CN115038676A

CN115038676A - Sprayable cementitious compositions

Info

Publication number: CN115038676A
Application number: CN202080094989.0A
Authority: CN
Inventors: 李志辉; 苏仲维; 朱贺
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-02-18
Filing date: 2020-05-14
Publication date: 2022-09-09
Also published as: TW202138334A; AU2020430725A1; TWM628911U; MX2022009511A; WO2021167635A1; JP2023513865A; AU2020430725B2

Abstract

A sprayable ductile metal-like cementitious composition (SDMCC) comprising: composite binder, fiber and water; wherein the composite binder comprises a cement component and a leucite fly ash component. The SDMCC exhibits swelling and strain hardening behavior upon curing. The SDMCC is useful for repairing and/or renovating building structures such as pipelines. Methods for preparing the SDMCC are also described.

Description

Sprayable cementitious compositions

Technical Field

The present invention relates to sprayable ductile metal-like cementitious compositions (SDMCC). The invention also relates to the use of SDMCC for repairing or renovating building structures such as underground pipelines and methods of using the same.

Background

Underground pipelines are an important infrastructure and can be used to transport and distribute water for a variety of purposes, including drinking water and waste water. Pipelines used for these purposes are often subjected to heavy mechanical loads and environmental stresses. Therefore, both metal pipes and concrete pipes are prone to problems such as cracking, flaking and debris accumulation. The metal pipe may corrode or deform. These problems may lead to pipeline failures if not repaired.

Trenchless pipeline rehabilitation is a technique that can be used to rehabilitate existing pipelines with minimal damage. Reduced construction costs, reduced environmental impact and reduced public interference mean that trenchless pipeline rehabilitation techniques are often preferred over trenching. Known trenchless pipeline rehabilitation methods include Cured In Place Pipe (CIPP) methods, slip liners, tight-fit pipe methods, spiral wound liners, segment splice liners, and spray liners. Spray liners with cement-based materials may provide advantages such as lower cost and faster construction compared to other methods. A continuous jointless spray liner may also be formed.

The spray-on lining method involves spraying a cementitious or polymer-based material onto the interior surface of an existing pipeline. Cementitious materials are low cost, but generally have poor corrosion protection for steel host pipes. Polymer-based materials generally have better corrosion resistance, but are more expensive. Once sprayed onto a substrate, the material must have good adhesion and cohesion to build up the desired thickness. The inner surface of the pipeline is generally not conducive to coating materials. Although the pipeline is typically cleaned prior to spraying, the lack of adhesion between the sprayed material and the inner pipe wall remains a major challenge.

Conventional cementitious materials are brittle and do not have tensile ductility. In order to obtain a high strength and dense microstructure, cementitious repair materials typically contain large amounts of fine and reactive powders and require low water content. This combination results in a high degree of shrinkage of the cementitious material, which can cause shrinkage cracking to be limited. After fracturing, the fluid in the pipeline penetrates the fracture and further corrodes the pipe. In addition, if the adhesion is poor, the broken repair material may peel off. Thus, the use of conventional cementitious materials often makes the repaired pipeline less durable and requires repeated maintenance.

To overcome the inherent brittleness of cement-based materials, fiber-reinforced composites known as Engineered Cementitious Composites (ECC) have been developed for spray repair. ECC exhibits a high strain capacity of greater than 3% under uniaxial tension. The high ductility of ECC is achieved by multiple tight cracks instead of a single crack typical of ordinary concrete. However, ECC mixtures typically have higher volume cement and no coarse aggregate when compared to ordinary concrete, so the drying shrinkage can reach-1500 μ epsilon at 28 days. When deformation is limited, the enhanced shrinkage may result in micro-fracturing. The presence of microcracks in an aggressive environment may affect the durability of spray repair. Examples of ECC are disclosed in the following patents.

Us patent No. 7,241,338 discloses sprayable cementitious compositions comprising hydraulic cement, such as Portland cement (Portland cement), non-newtonian additives, adhesives, superplasticizers, discontinuous short fibers, lightweight aggregate, and water.

U.S. patent No. 7,572,501 discloses cementitious composites comprising cement (such as portland cement), water, sand, fly ash, water reducing agents, and discontinuous short fibers (such as Polyethylene (PE) fibers). The rheology of the composition can be adjusted to provide a composite that can be pumped, cast, or sprayed.

U.S. Pat. No. 7,799,127 discloses a polyvinyl alcohol (PVA) fiber reinforced high early strength ECC material. The material comprises hydraulic cement, a mixture of chemical accelerators, polyvinyl alcohol fibres, a non-matrix interactive rupture initiator, one or more fine-grained aggregates and a mixture of chemical dispersants.

It is an object of the present invention to avoid the above drawbacks to some extent; and/or at least to provide the public with a useful choice.

Other objects of the invention will become apparent from the following description which is given by way of example only.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date.

Disclosure of Invention

In a first aspect, the present invention provides a sprayable cementitious composition comprising: composite binder, fiber and water; wherein the composite binder comprises a cement component and a puzzolan fly ash component.

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

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

In some embodiments, the ratio of water to composite binder is about 0.3.

In some embodiments, the cement component comprises a hydraulic cement and an expansion agent.

In some embodiments, the swelling agent is calcium sulfoaluminate.

In some embodiments, the amount of swelling agent is from about 10 wt% to about 60 wt%, based on the total cement component weight.

In some embodiments, the amount of swelling agent is from about 20 wt% to about 50 wt%, based on the total cement component weight.

In some embodiments, the average particle size of the bulking agent is from about 2 μm to about 500 μm or from about 10 μm to about 30 μm.

In some embodiments, the hydraulic cement comprises ordinary portland cement.

In some embodiments, the amount of hydraulic cement is from about 1 wt% to about 80 wt%, based on the total cement component weight.

In some embodiments, the amount of hydraulic cement is from about 20 wt% to about 80 wt%, based on the total cement component weight.

In some embodiments, the amount of hydraulic cement is from about 50 wt% to about 80 wt%, based on the total cement component weight.

In some embodiments, the amount of hydraulic cement is from about 60 wt% to about 80 wt%, based on the total cement component weight.

In some embodiments, the cement component comprises a reactive aluminosilicate, a calcium carbonate, or a mixture thereof.

In some embodiments, the reactive aluminosilicate is a calcined clay.

In some embodiments, the reactive aluminosilicate is metakaolin.

In some embodiments, the calcium carbonate is limestone.

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

In some embodiments, the cement component comprises the reactive aluminosilicate in an amount of from 0 wt% to about 50 wt%, or from about 20 wt% to about 40 wt%, or about 30 wt%, based on the total cement component weight.

In some embodiments, the cement component comprises calcium carbonate in an amount from about 0 wt% to about 30 wt%, or from about 10 wt% to about 20 wt%, or about 15 wt%, based on the total cement component weight.

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

In some embodiments, the cementitious component comprises about 10 wt% to about 50 wt% Ordinary Portland Cement (OPC), about 20 wt% to about 40 wt% metakaolin, and about 10 wt% to about 20 wt% limestone, based on the total cementitious mixture weight.

In some embodiments, the reactive aluminosilicate has an average particle size of from about 2 μm to about 40 μm or from about 2 μm to about 10 μm.

In some embodiments, the calcium carbonate has an average particle size of from about 2 μm to about 100 μm or from about 2 μm to about 20 μm.

In some embodiments, the leucite fly ash component is in an amount from about 1 to about 3 times the amount of the cement component by weight.

In some embodiments, the leucite fly ash component is in an amount from about 2 times to about 3 times the amount of the cement component by weight.

