Manufacturing method for composite materials

Abstract

The present invention relates to a method for producing a composite material from a cementitious body, aggregate, and reinforcing material. The cementitious body is produced by preparing a starting product containing at least 20% by mass of one or more components from ultramafic rock, weathered ultramafic rock, olivine, and / or industrial waste; homogenizing the starting product; and hydrothermally treating the homogenized starting product in a heat treatment apparatus at a temperature exceeding 100°C for at least 12 hours. Furthermore, the bound water of the converted starting product is dehydrated by heat treatment and / or reactive grinding. Subsequently, the converted and dehydrated starting product is used as a binder, and hardening water is added for hardening. The water / binder ratio is 1:2 or less. Before, after, and / or simultaneously with the addition of hardening water, aggregate and reinforcing material are added to the converted and dehydrated starting product to improve its load-bearing capacity. The reinforcing material is resistant to pH values ​​below 11 and / or provides protection against pH values ​​below 11. Additionally or alternatively, additives to increase the pH value of the pore solution in the cementitious material can be added to the starting product of the cementitious material.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a composite material from cementite, aggregate, and reinforcing material.

[0002] In current building construction, the use of reinforced concrete is essential. In reinforced concrete, the concrete absorbs compressive stress, while the reinforcing steel transmits tensile force. At the same time, the concrete protects the reinforcing steel from corrosion. This corrosion prevention is based on the very high pH value of the concrete's pore solution. When the pH value is approximately 11 or higher, ordinary reinforcing steel develops an extremely thin passivation layer on its surface, preventing rust. This layer blocks the penetration of oxygen and water from the reinforcing steel surface, preventing corrosion. The pore solution of concrete manufactured with cement compliant with DIN EN 197 has a pH value exceeding 12, and using these cements achieves effective corrosion prevention of reinforcing steel. Reinforced concrete is frequently used because it is a composite material that offers high performance and durability at a low cost. However, the production of conventional cement has a significant environmental impact. As a cement alternative, new binders have been proposed, particularly with the aim of reducing the carbon dioxide emissions of concrete. However, after hardening, some of these binders have a pH value below 11.5, losing their corrosion-preventive function for reinforcing steel, making them unsuitable for the production of reinforced concrete.

[0003] Various materials have been proposed as alternatives to steel reinforcement. Carbon fiber and glass fiber are particularly noteworthy. Both materials exhibit very high tensile strength and can be used for transmitting tensile forces in reinforced concrete. Another advantage is the corrosion resistance of both fiber types. Carbon fiber and glass fiber generally do not react with water or oxygen. However, high pH values ​​can negatively affect the composite effect and long-term durability of carbon fiber and / or glass fiber. Therefore, the use of these fibers in standard cements conforming to DIN EN 197 is difficult due to the high pH values ​​in the pore solution of these cements. In the case of glass fiber, such high pH values ​​can dissolve the fibers, potentially reducing their strength. For this reason, for use as reinforcement in concrete structures, glass types with high chemical resistance to alkalis must be used, or the glass must be protected from direct contact with the pore solution of the hardened cement with a protective layer. In the case of carbon fiber, the plastic (resin) used to bind the individual carbon fibers can degrade. Therefore, high pH values ​​can cause damage to both reinforcements.

[0004] The use of mineral fibers with inorganic binders (such as cement) is disclosed in DE2409231A1. To prevent the above problems, a method has been proposed to lower the pH value by additional treatment with CO2.

[0005] Furthermore, U.S. Patent No. 5,002,610 discloses a very fast-curing binder based on magnesium oxide and aluminum phosphate. However, its manufacturing process is extremely complex, requiring multiple drying and grinding steps and repeated mixing of different components. [Overview of the project] [Problems that the invention aims to solve]

[0006] Therefore, the present invention aims to provide a method for producing composite materials from cementitious bodies, aggregates, and reinforcing materials (which may include carbon fibers, glass fibers, and even reinforcing bars (steel reinforcements)). [Means for solving the problem]

[0007] This objective is achieved, according to the present invention, by a method having the features of claim 1. [Modes for carrying out the invention]

[0008] Further advantageous embodiments are shown in the dependent claims, detailed description, and exemplary embodiments.

[0009] According to claim 1, the manufacturing of the composite material according to the present invention is assumed to involve the use of at least a cementitious body, aggregate, and reinforcing material, similar to conventional concrete.

[0010] In this invention, the term "cementaceous body" is also used to refer to a hardened binder. In this invention, this hardened binder differs from conventional cementaceous bodies that contain a high proportion of hardened Portland cement. This invention mainly relates to the use of magnesium silicate-based binders that do not necessarily contain Portland cement clinker. These binders do not conform to DIN EN 197, but in the sense of this invention, the terms cementaceous body and concrete are used for products made from them.

