Alkali-activated cement composition with low co 2 emissions

Abstract

The present invention relates to a one-part alkali-activated cement composition (cement composed of solid precursor + solid activator), comprising blast furnace slag and alkaline activator, and optionally steel slag, calcined ultrafine, calcined clays, limestone filler and ultrafine filler. By mixing these materials, a binding material is created which, in contact with water and without the need for heat curing, enables the production of mortar and / or concrete elements for the construction industry.

Description

Alkali-activated cement composition with low CO2 emissions. FIELD OF THE INVENTION

[0001] The present invention relates to alkali-activated cement compositions comprising, on one hand, blast furnace and steelmaking slag, mining waste including ultrafine material from the magnetic separation process and kaolinitic waste, and an alkaline activator. It is also possible to use limestone or quartz waste / waste as filler. The mixture of these materials generates a binding material which, in contact with water and without the need for thermal curing, allows the production of mortar and concrete elements and products for the construction industry. BACKGROUND OF THE INVENTION

[0002] Due to the high levels of CO2 emissions worldwide, several initiatives are being evaluated to reduce the environmental impact associated with the generation of greenhouse gases. The main cement used in the world today is Portland cement; however, despite the undeniable qualities of this type of cement, it presents a high CO2 emission related to the decomposition of calcite and other processes necessary for its production, potentially emitting approximately 0.8 kg of carbon dioxide for every kg of cement produced (MÜLLER and HARNISCH, 2008; SCRIVENER and KIRKPATRICK, 2008). According to IPCC data (2014), Portland cement production represents approximately 13% of total global carbon dioxide (CO2) emissions related to industrial processes.Therefore, if the projected increase in consumption is confirmed for the coming years, especially in emerging countries, CO2 emission levels will become alarming and environmentally dangerous.

[0003] Due to this situation, some strategies are necessary to ensure development in a more environmentally sound manner, directly linked to reductions in CO2 emissions. One of these strategies is related to the use of alternative binders that have lower emissions. with lower CO2 content than Portland cement currently used. Among the existing options, the one that stands out the most and has a high chance of being implemented on a large scale in the coming years is alkali-activated cement, characterized by the absence of high-temperature heat treatments or clinkerization (DAVIDOVITS, 1991; DUXSON, et al., 2006; PROVIS and BERNAL, 2014).

[0004] Alkali-activated cements, in simplified terms, are derived from the reaction between an aluminosilicate mineral (precursor) and an alkaline solution (activator) in optimally proportioned mixtures. These aluminosilicate materials do not react with water, therefore they are not considered hydraulic cements; however, they can generate a material with binding characteristics when in contact with a high pH solution. The product generated from this reaction can exhibit mechanical and durability properties similar to or superior to traditional Portland cement-based cements (PROVIS and BERNAL, 2014).

[0005] Complementing this statement, Provis and Bernal (2014) highlight that to obtain adequate properties, the correct dimensioning of materials, as well as a low water / binder ratio (w / l), are fundamental, and the choice of materials is relative to their application. Similarly, Duxson et al. (2006) comment that when correctly dimensioned, alkali-activated cements can compose concretes with better mechanical and chemical properties when compared to those obtained by concretes with Portland cement.

[0006] The durability of cementitious materials used in construction is key to the development and application of technology, making research in this area fundamental. However, durability assessment is broad and often requires a long period, making the evaluation of isolated pathological effects or manifestations important. Therefore, to ensure applicability and widespread use, it becomes necessary to... Understanding the effect of component materials on the behavior of alkali-activated cements, as well as their influence on their durability.

[0007] In the most traditional method, the alkali-activated binder is a two-part product. The first part is in powder form, which must be aluminosilicate-based, also known as a precursor, and the second part is the activator, which must be an alkaline solution with a high pH, ​​in aqueous solution to allow homogeneity during mixing. To allow scalability and wide application of this technology, it is believed that a one-part formulation, where all constituents are solids and only require the addition of water, is the priority.

