Low-carbon concrete and preparation method thereof

Abstract

This invention discloses a low-carbon concrete and its preparation method, belonging to the field of concrete material technology. The concrete raw materials include: 1300-1600 parts fly ash, 300-400 parts slag powder, 400-600 parts solid waste composite alkaline activator, 400-600 parts sand and gravel aggregate, and 300-400 parts water. The fly ash and slag powder are dry-mixed, followed by the addition of the solid waste composite alkaline activator, water, and sand and gravel aggregate, and then further mixing is performed. This invention, by selecting the types of raw materials and adjusting their dosages, yields a low-carbon concrete that does not require high-temperature curing and can be cured at room temperature, achieving a 28-day compressive strength of over 39 MPa. The raw materials used in this invention are mainly derived from solid waste, possessing the characteristics of low cost, low carbon footprint, environmental friendliness, and simple preparation process, resulting in good environmental and economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of concrete materials technology, specifically relating to a low-carbon concrete and its preparation method. Background Technology

[0002] With the continuous development of society and the economy, the demand for various infrastructure constructions is constantly increasing worldwide, and concrete structures are one of the most widely used structural forms. Ordinary Portland cement, as one of the most widely used components in concrete, is also seeing its production increase, with annual demand projected to reach 3.68-4.38 Gt by 2050. However, due to its unique manufacturing process, the production of ordinary Portland cement inevitably brings many environmental problems. For example, the production of ordinary Portland cement consumes a large amount of energy and emits a large amount of carbon dioxide. Its energy consumption accounts for approximately 5% of natural resources, and its carbon dioxide emissions account for approximately 5-7% of global anthropogenic carbon dioxide emissions. The large-scale emission of greenhouse gases such as carbon dioxide is one of the main causes of global climate change. To address the negative impacts of ordinary Portland cement on natural resources and the environment, more and more researchers are dedicated to developing environmentally friendly cementitious materials to replace ordinary Portland cement-based cementitious materials, in order to develop new concrete materials with low-carbon and environmentally friendly benefits.

[0003] Geopolymers are a novel type of cementitious material primarily produced by activating aluminosilicate-rich precursor materials in an alkaline environment. Geopolymer concrete, made from geopolymers, is characterized by its low-carbon and environmentally friendly properties, energy conservation and emission reduction, and ability to utilize solid waste. Currently, precursor materials successfully used in the preparation of geopolymer concrete mainly include industrial and agricultural solid wastes such as fly ash, blast furnace slag, palm oil fuel ash, rice husk ash, and brick powder. The alkaline environment is typically provided by sodium hydroxide and sodium silicate solutions. As a low-energy-consumption green building material, geopolymer concrete not only effectively solves a series of environmental problems caused by the traditional cement industry, but also exhibits superior performance compared to ordinary Portland cement-based concrete in terms of impact resistance, sulfate resistance, high-temperature resistance, and splitting tensile strength, thus attracting widespread attention from the civil engineering and water conservancy industries.

[0004] Publication number CN110950584A discloses a silica fume and volcanic ash-based geopolymer concrete and its preparation method. However, the high-temperature curing method involved in its preparation process greatly limits the application of geopolymer concrete in practical engineering; furthermore, its maximum 28-day compressive strength is only 30.8 MPa, which is not conducive to the application of geopolymer concrete in critically vulnerable areas. Meanwhile, existing technologies typically use sodium hydroxide solution and sodium silicate solution as activators for geopolymers, which has relatively high economic costs, hindering the widespread application of geopolymer concrete.

[0005] Therefore, it is necessary to develop a low-carbon concrete that does not require high-cost activators or high-temperature curing, in order to address the shortcomings of existing technologies. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, this invention provides a low-carbon concrete and its preparation method, which can produce high-performance concrete without high-temperature curing.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides a low-carbon concrete, the raw materials of which, by weight, include: 1300-1600 parts fly ash, 300-400 parts slag powder, 400-600 parts solid waste composite alkaline activator, 400-600 parts sand and gravel aggregate, and 300-400 parts water.

