Low-carbon concrete using steel slag as aggregate and cementing material and preparation method of low-carbon concrete

Abstract

The invention discloses low-carbon concrete using steel slag as aggregate and a cementing material and a preparation method of the low-carbon concrete, and relates to the fields of cement-based composite materials, solid waste resource utilization and low-carbon green development. The cement-based composite material is prepared from 400 to 700 parts of steel slag particles, 300 to 600 parts of steel slag micro powder, 120 to 240 parts of an exciting agent, 4 to 10 parts of a water reducing agent, 70 to 200 parts of CO2 gas and 100 to 250 parts of water. The preparation method comprises the following steps: mixing the steel slag particles, the steel slag micro powder and the exciting agent, adding part of water, introducing CO2 gas, stirring, adding the rest water and the water reducing agent, and stirring. The mixing amount of the steel slag in the concrete is increased, the activity of the steel slag is enhanced through carbonization treatment, the use of cement and gravel aggregate is reduced, carbon emission is reduced, the carbonization depth, early strength and porosity of the concrete are improved, and remarkable environmental protection benefits and practical application value are achieved.

Description

Technical Field

[0001] The invention relates to the fields of cement-based composite materials, solid waste resource utilization and low-carbon green development, and in particular to low-carbon concrete using steel slag as aggregate and cementitious material and a preparation method thereof. Background Art

[0002] Steel slag is an inevitable byproduct of steel production. For every ton of steel produced, about 0.15-0.2 tons of steel slag is produced. As a major steel producer in the world, China's crude steel output accounts for 54% of the world's total, and it plays a pivotal role in the world's steel. At the same time, large-scale steel production leads to the production of a large amount of steel slag. Due to the difficulty in resource utilization, these steel slags are piled up in the open air, occupying a large amount of land resources and causing environmental pollution.

[0003] At present, the resource utilization of steel slag is mainly concentrated as a mineral admixture or a partial replacement of sand and gravel aggregates. For example, patent CN 114573276A discloses a process for preparing steel slag cement concrete using converter steel slag, wherein steel slag is added to concrete as a mineral admixture, which improves the resource utilization rate of steel slag and improves the plastic deformation capacity of concrete. Patent CN 114591061A discloses a low-carbon road concrete with steel slag as aggregate and a preparation method thereof, which uses steel slag to replace all aggregates in road concrete, solves the problem of shortage of natural road materials, and significantly improves the strength, wear resistance and crack resistance of concrete. Patent CN 109250980A discloses a steel slag concrete and a preparation method thereof, which uses steel slag as a mineral admixture and part of the aggregate to be added to concrete, improves the resource utilization rate of steel slag and enhances the mechanical properties of concrete.

[0004] Although the above patents have discussed the resource utilization of steel slag, they all have certain limitations. They are limited to completely replacing aggregates or partially replacing cementitious materials, and have not further increased the proportion of steel slag in concrete, and have not yet proposed a specific method for enhancing the activity of steel slag through carbonization treatment. Therefore, the field urgently needs a technical solution that can more efficiently utilize steel slag, improve the reaction activity of steel slag and reduce the use of non-renewable resources. Summary of the invention

[0005] In view of this, the present invention aims to propose a low-carbon concrete using steel slag as aggregate and cementitious material and a preparation method thereof, so as to solve the problems of low steel slag content, low activity and poor resource utilization in concrete in the prior art, while reducing the concrete production cost and carbon emissions, and improving the carbonization depth, early strength and porosity of the concrete.

[0006] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] A cement-based composite material using steel slag to replace aggregate and cement comprises the following components in parts by weight: 400-700 parts of steel slag particles, 300-600 parts of steel slag powder, 120-240 parts of activator, 4-10 parts of water reducer, 1-10 parts of CO2 gas and 100-250 parts of water.

[0008] As a further technical solution, the specific surface area of ​​the slag particles is 30-100m 2 / kg, free CaO content ≥10%.

[0009] As a further technical solution, the specific surface area of ​​the steel slag powder is ≥200m 2 / kg, free CaO content ≥10%.