[0011] According to the present invention, a starting product for producing a cement hardened body is prepared, and the starting product contains at least 20% by mass, preferably at least 40% by mass, more preferably at least 60% by mass, and even more preferably at least 80% by mass, of one or more of the following components. These components may be ultramafic rocks such as dunite, weathered products of ultramafic rocks such as serpentinite, olivine, or industrial waste. It is essential that all of these raw materials have a Mg concentration or Mg content of at least 5% by mass, preferably 10% by mass, more preferably 20% by mass or more, and ideally 30% by mass or more. The stated values ​​indicate the proportion of magnesium in the whole sample, and the element magnesium can exist in various phases such as olivine, enstatite, serpentinite, and other compounds. Therefore, the stated concentrations do not refer to the proportion of the MgO phase (periclase) in the starting product. Preferably, the starting product does not contain free MgO (periclase) and has magnesium at a predetermined elemental concentration. This starting product has a BET specific surface area of ​​0.1 m². 2 It has a fineness equivalent to or greater than / g. The BET specific surface area is 0.5m². 2 It is preferable that the BET specific surface area is 1.0 m² / g. 2 It is even more preferable that the BET specific surface area is 3.0 m² / g. 2 It is particularly preferable that the amount be 1 / g or more.

[0012] An important mineral in ultramafic rocks is olivine. This is a mixed crystal series with fayalite (Fe2SiO4), forsterite (Mg2SiO4), tefloite (Mn2SiO4), and other minerals in the form A2[SiO4] (where A can be various divalent ions or various combinations of cations). Natural olivine has been identified, and it is often a magnesium-rich material containing iron.

[0013] Serpentinite is a metamorphic rock formed by the weathering of ultramafic rocks and may contain mineral facies such as lizardite, antigorite, talc, other crystalline compounds, and amorphous compounds.

[0014] Examples of industrial waste or generated materials that can be used in the context of the present invention include foundry sand and refractory materials.

[0015] After the starting materials are prepared, homogenization is carried out as the next step, if necessary. The possible components of the starting materials listed above are often materials derived from natural rocks or natural mineral deposits. Empirically, these do not exist in a pure form and are not homogenized. Homogenization can be carried out, for example, using a mixer, or simultaneously during the grinding process to the desired fineness.

[0016] After homogenization, the prepared starting product is subjected to hydrothermal treatment. This is carried out in a heat treatment apparatus at a temperature above 100°C for at least 12 hours, preferably at least 24 hours. Examples of heat treatment apparatuses include heat treatment tunnels and autoclaves. An autoclave is generally understood to be an airtight, sealable pressure vessel that can be used for heat treatment of materials in an overpressure region. The heat treatment apparatus is preferably understood to be a combination of apparatus such as a container, an oven and a sealing mold, or an apparatus that encloses a volume. The treatment is preferably carried out at a temperature above 100°C, particularly above 150°C, more preferably above 200°C, and most preferably above 250°C. To obtain good conversion, it is advantageous to carry out the treatment for more than 36 hours, more preferably above 48 hours. However, particularly good results can be obtained by carrying out the treatment for a longer period of time, such as several days, for example, 4 days, preferably 7 days or more.

[0017] Furthermore, water is added to the homogenized starting product by direct addition of water, either before, after, or simultaneously with the homogenization process in the preceding step, and the water is mixed with the starting product. Alternatively or additionally, steam may also be introduced into the heat treatment apparatus.

[0018] During the hydrothermal treatment of the homogenized starting product, the presence of H2O causes the starting product to be at least partially magnesium hydroxide (Mg(OH)2) and magnesium silicate hydrate (Mg3Si2O5(OH)4, Mg3Si4O10 is at least partially converted to (OH)2). The underlying reaction is as follows, here shown simplified based on forsterite (Mg2SiO4).

[0019] [Chemical formula]

[0020] Here reaction (1) mainly occurs. This is also preferred in the context of the present invention because Mg3Si2O5(OH)4 is more suitable for subsequent curing than Mg3Si4O 10 (OH)2 and is thus preferred in the context of the present invention[[ID=??]] 。 Furthermore, it should be noted that the amounts and ratios of each product depend, inter alia, on the exact composition of the starting products.

[0021] Magnesium hydroxide (Mg(OH)2) may exist in the form of brucite. Magnesium silicate hydrates (Mg3Si2O5(OH)4, Mg3Si4O 10 (OH)2) may exist in the form of lizardite, antigorite, talc, etc. It should be noted that the stoichiometric water content may be lower than the values determined experimentally (16% to 20% by mass) (in the case of antigorite, in the range of 13% by mass). This can be explained by the fact that due to the very fine nature of part of the material, water can also adhere to its surface.

