Marine water as hydration agent for reactive magnesium oxide cement

Abstract

The systems and methods include a method. The method can include mixing, for a first time period, salt water with reactive magnesium oxide cement (RMC) at a first ratio to create a first mixture. The method can include mixing, for a second time period, the first mixture with an aggregate at a second ratio to create a second mixture. The method can include hydrating, for a third time period, the second mixture by molding and covering the second mixture. The method can include curing, for a fourth time period, the second mixture in a chamber to create an RMC-based composite, the chamber having a temperature value, a humidity value, and a CO2 concentration value.

Description

Atty. Dkt. No.: 046434-0902 MARINE WATER AS HYDRATION AGENT FOR REACTIVE MAGNESIUM OXIDE CEMENT CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to U.S. Provisional Patent App. No. 63 / 690,189 filed on September 3, 2024, the disclosure of which is incorporated herein by reference in its entirety for all purposes. TECHNICAL FIELD

[0002] The present disclosure relates generally to using marine water as the hydration agent for reactive magnesium oxide cement. BACKGROUND

[0003] Reactive magnesium oxide cement (RMC) samples, when subjected to accelerated carbonation curing, can achieve high strength comparable to those produced with ordinary Portland cement (OPC). However, the initial hydration and carbonation reactions form brucite and hydrated magnesium carbonate layers, which inhibit the further diffusion of CO2 into the RMC matrix, even under accelerated carbonation conditions. This significantly limits the conversion of MgO to hydrated magnesium carbonates (HMCs), hindering the CO2 sequestration (e.g., absorption) potential of RMC-based composites, which have potential to be sustainable building materials. Various approaches have been attempted to enhance the hydration and carbonation of RMC-based composites. However, due to the limited diffusion of CO2 by the shielding mechanisms of brucite and hydrated magnesium carbonate layers, the strength increase remains limited under prolonged carbonation for 28 days. SUMMARY

[0004] At least one aspect of the present disclosure is directed to a method. The method can include mixing, for a first time period, salt water with reactive magnesium oxide cement (RMC) at a first ratio to create a first mixture. The method can include mixing, for a second time period, the first mixture with an aggregate at a second ratio to create a second mixture. The method can include hydrating, for a third time period, the second mixture by molding and covering the second mixture. The method can include curing, for a fourth time period, theAtty. Dkt. No.: 046434-0902 second mixture in a chamber to create an RMC-based composite, the chamber having a temperature value, a humidity value, and a CO2 concentration value.

[0005] In some implementations, the salt water can include Na+, Cl-, Mg2+, SO42-, and Ca2+. The aggregate can include ASTM C778 sand. The first ratio can be between 0.5 to 1, inclusive, water to RMC and the second ratio can be between 2.5 to 3.25, inclusive, sand to RMC. The first time period can be between 1 and 10 minutes, inclusive, the second time period can be between 2 to 12 minutes inclusive, the third time period can be between 0.5 to 5 days, inclusive, and the fourth time period can be between 3 to 40 days, inclusive.

[0006] In some implementations, the temperature value is between 25 to 35^C, inclusive, the humidity value is between 65 to 95%, inclusive, and the CO2 concentration value is between 10 to 30%, inclusive. The RMC can include at least 92% of reactive magnesium oxide (MgO). The method can include obtaining salt water including Na+, Cl-, Mg2+, SO42-, and Ca2+. The method can include filtering the salt water to remove sand and contaminants. The RMC-based composite can include the RMC, the sand, and at least one of: brucite (Mg(OH)2), magnesite(MgCO3), calcite (CaCO3), nesquehonite (MgCO 3H O), hydromagnesite((Mg (CO ) (OH) 4H O)), periclase (MgO), or dypingite (Mg (CO ) (OH) 5H O).

