Sprayed cement-based composition

Abstract

A sprayable ductile metal-like cementitious composition (SDMCC) comprises a composite binder, fibers, and water, wherein the composite binder comprises a cement component and a pozzolanic component. The SDMCC may exhibit expansion upon hardening and strain-hardening behavior. The SDMCC is useful for repairing and / or improving building structures, such as pipelines. A method for preparing the SDMCC is also described.

Description

[Technical Field]

[0001]

[0001] The present invention relates to a sprayable ductile metal-like cementitious composition (SDMCC). The present invention also relates to the use of SDMCC for the repair or improvement of building structures such as underground pipelines, and to methods of using the same. [Background technology]

[0002]

[0002] Underground pipelines are a very useful infrastructure and can be used for the transport and distribution of water for various purposes, such as drinking water and wastewater. Pipelines used for these purposes are often subjected to severe mechanical loads and environmental stresses. As a result, both metal and concrete pipes are prone to problems such as cracking, spalling, and accumulation of debris. Metal pipes may corrode or deform. If left unrepaired, these problems can lead to the failure of the pipeline.

[0003]

[0003] Trenchless pipeline repair technology is a useful technology for repairing existing pipelines with minimal damage. Lower construction costs, less environmental impact, and less disruption to the public mean that trenchless pipeline repair technology is often preferable to open trench methods. Known trenchless pipeline repair methods include in-situ hardening pipe (CIPP) method, slip lining, close-fit pipe method, spiral wound method, splice segment lining, and spray lining. Compared to other methods, spray lining using cement-based materials offers advantages such as lower cost and faster construction. Spray lining can also be formed continuously without seams.

[0004]

[0004] The spray lining method involves spraying cement-based or polymer-based materials onto the inner surface of an existing pipeline. Cement-based materials are low-cost but typically provide insufficient corrosion protection for steel host pipes. Polymer-based materials typically offer better corrosion resistance but are more expensive. After being sprayed onto the substrate, the material needs to have good adhesion and cohesiveness to deposit to the desired thickness. The inner surface of the pipeline is usually unsuitable for coating with the material. Although pipelines are usually cleaned before spraying, insufficient adhesion between the sprayed material and the inner wall of the pipe remains a major problem.

[0005]

[0005] Conventional cement-based materials are brittle and lack tensile ductility. To achieve high strength and a dense microstructure, cement-based repair materials typically require a large amount of fine reactive powder and a low water content. As a result of this combination, the cement-based material shrinks significantly, which can cause constrained shrinkage cracks. After cracking, the fluid in the pipeline penetrates the cracks and further corrodes the pipe. Furthermore, if the adhesive strength is insufficient, the crack repair material may peel off. Therefore, using conventional cement-based materials often results in low durability of the repaired pipeline, requiring repeated maintenance.

[0006]

[0006] To overcome the inherent brittleness of cement-based materials, fiber-reinforced composites called high-toughness cement-based composites (ECCs) have been developed for spray-on repairs. ECCs exhibit high strain capacity exceeding 3% under uniaxial tension. The high ductility of ECCs is achieved by multiple dense cracks rather than the single cracks typical of ordinary concrete. However, ECC mixtures generally have a larger volume of cement and no coarse aggregate compared to ordinary concrete, and therefore drying shrinkage can reach -1500 με in 28 days. Increased shrinkage can lead to microcracks when deformation is constrained. The presence of microcracks in aggressive environments can affect the durability of spray-on repairs. Examples of ECCs are disclosed in the following patents.

[0007]

[0007] U.S. Patent No. 7,241,338 discloses a sprayed cement composition comprising a hydraulic cement such as Portland cement, a non-Newtonian additive, a viscosity agent, a fluidizer, short discontinuous fibers, a lightweight aggregate, and water.

[0008]

[0008] U.S. Patent No. 7,572,501 discloses a cement-based composite material comprising cement such as Portland cement, water, sand, fly ash, a water-reducing agent, and discontinuous short fibers such as polyethylene (PE) fibers. The rheology of the composition can be adjusted to obtain a composite material that can be pumped, molded, or sprayed.

[0009]

[0009] U.S. Patent No. 7,799,127 discloses a type of polyvinyl alcohol (PVA) fiber-reinforced high-initial-hardness ECC material. This material comprises a hydraulic cement, a chemical accelerator mixture, polyvinyl alcohol fibers, a non-matrix interactive crack initiator, one or more fine aggregates, and a chemical dispersant mixture.

[0010]

[0010] An object of the present invention is to provide a method for avoiding the above-mentioned drawbacks and / or to provide at least a publicly useful option.

[0011]

[0011] Another object of the present invention will become apparent from the following description, which is provided merely as an example.

[0012]

[0012] Any discussion of literature, acts, materials, apparatus, articles, etc. included herein is solely for the purpose of illustrating the context of the present invention. It should not be construed that any or all of these matters form part of the foundation of the prior art or are common general knowledge in the art relevant to the present invention as they existed before the priority date. [Overview of the project]

[0013]

[0013] In a first aspect, the present invention provides a spray-on cement-based composition comprising a composite binder, fibers, and water, wherein the composite binder comprises a cement component and a pozzolanic component.

[0014]

[0014] In some embodiments, the ratio of water to composite binder is about 0.2 to about 0.5.

[0015]

[0015] In some embodiments, the ratio of water to composite binder is about 0.2 to about 0.4.

[0016]

[0016] In some embodiments, the ratio of water to composite binder is approximately 0.3.

[0017]

[0017] In some embodiments, the cement component includes hydraulic cement and an expansive agent.

[0018]

[0018] In some embodiments, the leavening agent is calcium sulfoaluminate.

[0019]

[0019] In some embodiments, the amount of the expansive agent is about 10% to about 60% by weight based on the weight of the total cementitious components.

[0020]

[0020] In some embodiments, the amount of the expansive agent is about 20% to about 50% by weight based on the weight of the total cementitious components.

[0021]

[0021] In some embodiments, the average particle size of the expansive agent is about 2 μm to about 500 μm, or about 10 μm to about 30 μm.

[0022]

[0022] In some embodiments, the hydraulic cement includes ordinary Portland cement.

[0023]

[0023] In some embodiments, the amount of the hydraulic cement is about 1% to about 80% by weight based on the weight of the total cementitious components.

[0024]

[0024] In some embodiments, the amount of the hydraulic cement is about 20% to about 80% by weight based on the weight of the total cementitious components.

[0025]

[0025] In some embodiments, the amount of the hydraulic cement is about 50% to about 80% by weight based on the weight of the total cementitious components.

[0026]

[0026] In some embodiments, the amount of the hydraulic cement is about 60% to about 80% by weight based on the weight of the total cementitious components.

[0027]

[0027] In some embodiments, the cementitious components include reactive aluminosilicate, calcium carbonate, or a mixture thereof.

[0028]

[0028] In some embodiments, the reactive aluminosilicate is calcined clay.

[0029]

[0029] In some embodiments, the reactive aluminosilicate is metakaolin.

[0030]

[0030] In some embodiments, calcium carbonate is limestone.

[0031]

[0031] In some embodiments, the cement component includes reactive aluminosilicate, calcium carbonate, or a mixture thereof in an amount of about 1 to about 80% by weight, or about 30 to about 60% by weight, or about 40 to 50% by weight, based on the total weight of the cement component.

[0032]

[0032] In some embodiments, the cement component contains reactive aluminosilicate in an amount of 0 to about 50% by weight, or about 20 to about 40% by weight, or about 30% by weight, based on the total weight of the cement component.

[0033]

[0033] In some embodiments, the cement component contains calcium carbonate in an amount of about 0 to about 30% by weight, or about 10 to about 20% by weight, or about 15% by weight, based on the total weight of the cement component.

[0034]

[0034] In some embodiments, the ratio of reactive aluminosilicate to calcium carbonate is 2:1.

[0035]

[0035] In some embodiments, the cement component comprises, based on the total weight of the cement mixture, about 10 to about 50% by weight of ordinary Portland cement (OPC), about 20 to about 40% by weight of metakaolin, and about 10 to about 20% by weight of limestone.