[0008] Typically, activators are used in aqueous form to allow for the desired workability and plasticity of the mixture in its fresh state. Traditional activators include hydroxides (Na, Ca, and K), silicates (Na and K), and some carbonates. It is also common to mix different types of activators, so that each provides a specific property to the materials. As mentioned earlier, the scalability of the technology depends on mixing parts, therefore the use of a solid activator is crucial. Sodium silicate is composed of SiO2, Na2O, and H2O, where the silica modulus of the silicate is measured by the SiO2:Na2O molar ratio, which predicts the pH of the solution as well as its viscosity (PROVIS, 2009).

[0009] The most traditional and widely used precursors are industrial waste and / or byproducts, including blast furnace slag (DUXSON; PROVIS, 2008; SHI et al., 2006) and fly ash (CRIADO et al., 2005; SILVA et al., 2014; CRIADO, FERNÁNDEZ-JIMÉNEZ and PALOMO, 2007). However, these traditional precursors are already widely used in Portland cement compositions; therefore, the scalability of the technology depends on the development of precursors with high availability.

[0010] The cements proposed here aim to utilize blast furnace slag, combined with mining tailings and other slags, including ultrafine sandy tailings and a wide range of mining waste. Incorporating these materials into cement formulations reduces the social impact associated with their disposal, adds value to these materials, and at the same time reduces the need for stockpiles and dams for waste disposal.

[0011] The development of cements using industrial waste must, first and foremost, provide durability and adequate mechanical behavior to the cement produced, so that its application and use are viable. Therefore, the formulations proposed here will only be considered adequate when they exhibit strengths greater than 32 MPa, which is the minimum strength allowed in Brazil for Portland cement, using the same regulations for determining this strength. Thus, the cements will be classified into strength ranges.

[0012] The development of one-part alkali-activated cements with these materials combined in their composition is a new and disruptive solution for the construction industry.

[0013] Currently, iron ore processing plants use magnetic separation and flotation processes to remove the less iron-rich fraction, rich in quartz and clay minerals. Flotation processes followed by desliming result in an ultrafine residue composed of quartz, iron oxides, and clay minerals (including kaolinite). Once generated, this material is in the form of sludge, and its disposal is carried out in tailings dams. Therefore, its proper disposal is an environmental necessity. Given its small particle size and the content of kaolinite and other clays in this material, it becomes a potential material for use in alkali-activated cements. Depending on the desired content, increased reactivity can be achieved through a complementary calcination process.

[0014] Similarly, mining waste is all the material that needs to be removed to allow access to the ore of interest, such as an iron-rich ore. The composition of waste is variable, and it can contain different types of rocks with different formations and compositions. The mineralogical composition of some The presence of these waste materials makes them suitable for application in alkali-activated cements. The presence of kaolinite, silica in amorphous or semi-crystalline phase, as well as the presence of calcium, allows their use. Depending on the content used, as well as the mineralogical composition, the reactivity of some waste materials can be increased through a complementary calcination process. The waste materials prioritized in this invention are those containing kaolinitic clay.

[0015] Given the interest in disclosing the invention patent, a broad search was conducted to verify the prior art of the subject matter. No relevant works were found in the literature that address the proposed invention, including the use of these materials and the combined electrified process, nor were any works that demonstrate mechanical and environmental performance that would allow for its widespread use.

[0016] Some applications that approximate the present invention will be described below.

[0017] Document CN 102875041 describes a single-component alkali-activated cement that not only has a low setting temperature but also cures at room temperature.

[0018] Document CN 108516711 also describes a single-component alkali-activated cement containing slag, fly ash, and silicate salts as activators.

[0019] Document CN 108275899 describes an alkali-activated cement using industrial waste and alkaline activators as raw materials. The industrial waste consists of a mixture of steelmaking slag and fly ash, metakaolin, and alkaline activators.