[0007] At least one aspect of the present disclosure is directed to a system for producing a reactive magnesium oxide cement (RMC)-based composite. The system can include a first mixer to mix, for a first time period, marine water with RMC at a first ratio to create a first mixture. The system can include a second mixer to mix, for a second time period, the first mixture with sand at a second ratio to create a second mixture. The system can include a mold to hold the second mixture for a third time period, wherein the mold is covered to hydrate the second mixture. The system can include a curing chamber to cure a hydrated second mixture at a temperature, humidity, and CO2 concentration for a fourth time period, the curing chamber to output the RMC-based composite at an end of the fourth time period.

[0008] In some implementations, the first time period is between 1 and 10 minutes, inclusive, the second time period is between 2 to 12 minutes inclusive, the third time period is between 0.5 to 5 days, inclusive, and the fourth time period is between 3 to 40 days, inclusive. In some implementations, the temperature is between 25 to 35^C, inclusive, the humidity is between 65 to 95%, inclusive, and the CO2 concentration is between 10 to 30%, inclusive. TheAtty. Dkt. No.: 046434-0902 first ratio can be between 0.5 to 1, inclusive, water to RMC and the second ratio can be between 2.5 to 3.25, inclusive, sand to RMC.

[0009] In some implementations, the RMC includes at least 92% by weight reactive magnesium oxide (MgO). The RMC-based composite can include the RMC, the sand, and at least one of: brucite (Mg(OH)2), magnesite (MgCO3), calcite (CaCO3), nesquehonite(MgCO 3H O), hydromagnesite ((Mg (CO ) (OH) 4H O)), periclase (MgO), or dypingite(Mg (CO ) (OH) 5H O). The marine water is filtered before being mixed with the RMC. Themarine water can include Na+, Cl-, Mg2+, SO42-, and Ca2+. The marine water can include the Na+in a concentration between 15,000 to 20,000 parts per million (ppm), the Cl- in a concentration between 29,000 to 35,000 ppm, the Mg2+in a concentration between 1,500 to 3,000 ppm, the SO42-in a concentration between 3,500 and 6,500 ppm, and the Ca2+in a concentration between 500 and 3,000 ppm.

[0010] At least one aspect of the present disclosure is directed to a material. The material can include reactive magnesium oxide cement (RMC), fine aggregate, coarse aggregate, brucite(Mg(OH)2), magnesite (MgCO3), calcite (CaCO3), nesquehonite (MgCO 3H O), andhydromagnesite ((Mg (CO ) (OH) 4H O)).

[0011] In some implementations, the fine aggregate has a size of between 0.075 to 4.75 millimeters (mm) and the coarse aggregate has a size of between 4.75 to 38 mm.

[0012] It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the subject matter disclosed herein. BRIEF DESCRIPTION OF THE FIGURES

[0013] The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several implementations in accordance with the disclosure and are therefore not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings.Atty. Dkt. No.: 046434-0902

[0014] FIG.1 is a block diagram of an example system for creating a reactive magnesium oxide cement (RMC)-based composite, according to some implementation of the present disclosure;

[0015] FIG.2 is a chart of X-ray diffraction (XRD) results of RMC with marine water samples at 7, 14, and 28 days of curing;

[0016] FIG.3 is a chart of nuclear magnetic resonance (NMR) results of RMC with marine water and RMC with magnesium acetate samples at 28 days of curing; and

[0017] FIG.4 is a flow diagram of an example method, according to some implementation of the present disclosure.

[0018] Reference is made to the accompanying drawings throughout the following detailed description. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative implementations described in the detailed description, drawings, and claims are not meant to be limiting. Other implementations may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and made part of this disclosure. DETAILED DESCRIPTION

[0019] Implementation described herein relate generally to reactive magnesium oxide cement (RMC) with marine water as a hydration agent. RMC can be a sustainable alternative to ordinary Portland cement (OPC) due to its lower production temperatures, ability to sequester CO2, and recyclability. Using marine water can address challenges of freshwater scarcity and aims to reduce the carbon footprint associated with OPC production as RMC is capable of carbon sequestration.