[0009] As a preferred embodiment of the present invention, the fly ash contains 52-55 wt% SiO2, 34-38 wt% Al2O3, and 1.9-2.2 wt% CaO; the average particle size (d50) of the fly ash is 9-10 μm.

[0010] As a preferred embodiment of the present invention, the slag powder contains 31-33 wt% SiO2, 16-18.5 wt% Al2O3, and 33-35 wt% CaO; the average particle size (d50) of the slag powder is 9-10 μm.

[0011] As a preferred embodiment of the present invention, the solid waste composite alkaline activator is a mixture containing carbide slag alkaline activating powder and sodium silicate solution; the sodium silicate is Na2O·nSiO2, where n is 3 to 3.3; in the mixture, the mass ratio of carbide slag alkaline activating powder to sodium silicate solution is 1:(3.5 to 4.5), and the mass ratio of H2O to Na2O·nSiO2 in the sodium silicate solution is 7 to 10.

[0012] As a preferred embodiment of the present invention, the preparation method of the carbide slag alkaline activated powder includes the following steps:

[0013] Using carbide slag, a byproduct of industrial production, as raw material, and passing it through a 200-mesh sieve to obtain powder; the prepared powder is washed and cleaned, and then subjected to pressure filtration to remove impurities; subsequently, it is dried at 60-80℃, preferably at 70℃, and then ground and passed through a 200-mesh sieve to remove impurities; the obtained ash is chemically activated to stimulate its reactivity; the chemically activated ash is then pressure filtered, dried, ground, and passed through a 200-mesh sieve; then it undergoes physical activation to physically activate its reactivity; finally, it is ground and passed through a 200-mesh sieve to obtain the carbide slag alkali-activated powder.

[0014] As a preferred embodiment of the present invention, the specific method of the chemical activation treatment is as follows: First, the ash is placed in a sodium phosphate solution with a mass fraction of 0.8-1.2%, and the mass ratio of ash to sodium phosphate solution is 1:(2.5-3.5). The solution is soaked for 18-36 hours, and then the solid and liquid are separated. The obtained solid is then placed in an ammonium bicarbonate solution with a concentration of 0.05-0.15 mol / L, and the mass ratio of solid to ammonium bicarbonate solution is 1:(2.5-3.5). The solution is soaked for 18-36 hours, and then the solid and liquid are separated again.

[0015] As a preferred embodiment of the present invention, the physical activation treatment method is as follows: heat treatment at 650-750°C for 1.5-2.5 hours, preferably at 700°C for 2 hours.

[0016] This invention improves the reactivity of carbide slag through chemical and physical activation, and provides a method for preparing a composite alkaline activator for solid waste, which can effectively reduce the environmental and energy consumption impact of sodium hydroxide in traditional alkaline activators.

[0017] The present invention also provides a method for preparing a low-carbon concrete according to the above description, comprising the following steps:

[0018] (1) Weigh each raw material according to the weight parts. First, dry mix fly ash and slag powder to obtain a uniformly dispersed precursor powder.

[0019] (2) Subsequently, the solid waste composite alkaline activator, water and sand and gravel aggregate are added to the precursor powder and mixed to obtain the low-carbon concrete.

[0020] As a preferred embodiment of the present invention, the method further includes the steps of loading the low-carbon concrete into a test mold, curing it in an indoor environment at 20-25°C for 24-48 hours, demolding it, and then curing it under standard conditions of ambient temperature 20±2°C and relative humidity of 95% until the test age.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) This invention uses fly ash, slag powder, solid waste composite alkaline activator, water and sand and gravel aggregate as raw materials. By selecting the types of raw materials and adjusting the dosage, low-carbon concrete is obtained.

[0023] (2) The concrete material provided by the present invention does not require high-temperature curing. It can be cured at room temperature to obtain a low-carbon concrete with a 28-day compressive strength of more than 39 MPa.