[0010] As a further technical solution, the activator is one or more of grade 42.5 silicate cement, ordinary silicate cement, slag silicate cement, fly ash silicate cement, pozzolanic silicate cement, composite silicate cement, or one or more of sodium hydroxide, sodium silicate, potassium hydroxide, and calcium hydroxide.

[0011] As a further technical solution, the water reducer is one or more of a polycarboxylic acid water reducer, a naphthalene-based water reducer, and a sodium lignin sulfonate water reducer.

[0012] As a further technical solution, the CO 2 The concentration of the gas is 15-100%.

[0013] Among them, CO 2 Too low gas concentration will affect the carbonization reaction rate and effect. Below 15%, longer carbonization time will be required and the crystallinity of calcium carbonate will be relatively poor.

[0014] The present invention also includes a method for preparing low-carbon concrete using steel slag as aggregate and cementitious material, comprising the following steps:

[0015] Step 1: Weigh steel slag particles, steel slag powder and activator by weight and mix them thoroughly to form a uniform dry mix.

[0016] Step 2: Weigh 1 / 2 of the water by weight and stir thoroughly with the mixture in step 1 and introduce CO into the mixture during stirring. 2 gas.

[0017] Step 3: Weigh the remaining 1 / 2 of the water and the water reducing agent weighed by weight, mix them thoroughly, and stir them thoroughly with the mixture in step 2 to finally obtain a low-carbon concrete using steel slag as aggregate and cementitious material.

[0018] As a further technical solution, the stirring time in step 2 is 10-30 minutes, and the stirring time in step 3 is 3-5 minutes.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) Use steel slag to replace all gravel aggregates: Compared with traditional gravel aggregates, steel slag particles provide more volcanic ash materials, increase the amount of hydration reaction products, and promote the improvement of concrete strength. In addition, the filling effect of steel slag particles effectively reduces the porosity in concrete, further improving the density and mechanical properties of the material.

[0021] (2) Carbonization reaction promotes early strength: slag particles and micropowder react with CO during the mixing process 2 The gas undergoes a carbonization reaction, rapidly generating a large number of nano calcium carbonate particles. These particles increase the density of concrete through a dense stacking effect, and provide abundant reaction sites for subsequent hydration reactions through a nucleation effect, accelerating the hydration process and significantly improving early strength.

[0022] (3) Low carbon and resource utilization: By optimizing the synergistic effect of steel slag particles and micro powder, a high proportion of traditional sand and gravel aggregates and cement are replaced, greatly improving the resource utilization efficiency of steel slag. While effectively reducing the consumption of non-renewable resources, carbon emissions are significantly reduced, meeting the technical requirements of low-carbon green development. DETAILED DESCRIPTION

[0023] The technical solutions disclosed in the present invention will be described clearly and completely below in conjunction with 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 creative work are within the scope of protection of the present invention.

[0024] In the following embodiments and comparative examples:

[0025] Example 1

[0026] A low-carbon concrete using steel slag as aggregate and cementitious material and a preparation method thereof, comprising the following steps:

[0027] Step 1: Weigh 400 parts of steel slag particles, 300 parts of steel slag powder and 120 parts of activator (42.5 grade ordinary Portland cement) by weight and mix them thoroughly to form a uniform dry mix.

[0028] Step 2: Weigh 50 parts of water by weight and add it to the dry mix, stir evenly and introduce 5 parts of CO 2 Gas (CO 2The gas concentration is 100%) and stirred for 10 minutes to fully carbonize the slag particles and fine powder.

[0029] Step 3: Weigh the remaining 50 parts of water and 4 parts of water reducer (polycarboxylate water reducer) by weight, mix them, add them to the mixture in step 2, and continue stirring for 4 minutes to form a uniform concrete slurry. Inject the slurry into the mold, cure it in a standard curing environment (temperature 20±2℃, humidity ≥95%) for 7 days to test the compressive strength, porosity and carbonization depth, and continue curing for 28 days to test the compressive strength.