[0020] Although these documents describe alkali-activated cements, they are all silent regarding the use of blast furnace slag in conjunction with activators. Furthermore, the present invention also describes the use of limestone or ultrafine fillers and mining waste and does not foresee the use of fly ash.

[0002] ] Thus, the present invention is not only novel compared to the available state of the art, but also inventive. SUMMARY OF THE INVENTION

[0022] In one aspect, the present invention presents a one-part alkali-activated cement composition. This composition exhibits mechanical performance similar to traditional cements available on the market. Its applicability and durability should also be compatible with the intended use.

[0023] The present invention also aims to maximize the use of mining tailings, thereby reducing storage in dams or stockpiles, as well as promoting the circular economy of the mining sector.

[0024] Furthermore, given the global environmental conditions, the proposed cement composition aims to minimize greenhouse gas emissions, represented here by CO2eq, so that this value does not exceed 200 kg of CO2 / Ton of alkali-activated cement produced, a value much lower than the national average for Portland cement (> 650 kg / Ton).

[0025] In a preferred embodiment, the composition of alkali-activated cement with low CO2 emissions comprises: a) 42 to 94% w / w of blast furnace slag as a precursor; b) 0 to 50% w / w of steelmaking slag as a precursor; c) 0 to 50% w / w of calcined ultrafine aggregate as a precursor; d) 0 to 50% w / w of calcined clays as a precursor; e) 0 to 25% w / w of a limestone filler; f) 0 to 25% w / w of ultrafine filler; g) 3 to 14% w / w of an activator; where the CO2 emission is less than 200 kg CO2 / t.

[0026] In a preferred embodiment, the calcined clays are selected from commercial metakaolin and / or calcined kaolinitic waste.

[0027] One of the advantages of the present invention is the fact that it is a one-part solid alkali-activated cement, whereas most are two-part, i.e., solid precursor + liquid activator, mixed only in the The application should be done in conjunction with water. Furthermore, the curing process does not require water. BRIEF DESCRIPTION OF THE FIGURES

[0028] Figure 1 - Stages of the steelmaking process.

[0029] Figure 2 - Iron ore concentration and ultrafines generation process.

[0030] Figure 3. Compressive strength results 1 to 28 days (EAF 01) with sodium silicate as per Table 4.

[0031] Figure 4. Compressive strength results 1 to 28 days (EAF 01) with anhydrous sodium silicate as per Table 5.

[0032] Figure 5. Compressive strength results 1 to 28 days (EAF 01) with sodium silicate pentahydrate as per Table 6.

[0033] Figure 6. Compressive strength results 1 to 28 days (EAF 02) as per Table 7.

[0034] Figure 7. Compressive strength results 1 to 28 days (EAF 03) as per Table 8.

[0035] Figure 8. Compressive strength results 1 to 28 days (EAF 01 + limestone filler + 5.5% sodium silicate).

[0036] Figure 9. Compressive strength results 1 to 28 days - (EAF 01 + limestone filler + 8% sodium silicate).

[0037] Figure 10. Compressive strength results 1 to 28 days - (EAF 01 + limestone filler + 11% sodium silicate).

[0038] Figure 11. Compressive strength results from 1 to 28 days for EA 01.

[0039] Figure 12. Compressive strength results from 1 to 28 days for EA 02.

[0040] Figure 13. Compressive strength results from 1 to 28 days for EA 03.

[0041] Figure 14. Compressive strength results from 1 to 28 days for EA 04.

[0042] Figure 15. Compressive strength results from 1 to 28 days for 8% silicate and ultrafine filler.

[0043] Figure 16. Compressive strength results from 1 to 28 days for 11% silicate and ultrafine filler.

[0044] Figure 17. Compressive strength results from 1 to 28 days for formulation with calcined ultrafine filler.