[0024] (3) The raw materials used in this invention are mainly derived from solid waste, which have the characteristics of low cost, low carbon and environmental protection, and simple preparation process. They have good environmental and economic benefits and are suitable for widespread use. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a flowchart illustrating the preparation process of low-carbon concrete according to Embodiment 1 of the present invention. Detailed Implementation

[0027] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0028] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0029] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0030] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0031] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0032] This invention provides a low-carbon concrete, the raw materials of which, by weight, include: 1300-1600 parts fly ash, 300-400 parts slag powder, 400-600 parts solid waste composite alkaline activator, 400-600 parts sand and gravel aggregate, and 300-400 parts water.

[0033] In some embodiments, the fly ash used has a SiO2 content of 52-55 wt%, an Al2O3 content of 34-38 wt%, and a CaO content of 1.9-2.2 wt%; the average particle size (d50) of the fly ash used is 9-10 μm.

[0034] In some preferred embodiments, the fly ash used has a SiO2 content of 54.14 wt%, an Al2O3 content of 36.41 wt%, a CaO content of 2.03 wt%, and an average particle size (d50) of 9.475 μm.

[0035] In some embodiments, the slag powder used has a SiO2 content of 31-33 wt%, an Al2O3 content of 16-18.5 wt%, and a CaO content of 33-35 wt%; the average particle size (d50) of the slag powder is 9-10 μm.

[0036] In some preferred embodiments, the slag powder used has a SiO2 content of 32.36 wt%, an Al2O3 content of 17.93 wt%, a CaO content of 34.11 wt%, and an average particle size (d50) of 9.284 μm.

[0037] In some embodiments, the solid waste composite alkaline activator used is a mixture containing carbide slag alkaline activating powder and sodium silicate solution; wherein the sodium silicate is Na2O·nSiO2, n is 3 to 3.3, the mass ratio of carbide slag alkaline activating powder to sodium silicate solution in the mixture is 1:(3.5 to 4.5), and the mass ratio of H2O to Na2O·nSiO2 in the sodium silicate solution is 7 to 10.

[0038] In some preferred embodiments, the sodium silicate solution is Na2O·3.28SiO2, and the mass ratio of the carbide slag alkaline activation powder to the sodium silicate solution in the mixed solution is 1:4. The mass percentages of Na2O, SiO2 and H2O in the sodium silicate solution are 8.35%, 26.54% and 65.11%, respectively.

[0039] In some embodiments, the preparation method of the carbide slag alkaline activated powder includes the following steps:

[0040] (1) Use carbide slag, a by-product of industrial production, as raw material and screen it to obtain powder;

[0041] (2) The prepared powder is washed and cleaned, and then filtered to remove impurities;

[0042] (3) It is then dried at 60-80℃ and then ground and sieved through a 200-mesh sieve to remove impurities;

[0043] (4) Soak in sodium phosphate solution with a mass fraction of 0.8-1.2% for 18-36 hours, and soak in ammonium bicarbonate solution with a concentration of 0.05-0.15 mol / L for 18-36 hours to activate the ash reaction activity;

[0044] (5) The chemically activated ash is subjected to pressure filtration, drying, grinding, and sieve treatment through a 200-mesh sieve;

[0045] (6) Then, keep warm at 650-750℃ for 1.5-2.5h to activate the ash activity using physical methods;

[0046] (7) After final grinding and sieve treatment with a 200-mesh sieve, carbide slag alkali activated powder is obtained.

[0047] The present invention also provides a method for preparing the aforementioned low-carbon concrete, comprising the following steps:

[0048] (1) Weigh each raw material according to the weight parts. First, dry mix fly ash and slag powder to obtain a uniformly dispersed precursor powder.

[0049] (2) Subsequently, solid waste composite alkaline activator, water and sand and gravel aggregate are added to the precursor powder and mixed to obtain low-carbon concrete.

[0050] In some embodiments, the method further includes the steps of loading low-carbon concrete into a mold, curing it at 25–35°C for 24–48 hours, demolding it, and then curing it at standard conditions of 20±2°C and 95% relative humidity until the test age.