[0022] Similarly, such deviations from stoichiometry also apply to the ratio of Mg to Si. Furthermore, foreign ions such as Fe may also be incorporated into the reaction products. However, other reaction products such as hydromagnesite, hematite, magnetite, gibbsite, etc. may also be formed. This depends respectively on the exact composition of the starting products. All or part of the reaction products may contain iron, carbonate, alkali, and other foreign ions.

[0023] It should be noted that there seems to be an issue with the numbering in the original Japanese text where an "??" is shown for [[ID=??]] which might be an error in the original. The translation is done as accurately as possible based on the provided text.During the process, magnesium silicates such as olivine and enstatite contained in the starting product are not decomposed into oxides, and free SiO2 is not generated, whether in crystalline or amorphous form. SiO2 is not generated from magnesium silicate even in subsequent processing steps.

[0024] The converted starting product is then at least partially dehydrated from the bound water by heat treatment and / or reactive grinding. Bound water is sometimes also called water of crystallization. This must be distinguished from free water (which can be regarded as free H2O). Complete dehydration requires a great deal of effort. According to the present invention, the water content derived from bound water should be reduced by at least 60%, preferably at least 80%.

[0025] In heat treatment, the converted starting product can be heated in a temperature range of 180°C to 1000°C. Depending on the fineness, heating for a few minutes may already be sufficient. The heat treatment should not be carried out for more than 1 hour. A temperature range of 300°C to 800°C is preferred, and a temperature range of 500°C to 700°C is even more advantageous. Alternatively or additionally, the converted starting product can be subjected to reactive grinding to rearrange the crystal structure. In so-called reactive grinding, by rearranging the crystal structure, the water in the crystal structure can be removed from the converted starting product. For this purpose, auxiliary materials such as quartz can be added in the grinding process.

[0026] In this step, by dehydration, magnesium hydroxide (Mg(OH)2) present in the converted starting product is at least partially converted into magnesium oxide (MgO, periclase), and the existing magnesium silicate hydrate (Mg3Si2O5(OH)4, Mg3Si4O 10 (OH)2) is at least partially converted into dehydrated magnesium silicate hydrate. The dehydrated magnesium silicate hydrate can be simplified and represented as xMgO·SiO2·yH2O. Here, dehydration refers to the reduction of the water of crystallization in the converted starting product, that is, the water in the crystal structure.

[0027] The chemical process behind this, when simplified again, is as follows:

[0028] [ka]

[0029] In equation (4), a mainly amorphous reaction product is produced with a Mg-to-Si ratio of 1.5 to 2 and a residual water content of approximately 3%. The reaction product produced in equation (5) has a lower Mg-to-Si ratio. Therefore, variables a, b, c, x, y, and z exist. These depend on the exact composition of the starting products and the processing parameters, respectively.

[0030] After dehydration, the water content of bound water in the converted and dehydrated starting products is preferably less than 10% by mass, more preferably less than 5% by mass, even more preferably less than 3.5% by mass, and most preferably less than 2.5% by mass.

[0031] The converted and dehydrated starting products thus exist as multiphase products. Other possible subphases include hematite, magnetite, enstatite, feldspar, pyroxene, quartz, and amorphous phases.

[0032] At least partially converted and dehydrated starting products are used as a binder. Aggregate and curing water are added to the converted and dehydrated starting products for curing. The water / binder ratio is particularly in the range of 1:2 or less. In other words, converted and dehydrated starting products are used as a complete or partial cement substitute in the manufacture of cementitious bodies. The water-to-binder ratio is preferably 1:2 or less. This means a ratio of 1:2.22, preferably 1:2.5, ideally 1:2.86, and even more preferably 1:3.33 or less. Higher ratios, i.e., higher water content, have been found to prolong the curing process and reduce strength. Concrete manufactured in this way fixes CO2 from the ambient air even at room temperature and normal humidity. The partial pressure of CO2 should not exceed 1000 ppm, as exceeding this may increase shrinkage. During the curing process, no heat treatment, especially heating, should be performed to raise the reaction temperature.

[0033] After mixing with water, a chemical reaction occurs between the converted and dehydrated starting products and the mixed water. The phases formed in the previous calcination step (MgO, xMgO·SiO2·yH2O, aMgO·SiO2·bH2O, etc.) re-react with water. 、 Mg(OH)2, Mg3Si2O5(OH)4, Mg3Si4O 10 It forms hydrated compounds such as (OH)2 and other compounds. This corresponds to equations (3) to (5) with the reaction arrows reversed. The time course of the hydration reaction can be monitored by calorimetry (see Figure 1). The rate of heat release depends on several factors.