[0036]

[0036] In some embodiments, the average particle size of the reactive aluminosilicate is about 2 μm to about 40 μm, or about 2 μm to about 10 μm.

[0037]

[0037] In some embodiments, the average particle size of calcium carbonate is about 2 μm to about 100 μm, or about 2 μm to about 20 μm.

[0038]

[0038] In some embodiments, the amount of pozzolanic component is about 1 to 3 times the amount of cement component by weight.

[0039]

[0039] In some embodiments, the amount of pozzolanic component is about 2 to 3 times the amount of cement component by weight.

[0040]

[0040] In some embodiments, the amount of pozzolanic component is about 2 to 2.5 times the amount of cement component by weight.

[0041]

[0041] In some embodiments, the pozzolanic component includes a material selected from the group consisting of fly ash, steelmaking slag, granular blast furnace slag, calcined clay such as diatomaceous earth, silica fume, and metakaolin, calcined silica-rich organic matter such as calcined shale, volcanic ash, pumice, and rice husk ash, and mixtures of any two or more thereof.

[0042]

[0042] In some embodiments, the fly ash is selected from the group consisting of type C fly ash, type F fly ash, and mixtures thereof.

[0043]

[0043] In some embodiments, the fibers are selected from the group consisting of polymer fibers, inorganic fibers, metal fibers, carbon fibers, plant fibers, and mixtures of two or more of these.

[0044]

[0044] In some embodiments, the polymer fiber comprises a polymer material selected from the group consisting of polyolefins, polyacrylics, polyesters, polyvinyl alcohols, polyamides, and combinations of two or more thereof.

[0045]

[0045] In some embodiments, the polymer fiber is selected from the group consisting of polyethylene fiber, high-tenacity polypropylene fiber, polyvinyl alcohol fiber, and mixtures of two or more of these.

[0046]

[0046] In some embodiments, the amount of fiber is about 0.1 to less than 4 v / v%, or about 1 to about 3 v / v%, or about 1.5 to about 2.3 v / v%, based on the total volume of the composition (i.e., the volume of the composition including water).

[0047]

[0047] In some embodiments, the fiber length is approximately 4 mm to approximately 25 mm, or approximately 6 mm to approximately 20 mm, or approximately 8 mm to approximately 12 mm.

[0048]

[0048] In some embodiments, the fiber diameter is about 10 μm to about 150 μm, or about 10 μm to about 60 μm.

[0049]

[0049] In some embodiments, the sprayed cement composition further comprises one or more components selected from the group consisting of a fluidizer, aggregate, viscosity agent, and retarder.

[0050]

[0050] In some embodiments, the amount of fluidizer is about 0.1 to 10% by weight, or about 0.3 to 3% by weight, or about 0.5 to 1.5% by weight, based on the total weight of the composition.

[0051]

[0051] In a further embodiment, the present invention relates to a spray-on cement-based composition comprising a composite binder, fibers, and water, wherein the composite binder comprises a cement component and a pozzolanic component, and the spray-on cement-based composition hardens to: (i) Tensile strength of at least about 2.50 MPa, (ii) Tensile strain capacity of at least approximately 3% on the 28th, (iii) Crack width less than approximately 100 μm at ε < 2%, and (iv) Maximum expansion of at least about 1210 με, The present invention provides a sprayed cement-based composition that achieves one or more properties selected from the group consisting of the following.

[0052]

[0052] In a further embodiment, the present invention relates to a method for preparing a sprayed cement composition: (i) To provide a binder composition containing cement components and pozzolanic components, (ii) Mixing the binder composition with water to form a wet mixture, (iii) Adding fibers to a wet mixture, This provides a method that includes [something].

[0053]

[0053] In some embodiments, the method further includes mixing cement components and pozzolanic components to obtain a binder composition.

[0054]

[0054] In some embodiments, a fluidizing agent is added to the water before step (ii).

[0055]

[0055] In a further embodiment, the present invention relates to a method for repairing and / or improving a building structure: (i) the step of providing a sprayed cement composition of the present invention; (ii) spraying a cement-based composition onto the surface of a building structure to at least partially cover the surface with the cement-based composition; (iii) A step of setting the cement-based composition on the surface, This provides a method that includes [something].

[0056]

[0056] In some embodiments, the spraying step (ii) is performed by a manual spraying system or an automatic spraying system.

[0057]

[0057] In some embodiments, the building structure is a pipeline.

[0058]

[0058] In some embodiments, the surface is the inner surface of the pipeline.

[0059]

[0059] In some embodiments, the pipeline is modified to increase the lifespan of the pipeline, to increase the load-bearing capacity of the pipeline, and / or to strengthen the pipeline.

[0060]

[0060] In another embodiment, the present invention provides the use of the spray cement composition of the present invention for the repair and / or improvement of building structures.

[0061]

[0061] In some embodiments, the building structure is a pipeline.

[0062]

[0062] In another embodiment, the present invention provides a dry premix for preparing a spray cement composition of the present invention, wherein the dry premix comprises a composite binder and fibers, and the composite binder comprises a cement component and a pozzolanic component.

[0063]

[0063] In another aspect, the present invention relates to a method for preparing a sprayed cement composition of the present invention: (i) To provide the dried premix of the present invention, (ii) Mixing the dry premix with water to form a spray cement-based composition, This provides a method that includes [something].

[0064]

[0064] The present invention may also be broadly said to consist of parts, elements, and features that are referred to or shown individually or collectively in this specification, as well as any combination of any two or more of the above parts, elements, or features, and where any particular integer known to be equivalent in the art to which the present invention relates is referred herein, such known equivalent shall be deemed to be incorporated herein as if it were described separately.

[0065]

[0065] Furthermore, if any feature or aspect of the present invention is described in terms of a Markush group, a person skilled in the art will recognize that the present invention is also described in terms of any individual component or subgroup of components of the Markush group.

[0066]

[0066] As used herein, "(s)" following a noun means the plural and / or singular form of that noun.

[0067]

[0067] As used herein, the term "and / or" means "and" or "or" or both.

[0068]

[0068] As used herein, the term “comprising” means “consisting of at least part of.” When interpreting each expression herein that contains the term “comprising,” there may be features other than the one or more features that the term precedes. Related terms such as “comprise” and “comprises” should be interpreted in the same manner.

[0069]

[0069] Any reference to a range of numbers disclosed herein (e.g., 1 to 10) is intended to also include references to all rational numbers within that range (e.g., 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9, and 10) and to any range of rational numbers within that range (e.g., 2 to 8, 1.5 to 5.5, and 3.1 to 4.7), and thus references to all partial ranges of any range expressly disclosed herein are disclosed herein. These are merely examples of what is particularly intended, and all possible combinations of numbers between the lowest and highest values ​​listed should likewise be considered expressly referred to herein.

[0070]

[0070] Although the present invention is broadly defined as described above, those skilled in the art will recognize that the present invention is not limited thereto and also includes embodiments illustrated by the following description. [Brief explanation of the drawing]

[0071]

[0071] The present invention will now be described with reference to the figures.

[0072] [Figure 1]

[0072] The shrinkage / expansion of SDMCC prepared using OPC and CSA-K cement is shown (where CSA-K contains 7, 10, and 13 wt% of composite binder, respectively). [Figure 2]

[0073] The shrinkage / expansion of SDMCC prepared using OPC and LC3 / CSA-K cement is shown (where CSA-K contains 10% and 13% by weight of composite binder, respectively). [Figure 3]

[0074] This shows the shrinkage / expansion of SDMCC prepared with CSA-R cement (where anhydrous gypsum contains 0, 10, 15, and 20% by weight of CSA-R, respectively). [Figure 4]

[0075] This shows the maximum allowable expansion of SDMCC for repairing C40 concrete pipes. [Figure 5]

[0076] The average strain of steel rings measured by three strain gauges of SDMCC prepared using LC3 / CSA-K cement and CSA-K cement is shown (where CSA-K contains 13 wt% composite binder). [Figure 6]

[0077] This shows the residual interfacial pressure between the steel ring and the SDMCC prepared using LC3 / CSA-K cement and CSA-K cement (where CSA-K contains 13 wt% of a composite binder). [Figure 7]

[0078] Figures 1 and 2 show the tensile stress-strain behavior of the compositions shown over 28 days. [Figure 8]

[0079] This shows the self-recovery of ultimate tensile strength and strain capacity of SDMCC prepared with OPC, LC3, and LC3 / CSA-K cement after seven wet-dry cycles. [Figure 9]

[0080] This shows the permeability coefficients of SDMCC prepared using OPC and LC3 / CSA-K cement, tested on the 14th day after pre-crack formation occurred in the test specimens over a 28-day period. [Figure 10]

[0081] This shows a pipe repair protocol using craft tubing. [Figure 11]

[0082] This shows the relationship between limit load and displacement for concrete pipes and pipes repaired with SDMCC. [Modes for carrying out the invention]

[0073]

[0083] The inventors have surprisingly discovered SDMCC, which possesses properties more advantageous than conventional cement and concrete. For example, SDMCC may exhibit expansion during hardening and strain hardening behavior.