[0051] In some preferred embodiments, low-carbon concrete is placed into a mold, cured for 24 hours in an indoor environment at 20°C, demolded, and then cured to the test age under standard conditions of ambient temperature 20±2°C and relative humidity 95%.

[0052] In the following examples and comparative examples, all raw materials used were commercially available. Unless otherwise specified, the cement was ordinary Portland cement; the fly ash was Grade I fly ash, purchased from Henan Borun Foundry Materials Co., Ltd., with a SiO2 content of 54.14 wt%, an Al2O3 content of 36.41 wt%, a CaO content of 2.03 wt%, and an average particle size (d50) of 9.475 μm; the slag powder used was S95 slag powder, purchased from Henan Borun Foundry Materials Co., Ltd., with a SiO2 content of 32.36 wt%, an Al2O3 content of 17.93 wt%, a CaO content of 34.11 wt%, and an average particle size (d50) of 9.284 μm; the maximum particle size of the sand and gravel aggregate used was 1 mm, and the average particle size (d50) was 0.645 mm.

[0053] The following description will not be repeated.

[0054] Example 1

[0055] Concrete mixtures were prepared using the raw materials shown in Table 1. The preparation method of the solid waste composite alkaline activator was as follows: carbide slag alkaline activating powder and sodium silicate solution (sodium silicate chemical formula is Na2O·3.28SiO2) were mixed. The mass ratio of carbide slag alkaline activating powder to sodium silicate solution was 0.2:0.8. The mass percentage contents of Na2O, SiO2 and H2O in the sodium silicate solution were 8.35%, 26.54% and 65.11%, respectively. This mixture is the solid waste composite alkaline activator.

[0056] The preparation steps of the calcium carbide slag alkaline activated powder are as follows:

[0057] (1) Use carbide slag, a by-product of industrial production, as raw material and pass it through a 200-mesh sieve to obtain powder;

[0058] (2) The prepared powder is washed and cleaned, and then filtered to remove impurities;

[0059] (3) It is then dried at 70°C and then ground and sieved through a 200-mesh sieve to remove impurities;

[0060] (4) The ash obtained in step (3) is placed in a sodium phosphate solution with a mass fraction of 1% and the mass ratio of ash to sodium phosphate solution is 1:3. After soaking for 24 hours, the solid and liquid are separated. The obtained solid is then placed in a 0.1 mol / L ammonium bicarbonate solution with a mass ratio of solid to ammonium bicarbonate solution of 1:3. After soaking for 24 hours, the solid and liquid are separated again to activate the ash reaction activity.

[0061] (5) The ash after chemical activation in step (4) is subjected to pressure filtration, drying, grinding and sieving through a 200-mesh sieve;

[0062] (6) Then, the ash was kept at 700℃ for 2 hours to activate the ash activity using physical methods;

[0063] (7) After final grinding and sieve treatment with a 200-mesh sieve, carbide slag alkali activated powder is obtained.

[0064] The preparation steps for concrete mixture are as follows:

[0065] (1) Weigh each raw material according to the weight parts in Table 1. First, dry mix fly ash and slag powder to obtain a uniformly dispersed precursor powder.

[0066] (2) Subsequently, solid waste composite alkaline activator, water and sand and gravel aggregate are added to the precursor powder and mixed to obtain low-carbon concrete.

[0067] The preparation flow chart of the low-carbon concrete in this embodiment is as follows: Figure 1 As shown.

[0068] Example 2

[0069] Concrete mixtures were prepared using the raw materials shown in Table 1. The preparation method of the solid waste composite alkaline activator was as follows: carbide slag alkaline activating powder and sodium silicate solution (sodium silicate chemical formula is Na2O·3.28SiO2) were mixed and water was added. In the resulting mixed solution, the mass ratio of carbide slag alkaline activating powder to sodium silicate solution was 1:4.5. The mass percentage contents of Na2O, SiO2 and H2O in the sodium silicate solution were 8.35%, 26.54% and 65.11%, respectively, which constituted the solid waste composite alkaline activator.

