Low-carbon red-mud-based fully-recycled concrete and preparation method thereof
By combining modified red mud, regenerated fine powder, recycled sand and multifunctional powder modifier in concrete, the problem of insufficient application of red mud and construction waste in concrete is solved, and low-carbon and environmentally friendly concrete preparation is achieved, which significantly reduces carbon emissions and environmental pollution.
Patent Information
- Application Number
- CN202411597250.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-11
- Publication Date
- 2025-03-14
AI Technical Summary
There are insufficient separate applications of red mud and construction waste in concrete. Red mud has low hydration reaction activity and contains heavy metals. The complex composition of construction waste leads to poor concrete performance. The huge output of the two leads to environmental pollution and increased landfill pressure.
Low-carbon red mud-based fully recycled concrete is used to prepare high-performance concrete by combining modified red mud and regenerated fine powder, using alkaline and regenerated sand and regenerated coarse aggregate in red mud, combined with multifunctional powder modifiers and alkali exciters.
It significantly reduces the amount of cement used in traditional concrete, reduces the dependence on natural resources, achieves the goal of low-carbon environmental protection, reduces solid waste accumulation, and improves the safety and environmental protection of materials.
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Figure CN119613075A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of low-carbon building materials, in particular to a low-carbon red mud-based fully recycled concrete and a preparation method thereof. Background Art
[0002] Red mud is an industrial waste generated during the Bayer process of producing alumina from bauxite. About 120 million tons of red mud are produced worldwide each year, and the amount of red mud is huge. Since red mud contains a large amount of iron oxide, aluminum oxide, silicon oxide and other components, it has potential utilization value. However, the large amount of red mud accumulation not only occupies a large amount of land resources, but also may cause environmental problems such as soil alkalinization and groundwater pollution. Therefore, how to effectively utilize red mud resources has become a topic that needs to be solved urgently.
[0003] Construction waste is solid waste generated during construction, demolition and decoration, mainly including waste concrete, waste bricks, waste mortar, etc. With the acceleration of urban renewal, the amount of construction waste is increasing. According to a report by the World Bank, the annual output of global construction and demolition waste is estimated to be between 2 billion and 3.5 billion tons. These wastes not only occupy a large amount of landfill space, but also cause serious pollution to the environment. Therefore, the resource utilization of construction waste is also an important issue that needs to be solved urgently.
[0004] Although the application of red mud and construction waste in concrete has been studied, there are certain shortcomings when using each of them alone. For example, when red mud is used as a cementitious material, its hydration reaction activity is low, and it is difficult to provide sufficient cementing capacity when used alone. At the same time, red mud contains heavy metals, which poses potential environmental and health risks when used in building materials products. The composition of construction waste is complex, and during the reuse process, it often causes problems such as poor workability of concrete and weak interface transition zone, which limits its application in building materials. In addition, the output of these two wastes is huge, and there is an urgent need to find ways to utilize them on a large scale to reduce negative impacts on the environment and landfill needs. Summary of the invention
[0005] Based on the problems existing in the prior art, the present invention proposes a low-carbon red mud-based fully recycled concrete and a preparation method thereof. Red mud has many silicon-aluminum phase components, and recycled micropowder has many calcium components, and the two components are complementary; and red mud has high alkalinity, and only a small amount of alkali activator needs to be added to prepare a red mud-based polymer cementitious material that replaces cement. In addition, the use of recycled sand and recycled coarse aggregate as concrete aggregate can greatly reduce dependence on natural sand and gravel, and reduce the production cost and carbon emissions of building materials. It provides a feasible path for the resource utilization of red mud and construction waste.
[0006] In order to achieve the above purpose, the present invention adopts the following technical means:
[0007] A low-carbon red mud-based fully recycled concrete comprises the following components in parts by weight: 50-70 parts of modified red mud, 30-50 parts of recycled micro powder, 130-150 parts of recycled sand as fine aggregate, 280-300 parts of recycled coarse aggregate as coarse aggregate, 40-50 parts of water, and 1-3 parts of a multifunctional powder modifier; an alkali activator is also included.
