NL2023853B1 - Methods and system for forming structures using coral material - Google Patents

Abstract

A method of forming a structure includes a) obtaining coral material; b) mixing the coral material With a binder system to form a mixture; and c) forming a structure from the mixture. The binder system can be a geopolymer binder system. Such a structure can be placed underwater for building or rebuilding underwater environments.

Description

METHODS AND SYSTEM FOR FORMING STRUCTURES USING CORAL MATERIAL

BACKGROUND A coral reef is an underwater ecosystem which 1s formed of reef-building corals. Reefs are often formed of colonies of coral polyps held together by a calcium based (e.g., calcium carbonate) substructure. Due to environmental changes, many corals are degrading or dying. This is typically known as “bleaching of the reefs.” The term “bleaching of the reefs” is used due to the coral turning white after expelling algae that live inside their tissue and provides up to 90 percent of the corals energy. A number of environmental factors directly cause this, including temperature rises in oceans, rising acidity levels, accumulation of debris and dead coral and sanding over blocking sunlight to the living coral.

Due to increased acidity, the calcium based substructure is dissolved in the sea water environment, decreasing the overall stability of the coral structure or reef. The rising temperatures also cause the total amount of coral organisms to decrease.

Efforts to combat the bleaching of the reefs typically include either sinking old ships to create new barrier structure or placing concrete blocks and/or tires on the sea bed. However, old ships often contain other materials which may similarly harm the environment once place, and the steel structures will eventually collapse due to corrosion, collapsing any rebuilt coral structures with it.

The use of cement-based products is described in WO 2018/104734, where an underwater structure is built of a plurality off concrete blocks. The blocks have a central cavity which is said to protect and encourage the growth of marine life and corals. The blocks are formed of stone, sand, cement, high-rage plasticizer, microsilica and silica fibres. The micro silica and silica fibres are said to be used for strength and to minimize the leaching of any concrete toxins.

SUMMARY According to a first aspect of the invention, a method of forming a structure comprises a) obtaining coral material; b) mixing the coral material with a binder system to form a mixture; and c) forming a structure from the mixture. Optionally, the binder system is a geopolymer binder system. Such a method can be used to form structures for underwater use, such as in rebuilding coral reefs. Forming a structure with coral material can help support the natural biodiversity and underwater ecosystem, while not introducing or releasing new pollutants of the reef or other area in which the structure is to be used through the use of the coral material and a suitable binder system. Such a suitable binder system is a geopolymer binder system, which could be suitable for forming a strong structure that can be placed in an aquatic environment and not add pollutants.

According to an embodiment, step ¢) comprises placing the mixture into a mould to form the structure. This can be, for example, pouring the mixture from a mixing vessel into a mould and allowing gravity to ensure the mixture flows into the mould properly. Optionally, this can further comprise allowing the mixture to set in the mould, and then removing the mould. This can vary based on the mixture, but be for example, 0-10 days, preferably 1-5 days, more preferably 1-3 days. Allowing the mixture to just set enough that it holds the shape when the mould is removed (as opposed to further or full curing) allows for faster mould removal and reuse.

According to an embodiment, the method further comprises curing the structure. Curing can depend on the desired use of the structure, the mixture used, the configuration and size of the structure, the curing conditions, etc. A suitable curing time could be, for example, 1-28 days, preferably 1-14 days, more preferably 2-7 days. Curing would generally be at room temperature, though in some embodiments, heat and/or pressure could be applied for faster curing.

According to an embodiment, step a) comprises collecting coral material. The coral material can be collected in different ways, for example, dredging or other collection from the seabed, collection from a beach, etc. In other embodiments, the coral According to an embodiment, step a) comprises obtaining indigenous coral material from a location where the structure is to be placed. Obtaining indigenous coral material from a location where the structure is to be placed ensures that the structure is formed of materials that won’t disrupt the biological ecosystem or environment. By using indigenous coral material, local organisms will be supported and no potentially invasive material is introduced by placing the structure in the location of use.

According to an embodiment, step b) comprises mixing the coral material with one or more activators, one or more binders, and liquid to form the mixture. The one or more activators can include one or more of: Sodiumsilicate with Na20 (8-20%) and S102 (25-30%); Metasilicate; Alkali carbonate; Sodium Hydroxide; Potassium Hydroxide; Aluminate; Calcium Hydroxide and Magnesium Oxide. The one or more binders can be geopolymer binders, such as blast furnace slag, basic oxygen furnace slag, fly ash, metakaolin, thermally modified clays and iron aluminate silicates. The liquid can be water.