In some embodiments, the leucite fly ash component is in an amount from about 2 times to about 2.5 times the amount of the cement component by weight.

In some embodiments, the leucite fly ash component comprises a material selected from the group consisting of: fly ash, steel slag, granulated blast furnace slag, diatomaceous earth, silica fume, calcined clays such as metakaolin, calcined shale, volcanic ash, pumice, silica-fired organic materials such as rice hull ash, and mixtures of any two or more thereof.

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

In some embodiments, the fibers are selected from the group consisting of: polymeric fibers, inorganic fibers, metal fibers, carbon fibers, plant-based fibers, and mixtures of any two or more thereof.

In some embodiments, the polymeric fiber comprises a polymeric material selected from the group consisting of: polyolefins, polyacrylic acids, polyesters, polyvinyl alcohols, polyamides, and combinations of any two or more thereof.

In some embodiments, the polymeric fiber is selected from the group consisting of: polyethylene fibers, high tenacity polypropylene fibers, polyvinyl alcohol fibers, and mixtures of any two or more thereof.

In some embodiments, the amount of fiber is from about 0.1 v/v% to less than 4 v/v% or from about 1 v/v% to about 3 v/v% or from about 1.5 v/v% 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 fibers have a length of about 4mm to about 25mm or about 6mm to about 20mm or about 8mm to about 12 mm.

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

In some embodiments, the sprayable cementitious composition further comprises one or more components selected from the group consisting of: a superplasticizer, aggregate, a viscosity agent and a retarder.

In some embodiments, the amount of superplasticizer is from about 0.1 wt% to 10 wt%, or from about 0.3 wt% to about 3 wt%, or from about 0.5 wt% to about 1.5 wt%, based on the total composition weight.

In another aspect, the present invention provides a sprayable cementitious composition comprising: composite binder, fiber and water; wherein the composite binder comprises a cement component and a leucite fly ash component, and wherein the sprayable cementitious composition, when cured, achieves one or more characteristics selected from the group consisting of:

(i) a tensile strength of at least about 2.50MPa,

(ii) a tensile strain capacity of at least about 3% at 28 days,

(iii) a crack width at < 2% ε of less than about 100 μm, an

(iv) A maximum expansion of at least about 1210 mu epsilon.

In yet another aspect, the present invention provides a method of preparing a sprayable cementitious composition, the method comprising:

(i) providing a binder composition comprising a cement component and a leucite fly ash component,

(ii) mixing the binder composition with water to form a wet mixture,

(iii) fibers are added to the wet mixture.

In some embodiments, the method further comprises mixing the cement component and the leucite fly ash component to obtain the binder composition.

In some embodiments, a superplasticizer is added to the water prior to step (ii).

In yet another aspect, the present invention provides a method of repairing and/or renovating a building structure, the method comprising the steps of:

(i) providing a sprayable cementitious composition of the present invention;

(ii) spraying a cementitious composition on a surface of the building structure to at least partially coat the surface with the cementitious composition; and

(iii) allowing the cementitious composition to set on the surface.

In some embodiments, the spraying step (ii) is performed by a manual spray system or an automated spray system.

In some embodiments, the building structure is a pipeline.

In some embodiments, the surface is an inner surface of a pipeline.

In some embodiments, the pipeline is trimmed to extend the life of the pipeline, increase the load bearing capacity of the pipeline, and/or strengthen the pipeline.

In another aspect, the present invention provides the use of the sprayable cementitious composition of the present invention for repairing and/or renovating a building structure.

In some embodiments, the building structure is a pipeline.

In another aspect, the present invention provides a dry premix for use in preparing the sprayable cementitious composition of the present invention, the dry premix comprising a composite binder and fibers; wherein the composite binder comprises a cement component and a leucite fly ash component.

In another aspect, the present invention provides a method of preparing the sprayable cementitious composition of the present invention, the method comprising:

(i) providing a dry pre-mix according to the invention,

(ii) the dry premix is mixed with water to form a sprayable cementitious composition.

The invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which the invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

Additionally, where features or aspects of the invention are described in terms of Markush groups (Markush groups), those skilled in the art will appreciate that the invention is also thereby described in terms of any individual member or subgroup of members of the Markush group.

As used herein, "following" a noun means the plural and/or singular form of the noun.

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

As used in this specification, the term "comprising" means "consisting at least in part of … …". When interpreting statements in this specification which include the term "comprising", features other than one or more of the features prefaced by the term may also be present. Related terms such as "comprise/comprise" are to be interpreted in the same way.

It is intended that reference to a range of values (e.g., 1 to 10) disclosed herein also includes reference to all reasonable values within that range (e.g., 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9, and 10) and any range of reasonable values within that range (e.g., 2 to 8, 1.5 to 5.5, and 3.1 to 4.7), and therefore all sub-ranges of all ranges explicitly disclosed herein are explicitly disclosed. These are merely examples of what is specifically intended, and all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this application in a similar manner.

While the invention is broadly as defined above, it will be understood by those skilled in the art that the invention is not so limited and that the invention also includes embodiments of the examples given in the description below.

Drawings

The invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 shows the shrinkage/expansion of SDMCC prepared with OPC and CSA-K cements (where CSA-K accounts for 7 wt%, 10 wt% and 13 wt% of the composite binder, respectively);

FIG. 2 shows the shrinkage/expansion of SDMCC prepared with OPC and LC3/CSA-K cements (where CSA-K is 10 wt% and 13 wt% of the composite binder, respectively);

FIG. 3 shows the shrinkage/expansion of SDMCC prepared with CSA-R cement (where anhydrite comprises 0, 10, 15, and 20 weight percent of CSA-R, respectively);

FIG. 4 depicts the maximum allowable expansion of SDMCC for repairing C40 concrete pipes;

FIG. 5 shows the steel ring average strain measured by 3 strain gauges for SDMCC prepared with LC3/CSA-K cement and CSA-K cement (where CSA-K is 13 wt% of the composite binder);

FIG. 6 depicts the residual interface pressure between the steel ring and SDMCC prepared with LC3/CSA-K cement and CSA-K cement (where CSA-K is 13 wt% of the composite binder);

FIG. 7 depicts the 28-day tensile stress-strain behavior of the compositions shown in FIGS. 1 and 2;

FIG. 8 shows the self-healing of ultimate tensile strength and strain capacity after 7 wet-dry cycles for SDMCC prepared with OPC, LC3 and LC3/CSA-K cement;

FIG. 9 shows permeability coefficients tested at day 14 for SDMCC prepared with OPC and LC3/CSA-K cement after pre-fracturing of the test specimen at day 28;

FIG. 10 shows a pipeline rehabilitation protocol cast with kraft paper pipe; and

figure 11 shows the relationship between peak load and displacement for concrete pipes and pipes repaired with SDMCC.

Detailed Description

The inventors have unexpectedly discovered SDMCC which has advantageous properties compared to conventional cements and concretes. For example, SDMCC may exhibit swelling and strain hardening behavior upon curing.

Accordingly, in one aspect, the invention provides an SDMCC comprising: composite binder, fiber and water; wherein the composite binder comprises a cement component and a leucite fly ash component. Sprayable cementitious compositions are useful, for example, for repairing and/or finishing pipelines.

The cement component comprises hydraulic cement and may further comprise additional materials such as an expanding agent, a reactive aluminosilicate, and/or calcium carbonate.

The SDMCC may further comprise other components such as superplasticizers, aggregates, and/or other additives.