[0008] Furthermore, the amount of the alkali activator is designed according to the residual alkalinity of the red mud and the soluble sodium content of the red mud, and the preparation method thereof is as follows:
[0009] Step A1: Take the dried red mud, put it in an extraction bottle, add pure water, cover the bottle tightly, shake at room temperature, and filter to obtain the leachate;
[0010] Step A2: Use inductively coupled plasma optical emission spectrometry to measure the sodium ion concentration c in the leachate Na , unit: mg / L, then the leached Na2O content in red mud for:
[0011]
[0012] Step A3: Calculate the total mass of Na2O in red mud using the following formula:
[0013]
[0014] in, is the total mass of Na2O in red mud, m 赤泥 is the mass of red mud;
[0015] Step A4: Determine the target alkali equivalent N and modulus M of the alkali activator, calculate the amount of SiO2 required from the water glass and the amount of Na2O additionally added from the NaOH, and obtain the result by the following formula:
[0016]
[0017]
[0018] Among them, m 再生微粉 To improve the quality of recycled micro powder, is the total mass of Na2O in water glass, is the total mass of Na2O in NaOH;
[0019] The target alkali equivalent N = 1%-3%, modulus M = 1.1-1.3;
[0020] Step A5: Determine the original water glass modulus and alkali equivalent, and calculate the target water glass m 水玻璃 With sodium hydroxide NaOH The dosage is obtained by the following formula:
[0021]
[0022] in, is the content of SiO2 in water glass;
[0023] Step A6: Mix water glass and sodium hydroxide in a uniform ratio, and obtain the alkaline activator after the heat release ends.
[0024] Preferably, the sodium ion concentration c in step A2 is Na The average value was taken for three parallel experiments.
[0025] Preferably, the modified red mud is red mud that has been mechanically ball-milled using a planetary ball mill with a rotation speed of 400-550 r / min for 20-60 s, and the median particle size is 10-48 μm.
[0026] Preferably, the strength activity index of the regenerated micropowder is greater than 0.65.
[0027] Preferably, the regenerated sand is Class I regenerated fine aggregate with a particle size of 0.2-1.0 mm.
[0028] Preferably, the recycled coarse aggregate is Class II or above recycled coarse aggregate after particle shaping.
[0029] Preferably, the multifunctional powder modifier is one of a polycarboxylic acid water reducer, sodium hexametaphosphate, and sodium tripolyphosphate having both water reducing properties and heavy metal chelating properties.
[0030] The present invention also provides a method for preparing the low-carbon red mud-based fully recycled concrete, comprising the following steps:
[0031] Step B1: Weigh the modified red mud and the regenerated micro powder, add them into a mixer and mix them evenly for 1-3 minutes, then add the regenerated sand and stir for 1-3 minutes, and finally add the regenerated coarse aggregate and mix for 2-4 minutes to obtain a mixture;
[0032] Step B2: Divide the water into two parts, dissolve the alkali activator in one part and dissolve the multifunctional powder modifier in the other part, add them into the mixture respectively, stir for 3-5 minutes, and form a uniform new low-carbon red mud-based fully recycled concrete;
[0033] Step B3: Pour the concrete into the mold and demould it one day after molding, and then standardly cure it for 28 days.
[0034] The carbon emission of the obtained low-carbon red mud-based fully recycled concrete is 40-100kg CO2-eq / m 3 .
[0035] The present invention has the following beneficial effects:
[0036] 1. The present invention uses red mud and construction waste as the main raw materials, which can significantly reduce the amount of cement in traditional concrete and reduce the dependence on natural resources such as natural sand and gravel. This not only effectively reduces carbon emissions and energy consumption, achieves the green and low-carbon environmental protection goals, but also greatly reduces the accumulation of solid waste, alleviates environmental pressure, and promotes the resource utilization of waste.
[0037] 2. In the process of formula design and calculation, the alkali content originally contained in the red mud was fully considered, and these residual alkalis were used as part of the alkali activator, reducing the use of additional alkali activators. This method not only reduces production costs, but also avoids the alkali problem that may be caused by excessive addition of alkali activators, and improves the overall performance and stability of the material.
[0038] 3. The use of multifunctional powder modifiers not only effectively improves the working performance of concrete and reduces water consumption, but also utilizes its heavy metal chelating properties to effectively chelate and stabilize heavy metal ions in red mud. This makes the application of red mud in concrete safer, reduces the potential pollution risk of heavy metals to the environment, and further improves the environmental protection and safety of the material. BRIEF DESCRIPTION OF THE DRAWINGS
[0039] Figure 1 The present invention is a flow chart of a method for preparing low-carbon red mud-based fully recycled concrete. DETAILED DESCRIPTION
[0040] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.