[0045] Figure 18. Compressive strength results from 1 to 28 days for formulation with commercial metakaolin. DETAILED DESCRIPTION OF THE INVENTION

[0046] The examples described here are intended only to illustrate some of the numerous ways in which the invention can be carried out, and should not be considered limiting.

[0047] Blast furnace slag and steelmaking slag

[0048] Blast furnace slag is a byproduct of pig iron production from iron ore. During the blast furnace process (Figure 1), iron ore is heated to high temperatures along with coke and limestone in a blast furnace to produce liquid pig iron. Impurities present in the iron ore and coke combine with the limestone to form slag, which is less dense than pig iron and floats on the surface of the liquid metal. It is then removed from the blast furnace and subsequently cooled, solidifying.

[0049] The average chemical composition of blast furnace slag can vary depending on the production process conditions, the type of iron ore, and the additives used. However, a typical average chemical composition of blast furnace slag is as follows (GOSH and CHATTERJEE, 2008; FRUEHAN, 1998): Silicon dioxide (SiO2): 35-45%; Calcium dioxide (CaO): 35-45%; Aluminum dioxide (Al2O3): 10-20%; Magnesium dioxide (MgO): 5-10%; Iron oxide (FeO): 0-10%; Manganese dioxide (MnO): 0-5%; Titanium dioxide (TiO2): 0-5%.

[0050] Steelmaking slag is a byproduct of the conversion of liquid pig iron into steel, through the removal of impurities such as carbon, silicon, and manganese. The steelmaking process can be carried out by different methods, such as... Oxygen converters, electric arc furnaces, ladle furnaces, among others (Figure 1). Scrap iron can also be reused at this stage.

[0051] The chemical composition of steelmaking slag varies depending on the type of process used and the additive materials; in general, it is mainly composed of calcium, silicon, aluminum, and magnesium oxides, in addition to other minor elements.

[0052] Alkali-activated cements that use slag as a precursor are called high calcium, due to a higher amount of calcium present in the materials.

[0053] Blast furnace and steelmaking slags are attractive materials for the production of alkali-activated cements and concrete because they are abundant and inexpensive, possess reactive properties due to the presence of calcium, silicon, and aluminum oxides, and offer environmental benefits as byproducts of the steel industry.

[0054] Blast furnace slag is present in a range of 42% to 94% w / w of the composition of alkali-activated cement as the main precursor, and steelmaking slag is present in a range of 0% to 50% w / w of the composition as a secondary precursor. Calcined Clays (Kaolinitic Waste from Mining) In the mining of valuable minerals, such as iron or base metals, waste rock consists of materials that do not contain significant quantities of valuable minerals, such as ferrous or metallic minerals, and are removed during the mineral extraction process to access more valuable materials. They can have significant environmental impacts and require proper management. Some waste rock may possess desirable properties for application in alkali-activated cements, especially if they are kaolinitic clays (Si:Al = 1:1) rich in silicon and alumina. When kaolinitic clay is calcined at high temperatures (generally above 700 °C), dehydroxylation of the kaolinite occurs, thus forming metakaolinite. Metakaolinite is a highly reactive material in alkaline environments. Therefore, with the addition of an activator such as sodium silicate, it reacts to form a hardened cementitious matrix. Metakaolin is a calcined clay with a high metakaolinite content, widely used in the manufacture of this type of cement. Another advantage of using calcined clays in alkali-activated cements is that they can help reduce the carbon footprint of cement production. Portland cement manufacturing is responsible for 5 to 8% of global carbon dioxide (CO2) emissions due to the burning of fossil fuels to reach high temperatures (=1450°C) and the CO2-releasing reaction of limestone (CaCO3) to become CaO, which will later be part of the cement clinker. Metakaolinite production, on the other hand, is less intensive in terms of CO2 emissions, as it requires lower temperatures (700°C) and does not release chemically bound CO2 like limestone. Alkali-activated cements that use calcined clay as a precursor are classified as low-calcium due to the low amount of calcium present in this material. Ultrafine tailings

[0055] The iron ore concentration process generates a sandy tailings mixture with an ultrafine sandy clay material (particle size less than 40 µm), also called sludge. The removal of this ultrafine fraction (or desliming, circled in red in Figure 2) is carried out by cycloning, thickening, centrifugation or similar methods, or by a combination of these unit operations.