[0034] For example, if a starting product already contains at least 20% by mass of magnesium silicate hydrate (preferably at least 40% by mass, more preferably at least 60% by mass, and even more preferably at least 80% by mass), such as serpentinite, the water addition step and the hydrothermal treatment step can be omitted. In other words, this starting product can be processed only by the crushing step and the dehydration step, and no transformation step is required. Serpentinite is a metamorphic rock formed by the natural transformation (especially weathering) of ultramafic rocks.

[0035] To produce the composite material of the present invention, aggregates such as sand and gravel are added to the converted and dehydrated starting product before, after, and / or simultaneously with the addition of hardening water. For simplicity, within the scope of the invention, starting products containing serpentinite, which do not strictly require conversion, are also referred to as converted starting products.

[0036] In the construction industry, natural and artificial rock particles are collectively called aggregates. These are obtained from natural mineral deposits, recycled building materials, and industrial by-products. While nearly synonymous in the construction industry, these terms are now obsolete and include concrete aggregates, mineral mixtures, mineral mixtures, and mineral materials.

[0037] Furthermore, if necessary, reinforcing materials are added to the converted and dehydrated starting products before, after, and / or simultaneously with the hardening water to enhance their load-bearing capacity. For this purpose, reinforcing materials tolerant of pH values ​​below 11 are selected. Reinforcing materials protected from pH values ​​below 11, and / or additives that raise the pH of the pore solution of the hardened cement to above 11.0, are added to the starting products, particularly the converted and dehydrated starting products.

[0038] According to the present invention, it is recognized that by combining the discharge of crystalline water from natural materials such as ultramafic rocks with hydrothermal treatment, an intermediate material suitable for water-based hardening and self-solidification can be produced.

[0039] Olivine rocks usable in this invention include, for example, dunite, wahllite, and harzburgite. These rocks are often of low weathering. However, weathered rocks with similar chemical composition and higher water content can also be used. Weathered rocks include, for example, serpentinite.

[0040] Another fundamental concept of the present invention lies in the use of intermediate materials different from known Portland cement-based cements, which have relatively high pH values. According to the present invention, it is recognized that the pore solution of cementified bodies produced from converted and dehydrated starting products typically has a pH value of less than 11. This allows for the use of reinforcing materials consisting of glass fibers, carbon fibers, or composites thereof, which would otherwise lack stability in media with a pH value above 11 without additional treatment.

[0041] When using other reinforcing materials such as steel reinforcements, it is desirable to protect them from pH values ​​of less than 11 present in the pore solution of the cement hardened body of the present invention.

[0042] As an alternative or additional measure, depending on the reinforcing material used, other additives can be added to the serpentinite and / or olivine-based binder to raise the pH value of the pore solution above 11.0. For this purpose, for example, slaked lime, quicklime, alkalis such as sodium hydroxide or potassium hydroxide, and CKD (cement kiln dust, furnace dust from cement manufacturing) can be added.

[0043] At least when calcined (strengthened) serpentinite is used as the starting material, and preferably when natural or artificial olivine sources are used, it is desirable that the starting material does not contain erylite and belite, as these can cause hardening problems.

[0044] It is desirable that the pH value of the pore solution of the hardened cement is 11 or less. This is especially true when the hardened cement of the present invention is composed of substantially converted and dehydrated starting products. This eliminates the need for additional adjustments to the starting materials of the hardened cement when used in combination with reinforcing materials made of glass fibers and / or carbon fibers.

[0045] In principle, any reinforcing material can be used in accordance with the present invention. However, it is particularly advantageous to select reinforcing materials containing carbon, mineral fibers (especially basalt fibers), and / or glass fibers. These fibers have the advantage of being lighter than conventional steel reinforcing materials, while also having significantly lower CO2 emissions during the manufacturing process.

[0046] According to one embodiment, a reinforcing material formed without a protective layer that can withstand pH values ​​below 11 can be selected. This is particularly possible with reinforcing materials made of carbon fiber and / or glass fiber. However, in principle, a protective layer can be applied even to such low pH values. This is particularly applicable to steel reinforcing materials.

[0047] It is also advantageous to select reinforcing materials containing carbon fibers, mineral fibers (especially basalt fibers), and / or glass fibers in the form of fiber reinforcements, mat reinforcements, rod reinforcements, and / or other reinforcement forms. The advantage of using carbon fibers, mineral fibers (especially basalt fibers), and / or glass fibers is that they can be molded into any shape and used in the manufacture of composite materials. This makes it possible to select the optimal reinforcement form depending on the expected load.