[0020] Cement is a powder substance that acts as a binding agent when mixed with water, aggregates (e.g., sand), and other materials which then hardens and sets over time. Cement is used in a variety of applications such as for concrete, plastering, structural components of buildings, and the like. OPC is a widely used cement due to its strength, versatility, andAtty. Dkt. No.: 046434-0902 relatively low cost but is also associated with significant CO2emissions produced during the manufacturing process of OPC. RMC is primarily composed of reactive MgO and is used in a variety of applications with a reduced environmental impact compared to OPC due to lower CO2 emissions produced during the manufacturing process. The reactive MgO can be produced by calcining minerals with magnesium at low temperatures (e.g., 600 to 750^C), thus retaining the reactive properties of MgO with water. Alternatively, non-reactive MgO can be produced by calcining the minerals with magnesium at temperatures of 1000^C or more. Calcining the minerals at low temperatures results in a higher reactivity, higher surface area, and greater porosity of the MgO compared to calcining at high temperatures.

[0021] Cement is formed and activated in multiple steps, first, by combining raw meal, limestone, and other materials in traditional cement, with water (e.g., the hydration agent) and other materials. The other materials can include aggregates to bulk and structural integrity. This causes the cement to undergo hydration where the cement undergoes a chemical reaction with water which contributes to the material properties of the cement. Following hydration, cement can also be carbonated where CO2is introduced to the cement, and chemical reactions occur with the CO2 to enhance the material properties of the cement. Both the hydration and carbonation process can last days until the cement reaches its resulting material properties.

[0022] The use of marine water, which contains dissolved salts such as MgCl2 and MgSO4, can enhance the initial hydration and later carbonation processes of RMC. For example, the MgCl2 and MgSO4 reacts with water (e.g., H2O) and CO2 to enhance material properties (e.g., strength) of an RMC-based composite following hydration and carbonation. The enhanced material properties can be contributed to the presence of magnesite, formed by marine water and RMC. The dense and stable crystalline structure of magnesite can improve the compressive strength and overall toughness of the RMC-based composite material. By using marine water, the reliance on freshwater or tap water resources can be reduced, which is particularly beneficial in regions with limited freshwater availability (e.g., coastal, desert areas). This can both promote water conservation and environmental sustainability.

[0023] The CO2 sequestration enhancement of the RMC-based composite contributes to a lower carbon footprint of RMC compared to OPC. Additionally, enhanced carbonation of RMC-based composites can contribute to CO2 sequestration, further reducing the overall environmental impact. The RMC-based composite can sequester CO2during the manufacturing process, and can continue to sequester CO2 following curing and application.Atty. Dkt. No.: 046434-0902 For example, the CO2absorbed during a carbonation period of 28 days of the RMC-based composite was quantified and normalized to an MgO weight of the RMC-based composite to be about 38% (e.g., 0.38 mass of CO2absorbed per mass of RMC-based composite). The RMC- based composite can also be durable due to the presence of magnesite which is known for its superior thermal and chemical stability compared to other magnesium carbonates. Magnesite has an anhydrous nature which can contribute to its stability under various environmental conditions. Also, the presence of salts in marine water can improve the durability and thereby the resistance of RMC to aggressive environmental conditions, making it particularly suitable for marine and coastal construction applications.

[0024] FIG. 1 is a flow diagram of an example system 100 for creating a reactive magnesium oxide cement (RMC)-based composite, according to some implementation of the present disclosure. The system 100 can include a first mixer 102A (e.g., stand mixer, etc.). The first mixer 102A can include one or more inputs, and mix (e.g., blend, etc.) the inputs together. The first mixer 102A can receive a first solute 104A. The first solute 104A can be a cement (e.g., a binding agent). In various implementation, the first solute 104A can be RMC which can include reactive MgO, additives, supplementary cementitious materials (SCMs), activators, chemical admixtures, and / or fillers. The RMC may be composed of at least 92% or more reactive MgO. A remaining composition (e.g., about 8%) may include impurities such as, but not limited to, quartz (SiO2) and calcite (CaCO3). In some implementation, the RMC may be composed of 92% or less of reactive MgO.