[0056] The extraction and use of ultrafine aggregate (sludge) in other industrial sectors (such as in the production of Portland cement or alkali-activated cement) minimizes environmental impact by reducing the volume destined for tailings dams, thus decreasing the risk of disasters. Ultrafine aggregate can be applied as filler in its natural form, or it can be calcined to become reactive, due to the clay content present, and act as a secondary precursor.

[0057] The ultrafine material is present in a range that varies from 0% to 25% w / w of the composition when used as a filler, and in a range that varies from 0% to 50% w / w of the composition when used as a secondary precursor.

[0058] Limestone filler

[0059] Filler is any inert, fine material, usually in powder form, that is added in small quantities to cement, mortar, or concrete mixtures. Its main function is to fill the voids between cement particles and aggregates (crushed stone and / or sand), improving compaction, increasing the compressive strength of the material, and reducing the use of other materials that are more expensive or emit more CO2.

[0060] Limestone filler is obtained from grinding limestone, which is a sedimentary rock composed mainly of calcium carbonate (CaCO3), commonly used as a raw material in the production of cement, lime, and other chemicals. It is important to ensure that the limestone filler has the appropriate purity and particle size for its intended use, to guarantee the quality and consistency of the product.

[0061] The limestone filler is present in a range that varies from 0% to 25% w / w of the composition.

[0062] Activator

[0063] The activator of the present invention may be chosen from the group comprising sodium silicate, potassium silicate; sodium hydroxide, potassium hydroxide, calcium hydroxide; sodium carbonate; sodium sulfate and combinations thereof.

[0064] The activator is present in a range that varies from 3% to 14% w / w of the composition.

[0065] Preferably, the sodium silicate (Na2SiOs) used as the sole activator should be in solid form, with a molar ratio of SiO2 / Na2O oxides ranging between 0.8 and 1.5.

[0066] Materials processing

[0067] Blast furnace slag, steelmaking slag, and filler are previously dried and ground until they meet the requirements of NBR 12653, which consists of grinding until less than 20% of the material is retained on a 45 micrometer sieve.

[0068] Kaolinitic and ultrafine clays (ultrafine clays generally already have the appropriate fineness) can be ground to meet the same requirements as the others (NBR 12653) and then calcined in a furnace at 700°C to make them reactive. The range of this calcination temperature can vary from 600 to 900°C. The thermal process causes the dehydroxylation of kaolinite, making the calcined material reactive in an alkaline medium. It is worth noting that if they are not calcined, these materials can act as filler in suitable particle sizes.

[0069] The sodium silicate used for activation can be commercially available or homemade. EXAMPLES

[0070] Example 1 - Physical Characteristics of Materials

[0071] The actual density was determined using the helium pycnometry technique with a helium (He) gas stereopycnometer, and the specific surface area and pore size were determined using the BET technique with a QuantaChrome Nova 1000e instrument, and the results are presented in Table 1. Table 1. General characteristics of raw materials as is. Awaiting results

[0072] Example 2 - Chemical characteristics

[0073] Chemical composition

[0074] The chemical composition was determined by identifying the oxides present in the sample using the X-ray fluorescence technique shown in Table 2. Table 2. Chemical composition of raw materials. Awaiting results PPC - Loss on ignition

[0075] Example 3 - Formulations and results of compressive strength (NBR 7215)

[0076] Blast furnace slag

[0077] Blast furnace slags were tested with activator percentages ranging from 3% to 14% to determine optimal levels. Generally, a 5.5% activator concentration provides a minimum strength of 32 MPa at 28 days in different formulations. The optimal concentration ranges from 11-12%, yielding approximately 60 MPa at 28 days. Activator concentrations above 14% do not significantly increase strength and may even lead to decreased values ​​in some cases.