[0048] In yet another embodiment, steel reinforcements may be used as an alternative or additional component in the composite material of the present invention. When these are used, it is particularly preferable to add Portland cement clinker to the converted and dehydrated starting product in addition to the cement hardened body. This is particularly suitable for raising the pH value, thereby preventing corrosion of the steel reinforcements due to low pH values. Furthermore, compared to other substances that affect the pH value, Portland cement clinker has the advantage of contributing to increased strength itself.

[0049] Furthermore, to protect against alkaline environments with a pH value below 11, it is possible to provide at least one protective layer on the reinforcing material. This protective layer can be formed, for example, by applying paint and / or varnish. The protective layer can be plastic-based. Another option is to hot-dip galvanize the steel reinforcing material.

[0050] The step of hydrothermally treating the homogenized starting product to convert it at least partially to magnesium hydroxide and / or magnesium silicate hydrate is one of the most time-consuming steps in this invention. Therefore, it is desirable to perform one or more treatments to accelerate the reactions that occur during the hydrothermal treatment. There are various treatment methods available for this purpose, which can be performed individually or in combination with each other. These will be described in more detail below. Here, all or some of the treatment methods described can be combined with each other.

[0051] To facilitate the transformation, one option is to continuously or intermittently grind or crush the homogenized starting product in a heat treatment facility during or between hydrothermal treatments, particularly to an extremely fine state.

[0052] Continuous or intermittent grinding can prevent or reduce material aggregation and clumping during hydrothermal treatment. This ensures sufficient surface area for the processes described above to proceed. Several options exist for precise implementation.

[0053] On the other hand, one could consider interrupting the hydrothermal treatment, removing the material from the heat treatment device, crushing or grinding it (for example, grinding it), and then supplying it back to the heat treatment device.

[0054] On the other hand, it is also possible to install a corresponding grinding device within the heat treatment apparatus and perform grinding continuously or intermittently during hydrothermal treatment.

[0055] Another option is to operate a heat treatment apparatus (especially a continuous one), discharge a portion of the material from the heat treatment apparatus during hydrothermal treatment, grind it, and return it to the heat treatment apparatus. This is particularly useful when the starting product is present in a suspension within the heat treatment apparatus, or at least in a form that can be pumped. In this case, it is possible to install piping, for example, from the autoclave to a grinding apparatus (such as a mill) and then back to the autoclave, which is an example of a heat treatment apparatus in the sense of the present invention. This can be called an uninterrupted circulation process.

[0056] Another possibility for accelerating the reaction is the hydrothermal treatment of homogenized starting products in a heat treatment apparatus, where the homogenized starting products are present in a suspension and continuously or intermittently stirred during the hydrothermal treatment. In this case, a stirrer can be provided, for example, to ensure the flow of the suspension.

[0057] In this context, as mentioned above, a grinding step can also be provided as an alternative or additional means. Wet grinding is particularly suitable here because a portion of the suspension can be removed from the heat treatment apparatus, wet-ground, and then returned to the apparatus. However, wet grinding can also be performed directly within the heat treatment apparatus.

[0058] Before the dehydration step, i.e., the separation of bound water, it may be advantageous to dry the homogenized and transformed starting products to remove free water. This is particularly recommended and useful when the hydrothermal treatment of the starting products is carried out in an aqueous suspension.

[0059] The dried starting product is then supplied to the dehydration process. The heat treatment proposed for this purpose is also called tempering or calcination. This can be carried out using heat treatment equipment such as a rotary kiln or a fluidized bed with circulating high-temperature gas. When using a fluidized bed, dehydration is completed within a few seconds. Alternatively, the necessary energy can be supplied electrically, for example, in a muffle furnace. In this case, it takes about 5 to 10 minutes. In principle, a system in which the material does not come into direct contact with the flame is preferred, because it is easier to precisely maintain the combustion temperature. Furthermore, an open system is preferred in order to remove the generated water vapor and promote the reaction.

[0060] It is desirable that the temperature distribution of the heat treatment apparatus be substantially uniform. This allows for good dehydration without forming undesirable by-products. Therefore, in order to maintain the desired dehydration temperature in the furnace as accurately as possible and for most of the material's residence time, it is advantageous not to heat the furnace with a direct flame. When the furnace is heated with a direct flame, the material is temporarily exposed to very high temperatures, resulting in the formation of olivine. For example, the temperature distribution in a directly heated rotary kiln is too uneven. Therefore, it is advantageous to use a rotary kiln as a heat treatment apparatus, especially an indirectly heated rotary kiln without an open flame in the reaction chamber. The temperature during heat treatment (also called the firing temperature) can be controlled particularly accurately in an electric heating furnace. Electric heating should be used, especially to precisely maintain the target temperature inside the furnace. Heating the furnace with electricity from renewable energy sources is advantageous because it does not produce CO2 emissions or exhaust gases and does not consume fuel. On the other hand, preheating can also be performed using other heat sources, especially heat exchangers. This heat exchanger extracts some of the heat from dehydrated starting materials, such as calcined serpentinite, and cools them while simultaneously supplying this heat to uncalcined serpentinite. The use of exhaust gases from the combustion process should also be avoided as much as possible, as this could, for example, cause uncontrolled CO2 bonding.