Such materials are typically added in ratios to each other depending on the structural and strength requirements of the final structure. For example, the one or more activators could form 1-13 wt% of the mixture based on total weight of the mixture, with the one or more binders forming 1-40 wt% of the mixture based on total weight of the mixture, the coral material forming 33-75 wt% of the mixture based on total weight of the mixture, and liquid forming 3-20 wt% of the mixture based on total weight of the mixture. Preferably, the mixture would be formed of 3-4 wt% activator, 15-20 wt% binder, 65-73 wt% coral material (which could include other aggregate) and 6-8 wt% liquid based on total weight of the mixture.

The mixture can include one or more of the following, typically in the wt % of overall total weight given, though can vary: 3-4 wt % Sodium silicate with Na20 (8- 20%) and S102 (25-30%); 3-4 wt % Sodium Hydroxide; 3-4 wt % Potassium Hydroxide; 15-20 wt % Blast Furnace Slag; 15-20 wt % Basic Oxygen Furnace Slag; 15-20 wt % Fly Ash; 15-20 wt % Metakaolin.

Optionally, one or more additives and/or leaching components can also be added to form the mixture. These could include one or more of: modified starch, polyglycols, superplasticizers, saturated hydrocarbons C6-C20, Polypropylene, polyproylene fibres, calcium carbonate and iron oxide. Leaching components can be included in the mixture such that when the formed structure is placed in the aquatic environment for use, the leaching component will be slowly released and can help to promote microorganism and/or coral growth in the environment. Other additives are useful for mix cohesion and leaching rate control.

According to a further aspect of the invention, a structure comprises a geopolymer binding system; and coral material. Such a structure can be formed in many different shapes and configurations, and can be used as a natural way to build and/or rebuild underwater arrangements, such a coral reefs. Using coral material and a geopolymer binding system to form a structure ensures that when placed in the underwater location of use, little to no invasive or pollutants are introduced to the environment. Further, the use of coral material and geopolymer binder to form the structure can actually help to encourage the growth and flourishing of the natural biodiversity already in the area, for example, by providing or forming structures which protect and support the growth of indigenous plants, animals and other organisms.

According to an embodiment, the coral material is indigenous to the location where the structure is to be used. Using indigenous materials further promotes the promotion of the natural ecosystem in existence and further reduces the chance of introducing pollutants or invasive species to the environment in which the structure is to be placed.

According to an embodiment, the geopolymer binding system comprises at least one binder selected from: blast furnace slag, basic oxygen furnace slag, fly ash, metakaolin, thermally modified clays, and iron aluminate silicates; and at least one activator.

According to an embodiment, the at least one activator comprises one or more of: Sodium silicate with Na20O (8-20%) and S102 (25-30%), Metasilicate, Alkali carbonate, Sodium Hydroxide, Aluminate, Calcium Hydroxide, and Magnesium Oxide.

According to an embodiment, the structure comprises an exterior surface, an interior surface and at least one opening between the exterior surface and the interior surface. The structure can be, for example, in the form of a cylinder, conical, rectangular or any other shape. The structure could be open on the ends, partially covered or have fully covered ends. The structure can form an interior space within the structure, with the opening allowing access from outside the structure to inside the structure. Such a configuration can promote natural interaction with flora and fauna once place in an underwater environment as flora and fauna can move through the opening into the interior space and vice versa. The interior space can also help rebuilding of the underwater environment, providing protection for the flora and fauna and sheltered areas for natural protection of wildlife and regrowth of coral.

According to a further aspect of the invention, a mixture for forming a structure comprises a binder; an activator; and coral material. Such a mixture can be used to form structures suitable for building or rebuilding underwater structures such a coral reefs. According to an embodiment, the binder is one or more of: blast furnace slag, basic oxygen furnace slag, fly ash, metakaolin, thermally modified clays, and iron 5 aluminate silicates. Optionally, the activator comprises at least one of Sodium silicate with Na20 (8-20%) and SiO2 (25-30%), Metasilicate, Alkali carbonate, Sodium Hydroxide, Aluminate, Calcium Hydroxide, Magnesium Oxide. According to an embodiment, the mixture further comprises one or more additives and/or leaching components, such as modified starch, polyglycols, superplasticizers, saturated hydrocarbons C6-C20, Polypropylene, polyproylene fibres and calcium carbonate.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a schematic depiction of a method for forming a structure. FIG. 2 shows a sample structure.