[0030] Example 2

[0031] A low-carbon concrete using steel slag as aggregate and cementitious material and a preparation method thereof, comprising the following steps:

[0032] Step 1: Weigh 700 parts of steel slag particles, 600 parts of steel slag powder and 240 parts of activator (sodium hydroxide) by weight and mix them thoroughly to form a uniform dry mixture.

[0033] Step 2: Weigh 125 parts of water by weight and add it to the dry mix, stir evenly and introduce 10 parts of CO during the stirring process. 2 Gas (CO 2 The gas concentration is 100%) and stirred for 12 minutes to fully carbonize the slag particles and fine powder.

[0034] Step 3: Weigh the remaining 125 parts of water and 10 parts of water reducer (naphthalene water reducer) by weight, mix them, add them to the mixture in step 2, and continue stirring for 3 minutes to form a uniform concrete slurry. Inject the slurry into the mold, and test the compressive strength, porosity and carbonization depth for 7 days in a standard curing environment (temperature 20±2℃, humidity ≥95%). Continue to test the compressive strength after 28 days of curing.

[0035] Example 3

[0036] A low-carbon concrete using steel slag as aggregate and cementitious material and a preparation method thereof, comprising the following steps:

[0037] Step 1: Weigh 700 parts of steel slag particles, 400 parts of steel slag powder and 120 parts of activator (a mixture of sodium hydroxide and sodium silicate in a ratio of 1:1) by weight and mix them thoroughly to form a uniform dry mixture.

[0038] Step 2: Weigh 120 parts of water by weight and add it to the dry mix, stir evenly and introduce 3 parts of CO during the stirring process. 2 Gas (CO 3 The gas concentration is 75%) and stirred for 30 minutes to fully carbonize the slag particles and fine powder.

[0039] Step 3: Weigh the remaining 120 parts of water and 5 parts of water reducer (polycarboxylate water reducer) by weight, mix them, add them to the mixture in step 2, and continue stirring for 5 minutes to form a uniform concrete slurry. Inject the slurry into the mold, cure it in a standard curing environment (temperature 20±2℃, humidity ≥95%) for 7 days to test the compressive strength, porosity and carbonization depth, and continue curing for 28 days to test the compressive strength.

[0040] Example 4

[0041] A low-carbon concrete using steel slag as aggregate and cementitious material and a preparation method thereof, comprising the following steps:

[0042] Step 1: Weigh 550 parts of steel slag particles, 450 parts of steel slag powder and 160 parts of activator (sodium silicate) by weight and mix them thoroughly to form a uniform dry mixture.

[0043] Step 2: Weigh 105 parts of water by weight and add it to the dry mix, stir evenly and introduce 8 parts of CO during the stirring process. 2 Gas (CO 2 The gas concentration is 45%) and stirred for 20 minutes to fully carbonize the slag particles and the fine powder.

[0044] Step 3: Weigh the remaining 105 parts of water and 7 parts of water reducer (sodium lignin sulfonate water reducer) by weight, mix them, add them to the mixture in step 2, and continue stirring for 4 minutes to form a uniform concrete slurry. Inject the slurry into the mold, and test the compressive strength, porosity and carbonization depth for 7 days in a standard curing environment (temperature 20±2℃, humidity ≥95%). Continue to test the compressive strength after 28 days of curing.

[0045] Example 5

[0046] A low-carbon concrete using steel slag as aggregate and cementitious material and a preparation method thereof, comprising the following steps:

[0047] Step 1: Weigh 520 parts of steel slag particles, 580 parts of steel slag powder and 200 parts of activator (calcium hydroxide) by weight and mix them thoroughly to form a uniform dry mixture.

[0048] Step 2: Weigh 115 parts of water by weight and add it to the dry mix, stir evenly and introduce 10 parts of CO during the stirring process. 2 Gas (CO 2 The gas concentration is 60%) and stirred for 25 minutes to fully carbonize the slag particles and fine powder.