Hydraulic cement

Hydraulic cement is a material that sets and hardens when mixed with water. Hydraulic cements include, but are not limited to, portland cement, blended portland cement, phosphate cement, and belite cement (dicalcium silicate). Mixtures of any two or more thereof are also contemplated. Preferably, the hydraulic cement is portland cement.

Portland cement is a finely ground powder produced by grinding clinker consisting essentially of hydraulic calcium silicates. The cement may contain up to about 5% gypsum. The amount of gypsum present affects the setting time. The ASTM C150 portland cement standard specification defines portland cement standards that define 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 common Ordinary Portland Cement (OPC) suitable for all applications that does not require other types of special properties. Type III cement is chemically and physically similar to type I cement, except that it is more finely ground to produce higher early strength.

The cement component may comprise hydraulic cement in an amount of from about 1 wt% to about 80 wt%, or from about 20 wt% to about 80 wt%, or from about 50 wt% to about 80 wt%, or from about 60 wt% to about 80 wt%, based on the total cement component weight.

In some embodiments, the cementitious component comprises a reactive aluminosilicate such as calcined clay and/or a calcium carbonate such as limestone. Advantageously, the replacement of a portion of the hydraulic cement with the reactive aluminosilicate and/or calcium carbonate provides a more environmentally friendly composition by reducing the amount of carbon released during the manufacturing process.

SDMCC comprising reactive aluminosilicates and/or calcium carbonate can provide other advantages. For example, limestone calcined clay cement (LC3) slurries have been found to have a finer pore structure than slurries made with OPC. Advantageously, pore refining provides excellent resistance to chloride ingress, which is particularly important for the complex environment in pipelines, and good efficacy in the presence of sulfates.

Additionally, it has been unexpectedly found that the SDMCC comprising LC3 has a greater strain capacity and smaller crack width than the ECC prepared with OPC of the prior art. The reduced fracture width results in lower permeability. Such a situation may, for example, prevent the original pipe from being corroded by the fluid. A larger strain capacity SDMCC is expected to have greater deformability. Such a situation may, for example, result in a repaired pipe with higher load and deflection capacity.

The cementitious mixture may comprise the reactive aluminosilicate, calcium carbonate, or mixture thereof in an amount of from about 1 wt% to about 80 wt%, or from about 30 wt% to about 60 wt%, or from about 40 wt% to 50 wt%, based on the total cementitious component weight. For example, the cement component may comprise the reactive aluminosilicate in an amount of from 0 wt% to about 50 wt%, or from about 20 wt% to about 40 wt%, or about 30 wt%, based on the total cement component weight. For example, the cement component may comprise calcium carbonate in an amount of from about 0 wt% to about 30 wt%, or from about 10 wt% to about 20 wt%, or about 15 wt%, based on the total cement component weight. In some embodiments, the ratio of reactive aluminosilicate to calcium carbonate is 2: 1.

In some embodiments, the reactive aluminosilicate has an average particle size of from about 2 μm to about 40 μm or from about 2 μm to about 10 μm. In some embodiments, the calcium carbonate has an average particle size of from about 2 μm to about 100 μm or from about 2 μm to about 20 μm.

In some embodiments, the cementitious component comprises about 10 wt% to about 50 wt% OPC, about 20 wt% to about 40 wt% metakaolin, and about 10 wt% to about 20 wt% limestone based on the total cementitious mixture weight.

In some embodiments, a portion of the hydraulic cement may be displaced by the mining tailings. For example, the cement component may comprise the mine tailings in an amount of about 1 wt% to about 30 wt%, based on the total cement component weight.

Expanding agent

The swelling agent is a material that enhances the swelling of the SDMCC during the hydration process. In some embodiments, a swelling agent may be used to reduce shrinkage that occurs during curing of the composition. In other embodiments, a swelling agent may be used to provide SDMCC that swells during curing. Advantageously, enhancing SDMCC expansion may reduce the risk of rupture occurring during contraction.

The swelling agent may be used to tailor the swelling characteristics of the SDMCC such that the SDMCC exerts a swelling force on the pipeline internal surface when applied to the pipeline internal surface and cured. The expansive force reduces any space between the SDMCC and the interior surface and increases the mechanical friction therebetween. Advantageously, the increased mechanical friction may increase adhesion between the SDMCC and the interior surface. Thus, the repaired or refurbished pipeline may have higher load and deflection capacity than the original parent pipe. In addition, the increased adhesion may reduce release of the SDMCC from the surface and wrinkles and even buckling of the repair layer during post-repair service. The controlled expansion force exerted by the SDMCC on the host tubular may cause the repair layer to bond with the host tubular wall and cause a combined structural and functional repair, rather than just a functional repair, such as repairing a water leak. However, those skilled in the art will appreciate that in some embodiments, over-expansion should be avoided as it may result in deformation of the surface to which the SDMCC is applied or even host tube damage.

In addition to the pressure applied to the pipeline, the swelling characteristics also distinguish SDMCC from known sprayable ECCs, which typically have a large dry shrinkage of about-1500 μ ε after 28 days. The expanding SDMCC reduces the risk of limited shrinkage cracking, further improves the durability of the repaired pipeline, and reduces the risk of leakage after repair.

Those skilled in the art will appreciate that the preferred expansion characteristics of the SDMCC depend on various factors such as the diameter and tensile strength of the host pipe to be repaired or reconditioned (whether or not the host pipe is under ambient pressure) and the desired thickness of the SDMCC. In some embodiments, the SDMCC expands to at least about 1200 mu epsilon. In some other embodiments, the SDMCC expands at least about 3000 mu epsilon. The maximum SDMCC expansion may be, for example, about 3000. mu. epsilon., about 3375. mu. epsilon., about 4000. mu. epsilon. or about 4450. mu. epsilon.

Preferred expansion agents include Calcium Aluminate Cement (CAC) and calcium sulfoaluminate Cement (CSA). Preferably, the bulking agent is CSA. CaSO in CSA based on weight of CSA ₄ ·nH ₂ The amount of O is preferably from about 1 wt% to 50 wt%, where n can be 0, 0.5, 1 or 2.

The composite binder may comprise the swelling agent in an amount of from about 10 wt% to about 60 wt%, or from about 20 wt% to about 50 wt%, based on the total cement component weight. In some embodiments, the average particle size of the bulking agent is from about 2 μm to about 500 μm or from about 10 μm to about 30 μm.

Pomegranate ash (Pozzolans)

Leucite fly ash is a siliceous or siliceous and aluminous material that is typically provided in finely divided form. Leucite fly ash alone has little or no cementitious character, however, in the presence of water, leucite fly ash reacts with calcium hydroxide released by hydration of hydraulic cement to form calcium silicate hydrate and other cementitious compounds. Advantageously, the leucite fly ash can improve the binder fracture toughness of cementitious materials, leading to higher ductility of cured SDMCC. Leucite fly ash can also be used to adjust the SDMCC rheology. Advantageously, the SDMCC rheology can be adjusted to improve the pumpability and/or sprayability of the composition.

In general, any siliceous or siliceous and aluminous material that reacts with calcium hydroxide in the presence of water may be suitable for use in the binder. Examples of suitable leucite ashes include, but are not limited to, fly ash, steel slag, granulated blast furnace slag, diatomaceous earth, silica fume, calcined clays such as metakaolin, calcined shale, volcanic ash, pumice, silica-rich organic materials such as rice hull ash, and mixtures of any two or more thereof. Preferably, the leucite fly ash component comprises 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.

In some embodiments, the leucite fly ash component comprises silica fume. Advantageously, the silica fume can increase the SDMCC compressive strength and/or improve the fiber/matrix interface bond.