DETAILED DESCRIPTION Coral are sedentary aquatic invertebrate which live in aquatic environments. Coral are typically found in colonies of polyps in warm and tropical seas, and form coral reefs. A polyp normally has a hard exoskeleton, which is formed by excreting calcium carbonate. Some corals are soft with no hard exoskeleton, but are typically reinforced by sclerites made of calcium carbonate. Most corals rely on the presence of green algae in their tissues to obtain energy from sunlight, and bleaching of the coral occurs when the green algae is expelled and can no longer provide the coral with the nutrients needed. As discussed in the background, due to environmental changes (or other causes), many corals and coral reefs are degrading or dying, as shown by the bleaching occurring. When this happens, degraded or dying coral can eventually break off and form coral debris, which can be large or small pieces of coral. This can be mixed with other aquatic environmental debris, such as sand or other sediment found in the environment of the coral or coral reef. As used herein, coral material includes any coral or coral debris whether in the form of pieces, particles, fragments or granules of coral. The debris can be coral material which has broken off as described above, and/or coral material which

1s not broken off, but has been bleach, or died. Other debris can be included in the coral material, for example, sand, gravel, other seabed debris, etc., though typically, the coral material would consist of at least 50% calcium carbonate. FIG. 1 shows a schematic depiction of a method 10 for forming a structure using coral material. Method 10 involves the steps of obtaining coral material (step 12); mixing the coral material with a binder system to form a mixture (step 14); and forming a structure from the mixture (step 16). Step 12 of obtaining coral material can take a number of different forms. In some embodiments, coral material 1s collected from a specific reef or geological area. This specific reef or geological area can be an area where the structure is to be used after formation or an area which has similar biodiversity, for example, reefs which are homes to the same or similar animals and/or which are located in similar water conditions (e.g., temperature, depth, etc.). The collection of the coral can be done in a number of different manners, including suctioning or dredging the coral material, collection from a beach, etc. In some embodiments, the coral material could even be grown specifically for the purpose of using to form such structures. As mentioned above, the coral material can include other marine debris, such as sand, seabed debris and other microorganisms collected with the coral material. In some embodiments, the coral material could be simply bought from a supplier or obtained in another manner.

In step 14, the coral material is mixed with a binder system to form a mixture. The mixture could be first formed dry, for use later, or could be fully formed with the liquid added for immediate use.

The binder system can be a geopolymer binder system. The term geopolymer binder system is used to refer to the use of geopolymer cements to form the mixture.

These are typically slag-based, rock-based fly ash-based or ferro-isalate based; and involve the use of an aluminosilicate precursor material, an alkaline reagent and water. The binder material used can be one or more of blast furnace slag, basic oxygen furnace slag, fly ash, metakaolin, thermally modified clays and iron aluminate silicates.

The alkaline reagent is often termed user-friendly as the alkaline reagents used typically involve less safety products and procedures than other hostile reagents. Such reagents can be one or more activators, including but not limited to Sodiumsilicate with Na20 (8-20%) and S102 (25-30%); Metasilicate; Alkali carbonate; Sodium Hydroxide; Potassium Hydroxide; Aluminate; Calcium Hydroxide and Magnesium Oxide.

Additionally, one or more admixtures can be used to form the mixture. The admixtures can include, but are not limited to, modified starch, saturated hydrocarbons C6-C20 and polypropylene. Such admixtures can function to promote certain characteristics, such as pot life or workability of the mixture.

The mixture typically further includes an amount of liquid (e.g., water) and could include further aggregate beyond the coral material, for example, sand, gravel, stone or other materials. The additional aggregate can help to improve particle packing or “grading.