[0041] Example 1
[0042] A low-carbon red mud-based fully recycled concrete comprises the following components by mass: 60 parts of modified red mud, 40 parts of recycled micro powder, 9.37 parts of alkali activator, 150 parts of recycled sand as fine aggregate, 300 parts of recycled coarse aggregate as coarse aggregate, 45 parts of water and 2 parts of sodium hexametaphosphate. The strength activity index of the recycled micro powder is greater than 0.65. The recycled sand is Class I recycled fine aggregate with a particle size of 0.2-1.0 mm. The recycled coarse aggregate is Class II or above recycled coarse aggregate after particle shaping.
[0043] The preparation method of modified red mud is as follows: putting dried red mud into a planetary ball mill, controlling the ball-to-material ratio to 10:1, setting the rotation speed to 550 r / min, and after grinding for 60 seconds, obtaining modified red mud with a median particle size of 10 μm.
[0044] The alkaline activator is prepared by using water glass with a modulus of 3.37, a Na2O content of 8.8%, and a SiO2 content of 28.4% and analytically pure NaOH powder. The preparation method of the alkaline activator is as follows:
[0045] Step A1: Take 100 g of dried red mud, put it in an extraction bottle, add 1 L of pure water, cover the bottle tightly, shake at room temperature for 18 hours, and filter to obtain the leachate;
[0046] Step A2: Use an inductively coupled plasma emission spectrometer to measure the sodium ion concentration in the leachate. Perform three sets of tests and take the average value to obtain c Na =1198mg / L, then the leached Na2O content in red mud for:
[0047]
[0048] Step A3: The total mass of Na2O in the modified red mud is calculated based on 60 parts by mass, and the formula is as follows:
[0049]
[0050] Step A4: Determine the target alkali equivalent of the alkali activator N = 2%, modulus M = 1.2, and calculate the amount of SiO2 provided by water glass and the amount of Na2O added to NaOH according to the mass fraction: 60 parts of modified red mud and 40 parts of regenerated micropowder, which is obtained by the following formula:
[0051]
[0052] get:
[0053] Step A5: Determine the original water glass modulus and alkali equivalent, and calculate the target water glass m 水玻璃 With sodium hydroxide NaOH The dosage is obtained by the following formula:
[0054]
[0055] Step A6: Mix water glass and sodium hydroxide in a uniform ratio, and after the exotherm is finished, obtain 9.37 parts of the alkaline activator.
[0056] The method for preparing low-carbon red mud-based fully recycled concrete comprises the following steps:
[0057] Step B1: Weigh the modified red mud and the regenerated micro powder, add them into a mixer and mix them evenly for 1 minute, then add the regenerated sand and mix them for 1 minute, and finally add the regenerated coarse aggregate and mix them for 2 minutes to obtain a mixture;
[0058] Step B2: Divide the water into two parts, dissolve the alkali activator in one part and dissolve the sodium hexametaphosphate in the other part, and add them to the mixture respectively. Stir for 3 minutes to form a uniform new low-carbon red mud-based fully recycled concrete;
[0059] Step B3: Pour the concrete into the mold and demould it one day after molding, and then standardly cure it for 28 days.
[0060] Example 2
[0061] The formula of low-carbon red mud-based fully recycled concrete, the preparation method of alkali activator and the preparation method of concrete are the same as those in Example 1, except that the preparation method of modified red mud is as follows: putting dry red mud into a planetary ball mill, controlling the ball-to-material ratio to 10:1, setting the rotation speed to 400 r / min, and grinding for 20 seconds to obtain modified red mud with a median particle size of 48 μm.
[0062] Example 3
[0063] The method for preparing low-carbon red mud-based fully recycled concrete is the same as that in Example 1, except that:
[0064] The preparation method of modified red mud is as follows: putting dried red mud into a planetary ball mill, controlling the ball-to-material ratio to 10:1, setting the rotation speed to 500 r / min, and after grinding for 40 seconds, obtaining modified red mud with a median particle size of 15 μm.