The composite binder may comprise a leucite fly ash component in an amount from about 0 times to about 3 times the weight of the cement component. Preferably, the composite binder comprises the leucite fly ash component in an amount from about 1 to about 3 times, more preferably from about 2 to about 2.5 times the weight of the cement component.

Fiber

The fibers are intended to reinforce the cured SDMCC. Suitable fibers may be selected based on various characteristics of the fiber including desired cost, mechanical properties, physical properties, and bonding properties. The SDMCC properties may be affected by factors such as the length, diameter, chemical composition, stiffness, density and strength of the fibers. The fibers may be selected to transport the load across the fracture when the composite is loaded beyond the elastic stage. Its loading-carrying behavior can be tuned to balance fiber breakage with fiber slippage, i.e., controlled fiber bridging behavior. Excessive fiber fracture or fiber slippage during imposed loads on the composite is undesirable as it can limit composite ductility or result in crack widths that are too large to compromise composite durability. Advantageously, the fibers can improve the strain hardening and tensile ductility of the composite and limit crack width.

Fibers suitable for use in the SDMCC include, but are not limited to, polymeric fibers, inorganic fibers (e.g., basalt and glass fibers), metal fibers (e.g., steel fibers), carbon fibers, plant-based fibers (e.g., cellulosic and lignocellulosic fibers), and mixtures of any two or more thereof. Preferably, the fibers are polymeric fibers, i.e., fibers composed of a polymeric material such as a polyolefin (e.g., polyethylene or polypropylene), polyacrylic acid, polyester, polyvinyl alcohol, polyamide (e.g., nylon), or a combination of any two or more thereof. More preferably, the fibers are polypropylene fibers, more preferably high tenacity polypropylene fibers. In some embodiments, the fibers are discontinuous staple fibers.

The upper fiber concentration value is dictated by pumpability and sprayability requirements, while the lower value is dictated by the ability to provide strain hardening (ductility) behavior relative to brittle or quasi-brittle behavior. For example, the fibers may be present in an amount of from about 0.1 to less than 4 v/v% or from about 1 to about 3 v/v% or from 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 fibers have a length of about 4mm to about 25mm or about 6mm to about 20mm or about 8mm to about 12 mm. In some embodiments, the fiber diameter is from about 10 μm to about 150 μm or from about 10 μm to about 60 μm.

Plastic strengthening agent

In some embodiments, the SDMCC further comprises a superplasticizer, also known as a high amount water reducer. Superplasticizers may be added to the SDMCC to affect the composition rheology. Advantageously, the superplasticizer can reduce the amount of water required to maintain the pumpability and sprayability of the SDMCC.

Therefore, superplasticizers are typically added to the SDMCC in amounts effective to achieve a composition with the desired pumpability and sprayability. One skilled in the art will appreciate that the amount of superplasticizer needed to achieve the desired pumpability and sprayability may depend on other ingredients of the composition, such as the water content of the composition. For example, the superplasticizer may be included in the SDMCC in an amount of about 0.1 wt% to 10 wt%, or about 0.3 wt% to about 3 wt%, or about 0.5 wt% to about 1.5 wt%, based on the total composition weight.

In general, any superplasticizer known in the art is suitable for use in SDMCC. Such superplasticizers include, but are not limited to, sulfonated melamines (e.g., sulfonated melamine formaldehyde condensates), sulfonated naphthalenes (e.g., sulfonated naphthalene formaldehyde condensates), polycarboxylate ethers (e.g., sulfonated melamine formaldehyde condensates)

190) Modified lignosulfonates, and mixtures of any two or more thereof.

Aggregate material

The SDMCC may further comprise aggregates such as sand, millstone and lightweight aggregates. Incorporation of the lightweight aggregate can reduce the SDMCC density. The incorporation of lightweight aggregate may also allow for increased spray thickness, particularly on horizontal top surfaces. If the amount of lightweight aggregate is relatively large, the particle size becomes critical, otherwise strain hardening cannot be achieved. Generally, the average particle size is from about 10 μm to about 1000 μm or from about 10 μm to about 200 μm or from about 30 μm to about 100 μm.

Lightweight aggregates may include, but are not limited to, ground rubber (e.g., from scrap tires), hollow glass spheres, cenospheres, expanded mica, and microballoons (e.g., glass, ceramic, or polymer microballoons).

The SDMCC may further comprise gas bubbles in addition to or in place of the lightweight aggregate. The gas canIntroduced during the treatment of the cementitious composition by physical means such as foaming or aeration. Alternatively, the gas may be chemically induced, for example as hydrogen gas generated by the reaction of aluminum powder with an alkaline composition or the reaction of a Si-H functional silane with water. In some embodiments, a stabilizing substance is added to assist in preventing coalescence of adjoining bubbles. In some embodiments, the volume percent is limited to provide about 1400kg/m ³ Or higher, preferably 1500kg/m ³ Or higher curing density. If large voids exhibit substantial coalescence, the strength properties of the composite material, particularly the strain hardening behavior, may be compromised. The air bubbles can be used in combination with other lightweight aggregates. Advantageously, the volume fraction of bubbles in such formulations can be kept small to minimize coalescence. For example, at a target density of 1300kg/m ³ In the composite of (2), a gas or a gas precursor may be added to obtain about 1600kg/m ³ Or higher density, and other lightweight fillers are added to reduce the density to the target range.

Other additives

The SDMCC may further comprise other additives known in the art such as viscosity agents and/or set retarders.

For example, the adhesive may be a cellulose derivative such as Hydroxypropylmethylcellulose (HPMC). The adhesive may be included in the SDMCC in an amount of about 0 wt% to about 1 wt%, or about 0.03 wt% to about 0.5 wt%, or about 0.05 wt% to about 0.2 wt%, based on the total binder weight (i.e., the weight of the composition excluding water). The adhesive enhances the ability of the composite to build up thickness on the substrate and also helps to uniformly disperse the fibers in the matrix.

The SDMCC may contain a retarder. Conventional set retarders may be used. Preferably, the retarder is citric acid, which is advantageously compatible with CSA use. Retarders may be included in an amount of about 0.01 wt% to about 10 wt%, or about 0.1 wt% to about 2 wt%, or about 0.2 wt% to about 1.5 wt%, based on the total binder weight. The retarder may extend the working time of the SDMCC during the spraying process. However, one skilled in the art will appreciate that excess retarder can reduce the strength and ductility of SDMCC.

Water (W)

The amount of water in the SDMCC affects various properties of the composition. The water content should be sufficient to obtain a pumpable and sprayable composition. In general, higher water content reduces viscosity and improves sprayability, while lower water content increases cohesion and allows thicker applications. The amount of water required to provide a pumpable and sprayable composition can be readily determined by routine experimentation and can be reduced by including a superplasticizer as discussed above.

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

Preparation of cementitious compositions

The SDMCC of the invention can be prepared by conventional techniques. The ingredients may be mixed with water separately or certain ingredients may be pre-mixed. In some embodiments, water is added to a premix of dry binder ingredients to obtain a wet mixture to which fibers are added. In some embodiments, the superplasticizer is mixed with water to form a solution that is added to a premix of the dry binder ingredients to obtain a wet mixture to which the fibers are added. In some other embodiments, the dry ingredients may be provided in a "pre-mix" composition, such as a pre-mix of dry binder ingredients and fibers, that is mixed with water to form the SDMCC prior to use.