[0025] The first mixer 102A can hydrate the first solute 104A (e.g., undergo a hydration process). The first mixer 102A can hydrate the first solute 104A by mixing the first solute 104A with a solvent 106 (e.g., a hydration agent). The first mixer 102A can receive both the first solute 104A and the solvent 106, and mix the first solute 104A and the solvent 106 together. The solvent 106 can be water, tap water, fresh water, salt water, and / or marine water. The solvent 106 may be water used in industrial processes such as, but not limited to, water jet cutting. In various implementation, the solvent 106 is salt water, for example marine water. The marine water can be collected from the Persian Gulf (e.g., Arabian Gulf), and can contain a variety of dissolved salts, such as, but not limited to, NaCl, MgCl2, and MgSO4. For example, the Persian Gulf marine water can contain concentrations of Na+, Cl-, Mg2+, SO42-, Ca2+and K+. The Na+can have a concentration between 15,000 to 20,000 parts per million (ppm), the Cl- can have a concentration between 29,000 to 35,000 ppm, the Mg2+can have a concentrationAtty. Dkt. No.: 046434-0902 between 1,500 to 3,000 ppm, the SO42-can have a concentration between 3,500 and 6,500 ppm, and the Ca2+can have a concentration between 500 and 3,000 ppm. For example, the Na+has a concentration of 16,504 ppm, the Cl- has a concentration of 30,002 ppm, the Mg2+has a concentration of 2,074 ppm, the SO42-has a concentration of 4,467 ppm, and the Ca2+has a concentration of 1,639 ppm. In the case that the solvent 106 is marine water, following collection of the marine water, the marine water can be left to settle (e.g., left undisturbed) to allow gravity to separate sand and larger particles from the marine water. The marine water can be left to settle for 24 hours. In some implementations, the marine water can settle for less than 24 hours, such as 12 hours, or more than 24 hours, such as 36 hours. Following settling, the marine water can be filtered via a fine mesh filter to remove smaller impurities in the marine water. The smaller impurities can include, for example, seaweed and suspended solids.

[0026] The first mixer 102A can mix the first solute 104A with the solvent 106 at a first ratio for a first time period to create, generate, or otherwise make a first mixture 108A. The first ratio can be in a range of 0.5 to 1, inclusive, of the solvent 106 to the first solute 104A. The first mixer 104 can mix the first solute 104A and the solvent 106 at a constant speed. In some implementations, the fist ratio can have a range different than 0.5 to 1, such as 0.5 to 2. The first time period can be between 1 and 10 minutes, inclusive. For example, marine water and RMC can be mixed at a constant ratio of 0.7, marine water to RMC, for 3 minutes. In some implementations, the first time period can be less than 1 or more than 10 minutes. The first mixture 108A can include a hydration reaction product as a result of the first mixer 102A mixing the first solute 104A with the solvent 106. The hydration reaction product can be, for example, brucite (Mg(OH)2).

[0027] The system 100 can include a second mixer 102B. In some implementations, the second mixer 102B can be same as the first mixer 102A and in other implementations, the second mixer 102B can be different from the first mixer 102A. The second mixer 102B can receive the first mixture 108A and a second solute 104B. The second mixer 102B can mix the first mixture 108A and the second solute 104B at a constant speed. The second solute 104B can include aggregates such as, but not limited to, gravel, crushed stone, slag, and / or sand. The aggregates can include coarse aggregates (e.g., a size of 4.75 to 38 millimeters (mm)) and fine aggregates (e.g., a size of 0.075 to 4.75 mm). The second solute 104B can include coarse and fine aggregates in a ratio. For example, the second solute 104B can include fine aggregate in a range of 25 to 45 percent of a total volume of the second solute 104B, and the coarse aggregateAtty. Dkt. No.: 046434-0902 can be in a range of 55 to 75 percent of the total volume of the second solute 104B. In various implementation, the second solute 104B is ASTM C778 sand or construction sand. The second mixer 102B can mix the first mixture 108A and the second solute 104B to produce a second mixture 108B.