[0061] To achieve a sufficient residence time at the target temperature, a rotary kiln with a large volume and therefore high processing capacity is preferable. Rotary kilns are also characterized by their excellent thermal efficiency.

[0062] Another alternative is ultrasonic treatment of the homogenized starting product. Here, as in the grinding process, substances formed on the starting product (such as magnesium hydroxide or magnesium silicate hydrate) are separated from the remaining substances, and sufficient surface area is again provided for the reaction to proceed rapidly. This can be achieved using an ultrasonic horn or similar device.

[0063] Alternatively, nucleating agents, pH-raising agents, heterogeneous ions, and / or other additives that accelerate the reaction process may be added to the starting products at the start of the reaction, before homogenization, during homogenization, after homogenization, or in the heat treatment apparatus.

[0064] Nucleating agents such as brucite, lizardite, antigorite, pre-hydrated olivine-containing rock, or mixtures thereof can be added. It is preferable to add at least 2% by mass of the nucleating agent.

[0065] Substances that, upon addition, release NaOH, KOH, NaCl, KCl, Na2SO4, MgSO4, K2SO4, Na2CO3, Ca(OH)2 and / or K2CO3, thereby increasing the pH value of the solution and allowing the reaction to proceed more rapidly, can be added as pH-raising agents, thereby modifying the solution in which the reaction is proceeding.

[0066] Other additives that can accelerate the reaction include, for example, dolomite, feldspar, pyroxene, and mixtures thereof, but the addition of these substances may result in the formation of new reaction products. Examples of heterogeneous ions include aluminum, sulfates, or alkalis, which may also result in the formation of new reaction products. Additives containing magnesite, hydromagnesite, and / or nesquehonite should be avoided as they may delay the reaction under certain circumstances.

[0067] In principle, the reaction process in an autoclave can also be achieved by increasing the temperature. In particular, temperatures above 150°C, preferably above 200°C, and even more preferably above 250°C are applicable.

[0068] Starting product with a BET specific surface area of ​​0.1 m² 2 To adjust the fineness to a level equivalent to or greater than / g, it is desirable to subject the starting product to a grinding process, particularly a wet grinding process. Even if the starting product is already very fine due to natural weathering, it is usually not possible to obtain a finer grade than this. This fineness can be easily improved by grinding. Wet grinding is preferred here as well, as it is often more energy efficient than dry grinding. Since the starting product is then subjected to a hydrothermal treatment process in contact with water, the advantages of wet grinding can already be utilized in this process, as there is no need to dry the ground material.

[0069] Since the starting products provided according to the present invention are not usually pure substances, a considerable amount of impurities are present. However, it is advantageous that the molar ratio of Mg to Ca is at least 10:1, and / or the molar ratio of Si to Al is also at least 10:1. It has been shown that the presence of calcium and aluminum with respect to magnesium and silicon, respectively, delays the reaction and, in some cases, completely stops it. Therefore, it is important to shift the corresponding molar ratios significantly towards the magnesium and silicon side. Preferably, the molar ratio of Mg to Ca is at least 20:1, and / or the molar ratio of Si to Al is at least 20:1.

[0070] The present invention will be described in detail below with reference to the drawings and using exemplary embodiments. These drawings show the following: [Brief explanation of the drawing]

[0071] [Figure 1] Figure 1 shows the hydration curve of the product produced using the method of the present invention. [Examples]

[0072] To verify the present invention, experiments described in detail below were conducted. In the first experiment, pure forsterite was used, and in the second experiment, natural olivine was used. Furthermore, serpentinite was used in the fourth experiment.

[0073] Pure forsterite In the first experiment, pure forsterite (Mg2SiO4) was used. This pure forsterite was produced by calcining a mixture of magnesium carbonate hydroxide and amorphous SiO2 in a laboratory furnace. After calcination, the starting product was pulverized using a disc swing mill. The specific surface area obtained by the BET method was 1 m². 2 It was / g.