Repairing and refurbishing a pipeline

The SDMCC of the invention can be used for repairing pipelines such as gravity pipelines or pressure pipelines, particularly underground gravity pipelines or pressure pipelines. Such pipelines are found in various applications such as water, drain, sewer and oil pipelines. For example, SDMCC is used in a trenchless pipeline rehabilitation method. The method of repairing a pipeline of the present invention is compatible with various pipe geometries, such as pipes having circular or non-circular cross-sections, pipes having narrow or wide diameters, straight or curved pipes.

The inventors have also determined that the SDMCC of the present invention can be used to trim pipelines. In contrast to repair methods which aim to restore the original function of a damaged host pipe, refurbishment refers to a method in which the pipeline properties are enhanced. For example, the pipeline may be trimmed to extend the life of the pipeline, increase the load bearing capacity of the pipeline, and/or strengthen the pipeline. In some embodiments, the pipeline is trimmed for seismic strengthening of the pipeline. For this purpose, SDMCC may be applied to the pipeline to reduce the risk of drinking water or subsurface water leakage or contamination caused by seismic events.

The method of repairing or refurbishing a pipeline of the present invention may prevent common failure modes in pipelines repaired or refurbished by other methods such as CIPP, slip liner or spiral wound liner methods, or spray lining with known materials. Common failure modes that can be avoided include localized buckling, liner or pipeline fracture, water seepage, and liner or pipeline corrosion.

A method of repairing or refurbishing a pipeline includes providing SDMCC in the form of a wet mixture, applying the wet mixture to at least a portion of a pipeline surface, such as an inner wall of the pipeline, and curing the mixture. In some embodiments, the SDMCC is applied to the entire interior surface of the pipeline length. Advantageously, coating the entire inner surface may produce substantially a new inner tube. Continuous spraying of cementitious material along the length of a degraded pipeline can provide an inner coating with a reduced number of joints, and in some embodiments no joints. Joints are often weak points in pipelines, so advantageously, reducing the number of joints in a repaired pipeline can extend the useful life of the pipeline. Pipelines with continuous internal coatings with a reduced number of joints or no joints are also less susceptible to leakage, including in hazardous conditions such as earthquakes.

The cementitious composition may be applied to the pipeline surface by conventional methods. The SDMCC can be applied by a manual spray system or an automated spray system. For example, the SDMCC may be applied manually by pneumatically spraying the composition onto a surface at high speed through a nozzle. Alternatively, the SDMCC may be applied by an automated centrifugal spray system that sprays the material onto the interior surfaces of existing pipelines.

The cementitious composition is in a fluid state during pumping, but sets after spray application to a surface. The setting rate should be fast enough to allow for build-up of thickness against gravitational pull. The SDMCC of the present invention may be about 10mm to about 50mm in thickness when sprayed onto horizontal or vertical surfaces, including the top surface. In some embodiments, the SDMCC is about 20mm to about 40mm thick when sprayed onto a horizontal or vertical surface. In some embodiments, the SDMCC is about 20mm to about 30mm thick when sprayed onto a horizontal or vertical surface.

The SDMCC of the invention can be used for repairing and trimming pipelines. However, it will be appreciated by those skilled in the art that the SDMCC of the present invention may be used to repair and/or refurbish other building structures. In particular, building structures in which one or more of the improved properties described herein are beneficial. Suitable building structures may include tunnels, culverts, manholes, bridges, decks and roads, for example.

The following non-limiting examples are provided to illustrate the present invention and in no way limit its scope.

Examples

1. Material composition and treatment

Exemplary mixtures are listed in table 1. The Cement was portland type I Cement (PC1) from Lafarge Cement co. Two types of expansive cements from CTS ceramic Manufacturing Corp. and Royal White ceramic Inc. are used and are defined as CSA-K and CSA-R, respectively. Metakaolin (MK) is from Sika Corporation, NJ, USA

And M-100. Anhydrite is number 1 Terry-Alba from USG. Limestone (LS) is available from Omya Canada Inc

12-PT. Fly Ash (FA) is a class C fly ash from Boral Material Technologies Inc with a size distribution of 10 μm to 100 μm. The Superplasticizer (SP) is from GCP Applied Technologies

190. Hydroxypropyl methylcellulose (HPMC) adhesive was from Fisher Scientific. The amount of polypropylene (PP) fibres was 2% volume fraction, the diameter 12 μm, the length 10mm, the Young's modulus (Young's module) 6GPa andtensile strength was 850MPa and PP fiber was Brasilit from Saint-Gobain Brazil.

TABLE 1

The nomenclature in table 1 reflects the binder composition. OPC and LC3 refer to binders prepared from ordinary portland cement and limestone calcined clay cement, respectively. K07, K10 and K13 refer to CSA-K to binder ratios of 7 wt%, 10 wt% and 13 wt%. R13-C0, R13-C10, R13-C15 and R13-C20 represent 13 wt% of CSA-R and anhydrite to binder ratio, where the anhydrite ratio is 0 wt%, 10 wt%, 15 wt% and 20 wt% of the total weight of CSA-R and anhydrite. The wt% ratios of PC1, MK and LS in the LC3 cement were 55%, 30% and 15%.

SDMCC is prepared by mixing all dry ingredients (PC1, CSA, anhydrite, MK, LS, FA, and HPMC) in a drum mixer for 10 minutes. Water and SP were added gradually and mixed for 6 minutes. Finally PP fibres were added followed by mixing for 6 minutes.

2. Sprayability of cementitious compositions

The new characteristics of sprayable (often referred to as "jetted") ECC are critical. Sprayable cementitious compositions require high initial deformation for pumping, rapid build-up capability when sprayed onto a substrate, and optimal standing time. The rest time, defined as the time interval from completion of mixing to start of spraying, should be long enough to accommodate the time required for pumping and short enough to achieve the desired bulk thickness at the time of spraying.

The SDMCC composition is identical to LC3-K13 in Table 1 except for different SP content. Compared to prior art sprayed ECC comprising 2 v/v% PVA fibers, the SDMCC of the present invention employs 2 v/v% PP fibers, which are advantageously less costly than PVA fibers. However, at the same dose and fiber length, the number of PP fibers (12 μm) in SDMCC was 10.56 times the number of fibers (39 μm) in the prior art sprayed PVA-ECC. The large number of small diameter fibers requires careful control of the new rheology of the sprayable SDMCC.

The examples described below used a CARROUSEL pump from Quikspray inc. and a multi-jet-pole spray gun for spraying. The multiple air blast pole spray gun is particularly suitable for spraying cementitious materials with reinforcing fibers. The materials were mixed in a Hobart mixer and subsequently pumped through a CARROUSEL pump. After passing through a 1.25 "(31.75 mm) diameter material hose and reaching the multi-jet pole spray gun, the SDMCC was sprayed onto the plywood substrate at 560kPa gas pressure. Spray tests included spraying onto the substrate from both the vertical and top directions.

The optimum superplasticizer content was determined to be 0.8 wt% of the composite binder using a series of flow tests with varying amounts of superplasticizer. For the vertical plywood substrate spray test, the build-up thickness was 15mm after a 20 minute standing time. For a vertical plywood base, the maximum stack thickness may reach 50mm when the standing time is 40 minutes. For the top substrate, the maximum thickness may reach 25mm after a 20 minute rest time.

While the number of fibers in the SDMCC was 10.56 times the number of fibers of the prior art sprayed PVA-ECC, the sprayed SDMCC was found to have good atomization, allowing the material to be sprayed uniformly onto the substrate. SDMCC exhibits little or no rebound and does not drip or sag after being sprayed onto a substrate, exhibiting a number of advantages over conventional coating materials.