[0028] In some implementations, the first mixture 108A can be moved from the first mixer 102A to the second mixer 102B by an operator of the system 100. In other implementations, the system 100 can include one or more belts, funnels, or other transfer devices or mechanisms to automatically transfer the first mixture 108A from the first mixer 102A to the second mixer 102B. In some implementations, the first mixer 102A can include at least one inlet to receive the first solute 104A and the solvent 106. The first mixer 102AA can include at least one outlet to output the first mixture 108A. The second mixer 102B can include at least one inlet to receive the first mixture 108A and the second solute 104B. The second mixer 102B can include at least one outlet to output the second mixture 108B.

[0029] The second mixer 102B can mix the second solute 104B with the first mixture 108A at a second ratio for a second time period. The second ratio can be between 2.5 to 3.25, inclusive, second solute 104B to first solute 104A. In some implementations, the second ratio can be different from 2.5 to 3.25, such as 1 to 5. The second time period can be between 2 to 12 minutes, inclusive. For example, ASTM C778 sand can be added to a water and RMC mixture at a ratio of 2.75 ASTM C778 sand to RMC and blended for 5 minutes. In some implementations, the second time period can be less than 2 minutes or greater than 12 minutes.

[0030] Following generation of the second mixture 108B, to continue the hydration process, the second mixture 108B can be poured into a mold 110 and covered to prevent moisture loss. For example, the operator of the system 100 can remove the second mixture 108B from the second mixer 102B, and pour, place, or otherwise move the second mixture 108B into the mold 110. In some implementations, the second mixer 102B can pour the second mixture 108B into the mold 110. The mold 110 can be a frame or formwork that defines a shape, size, and surface finish of a cured second mixture 108B. The mold 110 can be formed from a material, such as at least one of metal, plastic, wood, or any other material. The mold 110 can include one or more core inserts to facilitate demolding. In some implementations, the mold 110 can include a release mechanism to facilitate a demolding process of a cured second mixture 108B.Atty. Dkt. No.: 046434-0902

[0031] The second mixture 108B can absorb (e.g., fully absorb) the solvent 106 while in the mold 110 to become a hydrated second mixture 108C. The mold 110 can be, for example, a 50 mm cube mold. The mold 110 including the second mixture 108B can be covered with, for example, a plastic sheet for a third time period. The mold 110 can hold the second mixture 108B for at least the third time period. The third time period can be between 0.5 and 5 days, inclusive. In some implementations, the third time period is less than 0.5 or greater than 5 days. In various implementation, the mold 110 including hydrated second mixture 108C can be demolded during the third time period. For example, the hydrated second mixture 108C can be demolded (e.g., removed from the mold 110) after 1 day, and then continue to be covered for another 2 days to complete the hydration process. In some implementations, the hydrated second mixture 108C is demolded at the end (e.g., expiration) of the third time period.

[0032] The hydrated second mixture 108C, can undergo carbonation by being placed in a curing chamber 112 for a fourth period of time to create a composite 114 (e.g., final product, RMC cement, etc.). The curing chamber 112 can be an environmentally controlled chamber with adjustable parameters. The adjustable parameters can include, but not limited to, temperature, humidity, and CO2 concentration. For example, for curing the hydrated second mixture 108C, the curing chamber 112 can have a temperature value between 25 to 35^C, inclusive, a humidity value between 65 to 95%, inclusive, and a CO2 concentration value between 10 to 30%. In some implementations, the temperature value can be less than 25 or greater than 35^C, the humidity value can be less than 65 or greater than 95%, and the CO2 concentration value can be below 10 or greater than 30%. The fourth period of time can be between 3 and 40 days, inclusive. In some implementations, the fourth period of time can be less than 3 days or greater than 40 days. For example, the hydrated second mixture 108C can be placed in the curing chamber 112 for 28 days with a temperature of 30^C, a humidity of 80%, and a CO2 concentration of 20%. The hydrated second mixture 108C can include marine water, RMC, ASTM C778 sand, and other elements. The temperature value, the humidity value, and the CO2 concentration value can be changed based on a composition of the hydrated second mixture 108C. For example, the humidity value can be lowered as a weight percent of marine water increases in the hydrated second mixture 108C.