The mixture can be formed by mixing specific portions of one or more binders and activators with coral material and liquid. Mixing can be done on the site of coral collection, on the site where the structure is to be used, or at a different location with the coral material being transported to a mixing site. In some embodiments, a dry mixture could be formed elsewhere, with just the liquid added at a separate mixing site. Mixing can be done with standard mixing equipment used in concrete mixture formation, for example a mixing vessel with several mixing blades with appendages, with ingredients added at specific ratios. The ingredients may be added to the mixing vessel from separate storage vessels, weighing and distributing the ingredients. Ingredients may be added all at the same time or separately. A possible order for mixing can be: aggregate, binder, solid activators, liquid activators in ascending alkalinity and admixtures. Mixing time can vary, and compressive strength typically increases with mixing time up to an optimal mixing time depending on the specific ingredients as well as the mixing vessel and apparatus. An example optimal mixing time is between 3 and 6 minutes. Typically, the specific ratios of ingredients are chosen in relation to the proposed end properties of the final structure, and can be, for example, 3-4 wt% activator; 15-20 wt% binder; 0-1wt% additives; 65-73 wt% coral material; and 6-8 wt% liquid based on total weight of the mixture. Once the mixture has been formed, a structure 20 (see Fig. 2) can be made from the mixture in step 16. Figure 2 shows structure 20 as cylindrical in shape with radial cutout portions 22, though the structure can be formed in many other shapes according to equipment and moulds available, and desired use. The forming of structure 20 can be through placing the mixture formed in step 14 into a mould. The mould sets the final shape of the structure, allowing the mixture to form into that shape before the mould is removed from the structure (though in some embodiments, the structure could simply be removed from the mould). The mould can include an inner mould, outer mould, one or more inserts, and one or more additional components to facilitate shaping and/or demoulding. Some embodiments would have a simple mould and not include all listed components, and some could include all components and possibly more if the structure to be formed required, for example due to extreme configuration and/or fragility requirements. Some structures may even be formed without moulds. The structure 20 can at least partially cure in the mould, and can partially cure outside the mould. For setting, time would vary based on mixture ingredients as well as structure configuration and size. If more binder and less coral material is used, time to set and then demould would be less, for example, one day. If a mixture used more coral material (or other aggregate) and less binder, the mixture would require more time to set before demoulding.

The use of more coral material and less binder would result in less strength, while using less coral material and more binder would result in a stronger structure. A stronger structure may be desirable for a base layer when a number of structures will be formed and stacked in the underwater environment. A stronger structure would then reduce the chances of degradation and/or collapse as more structures and/or aquatic life were placed or grew on top of the base layer. If a structure is to be used in a shallow area or underwater environment with few currents, the structure may not need as much strength and more coral material can be used instead to help promote the underwater ecosystem.

As seen in Fig. 2, structure 20 includes one or more openings or cut-out sections (typically formed by inserts in the mould). The one or more openings connect the external surface of the formed structure 20 with an internal surface of the structure, forming a passageway through the structure. Such one or more openings in structure 20 allow flora and fauna to “interact” with structure 20 in a natural way, allowing for movement into and/or through structure 20. The at least partially enclosed interior area of structure, accessed through the one or more openings (and/or ends) can form a naturally protective habitat for flora and fauna as well. Structure 20 shown in Fig. 2 is an example configuration, and other structures would have a different configuration, including size; shape; depth; number, placement and sizes of openings; etc.

Structure 20 can then be placed in an underwater environment, and used in helping to build and/or rebuild coral reefs which may be degrading or dying due to bleaching and other environmental factors. As mentioned in the background, efforts to combat the bleaching of the reefs typically include either sinking old ships to create new barrier structures or placing concrete blocks and/or tires on the sea bed. However, these all contain other materials which may similarly harm the environment once placed, and the steel structures will eventually collapse due to corrosion, collapsing any rebuilt coral structures with it.

The use of coral material, and sometimes even coral material that is indigenous to the reef being rebuilt, in the building of structure 20 results in a natural reef rebuilding structure that will support the biological life already present in the reef and avoid polluting the local environment with potentially invasive material. Use of a geopolymer binder means that the typical cement binder is not needed. As cement is said to be a direct contributor to the increase of climate change rates through contributing to the CO2 footprint, the avoidance of cement also helps to reduce one of the primary drivers of coral bleaching. Geopolymers also act as a strong binding material which is suitable for subsea applications as it is not vulnerable to sulphates (like cement is).

Additionally, variations in the binding mixture and/or leaching components may be added to the mixture to further promote benefits in the forming of structure and/or benefits after placement. Such leaching components are added to make the structure “bleed”, leaching or releasing inorganic products beneficiary to the growth of micro- organisms over a long period of time when the structure is placed into an aquatic environment, thereby further promoting growth of the reef. Such a suitable leaching component could be calcium carbonate, which could leach from the structure over a period to support the growth of new coral.

Additionally, the configuration of structure 20 helps in rebuilding the reef and promoting the natural wildlife. Forming structure 20 one or more openings 21 leading to an interior portion allows structure to act as a protection and/or home for flora and fauna. This promotes natural interaction of flora and fauna with the newly introduced structure 20, thereby promoting the natural support of the aquatic environment and regrowth of the reef. The size of openings can also help in protecting smaller organisms while keeping larger predators from being able to enter the interior of structure.

Examples A dry mixture with the following components was produced: EXAMPLE 1 A geopolymer binding mixture with the following components can be produced. Additionally, liquids in the form of liquids of sodium hydroxide, sodium silicate and water can be added, for example, in amounts of 5-10 wt%.