[0070] The preparation steps of the calcium carbide slag alkaline activated powder are as follows:

[0071] (1) Use carbide slag, a by-product of industrial production, as raw material and pass it through a 200-mesh sieve to obtain powder;

[0072] (2) The prepared powder is washed and cleaned, and then filtered to remove impurities;

[0073] (3) It is then dried at 60°C and then ground and sieved through a 200-mesh sieve to remove impurities;

[0074] (4) The ash obtained in step (3) is placed in a sodium phosphate solution with a concentration of 0.8 wt%, the mass ratio of ash to sodium phosphate solution is 1:3.5, and soaked for 18 hours. Then, solid-liquid separation is performed. The obtained solid is then placed in a 0.15 mol / L ammonium bicarbonate solution with a mass ratio of solid to ammonium bicarbonate solution is 1:2.5, and soaked for 36 hours. Solid-liquid separation is performed again to activate the ash reaction activity.

[0075] (5) The ash after chemical activation in step (4) is subjected to pressure filtration, drying, grinding and sieving through a 200-mesh sieve;

[0076] (6) Then, the ash was kept at 650℃ for 2.5 hours to activate its activity using physical methods;

[0077] (7) After final grinding and sieve treatment with a 200-mesh sieve, carbide slag alkali activated powder is obtained.

[0078] The preparation steps for concrete mixture are as follows:

[0079] (1) Weigh each raw material according to the weight parts in Table 1. First, dry mix fly ash and slag powder to obtain a uniformly dispersed precursor powder.

[0080] (2) Subsequently, solid waste composite alkaline activator, water and sand and gravel aggregate are added to the precursor powder and mixed to obtain low-carbon concrete based on solid waste activation.

[0081] Example 3

[0082] Concrete mixtures were prepared using the raw materials shown in Table 1. The preparation method of the solid waste composite alkaline activator was as follows: carbide slag alkaline activating powder and sodium silicate solution (sodium silicate chemical formula is Na2O·3.28SiO2) were mixed and water was added. In the resulting mixed solution, the mass ratio of carbide slag alkaline activating powder to sodium silicate solution was 1:3.5. The mass percentages of Na2O, SiO2 and H2O in the sodium silicate solution were 8.35%, 26.54% and 65.11%, respectively, which constituted the solid waste composite alkaline activator.

[0083] The preparation steps of the calcium carbide slag alkaline activated powder are as follows:

[0084] (1) Use carbide slag, a by-product of industrial production, as raw material and pass it through a 200-mesh sieve to obtain powder;

[0085] (2) The prepared powder is washed and cleaned, and then filtered to remove impurities;

[0086] (3) It is then dried at 80°C and then ground and sieved through a 200-mesh sieve to remove impurities;

[0087] (4) The ash obtained in step (3) is placed in a sodium phosphate solution with a concentration of 1.2 wt%, the mass ratio of ash to sodium phosphate solution is 1:2.5, and soaked for 36 hours. Then, solid-liquid separation is performed. The obtained solid is then placed in a 0.05 mol / L ammonium bicarbonate solution with a mass ratio of solid to ammonium bicarbonate solution is 1:3.5, and soaked for 18 hours. Solid-liquid separation is performed again to activate the ash reaction activity.

[0088] (5) The ash after chemical activation in step (4) is subjected to pressure filtration, drying, grinding and sieving through a 200-mesh sieve;

[0089] (6) Then, the ash was kept at 750℃ for 1.5 hours to activate its activity using physical methods;

[0090] (7) After final grinding and sieve treatment with a 200-mesh sieve, carbide slag alkali activated powder is obtained.

[0091] The preparation steps for concrete mixture are as follows:

[0092] (1) Weigh each raw material according to the weight parts in Table 1. First, dry mix fly ash and slag powder to obtain a uniformly dispersed precursor powder.