[0065] Raw material components: 60 parts of modified red mud, 40 parts of recycled micropowder, 4.45 parts of alkali activator, 150 parts of recycled sand as fine aggregate, 300 parts of recycled coarse aggregate as coarse aggregate, 45 parts of water and 1 part of sodium hexametaphosphate.
[0066] In the preparation process of the base activator, the target base equivalent N = 1%, the modulus M = 1.2, and the m obtained by calculation 水玻璃 =4.09 parts, m NaOH =0.36 parts, that is, the base activator is 4.45 parts.
[0067] Example 4
[0068] The difference from Example 1 is:
[0069] The preparation method of modified red mud is as follows: putting dried red mud into a planetary ball mill, controlling the ball-to-material ratio to 10:1, setting the rotation speed to 500 r / min, and after grinding for 40 seconds, obtaining modified red mud with a median particle size of 15 μm.
[0070] Raw material components: 60 parts of modified red mud, 40 parts of recycled micropowder, 14.28 parts of alkali activator, 150 parts of recycled sand as fine aggregate, 300 parts of recycled coarse aggregate as coarse aggregate, 45 parts of water and 1 part of sodium hexametaphosphate.
[0071] In the preparation process of the base activator, the target base equivalent N = 3%, the modulus M = 1.2, and the m obtained by calculation 水玻璃 =12.27 parts, m NaOH =2.01 parts, that is, the base activator is 14.28 parts.
[0072] The method for preparing low-carbon red mud-based fully recycled concrete comprises the following steps:
[0073] Step B1: Weigh the modified red mud and the regenerated micro powder, add them into a mixer and mix them evenly for 1 minute, then add the regenerated sand and mix them for 1 minute, and finally add the regenerated coarse aggregate and mix them for 3 minutes to obtain a mixture;
[0074] Step B2: Divide the water into two parts, dissolve the alkali activator in one part and dissolve the sodium hexametaphosphate in the other part, and add them to the mixture respectively. Stir for 5 minutes to form a uniform new low-carbon red mud-based fully recycled concrete;
[0075] Step B3: Pour the concrete into the mold and demould it one day after molding, and then standardly cure it for 28 days.
[0076] Example 5
[0077] The method for preparing low-carbon red mud-based fully recycled concrete and the method for preparing modified red mud are the same as those in Example 1, except that:
[0078] Raw material components: 60 parts of modified red mud, 40 parts of recycled micropowder, 8.76 parts of alkali activator, 130 parts of recycled sand as fine aggregate, 290 parts of recycled coarse aggregate as coarse aggregate, 50 parts of water and 3 parts of sodium hexametaphosphate.
[0079] In the preparation process of the base activator, the target base equivalent N = 2%, the modulus M = 1.1, and the m obtained by calculation 水玻璃 =7.50 parts, m NaOH =1.26 parts, that is, the base activator is 8.76 parts.
[0080] Example 6
[0081] The method for preparing modified red mud is the same as that in Example 1, except that:
[0082] Raw material components: 60 parts of modified red mud, 40 parts of recycled micropowder, 9.97 parts of alkali activator, 130 parts of recycled sand as fine aggregate, 290 parts of recycled coarse aggregate as coarse aggregate, 50 parts of water and 3 parts of sodium hexametaphosphate.
[0083] In the preparation process of the base activator, the target base equivalent N = 2%, the modulus M = 1.3, and the m obtained by calculation 水玻璃 =8.86 parts, m NaOH=1.11 parts, that is, the base activator is 9.97 parts.
[0084] The method for preparing low-carbon red mud-based fully recycled concrete comprises the following steps:
[0085] Step B1: Weigh the modified red mud and the regenerated micro powder, add them into a mixer and mix them evenly for 3 minutes, then add the regenerated sand and mix them for 3 minutes, and finally add the regenerated coarse aggregate and mix them for 2 minutes to obtain a mixture;
[0086] Step B2: Divide the water into two parts, dissolve the alkali activator in one part and dissolve the sodium hexametaphosphate in the other part, and add them to the mixture respectively. Stir for 5 minutes to form a uniform new low-carbon red mud-based fully recycled concrete;
[0087] Step B3: Pour the concrete into the mold and demould it one day after molding, and then standardly cure it for 28 days.