[0074]

[0084] Accordingly, in one embodiment, the present invention provides an SDMCC comprising a composite binder, fibers, and water, wherein the composite binder comprises a cement component and a pozzolanic component. This sprayed cement composition is useful, for example, for the repair and / or improvement of pipelines.

[0075]

[0085] This cement component includes hydraulic cement and may further include additional materials such as an expander, a reactive aluminosilicate, and / or calcium carbonate.

[0076]

[0086] SDMCC may further contain other components such as fluidizers, aggregates, and / or other additives.

[0077] Water-hardening cement

[0087] Hydraulic cement is a material that sets and hardens when mixed with water. Examples of hydraulic cement include, but are not limited to, Portland cement, blended Portland cement, phosphate cement, and beelite cement (dicalcium silicate). Mixtures of two or more of these are also considered. Preferably, the hydraulic cement is Portland cement.

[0078]

[0088] Portland cement is a finely ground powder produced by grinding clinker, which is essentially made from hydraulic calcium silicate. The cement can contain up to approximately 5% gypsum. The amount of gypsum present affects the setting time. Standards for Portland cement are defined in ASTM C 150, Standard Specification for Portland Cement, which specifies eight types of Portland cement: Type I, Type IA, Type II, Type IIA, Type III, Type IIIA, Type IV, and Type V. Type I cement is a general-purpose ordinary Portland cement (OPC) suitable for any use where the specific properties of other types are not required. Type III cement is chemically and physically similar to Type I cement, except that it is ground more finely to obtain higher initial strength.

[0079]

[0089] The cement component may contain hydraulic cement in an amount of approximately 1 to 80% by weight, or approximately 20 to 80% by weight, or approximately 50 to 80% by weight, or approximately 60 to 80% by weight, based on the total weight of the cement component.

[0080]

[0090] In some embodiments, the cement component includes a reactive aluminosilicate such as calcined clay and / or calcium carbonate such as limestone. Advantageously, replacing a portion of the hydraulic cement with a reactive aluminosilicate and / or calcium carbonate results in a more environmentally friendly composition by reducing the amount of carbon released during manufacturing.

[0081]

[0091] Another advantage can be obtained by using SDMCC containing reactive aluminosilicate and / or calcium carbonate. For example, limestone calcined clay cement (LC3) paste has been shown to have a finer pore structure than paste made using OPC. Advantageously, the improved pore structure provides excellent resistance to chloride penetration and exhibits superior performance in the presence of sulfates, which is particularly evident in the complex environments of pipelines.

[0082]

[0092] Furthermore, SDMCC containing LC3 has been found to have surprisingly higher strain capacity and smaller crack width than conventional ECC prepared using OPC. The reduced crack width results in lower permeability, which can, for example, prevent corrosion of the original pipe by fluids. SDMCC with higher strain capacity is expected to have a higher deformation density, which can, for example, allow the repaired pipe to have higher load and deflection capacity.

[0083]

[0093] The cement mixture may contain reactive aluminosilicate, calcium carbonate, or mixtures thereof in amounts of about 1 to about 80% by weight, or about 30 to about 60% by weight, or about 40 to 50% by weight, based on the total weight of the cement components. For example, the cement components may contain reactive aluminosilicate in amounts of 0 to about 50% by weight, or about 20 to about 40% by weight, or about 30% by weight, based on the total weight of the cement components. For example, the cement components may contain calcium carbonate in amounts of about 0 to about 30% by weight, or about 10 to about 20% by weight, or about 15% by weight, based on the total weight of the cement components. In some embodiments, the ratio of reactive aluminosilicate to calcium carbonate is 2:1.

[0084]

[0094] In some embodiments, the average particle size of the reactive aluminosilicate is approximately 2 μm to 40 μm, or approximately 2 μm to 10 μm. In some embodiments, the average particle size of the calcium carbonate is approximately 2 μm to 100 μm, or approximately 2 μm to 20 μm.

[0085]

[0095] In some embodiments, the cement component comprises, based on the total weight of the cement mixture, about 10 to about 50% by weight of OPC, about 20 to about 40% by weight of metakaolin, and about 10 to about 20% by weight of limestone.

[0086]

[0096] In some embodiments, a portion of the hydraulic cement can be replaced with mining tailings. For example, the cement component may contain mining tailings in an amount of about 1 to about 30% by weight, based on the total weight of the cement component.

[0087] leavening agent

[0097] A swelling agent is a material that increases the expansion of SDMCC during the hydration process. In some embodiments, a swelling agent can be used to reduce shrinkage that occurs during the curing of the composition. In another embodiment, a swelling agent can be used to obtain SDMCC that expands during curing. Advantageously, the increased expansion of SDMCC can reduce the risk of cracking that occurs during shrinkage.

[0088]

[0098] An expanding agent can be used to adjust the expansion properties of SDMCC so that, when applied to the inner surface of a pipeline and cured, SDMCC generates an expanding force against the inner surface of the pipeline. This expanding force reduces the space between the SDMCC and the inner surface, increasing the mechanical friction between them. Advantageously, the increased mechanical friction can increase the adhesion between the SDMCC and the inner surface. As a result, the repaired or improved pipeline can have higher load and deflection capacities than the original host pipe. Furthermore, the increased adhesion can reduce delamination from the surface of the SDMCC, reducing wrinkles and even buckling of the repair layer during use after repair. The controlled expanding force acting on the host pipe by SDMCC can bond the repair layer to the host pipe wall, enabling both structural and functional repairs, not just functional repairs such as leak repairs. However, those skilled in the art will recognize that excessive expansion should be avoided, as in some embodiments, deformation or even damage may occur to the surface of the host pipe to which the SDMCC is applied.

[0089]

[0099] In addition to applying pressure to the pipeline, SDMCC's expansion properties distinguish it from the well-known sprayed ECC, which typically exhibits a large drying shrinkage of approximately -1500 με after 28 days. The expansion properties of SDMCC reduce the risk of confinement shrinkage cracking, further increasing the durability of the repaired pipeline and reducing the risk of leaks after repair.

[0090]

[0100] Those skilled in the art will recognize that the preferred expansion characteristics of SDMCC are determined by various factors, including the diameter and tensile strength of the host pipe to be repaired or improved, whether the host pipe is under sealing pressure, and the intended thickness of the SDMCC. In some embodiments, the expansion of the SDMCC is at least about 1200 με. In some other embodiments, the expansion of the SDMCC is at least about 3000 με. The maximum expansion of the SDMCC may be, for example, about 3000 με, about 3375 με, about 4000 με, or about 4450 με.

[0091]

[0101] Preferred leavening agents include calcium aluminate cement (CAC) and calcium sulfoaluminate cement (CSA). Preferably, the leavening agent is CSA. The amount of CaSO4·nH2O in the CSA is preferably about 1 to 50% by weight, based on the weight of the CSA, where n may be 0, 0.5, 1, or 2.

[0092]

[0102] The composite binder may contain an amount of expansive agent in the form of approximately 10 to 60% by weight, or approximately 20 to 50% by weight, based on the total weight of the cement components. In some embodiments, the average particle size of the expansive agent is approximately 2 μm to 500 μm, or approximately 10 μm to 30 μm.