[0078] Three different alkaline activators were tested for EAF 01, one of which was manufactured in-house (anhydrous sodium silicate) and two others commercially available (anhydrous silicate and pentahydrate silicate). The anhydrous silicate showed very similar results to the sodium silicate, while the pentahydrate silicate showed inferior results compared to the others. Table 3. Summary of compressive strength results at 28 days (MPa) of blast furnace slags.

[0079] The tested formulations of Usiminas EAF 01 blast furnace slag, using different sources of sodium silicate, are detailed in Tables 4, 5 and 6, and the compressive strength results are detailed in the Figures. 3, 4 and 5.

[0080] The tested formulations of blast furnace slag EAF 02 are detailed in Table 7, and the compressive strength results are detailed in Figure 6.

[0008] ] The tested formulations of blast furnace slag EAF 03 are detailed in Table 8 and the compressive strength results are detailed in Figure 7. Table 4. EAF 01 Formulations - Sodium silicate. Table 6. EAF 01 Formulations - Commercial Pentahydrate Silica. Table 7. EAF 02 Formulations. Table 8. EAF 03 Formulations.

[0082] Limestone filler

[0083] Limestone filler (CaCOs) was initially tested as a replacement for blast furnace slag EAF 01 at levels of 5 to 25% and at three sodium silicate contents (5.5%, 8% and 11%). At high activator contents, the calcium carbonate (CaCOs) in the filler reacts with the remaining Na from the activator + precursor reaction to form Na2COs.

[0084] When CaCO3 comes into contact with NaOH, it forms Portlandite and sodium carbonate, thus accelerating the dissolution reaction, but the gain in strength is... slower. In this specific case, the filler has 90% of its particles smaller than 26.19 µm and an average diameter of 13.90 µm.

[0085] The results (Figures 8, 9 and 10, and Table 9) show that a substitution of up to 10% does not significantly affect the compressive strength for the three cement formulations (5.5%, 8% and 11% sodium silicate). However, substitutions of up to 25% can be evaluated, provided that the filler has adequate particle size distribution. Table 9. Formulations for tests with limestone filler. Steelmaking slag

[0086] Steelmaking slags were evaluated as a replacement for blast furnace slag, with contents ranging from 10 to 50% of the total mass. To evaluate these slags, a fixed sodium silicate content of 8% was adopted, and the remaining percentage corresponded to blast furnace slag EAF 01. In general, EA 01 proved beneficial up to 20% replacement, while EA 02 proved beneficial up to 10% replacement. Regarding Gerdau slags, EA 03 showed consistent results, allowing a replacement of up to 50% with similar strengths. Finally, EA 04 showed good results up to 20% replacement. Table 10. Summary of compressive strength (MPa) results at 28 days for steelmaking slags.

[0087] Figures 11 to 14 show the results obtained, and Table 11 summarizes the compositions tested. Table 11. Formulations for tests with steelmaking slag.

[0088] Ultrafine Waste

[0089] Ultrafine reject as filler

[0090] Raw ultrafine filler was tested as a replacement for blast furnace slag (EAF 01) at levels of 5 to 25% and at two sodium silicate contents: 8% and 11%. In the 11% sodium silicate formulation, the ultrafine filler performed below expectations when compared to the reference with and without the addition of limestone filler (Figure 16 and Table 13). In the 8% silicate formulation (Figure 15 and Table 12), up to 10% ultrafine filler provided an improvement in strength when compared to the reference with and with the addition of limestone filler. Table 12. Formulations for testing with ultrafine filler containing 8% sodium silicate.