3. Expansion characteristics

The sample for measuring shrinkage/expansion was cast into a prism mold (25X 300 mm). The shrinkage/expansion measurements were made as early as possible after demolding without damaging the specimen and are labeled as deformation "zero". For the mixtures in table 1, the demold time was 20 hours for OPC; 10 hours for K07; 5 hours for K10, K13, and LC 3-K13; 8 hours for LC 3-K10; 3 hours for R13-C0, R13-C10, R13-C15 and R13-C20. The samples were stored at 20 ℃. + -. 2 ℃ and 40%. + -. 5% Relative Humidity (RH) environment. The specimen length change was measured according to ASTM C490/C490M-17.

3.1 drying shrinkage/expansion

The shrinkage/expansion versus time curves for the compositions in Table 1 are shown in FIGS. 1-3, where the negative sign (on the y-axis) indicates shrinkage and the positive sign indicates expansion. Table 2 lists the characteristic values of shrinkage/expansion at 28 days. For SDMCC prepared with OPC, the shrinkage increased continuously to-1434. mu. epsilon.at 28 days. This relatively large shrinkage can lead to cracking under limited conditions, thereby reducing material durability. SDMCC with CSA-K shows a characteristic of contraction after initial swelling. Maximum expansion occurs over a period of about 2 days. The maximum swelling amplitudes of the compositions K07, K10 and K13 were 779. mu. epsilon., 2418. mu. epsilon. and 3756. mu. epsilon. as a function of the CSA-K ratio. However, with 7 wt% CSA-K cement in the composite binder, SDMCC still showed a-832 μ epsilon shrinkage at 28 days. The swelling at 28 days K10 and K13 were 1139. mu. epsilon. and 2026. mu. epsilon. respectively. The ECC expansion using LC3 is a little lower than the ECC expansion using OPC. The expansions of LC3-K10 and LC3-K13 were 838. mu. epsilon. and 1722. mu. epsilon.

CSA cement type can also affect the expansion amplitude. CSA-R is less CaSO than CSA-K ₄ CSA binder according to (1). Even when the CSA-R content was 13 wt% of the composite binder (R13-C0), the R13-C0 showed a shrinkage of-834. mu. epsilon. at 28 days and showed no swelling. CSA-R replacement with anhydrite increased, shrinkage decreased, and R13-C20 had a 489 μ ε expansion at 28 days. Without wishing to be bound by theory, it is believed that CaSO in CSA cement ₄ The amount of (gypsum or anhydrite) affects ettringite production. Ettringite is the major expansive hydration product of CSA cement.

3.2 minimum expansion

Assuming a linear material constitutive behavior, the pressure caused by expansion can be expressed as:

p＝E ₁ ε ₁ -E ₂ ε ₂ (1)

wherein p is the pressure applied by the swelling SDMCC; epsilon ₁ Maximum swelling for SDMCC; epsilon ₂ Is the difference between maximum expansion and residual strain at 28 days; e ₁ An effective modulus between zero and a maximum expansion time, and; e ₂ Effective modulus between the maximum swelling time and 28 days. Epsilon ₁ And epsilon ₂ Can be tested by performing the drying shrinkage/expansion test according to ASTM C490/C490M-17, and the values are listed in Table 2. E ₁ And E ₂ Is the effective modulus affected by stress relaxation and time evolution. The potential during the early phase (3 days ago) was more pronounced than the potential at the later phase (3-28 days). In addition, the elastic modulus at an early stage is small even if the SDMCC material is rapidly hardened.

Suppose E ₁ ＝kE ₂ The pressure can also be expressed as:

f＝(kε ₁ -ε ₂ )E ₂ (2)

where k is defined as the effective modulus coefficient. k is determined by the combined effect of the development of the elastic modulus of the material and the boundary-constrained conditions. Advantageously, to ensure that the SDMCC produces a coupling against the host tube, f should be greater than 0. In other words, k ε ₁ -ε ₂ Should be greater than 0. According to Zhu h et al, Double feedback control method for determining area-induced street of related use of detailed stress machinery materials,2018,11(7),1079, it seems reasonable to assume that k is 0.5.

TABLE 2

For the mixtures in table 2, the maximum swelling and post 28 day swelling of OPC were different from K07, K10 and K13; however, the difference between the maximum expansion and the 28-day expansion (i.e.,. epsilon. epsilon.) for OPC, K07, K10, and K13 ₂ ) Similarly. Epsilon of OPC-based SDMCC was found experimentally ₂ About 1531. mu. epsilon. and LC 3-based epsilon of SDMCC ₂ Is 605. mu. epsilon. Thus, for OPC-based SDMCC, the maximum expansion ε ₁ ＝ε ₂ Preferably,/k is at least 3062. mu. epsilon. (1531/0.5) to provide the desired coupling effect. The maximum swelling of the LC 3-based SDMCC is preferably at least 1210. mu. epsilon. (605/0.5).

3.3 maximum allowable expansion

As explained above, although SDMCC expansion is desirable, over-expansion should be avoided as it may cause parent pipe damage. According to the theory of elasticity of steel rings (Hossain A B, Weiss J. assembling residual stress reduction and stress relaxation in reinforced Concrete rings. center and Concrete Composites,2004,26(5):531-540), the elastic pressure exerted by the SDMCC on the main tube can be expressed as equation (3) and the maximum elastic stress of the main tube can be calculated by equation (4):

Δσ _{maximum of} ＝Δp _Elasticity C _3R (4)

Wherein Δ ε _ex Expanded for SDMCC; e _C And E _S Is the elastic modulus of the host and the SDMCC; and C _1R 、C _2R 、C _3R Can be assumed to be constant for a given geometry as shown in equations (5) through (7):

wherein v is _C And v _S Poisson's ratio of director and SDMCC; r _IS And R _OS Inner radius and outer radius of SDMCC, respectively; and R is _IC And R _OC Respectively the inner radius and the outer radius of the main tube.

Equations (3) through (7) indicate the maximum tensile strength in the host tube, host tube Internal Diameter (ID), SDMCC expansion and material mechanical properties affected by the SDMCC thickness. C40 concrete pipes with different diameters (ID 48 "(1219 mm), 60" (1524mm) and 90 "(2286 mm)) were used as examples. The tensile strength was 5MPa and the modulus of elasticity was 40 GPa. The average SDMCC elastic modulus during zero time and maximum expansion time is assumed to be 5 GPa. The poisson ratio for director and SDMCC is assumed to be equal to 0.18. Assuming that the relaxation stress during the early period (0-3 days) is 0.5 of the total elastic stress, the maximum allowable expansion under the condition that the maximum allowable tensile stress in the main tube is half of the tensile strength (2.5MPa) can be calculated using equations (3) to (7).

Fig. 4 plots the maximum allowable expansion of SDMCC for repairing C40 concrete pipes and the characteristic values are listed in table 3. The tensile stress in the host tube increases with the SDMCC thickness. For a 48 "(1219 mm) host tube repaired with 1.5" (38mm) thick SDMCC, the maximum allowable expansion is 3375. mu. epsilon. which is less than the maximum allowable expansion of K13 (3756. mu. epsilon.). Therefore, when used to repair 48 "(1219 mm) tubes, the K13 thickness should not exceed 1" (25 mm). The thickness may be increased to repair larger diameter pipes. For example, for a 90 "(2286 mm) tube repaired with 2" (51mm) thickness SDMCC, the maximum allowable expansion is 4450 μ ε.

Pipelines are usually buried underground under confining pressure. The confining pressure reduces the tensile stress of the main tube caused by the SDMCC expansion. Assuming a confining pressure of 0.3MPa as shown in table 3, the maximum allowable expansion is significantly increased compared to the maximum allowable expansion of the pipe without confining pressure.