[0049] Step 3: Weigh the remaining 115 parts of water and 8 parts of water reducer (sodium lignin sulfonate water reducer) by weight, mix them, add them to the mixture in step 2, and continue stirring for 5 minutes to form a uniform concrete slurry. Inject the slurry into the mold, cure it in a standard curing environment (temperature 20±2℃, humidity ≥95%) for 7 days to test the compressive strength, porosity and carbonization depth, and continue to cure it for 28 days to test the compressive strength.

[0050] Comparative Example 1

[0051] Step 1: Weigh 800 parts of steel slag particles, 700 parts of steel slag powder and 100 parts of activator (calcium hydroxide) by weight and mix them thoroughly to form a uniform dry mixture.

[0052] Step 2: Weigh 115 parts of water by weight and add it to the dry mix, stir evenly and introduce 0 parts of CO during the stirring process. 2 Gas (CO 2 The gas concentration is 60%) and stirred for 5 minutes to fully carbonize the slag particles and fine powder.

[0053] Step 3: Weigh the remaining 115 parts of water and 8 parts of water reducer (sodium lignin sulfonate water reducer) by weight, mix them, add them to the mixture in step 2, and continue stirring for 2 minutes to form a uniform concrete slurry. Inject the slurry into the mold, and test the compressive strength, porosity and carbonization depth for 7 days in a standard curing environment (temperature 20±2℃, humidity ≥95%). Continue to test the compressive strength after 28 days of curing.

[0054] Comparative Example 2

[0055] Step 1: Weigh 400 parts of ordinary Portland cement and 1200 parts of sand and gravel aggregate by weight and mix them thoroughly to form a uniform dry mix.

[0056] Step 2: Weigh 200 parts of water and 6 parts of water reducer (polycarboxylate water reducer) by weight and add them to the dry mix, stir evenly for 20 minutes to fully mix all the raw materials.

[0057] Step 3: Inject the evenly mixed concrete slurry into the mold and cure it in a standard curing environment (temperature 20±2℃, humidity ≥95%) for 7 days to test the compressive strength, porosity and carbonization depth. Continue to cure for 28 days to test the compressive strength.

[0058] Comparative Example 3

[0059] Step 1: Weigh 700 parts of steel slag particles, 400 parts of steel slag powder and 120 parts of activator (a mixture of sodium hydroxide and sodium silicate in a ratio of 1:1) by weight and mix them thoroughly to form a uniform dry mixture.

[0060] Step 2: Weigh 120 parts of water by weight and add it to the dry mix, stir evenly and introduce 3 parts of CO during the stirring process. 2 Gas (CO 2 The gas concentration is 5%) and stirred for 5 minutes to fully carbonize the slag particles and fine powder.

[0061] Step 3: Weigh the remaining 120 parts of water and 5 parts of water reducer (polycarboxylate water reducer) by weight, mix them, add them to the mixture in step 2, and continue stirring for 7 minutes to form a uniform concrete slurry. Inject the slurry into the mold, cure it in a standard curing environment (temperature 20±2℃, humidity ≥95%) for 7 days to test the compressive strength, porosity and carbonization depth, and continue to cure it for 28 days to test the compressive strength.

[0062] Comparative Example 4

[0063] Step 1: Weigh 700 parts of steel slag particles, 400 parts of steel slag powder and 120 parts of activator (a mixture of sodium hydroxide and sodium silicate in a ratio of 1:1) by weight and mix them thoroughly to form a uniform dry mixture.

[0064] Step 2: Weigh 120 parts of water by weight and add it to the dry mix, stir evenly and introduce 3 parts of CO during the stirring process. 3 Gas (CO 3 The gas concentration is 5%) and stirred for 35 minutes to fully carbonize the slag particles and fine powder.

[0065] Step 3: Weigh the remaining 120 parts of water and 5 parts of water reducer (polycarboxylate water reducer) by weight, mix them, add them to the mixture in step 2, and continue stirring for 5 minutes to form a uniform concrete slurry. Inject the slurry into the mold, cure it in a standard curing environment (temperature 20±2℃, humidity ≥95%) for 7 days to test the compressive strength, porosity and carbonization depth, and continue curing for 28 days to test the compressive strength.