[0093] (2) Subsequently, solid waste composite alkaline activator, water and sand and gravel aggregate are added to the precursor powder and mixed to obtain low-carbon concrete based on solid waste activation.

[0094] Comparative Example 1

[0095] Similar to Example 1, the difference lies in the fact that the calcium carbide slag alkaline activation powder used is different from that in Example 1. The calcium carbide slag alkaline activation powder used in this comparative example has not undergone chemical and physical activation treatment. That is, the preparation steps of the calcium carbide slag alkaline activation powder used in this comparative example are as follows:

[0096] (1) Use carbide slag, a by-product of industrial production, as raw material and pass it through a 200-mesh sieve to obtain powder;

[0097] (2) The prepared powder is washed and cleaned, and then filtered to remove impurities;

[0098] (3) The powder is then dried at 70°C and then ground and sieved through a 200-mesh screen to remove impurities, thus obtaining carbide slag alkaline activated powder.

[0099] Comparative Example 2

[0100] Similar to Example 1, the difference lies in the fact that the calcium carbide slag alkaline activation powder used is different from that in Example 1. The calcium carbide slag alkaline activation powder used in this comparative example has not undergone chemical activation treatment. That is, the preparation steps of the calcium carbide slag alkaline activation powder used in this comparative example are as follows:

[0101] (1) Use carbide slag, a by-product of industrial production, as raw material and pass it through a 200-mesh sieve to obtain powder;

[0102] (2) The prepared powder is washed and cleaned, and then filtered to remove impurities;

[0103] (3) It is then dried at 70°C and then ground and sieved through a 200-mesh sieve to remove impurities;

[0104] (4) Then, the ash was kept at 700℃ for 2 hours to activate the ash activity using physical methods;

[0105] (5) After final grinding and sieve treatment with a 200-mesh sieve, carbide slag alkali activated powder is obtained.

[0106] Comparative Example 3

[0107] Similar to Example 1, the difference lies in the fact that the calcium carbide slag alkaline activation powder used is different from that in Example 1. The calcium carbide slag alkaline activation powder used in this comparative example was not activated by sodium phosphate solution. That is, the preparation steps of the calcium carbide slag alkaline activation powder used in this comparative example are as follows:

[0108] (1) Use carbide slag, a by-product of industrial production, as raw material and pass it through a 200-mesh sieve to obtain powder;

[0109] (2) The prepared powder is washed and cleaned, and then filtered to remove impurities;

[0110] (3) It is then dried at 70°C and then ground and sieved through a 200-mesh sieve to remove impurities;

[0111] (4) The ash obtained in step (3) is placed in a 0.1 mol / L ammonium bicarbonate solution with a mass ratio of solid to ammonium bicarbonate solution of 1:3. After soaking for 24 hours, the solid and liquid are separated to activate the ash reaction activity.

[0112] (5) The ash after chemical activation in step (4) is subjected to pressure filtration, drying, grinding and sieving through a 200-mesh sieve;

[0113] (6) Then, the ash was kept at 700℃ for 2 hours to activate the ash activity using physical methods;

[0114] (7) After final grinding and sieve treatment with a 200-mesh sieve, carbide slag alkali activated powder is obtained.

[0115] Comparative Example 4

[0116] Similar to Example 1, the difference lies in the fact that the calcium carbide slag alkaline activation powder used is different from that in Example 1. The calcium carbide slag alkaline activation powder used in this comparative example was not activated by ammonium bicarbonate solution. That is, the preparation steps of the calcium carbide slag alkaline activation powder used in this comparative example are as follows:

[0117] (1) Use carbide slag, a by-product of industrial production, as raw material and pass it through a 200-mesh sieve to obtain powder;

[0118] (2) The prepared powder is washed and cleaned, and then filtered to remove impurities;

[0119] (3) It is then dried at 70°C and then ground and sieved through a 200-mesh sieve to remove impurities;

[0120] (4) The ash obtained in step (3) is placed in a sodium phosphate solution with a mass fraction of 1% and the mass ratio of ash to sodium phosphate solution is 1:3. The solution is soaked for 24 hours and then the solid and liquid are separated to activate the ash reaction activity.