Under confining pressure, K13 can also be used to repair 48 "(1219 mm) pipelines of SDMCC with a thickness of 2" (51 mm). Without wishing to be bound by theory, the inventors propose maximum allowable expansion of SDMCC for rehabilitating a pipeline without and with confining pressure of 3000 μ ε and 4000 μ ε, respectively.

TABLE 3

And (4) supplementary notes: the units of swelling are μ ε.

3.4 constrained expansion test Using Steel Ring

Concrete was cast around the steel ring in the annular zone according to the restricted shrinkage test method ASTM C1581/C1581M-18 a. The strain caused by the concrete shrinkage that applies pressure to the steel ring is monitored and used to calculate the interface pressure.

The expanded steel ring test method is based on ASTM C1581/C1581-18a, but differs in that K13 or LC3-K13 is a solid cast inside a steel ring (rather than a hollow ring as used in the constrained test) with an outside diameter of 405mm and an inside diameter of 385 mm. Starting 5 hours after casting, K13 or LC3-K13 expansion applied pressure to the steel ring and the induced steel ring strain was monitored by 3 strain gauges.

Fig. 5 plots the average strain of the 3 strain gauges. Similar to the dry swell described in section 3.1, the constrained swell also initially increases and subsequently decreases. As shown in fig. 1 and 2, the maximum dry swelling occurred between 2 days and 3 days. However, due to creep and relaxation, the maximum constrained expansion occurs approximately the first day after casting. The maximum swelling of K13 was 123 μ ∈ and the maximum swelling of LC3-K13 was 104 μ ∈, followed by a decrease in the maximum swelling of K13 to 6 μ ∈andthe maximum swelling of LC3-K13 to 56 μ ∈onday 28. LC3-K13 has less swelling reduction than K13, which indicates that LC3-K13 can provide a more preferred coupling effect than K13.

The residual interface pressure between the steel ring and K13/LC3-K13 can be calculated by equation (8):

wherein p is _{Residue of} (t) is the residual interfacial pressure,. epsilon _Steel (t) Strain measured by 3 Strain gauges, E _Steel Is the Young's modulus of a steel ring, and R _{O steel} And R _{I steel} The outer diameter and the inner diameter of the steel ring.

Fig. 6 plots the residual interfacial pressure calculated by equation (8). After 1 day, the maximum pressure of K13 was 1.18MPa and the maximum pressure of LC3-K13 was 1.00 MPa. After 28 days, the pressure of K13 was only 0.06MPa, almost 0MPa, whereas the pressure of LC3-K13 was 0.54 MPa.

Compared to conventional repair materials, SDMCC (K13 or LC3-K13) is designed to apply pressure to the host pipe. Experimental data herein demonstrate this concept. Without wishing to be bound by theory, it is believed that the pressure improves the bond between the host tube and the SDMCC, thereby reducing or eliminating buckling and debonding problems due to poor adhesion. The inventors have unexpectedly discovered that advantageously, LC3 can provide less reduction in swelling over time compared to OPC, thereby causing continued pressure to be applied to the outer tube. Bonding can be achieved without adhesives, but by mechanical friction that increases with normal (radial) pressure applied to the host tube by the SDMCC.

4. Tensile characteristics

For tensile testing, the test specimens were cast into dog bone molds (see Felekoglu, B., et al, flame of matrix flow, and curing conditions on the mechanical performance of HTPP-ECC Composites Part B: Engineering,2014,60,359 370 for dog bone geometry). Uniaxial tensile testing was performed with an Instron servo hydraulic tester under displacement control at a rate of 0.5 mm/min. The strain was measured by two Linear Variable Displacements (LVDT) with a gauge length of 80 mm. The average crack width was calculated as the number of cracks by bit removal. The tensile results listed in table 2 are the average of 3 samples at 28 days.

Fig. 7 plots representative tensile stress and strain curves for the SDMCC in table 1. The ultimate tensile strength and tensile strain capacity of OPC were 3.41MPa and 3.69%. For SDMCC mixed with CSA-K, the ultimate tensile strengths of K07, K10, and K13 were 3.67MPa, 3.62MPa, and 3.85MPa, respectively. Inclusion of CSA-K increases ultimate tensile strength. The tensile strain capacities of K07, K10, and K13 were 4.79%, 5.17%, and 5.04%, respectively, each of which was greater than the tensile strain capacity of OPC. The average crack widths were about 60 μm, 80 μm and 90 μm at strains of 1%, 2% and 3%. The fracture width of SDMCC made with CSA-K is less than the fracture width of SDMCC made with OPC. The tensile strain capacities and crack widths of LC3-K10 and LC3-K13 were comparable to those of SDMCC prepared with OPC. However, the ultimate tensile strength is less than 3 MPa. While LC3 produced lower strength, SDMCC prepared with LC3 had greater strain capacity and used less cement. Advantageously, such an SDMCC may have good durability, lower cost and be more environmentally friendly than an SDMCC prepared with OPC. The durability and permeability of SDMCC are discussed further below.

Even though the SDMCC may experience micro-fracture damage under external load, the material may still undergo self-healing, which may be enhanced under the wet-dry environmental conditions typically present inside the pipeline. After 28 days of cure, the specimens were pre-fractured to 1% and 2% strain to intentionally cause damage to the SDMCC. Subsequently, the specimens were exposed to seven wet-dry cycles. Figure 8 plots the strength and strain capacity results after self-healing. The tensile strength of the sample after self-healing was higher than that of the virgin sample, although the sample was pre-fractured. The SDMCC prepared with LC3 cement showed higher strain capacity than the SDMCC prepared with OPC, which indicates that the SDMCC prepared with LC3 has comparable or even more preferred self-healing efficacy.

After 28 days of cure, the specimens were pre-fractured to 1% and 2% strain before permeability testing was performed following the procedure in Liu, H., et al, "infection of micro-cracking on the permeability of Engineered permeability Composites", center and conductor Composites,2016,72, 104-materials 113. Fig. 10 presents the permeability coefficient results after 14 days. As expected, the permeability coefficient increased with the crack width. The permeability of SDMCC (LC3-K13) is lower than that of SDMCC (OPC) due to its tight crack width mode. The permeability coefficient of SDMCC is almost two orders of magnitude smaller than conventional enhanced mortar (>150 μm fracture width) subjected to the same pre-fracture strain. The low permeability of this SDMCC should significantly improve the life performance of the pipeline and prevent leakage. Even at 2% pre-rupture strain, low permeability is desirable to reduce the risk of drinking water loss or subsurface water contamination, for example, after a seismic event.

5. Pipeline finishing test

To demonstrate the tailoring ability of SDMCC, a pipe crush test was performed according to ASTM C497M-19 a. FIG. 10 shows the pipeline sections before and after remediation with SDMCC (LC 3-K13). The SDMCC repair layer thickness shown in figure 10 is by way of example only. Those skilled in the art will appreciate that the actual SDMCC thickness may be selected based on the mechanical and functional requirements of a particular application. The length of the tubing was 36 "(914 mm). The original concrete pipe was mixed with 500g/L OPC, 1200g/L river sand, 200g/L water and 6g/L water reducer. The SDMCC mixture was identical to LC3-K13 in Table 1.7 days after the concrete casting, the concrete and kraft paper tubes were placed into a water tank. The kraft tube was demolded after 3 hours of immersion in water, after which SDMCC (LC3-K13) was cast.