[0093] Pozzollan

[0103] Pozzolanes are materials containing silica or silica and aluminum, typically provided in a finely ground form. Pozzolanes alone exhibit little to no cementitious properties, but in the presence of water, they react with calcium hydroxide released by the hydration of hydraulic cement to form calcium silicate hydrate and other cementitious compounds. Advantageously, pozzolanes can improve the bond fracture toughness of cementitious materials, thereby increasing the ductility of hardened SDMCC. Pozzolanes can also be used to modulate the rheology of SDMCC. Advantageously, the rheology of SDMCC can be modified to improve the pumpability and / or sprayability of the composition.

[0094]

[0104] In general, any silica-containing material that reacts with calcium hydroxide in the presence of water, or a material containing silica and aluminum, may be suitable for use in the binder. Suitable pozzolanes include, but are not limited to, fly ash, steelmaking slag, granular blast furnace slag, calcined clay such as diatomaceous earth, silica fume, and metakaolin, calcined shale, volcanic ash, pumice, rice husk ash, and mixtures of two or more of these. Preferably, the pozzolane component includes fly ash, for example, as defined in ASTM C618. In some embodiments, the fly ash is type C fly ash and / or type F fly ash.

[0095]

[0105] In some embodiments, the pozzolanic component includes silica fume. Advantageously, the silica fume can increase the compressive strength of SDMCC and / or improve the fiber / matrix interface bonding.

[0096]

[0106] The composite binder may contain a pozzolanic component in an amount approximately 0 to approximately 3 times the weight of the cement component. Preferably, the composite binder contains a pozzolanic component in an amount approximately 1 to approximately 3 times, more preferably approximately 2 to approximately 3 times, and more preferably approximately 2 to approximately 2.5 times the weight of the cement component.

[0097] fiber

[0107] The fibers are intended to reinforce the hardened SDMCC. Suitable fibers can be selected based on various properties such as the desired cost, mechanical properties, physical properties, and bonding properties of the fibers. The properties of SDMCC can be influenced by factors such as fiber length, diameter, chemical composition, stiffness, density, and strength. Fibers can be selected so that the load is transmitted throughout the crack when the composite material is loaded beyond the elastic stage. These load-carrying behaviors can be tuned to balance fiber fracture and fiber slip, i.e., for controlled fiber bridging behavior. Excessive fiber fracture or slip is undesirable while the composite material is loaded because it can limit the ductility of the composite material or result in excessively large crack widths that impair the durability of the composite material. Advantageously, fibers can improve the strain hardening and tensile ductility of the composite material and limit crack widths.

[0098]

[0108] Suitable fibers for use in SDMCC include, but are not limited to, polymer fibers, inorganic fibers (e.g., basalt fibers and glass fibers), metallic fibers (e.g., steel fibers), carbon fibers, plant fibers (e.g., cellulose fibers and cellulose fibers of rigs), and mixtures of two or more of these. Preferably, the fibers are polymer fibers, i.e., fibers composed of polymer materials such as polyolefins (e.g., polyethylene or polypropylene), polyacrylic, polyester, polyvinyl alcohol, polyamide (e.g., nylon), or combinations of two or more of these. More preferably, the fibers are polypropylene fibers, more preferably high-tenacity polypropylene fibers. In some embodiments, the fibers are discontinuous short fibers.

[0099]

[0109] The upper limit of the fiber concentration is determined by the requirements for pumpability and sprayability, while the lower limit is determined by the ability to obtain strain-hardening (ductile) behavior opposite to brittle or pseudo-brittle behavior. For example, fibers can be present in amounts of about 0.1 to less than 4 v / v%, or about 1 to about 3 v / v%, or about 1.5 to about 2.3 v / v%, based on the total composition volume (i.e., the volume of the composition including water). In some embodiments, the fiber length is about 4 mm to about 25 mm, or about 6 mm to about 20 mm, or about 8 mm to about 12 mm. In some embodiments, the fiber diameter is about 10 μm to about 150 μm, or about 10 μm to about 60 μm.

[0100] Flowing agent

[0110] In some embodiments, the SDMCC further comprises a fluidizer, also known as a high-performance water-reducing agent. The fluidizer may be added to the SDMCC to affect the rheology of the composition. Advantageously, the fluidizer can reduce the amount of water required to maintain the pumpability and sprayability of the SDMCC.

[0101]

[0111] Therefore, the fluidizer is typically added to the SDMCC in an amount effective to achieve the desired pumpability and sprayability of the composition. Those skilled in the art will recognize that the amount of fluidizer required to achieve the desired pumpability and sprayability may be determined by other components of the composition, such as the water content of the composition. For example, the fluidizer may be included in the SDMCC in an amount of about 0.1 to 10% by weight, or about 0.3 to about 3% by weight, or about 0.5 to about 1.5% by weight, based on the total weight of the composition.

[0102]

[0112] In general, any fluidizer known in the art is suitable for use in SDMCC. Such fluidizers include, but are not limited to, sulfonated melamine (e.g., sulfonated melamine formaldehyde condensate), sulfonated naphthalene (e.g., sulfonated naphthalene formaldehyde condensate), polycarboxylic acid ethers (e.g., ADVA® 190), modified lignosulfonates, and mixtures of two or more of these.

[0103] aggregate

[0113] SDMCC can further contain aggregates such as sand, crushed stone, and lightweight aggregates. The inclusion of lightweight aggregates can reduce the density of SDMCC. The inclusion of lightweight aggregates can also increase the thickness that can be sprayed, especially on horizontal overhead surfaces. When the amount of lightweight aggregate is large, particle size becomes important, otherwise strain hardening cannot be achieved. Generally, the average particle size is about 10 μm to about 1000 μm, or about 10 μm to about 200 μm, or about 30 μm to about 100 μm.

[0104]

[0114] Lightweight aggregates may include, but are not limited to, crushed rubber (e.g., from waste tires), hollow glass spheres, cenospheres, inflated mica, and microballoons (e.g., microballoons made of glass, ceramic, or polymer).

[0105]

[0115] In addition to, or instead of, lightweight aggregates, SDMCC may further contain air bubbles. During processing of the cement-based composition, gas may be introduced by physical means, such as foaming or aeration. Alternatively, gas may be introduced chemically, for example, as hydrogen gas produced by the reaction of aluminum powder with an alkaline composition, or by the reaction of Si-H functionalized silane with water. In some embodiments, stabilizing substances are added to promote the prevention of coalescence of adjacent air bubbles. In some embodiments, the amount is approximately 1400 kg / m³. 3 Preferably 1500 kg / m 3The volume percentage is limited so that the above hardening density is achieved. If a large amount of bonding creates large voids, the strength properties of the composite material, particularly its strain-hardening behavior, may be impaired. Bulbs can be used together with other lightweight aggregates. Advantageously, the volume percentage of bubbles in such a composition can be kept small to minimize bonding. For example, in a composite material with a target density of 1300 kg / m³, approximately 1600 kg / m³ 3 To obtain the above density, a gas or gas precursor can be added, and other lightweight fillers can be added to reduce the density to the target range.

[0106] Other additives

[0116] SDMCC may further contain other additives well known in the art, such as viscous agents and / or retarders.

[0107]

[0117] For example, the viscous agent may be a cellulose derivative such as hydroxypropyl methylcellulose (HPMC). The viscous agent can be added to the SDMCC in an amount of about 0 to about 1% by weight, or about 0.03 to about 0.5% by weight, or about 0.05 to about 0.2% by weight, based on the total weight of the binder (i.e., the weight of the composition excluding water). The viscous agent improves the properties of the composite material by increasing its thickness on the substrate and also promotes the uniform dispersion of fibers in the matrix.

[0108]

[0118] SDMCC may contain retarders. Conventional retarders can be used. A preferred retarder is citric acid, which is advantageously compatible with the use of CSA. The retarder may be included in an amount of about 0.01 to about 10% by weight, or about 0.1 to about 2% by weight, or about 0.2 to about 1.5% by weight, based on the total binder weight. The retarder can increase the working time of the SDMCC during the spraying process. However, those skilled in the art will recognize that excess retarder may reduce the strength and ductility of the SDMCC.