[0091] Ultrafine tailings as a secondary precursor

[0092] The ultrafine filler was calcined at a temperature of 750°C in a static muffle furnace for 1 h, and evaluated as a replacement for blast furnace slag (EAF 01) at levels of 10 to 50% in a formulation with 8% sodium silicate. In this formulation (FIGURE 17), the addition of calcined ultrafine filler is beneficial up to 20%.

[0093] Calcined clays

[0094] Commercial metakaolin

[0095] A commercial metakaolin was evaluated as a precursor in conjunction with blast furnace slag (EAF 01) at levels of 5 to 25% in a formulation with 9% sodium silicate. In this formulation (FIGURE 18), the 5% proportion of commercial metakaolin is beneficial for compressive strength at all ages.

[0096] Example 4 - CO2 Emissions

[0097] The compositions of the present invention emit 6 to 10 times less kg CO2 / ton than conventional Portland cement. The International Energy Agency (IEA, 2023) estimates that an average of 590 kg CO2 / ton is emitted. The Global Cement and Concrete Association (GCCA, 2023) estimates around 580 kg CO2 / ton of Portland cement; however, CPV-type cement has emissions exceeding 800 kg CO2 / ton. The compositions of the present invention, however, do not. Emissions range from 58 to 122 kg CO2 / t (Table 14). These values ​​are directly related to the activator content, which has the highest emission factor among the materials, as can be seen in Table 15. However, a higher activator content also provides greater mechanical strength in the early stages up to a certain point, which is essential for some applications in the precast and prefabricated industries, for example. Table 14. Most promising formulations and their respective CO2 emissions. Table 15. CO2 emission factors by material.

[0098] In conclusion, using steel and mining waste as raw material for cement production reduces the need to exploit new raw material deposits, contributing to the preservation of natural resources. Furthermore, alkali-activated cement itself emits 5 to 6 times less greenhouse gases, significantly reducing the potential for global warming.

[0099] Secondly, alkali-activated cement produced with steel and mining waste can exhibit mechanical and durability properties similar to or even superior to those of conventional Portland cement, depending on the characteristics of the waste used.

[0100] Finally, the waste materials used as alternative raw materials are potentially cheaper than the clinker used in the production of conventional Portland cement, offering significant economic opportunities.

[0101] REFERENCES

[0102] MÜLLER, N.; HARNISCH, J. A blueprint for a climate friendly cement industry. Report for the WWF-Lafarge Conservation Partnership., 2008.

[0103] SCRIVENER, K. L; KIRKPATRICK, RJ Innovation in use and research on cementitious material. Cement and Concrete Research, vol. 38, no. 2, p. 128-136, 2008.

[0104] IPCC (Intergovernmental Panel of Climate Change). Chapter 10 - Industry, In "Intergovernmental panel on climate change", Berlin, 2014.

[0105] DAVIDOVITS, J. Geopolymers: Inorganic polymeric new materials. Journal of thermal analysis, v. 37, p. 1633-1656, 1991.

[0106] DUXSON, P. The structure and thermal evolution of metakaolin geopolymers. Tese (Doutorado em Engenharia). 2006, Faculdade de Engenharia, Universidade de Melbourne, 2006.

[0107] PROVIS, J. L; BERNAL, S. A. Geopolymers and Related Alkali- Activated Materials. Annual Review of Materials Research, v. 44, n. 1 , p. 299- 327, 2014.

[0108] DUXSON, R; FERNÁNDEZ-JIMÉNEZ, A.; PROVIS, J. L; et al. Geopolymer technology: the current state of the art. Journal of Materials Science, v. 42, n. 9, p. 2917-2933, 2006

[0109] PROVIS, J. L; YONG, S. .; DUXSON, P. Nanostructure / microstructure of metakaolin geopolymers. In: PROVIS, J. L; VAN DEVENTER, J. S. J. (Eds.). Geopolymers: Structure, processing, Properties and industrial applications. Oxford - Cambridge - New Delhi: Woodhead Publishing Limited, 2009. p. 72-88.