After 28 days of curing in air, the pipe was cut into 8 "(203 mm) lengths by a diamond saw for use in the crush test. Crush tests were performed with concrete pipes and pre-fractured pipes repaired by LC 3-K13. Pre-fractured concrete pipes were used to simulate the effect of repairing fractured pipes using SDMCC.

When the load exceeds the crushing strength, the concrete pipe suddenly collapses due to its brittleness. However, pre-damaged pipe repaired with SDMCC can carry loads after a large crack occurs in the concrete pipe. Many microcracks occur in SDMCC. Cracks first appear in the inner surface of the SDMCC and then appear more cracks as the load increases. Instead of one giant crack in the concrete pipe, many tight cracks are distributed throughout the SDMCC.

This test also demonstrates that SDMCC eliminates buckling, a common problem in tubes repaired by CIPP methods. Buckling typically occurs due to the gap between the repair layer and the parent pipe, which is typically observed in CIPP methods. The expansion characteristics of the SDMCC can provide an SDMCC coating that is seamlessly joined to the host tube, thereby creating little or no gaps therebetween.

Figure 11 plots crush strength versus displacement test results. Both the crush strength and displacement capacity of the pipes repaired by LC3-K13 were greater than those of concrete pipes. This situation shows that trimming the tubing with SDMCC improves both the strength and displacement capacity of the tubing (also shown in table 4). The SDMCC retains residual load capacity even after a peak load. When the residual load drops to 4.89kN, which is equal to the load capacity of the original probe concrete pipe, the displacement is 3.63 times of the displacement capacity of the probe concrete pipe.

TABLE 4

6. Leak test

The SDMCC repaired tubes were used for leak testing. After the peak load was reached, the bottom portion of the ruptured SDMCC tube was sealed with cement on the plywood. Subsequently, the system was filled with water. There was no leakage from the system 24 hours after filling with water, regardless of the macro cracks in the main concrete pipe and the micro cracks in the SDMCC. The microcracks in the SDMCC extend from the inner surface to the outer tube. Without wishing to be bound by theory, it is believed that the plurality of tight cracks work in the form of plastic hinges and redistribute stress. The micro-cracks do not propagate into macro-cracks and no local cracks appear in the SDMCC. Thus, there is no leakage even after the peak load has been reached.

The scope of the invention is not intended to be limited to the examples mentioned above. As will be appreciated by a person skilled in the art, many variations are possible without departing from the scope of the invention as set out in the appended claims.

Claims

1. A sprayable cementitious composition comprising: composite binder, fiber and water; wherein the composite binder comprises a cement component and a leucite fly ash (pozzolan) component.

2. The sprayable cementitious composition of claim 1, wherein the ratio of water to composite binder is from about 0.2 to about 0.5.

3. The sprayable cementitious composition of claim 1 or 2, wherein the cement component comprises a hydraulic cement and an expansion agent.

4. The sprayable cementitious composition of claim 3 wherein the expansion agent is calcium sulfoaluminate.

5. The sprayable cementitious composition of claim 3 or 4, wherein the amount of expansion agent is from about 10 wt% to about 60 wt% based on the total cement component weight.

6. The sprayable cementitious composition of any one of claims 3 to 5, wherein the hydraulic cement comprises ordinary Portland cement.

7. The sprayable cementitious composition of any one of claims 3 to 6, wherein the amount of hydraulic cement is from about 1 wt% to about 80 wt% based on total cement component weight.

8. The sprayable cementitious composition of any one of claims 1 to 7, wherein the cement component comprises a reactive aluminosilicate, calcium carbonate, or a mixture thereof.

9. The sprayable cementitious composition of claim 8, wherein the reactive aluminosilicate is a calcined clay.

10. The sprayable cementitious composition of claim 8, wherein the calcium carbonate is limestone.

11. The sprayable cementitious composition of any one of claims 1 to 10, wherein the amount of the leucite fly ash component is from about 1 to about 3 times the amount of the cement component by weight.

12. The sprayable cementitious composition of any one of claims 1 to 11, wherein the leucite fly ash component comprises a material selected from the group consisting of: fly ash, steel slag, granulated blast furnace slag, diatomaceous earth, silica fume, calcined clays such as metakaolin, calcined shale, volcanic ash, pumice, silica-fired organic materials such as rice hull ash, and mixtures of any two or more thereof.

13. The sprayable cementitious composition of claim 12, wherein the fly ash is selected from the group consisting of: type C fly ash, type F fly ash and mixtures thereof.

14. The sprayable cementitious composition of any one of claims 1 to 13, wherein the fibers are selected from the group consisting of: polymeric fibers, inorganic fibers, metal fibers, carbon fibers, plant-based fibers, and mixtures of any two or more thereof.

15. The sprayable cementitious composition of claim 14, wherein the polymeric fibers comprise a polymeric material selected from the group consisting of: polyolefins, polyacrylic acids, polyesters, polyvinyl alcohols, polyamides, and combinations of any two or more thereof.

16. The sprayable cementitious composition of claim 14 or 15, wherein the polymeric fiber is selected from the group consisting of: polyethylene fibers, high tenacity polypropylene fibers, polyvinyl alcohol fibers, and mixtures of any two or more thereof.

17. The sprayable cementitious composition of any one of claims 1 to 16, wherein the sprayable cementitious composition further comprises one or more components selected from the group consisting of: superplasticizer, aggregate, adhesive and retarder.

18. A sprayable cementitious composition comprising: composite binder, fiber and water; wherein the composite binder comprises a cement component and a leucite fly ash component, and wherein the sprayable cementitious composition, when cured, achieves one or more characteristics selected from the group consisting of:

(i) a tensile strength of at least about 2.50MPa,

(ii) a tensile strain capacity of at least about 3% at 28 days,

(iii) a crack width at ε < 2% of less than about 100 μm, an

(iv) A maximum expansion of at least about 1210 mu epsilon.

19. A method of preparing a sprayable cementitious composition, the method comprising:

(ii) mixing the binder composition with water to form a wet mixture,

(iii) adding fibers to the wet mixture.

20. The method of claim 19, wherein the method further comprises mixing the cement component and the leucite fly ash component to obtain the binder composition.

21. A process as claimed in claim 19 or 20 wherein a superplasticiser is added to the water prior to step (ii).

22. A method of repairing and/or renovating a building structure, comprising the steps of:

(i) providing the sprayable cementitious composition of any one of claims 1 to 18;

(ii) spraying the cementitious composition on a surface of the building structure to at least partially coat the surface with the cementitious composition; and

(iii) allowing the cementitious composition to set on the surface.

23. The method of claim 22, wherein the spraying step (ii) is performed by a manual spray system or an automated spray system.

24. The method of claim 22 or 23, wherein the building structure is a pipeline.

25. The method of claim 24, wherein the surface is an interior surface of the pipeline.

26. The method of claim 24 or 25, wherein the pipeline is trimmed to extend the life of the pipeline, increase the bearing capacity of the pipeline, and/or strengthen the pipeline.

27. Use of the sprayable cementitious composition of any one of claims 1 to 18 for repairing and/or finishing a building structure.

28. The use of claim 27, wherein the building structure is a pipeline.

29. A dry premix for preparing the sprayable cementitious composition of any one of claims 1 to 18, the dry premix comprising a composite binder and fibers; wherein the composite binder comprises a cement component and a leucite fly ash component.

30. A method of preparing the sprayable cementitious composition of any one of claims 1 to 18, the method comprising:

(i) providing a dry pre-mix according to claim 29,

(ii) mixing the dry premix with water to form the sprayable cementitious composition.