[0109] water

[0119] The amount of water in SDMCC affects various properties of the composition. The water content should be sufficient to obtain a pumpable and sprayable composition. Generally, a higher water content reduces viscosity and improves sprayability, while a lower water content increases cohesive force, allowing for thicker coatings. The amount of water required to obtain a pumpable and sprayable composition can usually be easily determined by experiment and can be reduced by including a fluidizing agent, as mentioned above.

[0110]

[0120] In some embodiments, the ratio of water to binder is about 0.2 to about 0.5. Preferably, the ratio of to binder is about 0.2 to about 0.4, more preferably about 0.3.

[0111] Preparation of cement-based compositions

[0121] The SDMCC of the present invention can be prepared by prior art. The components can be mixed separately with water, or certain components can be pre-mixed. In some embodiments, a wet mixture is obtained by adding water to a premix of dry binder components, to which the fibers are added. In some embodiments, a wet mixture is obtained by mixing a fluidizing agent with water to form a solution, which is then added to a premix of dry binder components, to which the fibers are added. In some other embodiments, the dry components can be supplied in a "ready mix" composition, for example, in a premix of dry binder components and fibers, which is then mixed with water before being used to form the SDMCC.

[0112] Pipeline repair and improvement

[0122] The SDMCC of the present invention is useful for repairing pipelines such as gravity pipelines or pressure pipelines, particularly underground gravity pipelines or pressure pipelines. Such pipelines are found in a variety of applications, for example, water supply pipes, water distribution pipes, sewer pipes, and oil pipelines. For example, the SDMCC is useful in trenchless pipeline repair methods. The pipeline repair method of the present invention is suitable for various pipe shapes, for example, pipes with circular or non-circular cross-sections, pipes with narrow or wide diameters, straight pipes, or curved pipes.

[0113]

[0123] The inventors also demonstrate that the SDMCC of the present invention is useful for pipeline improvement. In contrast to repair methods intended to restore the original function of a damaged host pipe, improvement means methods that enhance the properties of a pipeline. For example, pipelines can be improved to increase their lifespan, increase their load-bearing capacity, and / or strengthen them. In some embodiments, pipelines can be improved for seismic reinforcement. For this purpose, SDMCC can be applied to pipes to reduce the risk of leakage or contamination of drinking water or groundwater caused by seismic events.

[0114]

[0124] The pipeline repair or improvement method of the present invention can protect against common damage modes that occur in pipelines that have been repaired or improved by CIPP, slip lining, spiral wound lining, or other methods such as spray lining using well-known materials. Common damage modes that can be avoided include local buckling, rupture of the lining or pipeline, water leakage, and corrosion of the lining or pipeline.

[0115]

[0125] A pipeline repair or improvement method comprises providing SDMCC as a wet mixture, applying the wet mixture to at least a portion of the pipeline surface, for example, the inner wall of the pipeline, and curing the mixture. In some embodiments, the SDMCC is applied to the entire inner surface along the length of the pipeline. Advantageously, coating the entire inner surface can result in a substantially new inner pipe. Continuous spraying of the cement-based material along the length of the deteriorated pipeline can form a seamless inner coating with a small number of joints, or in some embodiments, a seamless inner coating. Joints are typically weak points in a pipeline, and therefore, advantageously, reducing the number of joints in the repaired pipeline can extend the service life of the pipeline. Pipelines with a continuous inner coating with a small number of joints or no joints at all also have a reduced risk of leakage under hazardous conditions such as earthquakes.

[0116]

[0126] Cement-based compositions can be applied to the surface of pipelines by conventional methods. SDMCC can be applied by manual or automatic spraying systems. For example, SDMCC can be applied manually by air-pressurizing the composition and releasing it from a nozzle at high speed onto the surface. Alternatively, SDMCC can be applied by an automatic centrifugal spraying system that sprays the material onto the inner surface of an existing pipeline.

[0117]

[0127] The cement-based composition is in a fluid state during pumping, but sets after being sprayed onto a surface. The setting rate should be fast enough to increase the thickness while resisting the pulling force of gravity. The SDMCC of the present invention can have a thickness of about 10 mm to about 50 mm when sprayed onto a horizontal or vertical surface, such as an overhead surface. In some embodiments, the SDMCC has a thickness of about 20 mm to about 40 mm when sprayed onto a horizontal or vertical surface. In some embodiments, the SDMCC has a thickness of about 20 mm to about 30 mm when sprayed onto a horizontal or vertical surface.

[0118]

[0128] The SDMCC of the present invention is useful for the repair and improvement of pipelines. However, those skilled in the art will recognize that the SDMCC of the present invention may be useful for the repair and / or improvement of other building structures, particularly building structures where one or more of the aforementioned improved properties are beneficial. For example, suitable building structures include tunnels, culverts, manholes, bridges, slabs, and roads.

[0119]

[0129] The following non-limiting examples are provided to illustrate the present invention and are not intended to limit the scope of the invention in any way. [Examples]

[0120] 1. Composition and processing of materials

[0130] Representative mixtures are listed in Table 1. The cement was Type I Portland cement (PCI) from Lafarge Cement Co., MI, USA. Two types of expansive cements from CTS Cement Manufacturing Corp. and Royal White Cement Inc. were used, designated CSA-K and CSA-R, respectively. The metakaolin (MK) was Sikacrete® M-100 from Sika Corporation, NJ, USA. The anhydrous gypsum was Terry-Alba No. 1 from the USG. The limestone (LS) was Snowhite® 12-PT from Omya Canada Inc. The fly ash (FA) was Class C fly ash with a size distribution of 10-100 μm from Boral Material Technologies Inc. The superplasticizer (SP) was AVDA® 190 from GCP Applied Technologies. The viscous agent, hydroxypropyl methylcellulose (HPMC), was manufactured by Fisher Scientific. The polypropylene (PP) fiber content was 2% by volume, with a diameter of 12 μm, a length of 10 mm, a Young's modulus of 6 GPa, and a tensile strength of 850 MPa. It was Brasilit from Saint-Gobain Brazil.

[0121] [Table 1]

[0122]

[0131] The naming conventions in Table 1 reflect the composition of the binders. OPC and LC3 refer to binders prepared using ordinary Portland cement and calcined limestone clay cement, respectively. K07, K10, and K13 indicate that the ratio of CSA-K to the binder is 7, 10, and 13% by weight, respectively. R13-CO, 10, 15, and 20 indicate that the ratio of CSA-R and anhydrous gypsum to the binder is 13% by weight, with the proportion of anhydrous gypsum being 0, 10, 15, and 20% by weight of the total weight of CSA-R and anhydrous gypsum. The weight percentage ratios of PCI, MK, and LS in LC3 cement are 55%, 30%, and 15%, respectively.

[0123]

[0132] SDMCC was prepared by mixing all dry components (PCI, CSA, anhydrous gypsum, MK, LS, FA, and HPMC) in a drum mixer for 10 minutes. Water was gradually added along with SP and mixed for 6 minutes. Finally, PP fibers were added and mixed for another 6 minutes.

[0124] 2. Sprayability of cement-based compositions

[0133] The fresh properties of sprayable (often called "shot creaching") ECC are important. Sprayable cement compositions require high initial deformability for pumping, rapid deposition capacity when sprayed onto a substrate, and an optimal resting time. The resting time, defined as the time interval from the end of mixing to the start of spraying, should be long enough to accommodate the time required for pumping and short enough to achieve the desired deposition thickness through spraying.

[0125]

[0134] The composition of SDMCC was the same as LC3-K13 in Table 1, except for the difference in SP content. Compared to conventional sprayed ECC containing 2 v / v% PVA fibers, the SDMCC of the present invention uses 2 v / v% PP fibers, which are advantageously less expensive than PVA fibers. However, for the same amount and fiber length, the amount of PP fibers (12 μm) in SDMCC was 10.56 times the amount of fibers (39 μm) in conventional sprayed PVA-ECC. With a large amount of small diameter fibers, careful control of the fresh rheology of the sprayed SDMCC was necessary.