34.8 kg (16%) Sodium silicate

21.4 kg (10%) Sodium hydroxide

6.7 kg (3%) Sodium carbonate

159.1 (71%) Ground Granulated Blast Furnace Slag EXAMPLE 2 A 1000 kg structure was produced form the dry mixture as described in example 1. The following components were mixed in a mixer: 222 kg of geopolymer mixture as described in example 1 477 kg of coral material 159 kg of sand with a nominal maximum coarse diameter of 4 mm

0.33 kg admixture in the amount of 1.2 wt % of the dry mixture 105 kg of water The wet mass was poured into a mould and cured to obtain a structure block having the following mechanical strength values: Compressive strength, measured according to ASTM C39/C39M — 18c “Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens”: 1 day: 7 MPa 7 days: 35 MPa

28 days: 45 MPa Flexural strength, measured according to ASTM C78/C78M — 18 “Standard Test Method for Flexural Strength of Concrete (Using Simple Beam with Third-Point Loading): 28 days: 4 MPa Young modulus, measured according to ASTM C469/C469M — 14 “Standard Test Method for Static Modulus of Elasticity and Poisson’s Ratio of Concrete in Compression”: 28 days: 17 GPa While steps of the method are shown and described in a specific order, steps can be performed in a different order and/or some steps may be performed simultaneously. Alternately, some steps may be omitted in some situations depending on the desired method of foaming and/or the material used.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (22)

Conclusions A method of forming a structure, the method comprising: a) obtaining coral material; b) mixing the coral material with a binder system to form a mixture; and c) forming a structure from the mixture. The method of claim 1, wherein step c) comprises: placing the mixture in a mold to form the structure. The method of claim 2, wherein step c) further comprises solidifying the mixture in the mold and then removing the mold. A method according to any preceding claim and further comprising curing the structure. A method according to any one of the preceding claims, wherein step a) comprises: collecting coral material. The method of any preceding claim, wherein step a) comprises: obtaining originally present coral material from a location where the structure is to be placed. A method according to any preceding claim, wherein step b) comprises mixing the coral material with one or more activators, one or more binding agents, and liquid to form the mixture. The method of claim 7, wherein step b) further comprises adding one or more additives to form the mixture. The method of any one of claims 7-8, wherein step b) further comprises adding one or more leach components to form the mixture, the leach components being configured to form the structure when placed in an underwater environment. A method according to any one of claims 7-9, wherein the one or more binders comprises one or more of the following: blast furnace slag, basic oxygen furnace slag, fly ash, metakaolin, thermally modified clays and iron aluminate silicates. A method according to any preceding claim wherein step b) comprises mixing the coral material with a binder system to form a mixture which is 33% - 75% coral material. A method according to any one of the preceding claims, wherein the binder system is a geopolymeric binder system. 13. Structure comprising: a geopolymeric binder system; and coral material. The structure of claim 13, wherein the coral material is originally present at the location where the structure is to be used. The structure of any one of claims 13 to 14, wherein the geopolymeric binder system comprises: at least one binder selected from: blast furnace slag, basic oxygen furnace slag, fly ash, metakaolin, thermally modified clays and iron aluminate silicates; and at least one activator. The structure of claim 15, wherein the at least one activator is one or more of: Sodium Silicate with Na2O (8-20%) and SiO2 (25-30%), Meta silicate, Alkali Carbonate, Sodium Hydroxide, Aluminate, Calcium Hydroxide, and magnesium oxide. A structure according to any one of claims 13-16, wherein the structure comprises an outer surface, an inner surface and at least one gap between the outer surface and the inner surface. 18, Mixture for forming a structure, the mixture comprising: a binder; an activator; and coral material. A mixture according to claim 18, wherein the binder is one or more of: blast furnace slag, oxygen steel furnace slag, fly ash, metakaolin, thermally modified clays and iron aluminate silicates. A mixture according to any one of claims 18-19, wherein the activator is at least one of Sodium Silicate with Na2O (8-20%) and SiO2 (25-30%), Meta silicate, Alkali Carbonate, Sodium Hydroxide, Aluminate, Calcium Hydroxide, and magnesium oxide. The mixture of any one of claims 18 to 20, and further comprising one or more additives and/or leaching components. The mixture of claim 21, wherein the one or more additives and/or leaching components comprise one or more of: modified starch, polyglycols, superplasticizers, saturated hydrocarbons C6-C20, polypropylene, polypropylene fibers and calcium carbonate.