[0088] Example 7
[0089] The preparation method of modified red mud and the preparation method of alkali activator are the same as those in Example 1, except that:
[0090] Raw material components: 60 parts of modified red mud, 40 parts of recycled micropowder, 9.37 parts of alkali activator, 140 parts of recycled sand as fine aggregate, 280 parts of recycled coarse aggregate as coarse aggregate, 40 parts of water and 2 parts of polycarboxylic acid water reducer.
[0091] The method for preparing low-carbon red mud-based fully recycled concrete comprises the following steps:
[0092] Step B1: Weigh the modified red mud and the regenerated micro powder, add them into a mixer and mix them evenly for 2 minutes, then add the regenerated sand and mix them for 2 minutes, and finally add the regenerated coarse aggregate and mix them for 4 minutes to obtain a mixture;
[0093] Step B2: Divide the water into two parts, dissolve the alkali activator in one part and the polycarboxylic acid water reducer in the other part, and add them to the mixture respectively. Stir for 4 minutes to form a uniform new low-carbon red mud-based fully recycled concrete;
[0094] Step B3: Pour the concrete into the mold and demould it one day after molding, and then standardly cure it for 28 days.
[0095] Example 8
[0096] The preparation method of modified red mud and the preparation method of alkali activator are the same as those in Example 1, except that:
[0097] Raw material components: 60 parts of modified red mud, 40 parts of recycled micropowder, 9.37 parts of alkali activator, 140 parts of recycled sand as fine aggregate, 280 parts of recycled coarse aggregate as coarse aggregate, 40 parts of water and 2 parts of sodium tripolyphosphate.
[0098] The method for preparing low-carbon red mud-based fully recycled concrete comprises the following steps:
[0099] Step B1: Weigh the modified red mud and the regenerated micro powder, add them into a mixer and mix them evenly for 2 minutes, then add the regenerated sand and mix them for 2 minutes, and finally add the regenerated coarse aggregate and mix them for 4 minutes to obtain a mixture;
[0100] Step B2: Divide the water into two parts, dissolve the alkali activator in one part and dissolve the sodium tripolyphosphate in the other part, and add them to the mixture respectively. Stir for 4 minutes to form a uniform new low-carbon red mud-based fully recycled concrete;
[0101] Step B3: Pour the concrete into the mold and demould it one day after molding, and then standardly cure it for 28 days.
[0102] Example 9
[0103] The preparation method of modified red mud and the preparation method of alkali activator are the same as those in Example 1, except that:
[0104] Raw material components: 50 parts of modified red mud, 50 parts of recycled micropowder, 9.37 parts of alkali activator, 150 parts of recycled sand as fine aggregate, 300 parts of recycled coarse aggregate as coarse aggregate, 40 parts of water and 2 parts of sodium tripolyphosphate.
[0105] The method for preparing low-carbon red mud-based fully recycled concrete comprises the following steps:
[0106] Step B1: Weigh the modified red mud and the regenerated micro powder, add them into a mixer and mix them evenly for 1 minute, then add the regenerated sand and mix them for 2 minutes, and finally add the regenerated coarse aggregate and mix them for 3 minutes to obtain a mixture;
[0107] Step B2: Divide the water into two parts, dissolve the alkali activator in one part and dissolve the sodium tripolyphosphate in the other part, and add them to the mixture respectively. Stir for 4 minutes to form a uniform new low-carbon red mud-based fully recycled concrete;
[0108] Step B3: Pour the concrete into the mold and demould it one day after molding, and then standardly cure it for 28 days.
[0109] Example 10
[0110] The preparation method of modified red mud and the preparation method of alkali activator are the same as those in Example 1, except that:
[0111] Raw material components: 70 parts of modified red mud, 30 parts of recycled micropowder, 9.37 parts of alkali activator, 150 parts of recycled sand as fine aggregate, 300 parts of recycled coarse aggregate as coarse aggregate, 40 parts of water and 2 parts of sodium tripolyphosphate.
[0112] The method for preparing low-carbon red mud-based fully recycled concrete comprises the following steps:
[0113] Step B1: Weigh the modified red mud and the regenerated micro powder, add them into a mixer and mix them evenly for 3 minutes, then add the regenerated sand and mix for 3 minutes, and finally add the regenerated coarse aggregate and mix for 4 minutes to obtain a mixture;
[0114] Step B2: Divide the water into two parts, dissolve the alkali activator in one part and dissolve the sodium tripolyphosphate in the other part, and add them to the mixture respectively. Stir for 5 minutes to form a uniform new low-carbon red mud-based fully recycled concrete;
[0115] Step B3: Pour the concrete into the mold and demould it one day after molding, and then standardly cure it for 28 days.