[0121] (5) The ash after chemical activation in step (4) is subjected to pressure filtration, drying, grinding and sieving through a 200-mesh sieve;

[0122] (6) Then, the ash was kept at 700℃ for 2 hours to activate the ash activity using physical methods;

[0123] (7) After final grinding and sieve treatment with a 200-mesh sieve, carbide slag alkali activated powder is obtained.

[0124] Comparative Example 5

[0125] Similar to Example 1, the difference lies in the fact that the calcium carbide slag alkaline activation powder used is different from that in Example 1. The calcium carbide slag alkaline activation powder used in this comparative example did not undergo physical activation treatment. That is, the preparation steps of the calcium carbide slag alkaline activation powder used in this comparative example are as follows:

[0126] (1) Use carbide slag, a by-product of industrial production, as raw material and pass it through a 200-mesh sieve to obtain powder;

[0127] (2) The prepared powder is washed and cleaned, and then filtered to remove impurities;

[0128] (3) It is then dried at 70°C and then ground and sieved through a 200-mesh sieve to remove impurities;

[0129] (4) The ash obtained in step (3) is placed in a sodium phosphate solution with a mass fraction of 1% and the mass ratio of ash to sodium phosphate solution is 1:3. After soaking for 24 hours, the solid and liquid are separated. The obtained solid is then placed in a 0.1 mol / L ammonium bicarbonate solution with a mass ratio of solid to ammonium bicarbonate solution of 1:3. After soaking for 24 hours, the solid and liquid are separated again to activate the ash reaction activity.

[0130] (5) The ash after chemical activation in step (4) is subjected to pressure filtration, drying, grinding and sieve treatment to obtain carbide slag alkaline activated powder.

[0131] Comparative Example 6

[0132] Similar to Example 1, the difference is that the calcium carbide slag alkaline activation powder used is different from that in Example 1. The calcium carbide slag alkaline activation powder used in this comparative example is subjected to physical activation treatment at 900℃. That is, when preparing the calcium carbide slag alkaline activation powder, step (6) is: keep warm at 900℃ for 2 hours.

[0133] Comparative Example 7

[0134] Similar to Example 1, the difference is that the calcium carbide slag alkaline activation powder used is different from that of Example 1. The calcium carbide slag alkaline activation powder used in this comparative example is subjected to physical activation treatment at 500℃. That is, when preparing the calcium carbide slag alkaline activation powder, step (6) is: keep warm at 500℃ for 2 hours.

[0135] Comparative Example 8

[0136] Similar to Example 1, except that the mass ratio of carbide slag alkaline activating powder to sodium silicate solution in the solid waste composite alkaline activator used in this comparative example is different from that in Example 1. The mass ratio of carbide slag alkaline activating powder to sodium silicate solution in the solid waste composite alkaline activator used in this comparative example is 1:3, and the rest are the same as in Example 1.

[0137] Comparative Example 9

[0138] Similar to Example 1, except that the mass ratio of carbide slag alkaline activating powder to sodium silicate solution in the solid waste composite alkaline activator used in this comparative example is different from that in Example 1. The mass ratio of carbide slag alkaline activating powder to sodium silicate solution in the solid waste composite alkaline activator used in this comparative example is 1:5, and the rest are the same as in Example 1.

[0139] Table 1. Raw material ratios for Examples 1-3 and Comparative Examples 1-9 (precursors by weight).

[0140]

[0141] Effect verification

[0142] The concrete mixtures prepared in Examples 1-3 and Comparative Examples 1-9 were placed into molds, cured in an indoor environment at 20°C for 24 hours, demolded, and then moved to a standard curing room at 20±2°C and 95% relative humidity until the test age was reached, thus obtaining the test samples.

[0143] The compressive strength of the test samples prepared using concrete mixtures from Examples 1-3 and Comparative Examples 1-9 was tested, and the results are shown in Table 2.