[0126]

[0135] A CARROUSEL pump and multi-air jet pole gun from Quikspray Inc. were used for spraying in the embodiments described below. This multi-air jet pole gun was particularly suitable for spraying cement-based materials with reinforcing fibers. The material was mixed in a Hobart mixer and then pumped using a CARROUSEL pump. After passing the material through a 1.25-inch (31.75 mm) diameter hose and the multi-air jet pole gun, SDMCC was sprayed onto a plywood substrate at an air pressure of 560 kPa. The spraying tests included spraying onto the substrate from both vertical and overhead directions.

[0127]

[0136] Through a series of fluidity tests using various amounts of fluidizer, the optimal fluidizer content was determined to be 0.8% by weight of the composite binder. In the vertical plywood substrate spray test, the deposition thickness was 15 mm after a 20-minute resting period. With a 40-minute resting period on the vertical plywood substrate, a maximum deposition thickness of 50 mm could be reached. For overhead substrates, a maximum thickness of 25 mm could be reached after a 20-minute resting period.

[0128]

[0137] Although the fiber content in SDMCC was 10.56 times that of conventional spray-applied PVA-ECC, spray-applied SDMCC showed good atomization and was found to be able to uniformly spray the material onto the substrate. SDMCC showed almost no rebound and did not drip or sag after being sprayed onto the substrate, demonstrating a significant advantage over conventional coating materials.

[0129] 3. Expansion characteristics

[0138] Test specimens for shrinkage / expansion measurement were poured into a prismatic mold (25 × 25 × 300 mm). After demolding the specimens as quickly as possible without damaging them, shrinkage / expansion measurements were performed and recorded as the "zero time" of deformation. For the mixtures in Table 1, the demolding times were 20 hours for OPC; 10 hours for K07; 5 hours for K10, K13, and LC3-K13; 8 hours for LC3-K10; and 3 hours for R13-C0, R13-C10, R13-C15, and R13-C20. The test specimens were stored in an environment of 20 ± 2°C and 40 ± 5% relative humidity (RH). The change in length of the test specimens was measured in accordance with ASTM C490 / C490M-17.

[0130] 3.1 Drying shrinkage / expansion

[0139] The shrinkage / expansion versus time curves for the compositions in Table 1 are shown in Figures 1-3, where a negative sign (on the y-axis) represents shrinkage and a positive sign represents expansion. Table 2 lists the characteristic values ​​of shrinkage / expansion at 28 days. In the case of SDMCC prepared with OPC, shrinkage increased continuously to -1434 με at 28 days. Such relatively large shrinkage can lead to cracking under constrained conditions, thereby reducing the durability of the material. SDMCC using CSA-K exhibited a characteristic of expanding first and then shrinking. The maximum expansion occurred over a period of approximately 2 days. The magnitude of the maximum expansion was 779 με, 2418 με, and 3756 με for compositions K07, K10, and K13, which had different ratios of CSA-K, respectively. However, when 7 wt% CSA-K cement was used in the composite binder, SDMCC showed a further shrinkage of -832 με at 28 days. The expansion of K10 and K13 was 1139 με and 2026 με, respectively, at 28 days. The expansion of ECC using LC3 was slightly less than that of OPC. The expansion of LC3-K10 and LC3-K13 was 838 με and 1722 με, respectively.

[0131]

[0140] The type of CSA cement can also affect the magnitude of expansion. CSA-R is a CSA binder with less CaSO4 than CSA-K. Furthermore, when the CSA-R content was 13% by weight of the composite binder (R13-C0), the shrinkage of R13-C0 was -834 με at 28 days, and no expansion was observed. Increasing the substitution of CSA-R with anhydrous gypsum reduced the shrinkage, and R13-C20 showed an expansion of 489 με at 28 days. Although we do not wish to be constrained by theory, the amount of CaSO4 (gypsum or anhydrous gypsum) in the CSA cement is thought to affect the formation of ettringite. Ettringite is the main expansive hydration product of CSA cement.

[0132] 3.2 Minimum Expansion

[0141] Assuming linear material structural behavior, the pressure generated by expansion is: p = E1ε1 - E2ε2 (1) This can be expressed as follows: where p is the pressure arising from the expandable SDMCC, ε1 is the maximum expansion of the SDMCC; ε2 is the difference between the maximum expansion and the residual strain at 28 days; E1 is the effective modulus between time zero and the maximum expansion time; and E2 is the effective modulus between the maximum expansion time and 28 days. ε1 and ε2 can be tested by a dry shrinkage / expansion test in accordance with ASTM C490 / C490M-17, and their values ​​are listed in Table 2. E1 and E2 are effective moduli affected by stress relaxation and time evolution. During the early period (before 3 days), creep is much greater than during the later period (3 to 28 days). Furthermore, even in the case of rapid curing of SDMCC materials, the modulus of elasticity is smaller during the early period.

[0133]

[0142] Assuming E1 = kE2, the pressure is: f=(kε1-ε2)E2(2) It can also be expressed as follows, where k is defined as the coefficient of the effective modulus. k is determined by the combined effect of the development of the material's modulus and the boundary constraint conditions. Advantageously, f should be greater than 0 to ensure that the SDMCC produces a coupling effect on the host pipe. In other words, kε1-ε2 should be greater than 0. According to Zhu H. et al., Double feedback control method for determining early-age restrained creep of concrete using a temperature stress testing machine. Materials, 2018, 11(7), 1079, it seems reasonable to assume k=0.5.

[0134] [Table 2]

[0135]

[0143] For the mixtures in Table 2, the maximum expansion and expansion of OPC after 28 days differ from those of K07, K10, and K13, but the difference between the maximum expansion and the 28-day expansion (i.e., ε2) is similar for OPC, K07, K10, and K13. Experimentally, ε2 is found to be approximately 1531 με for OPC-based SDMCC and 605 με for LC3-based SDMCC. Therefore, for OPC-based SDMCC, the maximum expansion ε1 = ε2 / k required to obtain the desired coupling effect is preferably at least 3062 με (1531 / 0.5). The maximum expansion of LC3-based SDMCC is preferably at least 1210 με (605 / 0.5).

[0136] 3.3 Maximum Allowable Expansion

[0144] As described above, the expansion of SDMCC is desirable, but excessive expansion should be avoided because it may cause damage to the host pipe. According to the elastic theory of steel rings (Hossain A B, Weiss J. Assessing residual stress development and stress relaxation in restrained concrete ring specimens. Cement and Concrete Composites, 2004, 26(5): 531-540), the elastic pressure generated by SDMCC on the host pipe can be expressed as Equation (3), and the maximum elastic stress of the host pipe can be calculated by Equation (4):

Equation

Equation

[0137]

[0145] Equations (3) to (7) show that the maximum tensile strength of the host pipe is affected by the thickness of the SDMCC, the inner diameter (ID) of the host pipe, the expansion of the SDMCC, and the mechanical properties of the material. C40 concrete pipes with different diameters [ID = 48 inches (1219 mm), 60 inches (1524 mm), and 90 inches (2286 mm)] were used as examples. The tensile strength was 5 MPa and the modulus of elasticity was 40 GPa. The average modulus of elasticity of the SDMCC during zero time and maximum expansion time was assumed to be 5 GPa. The Poisson's ratio of the host pipe and SDMCC was assumed to be 0.18. Assuming that the relaxation stress during the early period (0-3 days) is 0.5 of the total stress, the maximum allowable expansion can be calculated using equations (3) to (7) under the condition that the maximum allowable tensile stress in the host pipe is half the tensile strength (2.5 MPa).

[0138]

[0146] Figure 4 plots the maximum allowable expansion of SDMCC for repairing C40 concrete pipes, and their characteristic values ​​are listed in Table 3. The tensile stress in the host pipe increased with the SDMCC thickness. For a 48-inch (1219 mm) host pipe repaired with 1.5-inch (38 mm) thick SDMCC, the maximum allowable expansion was 3375 με, which is smaller than the maximum value for K13 (3756 με). Therefore, when used to repair a 48-inch (1219 mm) pipe, the thickness of K13 should not exceed 1 inch (25 mm). When repairing pipes of larger diameter, the thickness could be increased. For example, when repairing a 90-inch (2286 mm) pipe with 2-inch (51 mm) thick SDMCC, the maximum allowable expansion was 4450 με.