[0116] Comparative Example
[0117] The method for preparing low-carbon red mud-based fully recycled concrete and the method for preparing modified red mud are the same as those in Example 1, except that:
[0118] Raw material components: 60 parts of modified red mud, 40 parts of recycled micropowder, 9.83 parts of alkali activator, 150 parts of recycled sand as fine aggregate, 300 parts of recycled coarse aggregate as coarse aggregate, 43 parts of water and 2 parts of sodium hexametaphosphate.
[0119] During the preparation of the alkali activator, the residual alkalinity in the red mud is not considered, and the m 水玻璃 =8.18 parts, m NaOH =1.65 parts, that is, the base activator is 9.83 parts.
[0120] The low-carbon red mud-based fully recycled concrete prepared in the above embodiment was tested for compressive strength according to GB / T 50081-2019 "Standard for Test Methods for Mechanical Properties of Ordinary Concrete", and the slump was tested according to GB / T 50080-2016 "Standard for Test Methods for Performance of Ordinary Concrete Mixtures", and the embodied carbon emissions of the concrete were calculated, as shown in Table 1:
[0121] Table 1 Concrete performance test results of Examples 1 to 11
[0122]
[0123] From the data in Table 1, it can be seen that the carbon emissions of Examples 1-10 are significantly lower than the carbon emissions of ordinary concrete (about 330 kgCO2-eq / m 3), which has the characteristics of green and low carbon. Comparing Example 1 and Example 2, the red mud is ball-milled for a longer time, the particle fineness is optimized, and the filling effect in the concrete system is more obvious, so the strength is improved. Comparing Example 1 and Examples 3-6, the effect of alkali equivalent on the compressive strength and fluidity of concrete is more significant than the modulus of the alkali activator. The increase in the amount of alkali activator increases the viscosity of the gelling system, and more water is needed to dissolve silicate ions and the silicon-aluminum phase substances depolymerized from the gelling system to participate in the reaction. Therefore, it shows that the greater the amount of alkali activator, the lower the compressive strength and fluidity. Comparing Example 1, Example 7 and Example 8, the three multifunctional powder modifiers have no effect on the compressive strength. In terms of fluidity, the polycarboxylic acid water reducer has a better effect, followed by sodium hexametaphosphate, and sodium tripolyphosphate is poor. Comparing Example 1, Example 9 and Example 10, the amount of red mud has a negative effect on compressive strength and fluidity. Example 1 and Comparative Example 1 compare whether the effect of alkali in red mud on the design of concrete alkali activator is considered. It is found that including the alkali in red mud in the alkali activator will reduce the amount of NaOH used, thereby reducing the dosage of the alkali activator, avoiding the efflorescence problem caused by excessive alkali dosage, improving the compressive strength, and making the formula design more reasonable.
[0124] According to HJ / T 299-2007 "Solid Waste Leaching Toxicity Leaching Method Sulfuric Acid and Nitric Acid Method", the heavy metal leaching concentration of low-carbon red mud-based fully recycled concrete is tested. The limit value is taken from GB 30760-2024 "Technical Specifications for Co-treatment of Solid Waste in Cement Kilns". The test results are shown in Table 2:
[0125] Table 2 Heavy metal leaching concentration test results of Example 1 to Example 11 (mg / L)
[0126] Case Cr Zn Cd Pb Cu Limits 0.2 1 0.03 0.3 1 Example 1 0.118 0.077 0.002 0.269 0.022 Example 2 0.183 0.137 0.027 0.223 0.072 Example 3 0.162 0.334 0.020 0.281 0.064 Example 4 0.082 0.046 0.005 0.279 0.024 Example 5 0.165 0.102 0.011 0.251 0.089 Example 6 0.119 0.065 0.015 0.159 0.028 Example 7 0.212 0.622 0.028 0.261 0.102 Example 8 0.091 0.415 0.006 0.243 0.099 Example 9 0.108 0.115 0.002 0.211 0.019 Example 10 0.194 0.625 0.028 0.277 0.355
[0127] It can be seen from the data in Table 2 that the heavy metal detection results of the examples all meet the limit requirements, which shows that the low-carbon red mud-based fully recycled concrete can stably solidify the heavy metals in the red mud, ensuring the safety of the material.