[0033] The curing chamber 112 can receive the hydrated second mixture 108C and output the composite 114. The composite 114 can thus be created by curing the hydrated second mixture 108C for the fourth period of time in the curing chamber 112. The composite 114 canAtty. Dkt. No.: 046434-0902 include the first solute 104A, the second solute 104B, and a plurality of carbonation reaction byproducts. For example, the hydration process (e.g., first mixer 102A) introduces the solvent 106 while the carbonation process (e.g., curing chamber 112) introduces CO2to the hydrated second mixture 108C. Hydration reactions, such as the formation of brucite from the reaction of MgO and water, may predominately occur in the first mixer 108A and the second mixer 108b. The hydration reaction can include MgO + H2O = Mg(OH)2.

[0034] Carbonate reactions may dominate the process in the curing chamber 112. For example, the carbonation process may result in the conversion, over time, of the majority of the brucite to various forms of magnesium carbonates. The plurality of reaction carbonationbyproducts in the composite 114 can include, for example, nesquehonite (MgCO 3H O),hydromagnesite (Mg (CO ) (OH) 4H O), and dypingite (Mg (CO ) (OH) 5H O). Forexample, the carbonate reactions can include at least one of Mg(OH)2 + CO2 + 2H2O MgCO3 ^ 3H2O (nesquehonite), 5Mg(OH)2+ 4CO2Mg5(CO3)4(OH)2^ 4H2O (hydromagnesite), or 5Mg(OH)2 + 4CO2 + H2O Mg5(CO3)4(OH) 2 ^ 5H2O (dypingite). Reactions for the formationof magnesite (MgCO ) from MgO or Mg(OH) in ambient carbonation conditions in the curingchamber 112 can include, but not limited to, at least one of Mg(OH)2+CO2 MgCO3+H2O orMgCO3 nH2O MgCO3+nH2O (e.g., conversion of at least one ofnesquehonite,hydromagnesite, or dypingite to magnesite upon at least one of dehydration or recrystallization).

[0035] The composite 114 can be a RMC-based composite. In this case, the composite 114can include nesquehonite, hydromagnesite, magnesite, brucite (Mg(OH) ), calcite (CaCO ),and periclase (MgO). As another example, the composite 114 can include the composite includes the RMC, the sand, and at least one of: brucite (Mg(OH)2), magnesite (MgCO3),calcite (CaCO3), nesquehonite (MgCO 3H O), hydromagnesite ((Mg (CO ) (OH) 4H O)),periclase (MgO), or dypingite (Mg (CO ) (OH) 5H O).

[0036] FIG.2 is a chart 200 of X-ray diffraction (XRD) results of RMC with marine water samples at 7, 14, and 28 days of curing. The RMC with marine water samples of the chart 200 can be created by the system 100. In this case, the first solute 104A is RMC, the solvent 106 is marine water collected from the Persian Gulf, the second solute 104B is ASTM C778 sand, and the samples were cured in the curing chamber 112 for 7, 14, and 28 days at a temperature of 30^C, a humidity of 80%, and a CO2 concentration of 20%. The samples cured for 7 days had a compressive strength of 53.2 MPa while the samples cured for 28 days had a compressiveAtty. Dkt. No.: 046434-0902 strength of 81.1 MPa. Samples of RMC with freshwater (e.g., tap water) had compressive strengths of 30-40 MPa when cured for 28 days at 30^C, a humidity of 80%±5%, and a CO2 concentration of 10-20%.

[0037] Referring further to the chart 200, an increased intensity of both magnesite and nesquehonite within the RMC-composite can correlate to the higher strength of the RMC- composite compared to, for example OPC.