[0139]

[0147] Pipelines are typically buried underground with sealing pressure. This sealing pressure reduces the tensile stress on the host pipe caused by the expansion of SDMCC. Assuming a sealing pressure of 0.3 MPa, as shown in Table 3, the maximum allowable expansion is significantly increased compared to pipes without sealing pressure.

[0140]

[0148] If sealing pressure is present, K13 can also be used to repair a 48-inch (1219mm) pipeline with 2-inch (51mm) thick SDMCC. While not wishing to be constrained by theory, the inventors propose maximum allowable expansion of SDMCC of 3000 με and 4000 με for repairing pipes without sealing pressure and pipes with sealing pressure, respectively.

[0141] [Table 3]

[0142] 3.4 Constrained expansion test using steel rings

[0149] Concrete was poured into the annular area surrounding the steel ring in accordance with the confined shrinkage test method ASTM C1581 / C1581M-18a. The strain caused by the shrinkage of the concrete and the resulting pressure on the steel ring was monitored and used to calculate the interfacial pressure.

[0143]

[0150] This expanded steel ring test method was based on ASTM C 1581 / C 1581-18a, but differed in that instead of the hollow ring used in the constraint test, K13 or LC3-K13 was integrally cast inside a steel ring with an outer diameter of 405 mm and an inner diameter of 385 mm. The expansion of K13 or LC3-K13 applied pressure to the steel ring, and the resulting strain of the steel ring was monitored with three strain gauges, starting 5 hours after casting.

[0144]

[0151] Figure 5 plots the average of the three strain gauges. Similar to the drying expansion described in Section 3.1, the constrained expansion also increased initially and then decreased. As shown in Figures 1 and 2, the maximum drying expansion occurred between 2 and 3 days. However, due to creep and relaxation, the maximum constrained expansion occurred around day 1 after casting. The maximum expansion was 123 με for K13 and 104 με for LC3-K13, then decreased to 6 με for K13 and 56 με for LC3-K13 by day 28. The decrease in expansion for LC3-K13 was less than that for K13, indicating that LC3-K13 can achieve a better coupling effect than K13.

[0145]

[0152] The residual interfacial pressure between the steel ring and K13 / LC3-K13 is given by equation (8):

number

[0146]

[0153] Figure 6 plots the residual interface pressure calculated by equation (8). After 1 day, the maximum pressure in K13 was 1.18 MPa, and the maximum pressure in LC3-K13 was 1.00 MPa. After 28 days, the pressure in K13 was only 0.06 MPa, almost 0 MPa, while the pressure in LC3-K13 was 0.54 MPa.

[0147]

[0154] Compared to conventional repair materials, SDMCC (K13 or LC3-K13) is designed to apply pressure to the host pipe. The experimental data presented herein demonstrate this concept. While we do not wish to be constrained by theory, it is believed that this pressure improves the coupling between the host pipe and the SDMCC, mitigating or eliminating problems of buckling and delamination due to insufficient adhesion. Surprisingly, the inventors have found that LC3 may exhibit less expansion over time than OPC, resulting in the maintenance of pressure applied to the outer pipe. This coupling is achieved by mechanical friction, which, although not adhesive, increases the normal (radial) pressure acting on the host pipe by the SDMCC.

[0148] 4. Tensile properties

[0155] For tensile testing, specimens were cast into a dog bone-shaped mold (for the shape of the dog bone, see Felekoglu, B., et al, Influence of matrix flowability, fiber mixing procedure, and curing conditions on the mechanical performance of HTPP-ECC Composites Part B: Engineering, 2014, 60, 359-370). Uniaxial tensile testing was performed using an Instron servo hydraulic tester at a speed of 0.5 mm / min under displacement control. Strain was measured using two linear variable displacement (LVDT) gauges with a gauge length of 80 mm. The average crack width was calculated by dividing the displacement by the number of cracks. The tensile results listed in Table 2 are the average values ​​of three specimens over 28 days.

[0149]

[0156] Figure 7 shows the tensile stress and stress curve plots for SDMCC in Table 1. The ultimate tensile strength and tensile strain capacity of OPC were 3.41 MPa and 3.69%, respectively. For SDMCC mixed with CSA-K, the ultimate tensile strengths were 3.67 MPa, 3.62 MPa, and 3.85 MPa for K07, K10, and K13, respectively. The inclusion of CSA-K increased the ultimate tensile strength. The tensile strain capacity was 4.79%, 5.17%, and 5.04% for K07, K10, and K13, respectively, each of which was greater than that of OPC. The average crack width was approximately 60 μm, 80 μm, and 90 μm for strains of 1%, 2%, and 3%, respectively. The crack width of SDMCC prepared with CSA-K was smaller than that of OPC. The tensile strain capacity and crack width of LC3-K10 and LC3-K13 were equivalent to those of SDMCC prepared using OPC. However, the ultimate tensile strength was less than 3 MPa. Although lower strength was obtained with LC3, SDMCC prepared using LC3 had a higher strain capacity and required less cement. Such SDMCC can advantageously have good durability, lower cost, and be more environmentally friendly than that prepared using OPC. The durability and permeability of SDMCC are discussed further below.

[0150]

[0157] SDMCC can develop microcrack damage under external load, but the material can self-heal, which can be improved under the wet-and-dry environmental conditions commonly found inside pipelines. After 28 days of curing, the specimens were intentionally damaged by inducing pre-cracking to 1% and 2% stress. Subsequently, the specimens were exposed to seven wet-and-dry cycles. Figure 8 plots the strength and strain capacity results after self-healing. Although pre-cracking was induced in the specimens, the tensile strength of the self-healed specimens was higher in all cases than that of the unused specimens. SDMCC prepared with LC3 cement showed higher strain capacity than that prepared with OPC, indicating that SDMCC prepared with LC3 has equivalent or even better self-healing performance.

[0151]

[0158] After 28 days of curing, prior to the permeability test, pre-cracking was induced in the specimens up to 1% and 2% strain, following the procedure in Liu, H., et al., “Influence of micro-cracking on the permeability of Engineered Cementitious Composites”, Cement and Concrete Composites, 2016, 72, 104-113. Figure 10 shows the permeability coefficient results after 14 days. As expected, the permeability coefficient increases with crack width. The permeability of SDMCC (LC3-K13) is lower than that of SDMCC (OPC) due to its dense crack width pattern. The permeability coefficient of SDMCC is almost two orders of magnitude lower than that of conventional reinforced mortar with the same pre-cracking strain (crack width > 150 μm). This low permeability of SDMCC will significantly improve the service life performance of pipelines and prevent leaks. Even under a 2% pre-crack strain, the low transmittance is expected to reduce the risk of, for example, a decrease in drinking water supply or groundwater contamination after an earthquake.

[0152] 5. Pipe Improvement Test

[0159] To demonstrate the improvement capabilities of SDMCC, a pipe failure test was performed in accordance with ASTM C497M-19a. Figure 10 shows cross-sections of the pipe before and after repair with SDMCC (LC3-K13). The thickness of the SDMCC repair layer shown in Figure 10 is merely an example. Those skilled in the art will recognize that the actual thickness of the SDMCC can be selected according to the mechanical and functional requirements of the individual application. The length of the pipe was 36 inches (914 mm). The original concrete pipe was mixed with 500 g / L of OPC, 1200 g / L of river sand, 200 g / L of water, and 6 g / L of water-reducing agent. The SDMCC mixture was the same as LC3-K13 in Table 1. Seven days after concrete pouring, the concrete and kraft pipe were placed in a water tank. Three hours after immersion in water, the kraft pipe was removed from the mold, and then SDMCC (LC3-K13) was poured.

[0153]

[0160] After curing in air for 28 days, the pipes were cut to an 8-inch (203 mm) length using a diamond saw and used for destructive testing. Destructive testing was performed using concrete pipes and pipes repaired with LC3-K13 that had been pre-cracked. The concrete pipes with pre-cracked defects were used to simulate the effectiveness of repairing cracked pipes with SDMCC.