[0074] Forsterite and a 1 molar NaOH solution were mixed in a 1:2.2 ratio and treated in an autoclave at a temperature of 200°C. The reaction was interrupted, and the material was dried and pulverized. After 4 weeks of treatment, forsterite was not detected in the treated and washed material by X-ray phase analysis. The ignition loss after autoclaving was 19.3% by mass.

[0075] Three g each of the dried and pulverized material was taken, placed in a platinum crucible, and fired in a muffle furnace at 450°C, 600°C, and 750°C for one hour each. The loss on ignition of the fired samples was 13.5% at 450°C, 2.8% at 600°C, and 0.52% at 750°C.

[0076] The reactivity of the materials as binders was investigated by measuring their water binding capacity after 7 days of hydration. For this purpose, materials calcined at different temperatures were ground in a mortar and pestle, mixed with water at a ratio of 0.40 (1:2.5), and stored in a sealed container at 22°C for 7 days. Subsequently, the samples were dried at 60°C to stop the hydration reaction, and the loss on ignition was measured by thermal analysis.

[0077] As a result, the ignition loss was 20.5% at 450°C, 25.3% at 600°C, and 7.1% at 750°C, respectively. Therefore, all three types of binders were hydrated and bound water.

[0078] The hydration process of a sample calcined at 600°C was investigated by calorimetry (DCA) at 25°C. The results showed an extremely rapid reaction, with the main hydration stage reaching its maximum approximately 2 hours later, and the reaction was completed in less than 24 hours. As shown in Figure 1, a total of approximately 450 J / g of heat was released.

[0079] Therefore, this binder reacts faster than most conventional cements. Analysis of the hydrated and dried samples after DCA analysis using 29Si MAS NMR spectroscopy revealed that all silicon existed as magnesium silicate hydrate.

[0080] Natural Olivine In the second experiment, natural olivine from Norway was used. Chemical analysis revealed the following composition: SiO2 41.9%, MgO 49.9%, Fe2O3 6.9%. 、 The Al2O3 content was 0.6%, CaO content was 0.1%, and the loss on ignition was 0.5%.

[0081] This material is ground in a ball mill and processed to 7300 cm². 2 The material was ground to a Blaine powder density of 1 / g, and then mixed with a 1 molar NaOH solution in a 1:2 ratio. Subsequently, it was autoclaved at 200°C for 22 days, with the process interrupted once during which the material was ground again.

[0082] After autoclaving, the intermediate product was dried and pulverized, and the loss on ignition (16.3%) was analyzed.

[0083] The water-binding capacity of each batch of intermediate product was evaluated by calcining at different temperatures and hydrating at 22°C for 7 days. The ignition loss before hydration (6.8% after 550°C, 3.1% after 600°C, 2.2% after 650°C, and 1.7% after 700°C) was lower than the values ​​after reaction with water and subsequent drying at 60°C (20.1% after 550°C, 23.7% after 600°C, 24.7% after 650°C, and 22.8% after 700°C).

[0084] Therefore, natural materials such as olivine can also be used in binder production, and hydration was confirmed after the above pretreatment.

[0085] pH value The pH of the cement hardened body according to the present invention was also analyzed. For this purpose, a binder made from pure synthetic forsterite free of heterogeneous ions was analyzed.

[0086] After a 6-month hydration reaction, the pH value in the sample was 9.5.

[0087] Furthermore, the pH value of the pore solution of the binder of the present invention was measured. For this purpose, serpentinite was used to measure 0.55 m 2 The material was ground until it reached a specific surface area of ​​1 / g, and 1 kg of the ground material was calcined at 700°C for 1 hour. After that, it was ground in a ball mill for 5 minutes to break up any agglomerations. The resulting binder was mixed with water to a water / binder ratio of 0.40. After the binder paste was cured at room temperature for 2 days, the pore solution was compressed using a high-pressure press (testing machine) and a press die. The pH value of the pore solution was measured to be 10.3.

[0088] Furthermore, a comparative sample was prepared with 1.6% NaOH added based on the binder. When the alkali-containing pore solution was compressed after curing, a pH value of 12.4 was measured. This result indicates that the addition of an alkali-containing compound can raise the pH value and prevent corrosion of the steel reinforcement.

[0089] Therefore, the use of forsterite, which belongs to the olivine family, makes it possible to produce binders for composite materials with a very low pH value compared to cementites produced from conventional Portland cement clinker. This low pH value allows for the use of glass fiber reinforcement and / or carbon fiber reinforcement for the first time without additional pretreatment.

