 with the third layer 60.

[0037] The third layer 60 is advantageously closed and continuous over the second layer 30 and this in particular over the entire extent of the second layer 30.

[0038] The third layer is used to trap substances whose migration in water is undesirable and / or is impermeable to ions. The third layer 60 comprises an addition having a Blaine specific surface area which is at least twice the Blaine specific surface area of ​​the cement.

[0039] Advantageously, the addition is the majority constituent by volume of the third layer. In this case, the addition is the majority constituent at the level of the interior free surface 62. Preferably, the addition constitutes by volume at least 50% of the third layer and more particularly at least 60% of the third layer, the remainder being in particular cementitious binder.

[0040] Preferably, the Blaine specific surface area of ​​the addition is greater than 0.6 m 2 / g or greater than 0.8 m 2 / g or greater than 1.0 m 2 / g or greater than 1.2 m 2 / g, and preferably less than 5.0 m 2 / g.

[0041] Advantageously, the addition consists of inorganic particles, in particular silica (SiC>2), the inorganic particles being finer and / or less dense than the cement.

[0042] Furthermore, the addition comprises or consists of one or more of the following mineral species: diatomite, moler, expanded perlite, andalusite, bentonite, chamotte, activated carbon, biochar, feldspar, graphite, graphene, halloysite, kaolin, mica, molochite, mullite, carbon black, talc and wollastonite.

[0043] Advantageously, the cement is based on Portland cement (CEM I) or slag cement (CEM III). The Portland cement (CEM I) or slag cement (CEM III) may comprise one or more of the following additions: calcite, pozzolans such as blast furnace slag, steelworks slag, silica fume, fly ash, metakaolin. More particularly, the slag cement may be CEM lll / A or CEM lll / B or CEM lll / C cement.

[0044] It should be noted that the interfaces between the various layers are not necessarily well defined, but the composition at the interface may change gradually between the compositions of adjacent layers. This may be due to the manufacturing process explained below.

[0045] The pipe element 10 according to the invention can be manufactured by a method comprising the following successive steps.

[0046] First, a mold is provided. The mold is in this case the support layer 12 and is for example made of gray cast iron or ductile iron or steel or more generally metal.

[0047] Then a mortar mixture is prepared including the cement binder, the filler, the addition and water.

[0048] Then, the cement mortar mixture is introduced in a non-solid state into the mold, advantageously set in rotation.

[0049] Then, the mold filled with the mortar mixture is centrifuged, for example so as to subject the mortar mixture to an acceleration of between 30 G and 300 G. By centrifugation, the mortar mixture is separated into a substantially liquid phase and a substantially solid phase. The substantially solid phase comprises, from the outside to the inside, a first layer of cement mortar, a second layer of cement paste and a third layer with addition. The layer of cement mortar corresponds to the first layer 20 of the element, the layer of cement paste corresponds to the second layer 30 of the element and the layer with addition corresponds to the third layer 60 of the element.

[0050] Due to the sedimentation process, here obtained by centrifugation, the resulting solid material is structured in its thickness according to a gradient of size and density of the particles. In fact, where appropriate, the aggregates and massive loads are close to the internal wall of the mold or the support layer 12, while the finest and least dense particles are close to the internal surface of the material.

[0051] Then the liquid phase is removed from the mold.

[0052] In the next step, the cement mortar mixture is allowed to solidify or set, resulting in element 10, in which the outer layer of cement mortar corresponds to the first layer 20 and the inner layer of cement paste corresponds to the second layer of element 10. The third layer with addition corresponds to the third layer 60 of the element. Since the particles of the high surface area addition are by definition finer or less dense than the cement, they are essentially concentrated on the inner surface of the cement binder material.

[0053] Alternatively, the centrifugation step is omitted and the mold filled with the cement mortar mix is ​​subjected to a force separating the phases of the mix by another sedimentation step.

[0054] Some examples of mixtures and their technical advantages will be described below.

[0055] Test specimens containing various additions were made by coating pipe sections with a CEM lll / B cement-based mortar. This mortar was applied at a surface mass of 16 kg / m 2 and implemented by centrifugation at 175 G. The sand used is silica sand with a grain size of 0 to 2 mm.

[0056] The high specific surface area additions tested were: diatomite, moler, expanded perlite, wollastonite. For comparison with a known embodiment, a sample with the addition of densified silica fume was also prepared, as well as a sample without addition. The specific surface areas of the additions, measured by the Blaine method, the density of the additions as well as the surface rate of the tested additions are shown in Table 1. [Table 1]

[0057] These specimens were tested according to the normative leaching protocol of EN 14944-3, and compared with the results of a coating without addition. The following Table 2 specifies the evolution of the pH or the migration of certain metals at the end of the migration in comparison with the reference without addition. In this Table 2, the values ​​which correspond to a significant improvement compared to the sample without addition are marked by a "plus" sign in brackets: [+], while those corresponding to a significant degradation are marked by a "minus" sign in parentheses: (-).