[0144] Table 2. Effect verification data of Examples 1-3 and Comparative Examples 1-9

[0145]

[0146] As shown in Table 2, the mechanical properties of the samples prepared from the mixtures of Examples 1 and Comparative Examples 8-9 show that the mechanical properties of the samples reach the optimal value when the mass ratio of carbide slag alkaline activating powder to sodium silicate solution is 1:4. This indicates that the low-carbon concrete prepared with the ratio of carbide slag alkaline activating powder to sodium silicate solution in the solid waste composite alkaline activator provided by the present invention of 1:4 has the best mechanical properties.

[0147] As shown in Table 2, the analysis of the mechanical property test data of Example 1 and Comparative Examples 1 to 7 shows that the method of combining chemical and physical activation at a certain temperature provided by the present invention can effectively improve the reactivity of the alkaline activated powder of industrial by-product carbide slag, thereby enabling low-carbon concrete to obtain the optimal mechanical properties.

[0148] The above description is merely a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A low-carbon concrete, characterized in that, The raw materials, by weight, include: 1300-1600 parts fly ash, 300-400 parts slag powder, 400-600 parts solid waste composite alkaline activator, 400-600 parts sand and gravel aggregate, and 300-400 parts water. The solid waste composite alkaline activator is a mixture containing carbide slag alkaline activating powder and sodium silicate solution; the sodium silicate is Na2O·nSiO2, and n is 3 to 3.3; in the mixture, the mass ratio of carbide slag alkaline activating powder to sodium silicate solution is 1:(3.5 to 4.5), and the mass ratio of H2O to Na2O·nSiO2 in the sodium silicate solution is 7 to 10; The preparation method of the carbide slag alkali-activated powder includes the following steps: using carbide slag, an industrial by-product, as raw material, and sieving it to obtain powder; washing and cleaning the powder, and then performing pressure filtration to remove impurities; subsequently drying it at 60-80℃, and then grinding and sieving it to remove impurities; then chemically activating the obtained ash; pressing, drying, grinding, and sieving the chemically activated ash; then performing physical activation treatment; finally grinding and sieving to obtain the carbide slag alkali-activated powder. The specific method of the chemical activation treatment is as follows: First, the ash is placed in a sodium phosphate solution with a mass fraction of 0.8-1.2%, and the mass ratio of ash to sodium phosphate solution is 1:(2.5-3.5). The solution is soaked for 18-36 hours, and then the solid and liquid are separated. The obtained solid is then placed in an ammonium bicarbonate solution with a concentration of 0.05-0.15 mol / L, and the mass ratio of solid to ammonium bicarbonate solution is 1:(2.5-3.5). The solution is soaked for 18-36 hours, and then the solid and liquid are separated again. The physical activation treatment method is as follows: keep warm at 650-750℃ for 1.5-2.5 hours.

2. The low-carbon concrete according to claim 1, characterized in that, The fly ash contains 52-55 wt% SiO2, 34-38 wt% Al2O3, and 1.9-2.2 wt% CaO; the average particle size of the fly ash is 9-10 μm.

3. The low-carbon concrete according to claim 1, characterized in that, The slag powder contains 31-33 wt% SiO2, 16-18.5 wt% Al2O3, and 33-35 wt% CaO; the average particle size of the slag powder is 9-10 μm.

4. A method for preparing low-carbon concrete according to any one of claims 1 to 3, characterized in that, The process includes the following steps: Weigh each raw material according to the weight proportions, and first dry mix the fly ash and slag powder to obtain a uniformly dispersed precursor powder; Subsequently, the solid waste composite alkaline activator, water, and sand and gravel aggregates are added to the precursor powder and mixed further to obtain the low-carbon concrete.

5. The method for preparing low-carbon concrete according to claim 4, characterized in that, It also includes the steps of loading the low-carbon concrete into a test mold, curing it in an indoor environment of 20-25℃ for 24-48 hours, demolding it, and then curing it under standard curing conditions of 20±2℃ and 95% relative humidity until the test age.

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