[0066] The test results of each embodiment and control example are shown in the following table.

[0067]

[0068] In summary, the present invention has achieved remarkable results in improving the early strength and density of concrete, reducing the carbonization depth, and achieving high-ratio replacement of cement and natural sand and gravel aggregates by optimizing the ratio of steel slag particles and micropowder and the carbonization treatment process. This technology not only effectively reduces carbon emissions, but also demonstrates outstanding environmental benefits and wide practical application potential. However, it should be pointed out that CO 2 Concentration, CO 2 Content and CO 2 The stirring time has a significant effect on the various properties of the material in the present invention. Specifically, when CO 2Concentration below 15% or CO 2 When the content is zero, the carbonation reaction cannot generate enough nano-calcium carbonate particles, and the generated calcium carbonate mostly exists in an amorphous form, which cannot provide nucleation sites for subsequent hydration reactions and effectively fill the internal pores of concrete, thus affecting the various properties of the material. 2 If the stirring time is too long, the nano-calcium carbonate generated by the carbonization reaction will be further converted into calcium carbonate particles of different crystal forms. However, due to the large particle size, it still cannot provide effective nucleation sites for the hydration reaction. 2 If the stirring time is too short, the carbonization reaction is incomplete and insufficient nano calcium carbonate particles can be generated. 2 Concentration, CO 2 Content and CO 2 Mixing time to ensure that the properties of the concrete meet the requirements.

[0069] Although the specific embodiments of the present invention are described above, those skilled in the art should understand that these are only examples, and the protection scope of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but these changes and modifications fall within the protection scope of the present invention.

Claims

1. A low-carbon concrete using steel slag as aggregate and cementitious material, characterized in that: The invention comprises the following components in parts by weight: 400-700 parts of steel slag particles, 300-600 parts of steel slag powder, 120-240 parts of activator, 4-10 parts of water reducer, 1-10 parts of CO2 gas and 100-250 parts of water.

2. The low-carbon concrete using steel slag as aggregate and cementitious material according to claim 1, characterized in that: The specific surface area of ​​the slag particles is 30-100m 2 / kg, free CaO content ≥10%.

3. The low-carbon concrete using steel slag as aggregate and cementitious material according to claim 1, characterized in that: The specific surface area of ​​the steel slag powder is ≥200m 2 / kg, free CaO content ≥10%.

4. The low-carbon concrete using steel slag as aggregate and cementitious material according to claim 1, characterized in that: The activator is one or more of grade 42.5 silicate cement, ordinary silicate cement, slag silicate cement, fly ash silicate cement, pozzolanic silicate cement, composite silicate cement, or one or more of sodium hydroxide, sodium silicate, potassium hydroxide, and calcium hydroxide.

5. The low-carbon concrete using steel slag as aggregate and cementitious material according to claim 1, characterized in that: The water reducer is one or more of polycarboxylic acid water reducer, naphthalene water reducer and lignin sulfonate sodium salt.

6. The low-carbon concrete using steel slag as aggregate and cementitious material according to claim 1, characterized in that: The concentration of the CO2 gas is 15-100%.

7. A method for preparing low-carbon concrete using steel slag as aggregate and cementitious material according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: Weigh steel slag particles, steel slag powder and activator by weight and mix them thoroughly to form a uniform dry mix. Step 2: Weigh 1 / 2 of the water by weight and stir it thoroughly with the mixture in step 1, and introduce CO2 gas during the stirring process. Step 3: Weigh the remaining 1 / 2 of the water by weight and the water reducing agent by weight, mix them thoroughly, and then stir them thoroughly with the mixture in step 2 to finally obtain low-carbon concrete.

8. The method for preparing low-carbon concrete using steel slag as aggregate and cementitious material according to claim 7, characterized in that: The stirring time in step 2 is 10-30 minutes, and the stirring time in step 3 is 3-5 minutes.

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