Claims

1. A method for producing a composite material from a cementite, aggregate and reinforcing material, For the manufacture of the aforementioned cement hardened body, a) A step of preparing a starting product containing at least 20% by mass of one or more of the following components, Ultramafic rocks, especially dunite, Weathering products of ultramafic rocks, especially serpentinite, Olivine, Industrial waste, Each of the above components has a Mg concentration of at least 5% by mass and a BET specific surface area of ​​0.1 m². ２ Having a fineness equivalent to / g or more, b) A step of homogenizing the starting product, c) A step of hydrothermally treating the homogenized starting product in a heat treatment apparatus at a temperature exceeding 100°C for at least 12 hours, d) Adding water to the homogenized starting product by the following method, Direct addition of water before, after, and / or simultaneously with homogenization in step b), and mixing of the starting product with the water, and / or The introduction of steam into the heat treatment apparatus, After step c), the starting product is H ２ At least partially magnesium hydroxide Mg(OH) in the presence of oxygen ２ and / or converted to magnesium silicate hydrate, e) A step of at least partially dehydrating the converted starting product by heat treatment and / or reactive grinding, During the heat treatment, the converted starting product is processed in a temperature range of 180°C to 1000°C. During the reactive grinding described above, a rearrangement of the crystal structure occurs in the converted starting product. After step e), the magnesium hydroxide present in the converted and dehydrated starting product is at least partially dehydrated to magnesium oxide, and the present magnesium silicate hydrate is at least partially dehydrated and thereby converted to dehydrated magnesium silicate hydrate. f) Using the converted and dehydrated starting product as a binder, a step is performed to add curing water to the converted and dehydrated starting product for curing, wherein the ratio of water to the binder is particularly 1:2 or less. When preparing the starting product (e.g., serpentinite) that already contains at least 20% by mass of magnesium silicate hydrate, steps c) and d) can be omitted. The aggregate, such as sand or gravel, is added to the converted and dehydrated starting product before, after, and / or simultaneously with the addition of the hardening water. The reinforcing material is added to the converted and dehydrated starting product before, after, and / or simultaneously with the addition of the curing water to improve load-bearing capacity. The reinforcing material is selected to be resistant to a pH value of less than 11. The reinforcing material is provided with a protective portion for pH values ​​below 11, and / or A method characterized in that an additive is added to the starting product such that the pH value of the pore solution of the cement hardened body is raised to 11 or higher.

2. The method according to claim 1, wherein the pH value of the pore solution in the cement hardened body is 11 or less.

3. The method according to claim 1 or 2, wherein the reinforcing material is selected to be a reinforcing means that does not form a protective layer capable of withstanding a pH value of less than 11.

4. The method according to any one of claims 1 to 3, wherein the reinforcing means selected as the reinforcing material includes carbon fibers, mineral fibers, particularly basalt fibers, and / or glass fibers.

5. The method according to claim 3 or 4, wherein the reinforcing means is selected as carbon fiber, mineral fiber, in particular basalt fiber and / or glass fiber, in the form of a fiber reinforcing material, a mat reinforcing material, a rod reinforcing material and / or other reinforcing forms.

6. The method according to any one of claims 1 to 5, wherein the reinforcing means includes a steel reinforcing material as the reinforcing material.

7. The method according to any one of claims 1 to 6, wherein the reinforcing material comprises a protective layer for protection from alkaline environments with a pH value of less than 11.

8. The method according to any one of claims 1 to 7, wherein the reinforcing material is hot-dip galvanized and / or comprises a layer of paint or lacquer, particularly plastic, so as to be protected from alkaline environments with a pH value of less than 11.

9. The method according to any one of claims 1 to 8, wherein in step c), one or more treatments are performed to promote the reaction occurring during the hydrothermal treatment for at least a partial conversion of the starting product.

10. The method according to any one of claims 1 to 9, wherein the homogenized starting product is continuously or intermittently pulverized, particularly finely pulverized, before the hydrothermal treatment in the heat treatment apparatus in step c), during the hydrothermal treatment, or between multiple hydrothermal treatments, in order to facilitate the conversion.

11. The method according to any one of claims 1 to 10, wherein, for the hydrothermal treatment of the homogenized starting product in the heat treatment apparatus, the homogenized starting product is present in a suspension, and the suspension is continuously and / or intermittently stirred during the hydrothermal treatment.

12. The method according to any one of claims 1 to 11, wherein in step c), ultrasonic treatment is performed on the homogenized starting product.

13. The aforementioned starting product has a BET specific surface area of ​​0.1 m². ２ The method according to any one of claims 1 to 12, wherein the starting product is subjected to a grinding step, particularly a wet grinding step, in order to impart a fineness equivalent to or greater than / g.

14. The method according to any one of claims 1 to 13, wherein the molar ratio of Mg to Ca in the starting product is 10:1 or more, and / or the molar ratio of Si to Al in the starting product is 10:1 or more.

Images