[0038] As shown in FIG.2, the RMC with marine water samples include magnesite, a concentration of the magnesite in the sample increasing from 7 to 28 days. The magnesite is a carbonation reaction byproduct (e.g., reaction byproduct of the carbonation process). Common carbonation phases found in RMC may include nesquehonite and hydromagnesite. However, these are considered metastable phases, and may be transformed to stable phases under certain conditions. The magnesite was formed by a reaction pathway facilitated by the ionic composition of the Persian Gulf marine water. Environmental factors contributing to the formation of magnesite can include ions from the marine water (e.g., salt water), CO2 concentration (e.g., during carbonation), pH (e.g., of the marine water), and temperature (e.g., during carbonation). In some implementation, a high ion concentration (e.g., compared to tap water) of the marine water may contribute to the formation of the magnesite.

[0039] FIG.3 is a chart 300 of nuclear magnetic resonance (NMR) results of RMC with marine water and RMC with magnesium acetate samples at 28 days of curing. As shown in the chart 300, the RMC with marine water samples include magnesite and hydroxy-hydrated magnesite. Magnesium acetate is a chemical agent which can also be added to RMC. The chart 300 also illustrates an increased amount of magnesite within the RMC with marine water compared to, for example, the RMC with magnesium acetate samples.

[0040] FIG. 4 is a flow diagram of an example method 400, according to some implementation of the present disclosure. Marine water (e.g., the solvent 106) is first mixed with RMC (e.g., the first solute 104A) to create a first mixture (e.g., the first mixture 108A) at block 402. The marine water can be mixed with RMC at a constant first ratio at block 404. The constant first ratio can be 0.7 water to RMC. The first mixture can then be mixed with sand (e.g., the second solute 104B) to create a second mixture (e.g., the second mixture 108B). The sand can be ASTM C7778 sand. At block 406, the second mixture can be hydrated. The second mixture can be hydrated by pouring the second mixture into a mold and covering the secondAtty. Dkt. No.: 046434-0902 mixture to allow the marine water to fully absorb into (e.g., hydrate) the RMC and sand. Hydrating the second mixture can create hydration reaction byproducts. In various implementation, the second mixture is poured into the mold, covered, removed from the mold, and then covered again. Hydrating the second mixture can take a time period of between 0.5 to 5 days, inclusive.

[0041] In some implementations, the method 400 can include obtaining the marine water. The marine water can include at least one of Na+, Cl-, Mg2+, SO42-, or Ca2+. The marine water can be filtered to remove sand and other contaminants or impurities, such as seaweed. The method 400 can include allowing the marine water to settle, such as by allowing gravity to pull larger aggregates, such as sand, from the water. The method 400 can include passing the marine water through a filter to remove smaller contaminants, such as seaweed parts and other impurities, prior to providing the marine water to be mixed with the RMC.

[0042] At block 408, the second mixture is cured. Following hydration of the second mixture, the second mixture is then placed into a chamber (e.g., the curing chamber 112). The second mixture is then cured for a time period ranging from 4 to 40 days, inclusive. The chamber can cure the second mixture at a temperature between 25 to 35^C, inclusive, a humidity between 65 to 95%, inclusive, and a CO2 concentration value is between 10 to 30%, inclusive. For example, the second mixture is cured for 28 days at 30^C, 80% humidity, and 20% CO2concentration. Curing the second mixture can create carbonation reaction byproducts. The cured second mixture can be a RMC-based composite (e.g., the composite 114). The RMC- based composite can include magnesite, and have been created with marine water as a hydration agent (e.g., the solvent 106). Definitions.

[0043] As used herein, the singular forms ^a,^ ^an,^ and ^the^ include plural referents unless the context clearly dictates otherwise. Thus, for example, the term ^a member^ is intended to mean a single member or a combination of members, ^a material^ is intended to mean one or more materials, or a combination thereof.

[0044] As used herein, the terms ^about^ and ^approximately^ generally mean plus or minus 10% of the stated value. For example, about 0.5 would include 0.45 and 0.55, about 10 would include 9 to 11, about 1000 would include 900 to 1100.Atty. Dkt. No.: 046434-0902

[0045] It should be noted that the term ^exemplary^ as used herein to describe various implementation is intended to indicate that such implementation are possible examples, representations, and / or illustrations of possible implementation (and such term is not intended to connote that such implementation are necessarily extraordinary or superlative examples).