[0128] The above description is only a preferred specific implementation manner of the present invention, and the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.
Claims
1. A low-carbon red mud-based fully recycled concrete, characterized in that: The invention comprises the following components in parts by weight: 50-70 parts of modified red mud, 30-50 parts of recycled micro powder, 130-150 parts of recycled sand as fine aggregate, 280-300 parts of recycled coarse aggregate as coarse aggregate, 40-50 parts of water, 1-3 parts of multifunctional powder modifier; and also comprises an alkali activator.
2. A low-carbon red mud-based fully recycled concrete according to claim 1, characterized in that: The amount of the alkali activator is designed according to the residual alkalinity of the red mud and the soluble sodium content of the red mud. The preparation method is as follows: Step A1: Take the dried red mud, put it in an extraction bottle, add pure water, cover the bottle tightly, shake at room temperature, and filter to obtain the leachate; Step A2: Use inductively coupled plasma optical emission spectrometry to measure the sodium ion concentration c in the leachate Na , unit: mg / L, then the leached Na2O content in red mud for: Step A3: Calculate the total mass of Na2O in red mud using the following formula: in, is the total mass of Na2O in red mud, m 赤泥 is the mass of red mud; Step A4: Determine the target alkali equivalent N and modulus M of the alkali activator, calculate the amount of SiO2 required from the water glass and the amount of Na2O additionally added from the NaOH, and obtain the result by the following formula: Among them, m 再生微粉 To improve the quality of recycled micro powder, is the total mass of Na2O in water glass, is the total mass of Na2O in NaOH; The target alkali equivalent N = 1%-3%, modulus M = 1.1-1.3; Step A5: Determine the original water glass modulus and alkali equivalent, and calculate the target water glass m 水玻璃 With sodium hydroxide NaOH The dosage is obtained by the following formula: in, is the content of SiO2 in water glass; Step A6: Mix water glass and sodium hydroxide in a uniform ratio, and obtain the alkaline activator after the heat release ends.
3. The low-carbon red mud-based fully recycled concrete according to claim 1, characterized in that: The sodium ion concentration c in step A2 Na The average value was taken for three parallel experiments.
4. The low-carbon red mud-based fully recycled concrete according to claim 1, characterized in that: The modified red mud is red mud that has been mechanically ball-milled using a planetary ball mill with a rotation speed of 400-550 r / min maintained for 20-60 seconds, and the median particle size is 10-48 μm.
5. The low-carbon red mud-based fully recycled concrete according to claim 1, characterized in that: The strength activity index of the regenerated micropowder is greater than 0.
65.
6. The low-carbon red mud-based fully recycled concrete according to claim 1, characterized in that: The regenerated sand is Class I regenerated fine aggregate with a particle size of 0.2-1.0 mm.
7. The low-carbon red mud-based fully recycled concrete according to claim 1, characterized in that: The recycled coarse aggregate is Class II or above recycled coarse aggregate that has been subjected to particle shaping.
8. The low-carbon red mud-based fully recycled concrete according to claim 1, characterized in that: The multifunctional powder modifier is one of a polycarboxylic acid water reducer, sodium hexametaphosphate and sodium tripolyphosphate having both water reducing performance and heavy metal chelating performance.
9. A method for preparing a low-carbon red mud-based fully recycled concrete according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step B1: Weigh the modified red mud and the regenerated micro powder, add them into a mixer and mix them evenly for 1-3 minutes, then add the regenerated sand and stir for 1-3 minutes, and finally add the regenerated coarse aggregate and mix for 2-4 minutes to obtain a mixture; Step B2: Divide the water into two parts, dissolve the alkali activator in one part and dissolve the multifunctional powder modifier in the other part, add them into the mixture respectively, stir for 3-5 minutes, and form a uniform new low-carbon red mud-based fully recycled concrete; Step B3: Pour the concrete into the mold and demould it one day after molding, and then standardly cure it for 28 days.
10. The preparation method according to claim 9, characterized in that: The carbon emission of the low-carbon red mud-based fully recycled concrete is 40-100kg CO2-eq / m 3 .