[0154]

[0161] When the load exceeds the fracture strength, the concrete pipe immediately collapses due to its brittleness. However, pipes that were pre-damaged and repaired with SDMCC were able to withstand the load after microcracks had formed within the concrete pipe. Many microcracks formed within the SDMCC. The cracks initially appeared on the inner surface of the SDMCC, and then more cracks were observed as the load increased. Rather than a single microcrack in the concrete pipe, there were many dense cracks distributed throughout the SDMCC.

[0155]

[0162] This test also demonstrates that buckling, a common problem in pipes repaired using the CIPP method, is eliminated by SDMCC. Buckling typically occurs due to the gap between the repair layer and the host pipe, which is commonly seen in the CIPP method. Due to the expansion properties of SDMCC, it is possible to obtain an SDMCC coating that bonds seamlessly with the host pipe, with little to no gap between them.

[0156]

[0163] Figure 11 plots the results of the fracture strength versus displacement test. Both the fracture strength and displacement capacity of the pipe repaired with LC3-K13 were greater than those of the concrete pipe. This indicates that the improvement of the pipe using SDMCC improves both the strength and displacement capacity of the pipe (also shown in Table 4). Even after peak loading, SDMCC maintains its residual load capacity. When the residual load decreased to 4.89 kN, which is equal to the load capacity of the original intact concrete pipe, the displacement was 3.63 times that of the intact concrete pipe.

[0157] [Table 4]

[0158] 6. Leak test

[0164] Leakage tests were conducted using pipes repaired with SDMCC. After reaching the peak load, the bottom of the cracked SDMCC pipe was sealed with cement on plywood. The system was then filled with water. Despite large cracks in the host concrete pipe and microcracks in the SDMCC, there was no leakage from the system 24 hours after filling with water. The microcracks in the SDMCC extended from the inner surface to the outer pipe. Although not theoretically constrained use, it is thought that multiple dense cracks acted like plastic hinges, redistributing the stress. The microcracks did not propagate to larger cracks, and no localized cracks occurred in the SDMCC. As a result, no leakage was present, even after reaching the peak load.

[0159]

[0165] The present invention is not intended to limit its scope to the embodiments described above. As will be apparent to those skilled in the art, many modifications are possible without departing from the scope of the invention as described in the appended claims.

Claims

1. A spray-applied cement-based composition comprising a composite binder, fibers, and water, wherein the composite binder comprises a cement component and a pozzolanic component, the cement component comprises hydraulic cement, a reactive aluminosilicate, calcium carbonate, and an expander, and the amount of the expander is approximately 32 to approximately 60% by weight based on the total weight of the cement component. The sprayed cement-based composition, upon hardening, achieves a maximum expansion of at least about 1210 με, its expansion after 28 days exceeds 50% of the maximum expansion, and it has a tensile strain capacity of at least about 3% after 28 days. A spray-applied cement-based composition.

2. The spray cement-based composition according to claim 1, wherein the ratio of water to composite binder is about 0.2 to about 0.

5.

3. The spray cement composition according to claim 1, wherein the expanding agent is calcium sulfoaluminate.

4. The spray cement composition according to any one of claims 1 to 3, wherein the amount of the expansive agent is about 32 to about 50% by weight, based on the total weight of the cement components.

5. The spray cement composition according to any one of claims 1 to 4, wherein the hydraulic cement comprises ordinary Portland cement.

6. The spray cement composition according to any one of claims 1 to 5, wherein the amount of the hydraulic cement is about 1 to about 80% by weight, based on the total weight of the cement components.

7. The spray cement-based composition according to any one of claims 1 to 6, wherein the reactive aluminosilicate is calcined clay.

8. The spray cement-based composition according to any one of claims 1 to 7, wherein the calcium carbonate is limestone.

9. A spray-applied cement-based composition according to any one of claims 1 to 8, wherein the amount of the pozzolanic component is about 1 to about 3 times the amount of the cement component, based on weight.

10. The spray cement composition according to any one of claims 1 to 9, wherein the pozzolanic component comprises a material selected from the group consisting of fly ash, steelmaking slag, granular blast furnace slag, calcined clay such as diatomaceous earth, silica fume, and metakaolin, calcined silica-rich organic matter such as calcined shale, volcanic ash, pumice, and rice husk ash, and mixtures of any two or more thereof.

11. The spray cement composition according to claim 10, wherein the fly ash is selected from the group consisting of type C fly ash, type F fly ash, and mixtures thereof.

12. The spray cement composition according to any one of claims 1 to 11, wherein the fiber is selected from the group consisting of polymer fibers, inorganic fibers, metal fibers, carbon fibers, plant fibers, and mixtures of two or more thereof.

13. The spray cement composition according to claim 12, wherein the polymer fiber comprises a polymer material selected from the group consisting of polyolefins, polyacrylics, polyesters, polyvinyl alcohols, polyamides, and combinations of two or more thereof.

14. The spray cement composition according to claim 12 or 13, wherein the polymer fibers are selected from the group consisting of polyethylene fibers, high-tenacity polypropylene fibers, polyvinyl alcohol fibers, and mixtures of two or more thereof.

15. The spray cement composition according to any one of claims 1 to 14, wherein the spray cement composition further comprises one or more components selected from the group consisting of a fluidizer, aggregate, viscosity agent, and retarder.

16. When the sprayed cement composition hardens: (i) Tensile strength of at least about 2.50 MPa, (ii) Crack width less than approximately 100 μm at ε < 2%, and A spray cement-based composition according to any one of claims 1 to 15, wherein one or more properties selected from the group consisting of the above are realized.

17. A method for preparing a spray cement-based composition according to any one of claims 1 to 16, (i) To provide a binder composition containing cement components and pozzolanic components, (ii) Mixing the binder composition with water to form a wet mixture, (iii) Adding fibers to the wet mixture, A method comprising, wherein the cement components include hydraulic cement, reactive aluminosilicate, calcium carbonate, and an expander, and the amount of the expander is approximately 32 to approximately 60% by weight based on the total weight of the cement components.

18. The method according to claim 17, further comprising mixing the cement component and the pozzolanic component to provide the binder composition.

19. The method according to claim 17 or 18, wherein a fluidizing agent is added to the water before step (ii).

20. A method for repairing and / or improving a building structure, (i) the step of providing a spray cement composition according to any one of claims 1 to 16; (ii) spraying the cement-based composition onto the surface of the building structure to at least partially cover the surface with the cement-based composition; (iii) The step of setting the cement-based composition on the surface, Methods that include...

21. The method according to claim 20, wherein the spraying step (ii) is performed by a manual spraying system or an automatic spraying system.

22. The method according to claim 20 or 21, wherein the building structure is a pipeline.

23. The method according to claim 22, wherein the surface is the inner surface of the pipeline.

24. The method according to claim 22 or 23, wherein the pipeline is improved for increasing the lifespan of the pipeline, increasing the load-bearing capacity of the pipeline, and / or strengthening the pipeline.

25. Use of the spray cement composition according to any one of claims 1 to 16 for the repair and / or improvement of building structures.

26. The use according to claim 25, wherein the aforementioned building structure is a pipeline.

27. A dry premix for preparing a spray cement composition according to any one of claims 1 to 16, wherein the dry premix comprises a composite binder and fibers, the composite binder comprises a cement component and a pozzolanic component, and the cement component comprises a hydraulic cement, a reactive aluminosilicate, calcium carbonate, and an expander.

28. A method for preparing a spray cement-based composition according to any one of claims 1 to 16: (i) To provide the dried premix described in claim 27, (ii) Mixing the dried premix with water to form the spray cement composition, Methods that include...

29. The spray cement composition according to any one of claims 1 to 16, wherein the amount of the pozzolanic component is about 2 to about 2.5 times the amount of the cement component by weight.

30. The method according to claim 22, wherein the cement-based composition generates an expansion force on the inner surface of the pipeline.

31. The method according to claim 30, wherein the cement-based composition is bonded to the inner surface of the pipeline.

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