[0046] As used herein, the terms ^coupled,^ ^connected,^ and the like mean the joining of two additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another.

[0047] It is important to note that the construction and arrangement of the various exemplary implementation are illustrative only. Although only a few implementation have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary implementation without departing from the scope of the present invention.

[0048] While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any inventions or of what may be claimed, but rather as descriptions of features specific to particular implementations of particular inventions. Certain features described in this specification in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

Claims

Atty. Dkt. No.: 046434-0902 WHAT IS CLAIMED IS:

1. A method, comprising: mixing, for a first time period, salt water with reactive magnesium oxide cement (RMC) at a first ratio to create a first mixture; mixing, for a second time period, the first mixture with an aggregate at a second ratio to create a second mixture; hydrating, for a third time period, the second mixture by molding and covering the second mixture; and curing, for a fourth time period, the second mixture in a chamber to create an RMC- based composite, the chamber having a temperature value, a humidity value, and a CO2 concentration value.

2. The method of claim 1, wherein the salt water comprises Na+, Cl-, Mg2+, SO42-, and Ca2+.

3. The method of claim 1, wherein the aggregate comprises ASTM C778 sand.

4. The method of claim 1, wherein the first ratio is between 0.5 to 1, inclusive, water to RMC and the second ratio is between 2.5 to 3.25, inclusive, sand to RMC.

5. The method of claim 1, wherein the first time period is between 1 and 10 minutes, inclusive, the second time period is between 2 to 12 minutes inclusive, the third time period is between 0.5 to 5 days, inclusive, and the fourth time period is between 3 to 40 days, inclusive.

6. The method of claim 1, wherein the temperature value is between 25 to 35^C, inclusive, the humidity value is between 65 to 95%, inclusive, and the CO2 concentration value is between 10 to 30%, inclusive.

7. The method of claim 1, wherein the RMC includes at least 92% of reactive magnesium oxide (MgO).

8. The method of claim 1, further comprising: obtaining salt water comprising Na+, Cl-, Mg2+, SO42-, and Ca2+; and filtering the salt water to remove sand and contaminants.Atty. Dkt. No.: 046434-0902 9. The method of claim 1, wherein the RMC-based composite includes the RMC, the aggregate, and at least one of: brucite (Mg(OH)2), magnesite (MgCO3), calcite (CaCO3),nesquehonite (MgCO 3H O), hydromagnesite ((Mg (CO ) (OH) 4H O)), periclase (MgO),or dypingite (Mg (CO ) (OH) 5H O).

10. The method of claim 1, wherein the salt water is marine water that is filtered before being mixed with the RMC.

11. The method of claim 10, wherein the marine water includes the Na+in a concentration between 15,000 to 20,000 parts per million (ppm), the Cl- in a concentration between 29,000 to 35,000 ppm, the Mg2+in a concentration between 1,500 to 3,000 ppm, the SO42-in a concentration between 3,500 and 6,500 ppm, and the Ca2+in a concentration between 500 and 3,000 ppm.

12. The method of claim 1, wherein the aggregate comprises a fine aggregate having a size of between 0.075 to 4.75 millimeters (mm) and a coarse aggregate having a size of between 4.75 to 38 mm.

13. A material, comprising: reactive magnesium oxide cement (RMC) containing at least 92% by weight reactive magnesium oxide (MgO); fine aggregate having a size of between 0.075 to 4.75 millimeters (mm); coarse aggregate having a size of between 4.75 to 38 mm.; brucite (Mg(OH)2); magnesite (MgCO3); calcite (CaCO3); nesquehonite (MgCO 3H O); andhydromagnesite ((Mg (CO ) (OH) 4H O)).

14. The material of claim 13, wherein the RMC has a range of 5 to 20 weight percent (wt.%), inclusive.

15. The material of claim 13, wherein the fine aggregate has a size of between 0.075 to 4.75 millimeters (mm) and the coarse aggregate has a size of between 4.75 to 38 mm.

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