[0058] [Table 2]

[0059] Surprisingly, the addition of moler or expanded perlite reduces aluminum migration by more than 70% compared to the sample without addition. Also surprisingly, the addition of moler or expanded perlite reduces vanadium migration by 67% to more than 90% compared to the sample without addition, and by 96% to more than 99% compared to the sample with silica fume. Also surprisingly, the addition of diatomite or wollastonite reduces antimony migration by 48% to more than 90% compared to the sample without addition. Finally, also surprisingly, the addition of moler or expanded perlite reduces the pH by 0.2 to 0.5.This observation is all the more surprising for the addition of moler or expanded perlite given the fact that the formulas used are richer in water than the formula without addition, and therefore form a material which is in principle more porous once hardened according to the usual knowledge of those skilled in the art.

[0060] In the context of the present invention, the specific surface area indicated is determined according to the Blaine method (defined by standard NF EN 196-6).

[0061] Alternatively, the support layer 12 is omitted or is only used as a mold during manufacture and, once the first layer 20, second layer 30 and third layer 60 have cured, the support layer 12 is removed. Thus, the pipe element 10 according to this variant essentially consists of the first layer 20, second layer 30 and third layer 60.

[0062] The high surface area particles described above can be used for the manufacture of any inorganic material implemented by centrifugation, by molding, by projection, by troweling, or by application with a brush. The high surface area particle material forming the addition can be applied to a pre-existing cementitious binder-based material, with the aim of reducing the migration of the constituent metals. Depending on its function in the final product and therefore its composition, the addition material can form an inner end layer resulting from the sedimentation of a cementitious mortar, or can be applied in the form of a whitewash or paint on a cementitious binder-based material.

[0063] The high specific surface area particulate material may be applied in particular to coatings or to the manufacture of the following products, the binder of which consists entirely or partly of Portland cement with, where appropriate, additions such as calcite or pozzolans such as blast furnace slag, steel slag, silica fume, fly ash or metakaolin:

[0064] - cement mortar coatings for gray or ductile cast iron pipes; cement mortar coatings for steel pipes;

[0065] - to cement mortar pipes; to cement mortar linings of metal tanks; to cement mortar tanks.

[0066] The foregoing description contains technical characteristics of the invention.

[0067] These technical features, although presented in a technical context and possibly in combination with other technical features, may be used individually each time, without the other technical features, as far as this is technically possible.

Claims

CLAIMS 1. Pipe or tank element (10) comprising: - at least a first layer (20) defining an inner side and an outer side, the first layer being made of cement mortar, the cement mortar comprising a filler (26) and a cement-based binder, and - an inner end layer with a free inner surface, arranged on the inner side of the first layer (20), characterized in that the inner end layer comprises an addition having a Blaine specific surface area of ​​at least twice the Blaine specific surface area of ​​the cement and in that the addition is by volume the majority constituent of the inner end layer.

2. The element of claim 1, wherein the Blaine specific surface area of ​​the addition is greater than 0.6 m 2 / g or greater than 0.8 m 2 / g or greater than 1.0 m 2 / g or greater than 1.2 m 2 / g, and is preferably less than 5.0 m 2 / g.

3. Element according to any one of claims 1 or 2, in which the addition consists of inorganic particles, in particular SiC>2, the inorganic particles being finer and / or less dense than the cement.

4. An element according to any one of claims 1 to 3, wherein the addition comprises or consists of one or more of the following mineral species: diatomite, moler, expanded perlite, andalusite, bentonite, chamotte, activated carbon, biochar, feldspar, graphite, graphene, halloysite, kaolin, mica, molochite, mullite, carbon black, talc and wollastonite.

5. Element according to any one of claims 1 to 4, in which the addition constitutes, by volume, at least 50% of the inner end layer, more particularly at least 60% of the inner end layer.

6. An element according to any one of claims 1 to 5, wherein the pipe or reservoir element comprises - a second layer (30) arranged on the first layer (20) on the inner side, the second layer being based on a cementitious binder and being substantially free of filler, and - a third layer (60) arranged on the second layer (30) on the inner side, the third layer being the inner end layer.

7. Element according to claim 6, in which the third layer (60) is closed and continuous on the second layer (30) and this in particular over the entire extent of the second layer.

8. Element according to any one of claims 1 to 7, in which the cement is based on Portland cement (CEM I) or slag cement (CEM III), in particular Portland cement or slag cement comprising one or more of the following additions: calcite, pozzolans such as blast furnace slag, steelworks slag, silica fume, fly ash, metakaolin.

9. Element according to any one of claims 1 to 8, in which the element comprises a support layer (12), which is made of metal, in particular gray cast iron or ductile cast iron or steel and which is an outer layer to the first layer (20).

10. An element according to any one of claims 1 to 9, wherein the element has an axially symmetrical shape.

11. Method for manufacturing an element according to at least claim 10, comprising the following successive steps: providing a mold (12), preparing a mortar mixture comprising the cement-based binder, the filler, the addition and water, introducing the cement mortar mixture in the non-solid state into the mold, the mold being in particular rotating, - centrifuging the mold filled with the mortar mixture so as to separate the mortar mixture into an essentially liquid phase and an essentially solid phase, the essentially solid phase comprising a first layer of cement mortar, and an inner layer comprising the addition, in particular the essentially solid phase further comprising a second layer of cement paste arranged between the first layer and the inner layer comprising the addition, solidifying the mortar mixture by obtaining the element in which the first layer of cement mortar corresponds to the first layer (20) of the element and the inner layer comprising the addition corresponds to the inner end layer of the element, in particular the second layer of cement paste corresponding to the second layer (30) of the element and the inner end layer corresponding to the third layer (60) of the element.

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