[0110] DUXSON, R; PROVIS, J. L. Designing precursors for geopolymer cements. Journal of the American Ceramic Society, v. 91 , n. 12, p. 3864-3869, 2008.

[0111] SHI, C.; KRIVENKO, R; ROY, D. Alkali-activated Cement and concretes. 1 o ed. New York: Taylor & Francis, 2006.

[0112] CRIADO, M.; PALOMO, A.; FERNANDEZ-JIMENEZ, A. Alkali activation of fly ashes . Part 1 : Effect of curing conditions on the carbonation of the reaction products. Fuel, v. 84, p. 2048-2054, 2005

[0113] SILVA, A.; VARGAS, D.; DAL, D. C. C.; et al. Cement & Concrete Composites Strength development of alkali-activated fly ash produced with combined NaOH and Ca(OH)2 activators. Cement and Concrete Composites, v. 53, p. 341-349, 2014.

[0114] CRIADO, M.; FERNÁNDEZ-JIMÉNEZ, A.; PALOMO, A. Alkali activation of fly ash: Effect of the SiO2 / Na2O ratio. Microporous and Mesoporous Materials, v. 106, n. 1-3, p. 180-191 , 2007.

[0115] Ahindra Ghosh and A. Chatterjee, Ironmaking and Steelmaking: Theory and practice. 2008.

[0116] Richard J. Fruehan, Steelmaking and Refining. Pittsburgh, PA, 1998.

[0117] IEA, “International Energy Agency - Cement - Analysis.” https: / / www.iea.org / reports / cement (accessed Mar. 08, 2023).

[0118] GCCA, “Global Cement and Concrete Association in Numbers.” https: / / gccassociation.org / sustainability-innovation / gnr-gcca-in-numbers / (accessed Mar. 08, 2023).

Claims

Claims 1. Alkali-activated cement composition with low CO2 emission characterized by comprising: a) 42 to 94% w / w of blast furnace slag as precursor; b) 0 to 50% w / w of steelmaking slag as precursor; c) 0 to 50% w / w of calcined ultrafine as precursor; d) 0 to 50% w / w of calcined clays as precursor; e) 0 to 25% w / w of a limestone filler; f) 0 to 25% w / w of ultrafine filler; eg) 3 to 14% w / w of an activator; where the CO2 emission is less than 200 kg.CO2 / t.

2. Composition according to claim 1, characterized in that the blast furnace slag comprises calcium oxide, silicon oxide, aluminum oxide and magnesium oxide.

3. Composition according to claim 1, characterized in that the steelmaking slag comprises calcium oxide, silicon oxide, aluminum oxide and magnesium oxide.

4. Composition according to claim 1, characterized in that the ultrafine filler is applied in its natural form or is calcined.

5. Composition according to claim 1, characterized in that the activator is chosen from the group comprising sodium silicate, potassium silicate; sodium hydroxide, potassium hydroxide, calcium hydroxide; sodium carbonate; sodium sulfate and combinations thereof.

6. Composition according to claim 5, characterized in that the activator is only sodium silicate with a molar ratio of SiO2 / Na2O oxides ranging from 0.8 to 1.

5.

7. Composition according to claim 1, characterized by comprising: a) from 79% to 84.5% w / w of blast furnace slag; b) from 5.5% to 11% w / w of activator; and c) 10% limestone filler.

8. Composition according to claim 1, characterized in that it comprises: a) 42 to 82% w / w of blast furnace slag; b) 10 to 50% w / w of steel mill slag; and c) 8% to 12% w / w of an activator.

9. Composition according to claim 1, characterized in that it comprises: a) 67 to 87% w / w of blast furnace slag; b) 8 to 11% w / w of an activator; and c) 5 to 25% w / w of ultrafine filler.

10. Composition according to claim 1, characterized in that the calcined clays are selected from commercial metakaolin and / or calcined kaolinitic waste.

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