CN115974511A - A kind of low-alkali vegetable-growing concrete based on steel slag and preparation method thereof - Google Patents

Abstract

The invention discloses a steel slag-based low-alkali vegetable-growing concrete and a preparation method thereof, which relates to the technical field of building materials and consists of the following components: steel slag aggregate, steel slag powder, granulated blast furnace slag powder, gypsum, calcium aluminate, reinforcing agent, water reducer, retarder, water, in parts by mass, the regenerated micropowder composite expansion agent is composed of the following components: 300-450 parts of steel slag aggregate, 20-30 parts of steel slag powder, granulated blast furnace slag powder 30-40 parts, 15-20 parts of gypsum, 3-5 parts of calcium aluminate, 3-5 parts of reinforcing agent, 0.2-0.5 parts of water reducing agent, 0.05-0.15 parts of retarder, 25-35 parts of water, the present invention The beneficial effect is: the preparation method is simple, a conventional concrete mixer can be used for on-site mixing construction, the process steps are relatively simple, and the steel slag, slag, phosphogypsum and calcium aluminate are all derived from industrial by-products. Vegetative concrete can be used in slopes, roads, landscapes, central isolation belts, etc. It has high strength, a steel slag utilization rate of more than 80%, low alkalinity, and is rich in low-concentration fertilizers and trace elements.

Description

A kind of low-alkali vegetable-growing concrete based on steel slag and preparation method thereof

technical field

The invention relates to the technical field of building materials, in particular to steel slag-based low-alkali vegetable-growing concrete and a preparation method thereof.

Background technique

Vegetative concrete has a certain ecological effect or specific ecological function. Compared with traditional concrete, this type of concrete generally has the functions of reducing the amount of cement, dust removal and noise reduction, water permeability and ventilation, water purification and heat storage, etc., and is environmentally friendly or biological. compatibility. It can be applied on roads, rivers, slope protection and other parts. While increasing greening, it can make the city, like a sponge, have good elasticity in adapting to environmental changes and dealing with natural disasters caused by rain.

In the prior art, plant-grown concrete is generally formed by covering the surface of natural coarse aggregate with a thin layer of cement paste and bonding each other to form a honeycomb structure with evenly distributed pores, so it has the characteristics of air permeability, water permeability and light weight. However, the interior of cement-based plant-growing concrete is alkaline, and the pH value in the pore solution reaches above 13, which adversely affects the growth of plants. Therefore, many scholars have adopted a variety of alkali suppression methods, (1) reduce the amount of cement or use low-alkali cement, but the reduction of the alkalinity of Portland cement also means that the hydration reaction is inhibited, and the mechanical properties are significantly reduced; (2) Alkali-reducing materials such as ferrous sulfate and oxalic acid are added, but the process is complicated and the economy is not good, and industrial application cannot be realized, which limits its application in the field of plant-growing concrete.

Substituting steel slag aggregate for natural aggregate can significantly improve the mechanical properties of plant-growing concrete, and its hardness, wear resistance and density are far superior to natural aggregate. It has certain advantages as the aggregate of plant-growing concrete; at the same time, steel slag powder Active dicalcium silicate, the alkalinity of the solution system after hydration is much lower than that of portland cement, and a new type of low-carbon cementitious material can be prepared through compounding and excitation technology, which is suitable as a cementitious material group for low-alkali plant-grown concrete point. Therefore, the combination of steel slag aggregate and steel slag powder into a new high-quality low-alkali plant-grown concrete product with high added value can not only reduce the land occupation and environmental pollution caused by industrial waste, but also reduce the material cost and pH value of plant-grown concrete. Increase the survival rate of vegetation.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a steel slag-based low-alkali plant-grown concrete and a preparation method thereof, which solves the problems raised in the above-mentioned background technology.

In order to achieve the above object, the present invention is achieved through the following technical solutions: a steel slag-based low-alkali vegetable concrete, consisting of the following components: steel slag aggregate, steel slag powder, granulated blast furnace slag powder, gypsum, calcium aluminate, reinforced agent, water reducer, retarder, water, in parts by mass, the regenerated micropowder composite expansion agent is composed of the following components: 300-450 parts of steel slag aggregate, 20-30 parts of steel slag powder, granulated blast furnace slag powder 30-40 parts, 15-20 parts of gypsum, 3-5 parts of calcium aluminate, 3-5 parts of reinforcing agent, 0.2-0.5 parts of water reducing agent, 0.05-0.15 parts of retarder, 25-35 parts of water.

Preferably in the present invention, the steel slag aggregate is granular steel slag discharged from steel mills, with a particle size of 5-20 mm, crushing value ≤ 15%, and water swell rate ≤ 1.0%.

Preferably in the present invention, the steel slag powder is obtained by grinding steel slag aggregates with a particle size of 0 to 5 mm, with a specific surface area ≥ 350 m ² /kg, an average particle size ≤ 28 μm, and an alkalinity coefficient ≤ 1.8, which belongs to low Alkalinity steel slag.

Preferably in the present invention, the calcium aluminate is water purifying agent calcium aluminate powder, with a specific surface area ≥ 400 m ² /kg.

Preferably in the present invention, the gypsum is phosphogypsum, which is weakly acidic, has a calcium sulfate dihydrate content ≥ 80%, and a specific surface area ≥ 300 m ² /kg.

Preferably in the present invention, the granulated blast furnace slag powder is S95 grade.

Preferably in the present invention, the water reducer is a polycarboxylate high-efficiency water-reducer and/or a naphthalene-based high-efficiency water-reducer, and the water-reducing rate is ≥ 30%.

Preferably in the present invention, the reinforcing agent is redispersible latex powder and/or modified polyacrylate.

Preferably in the present invention, the retarder is citric acid and/or sodium gluconate, and the water-cement ratio is 0.25-0.35.

A preparation method of low-alkali vegetable-growing concrete based on steel slag, comprising the following steps:

The first step: sieve the steel slag, the steel slag with a particle size of 5-20 mm is used as the aggregate of planting concrete, and the steel slag with a particle size of 0-5 mm is ground until the specific surface area is ≥ 350 m ² /kg;

Step 2: Mix steel slag powder, slag powder, phosphogypsum and calcium aluminate in proportion to prepare low-carbon cementitious materials;

Step 3: uniformly mix steel slag aggregate, low-carbon cementitious material, reinforcing agent, water reducer, retarder and water in proportion to obtain the plant-growing concrete.

A steel slag-based low-alkali vegetative concrete in which steel slag is a by-product of the steel process. Mainly CaO, SiO ₂ , Al ₂ O ₃ , MgO, Fe ₂ O ₃ etc. These components are tricalcium silicate (C ₃ S), dicalcium silicate (C ₂ S), aluminate and iron aluminum The main crystal form of C ₂ S is γ-C ₂ S. In the present invention, the steel slag is sieved, and the particle size is 5-20 mm as steel slag aggregate, and the steel slag with a particle size of 0-5 mm is ground into steel slag powder with a specific surface area ≥ 350 m ² /kg, that is, after mechanical activation treatment, Increased its hydration reactivity.

In the process of preparing a low-alkali vegetable-growing concrete based on steel slag, the invention consists of four phases of steel slag, slag, gypsum and calcium aluminate to prepare a novel low-carbon cementitious material. Calcium aluminate minerals have high hydration activity, fast hydration and coagulation hardening speed, and react quickly to form Ca (OH) ₂ and C ₃ AH ₆ after meeting water. Then, it reacts with C ₂ S in steel slag and CaSO ₄ ×H ₂ O in phosphogypsum to generate CSH gel and AFt. Calcium hydroxide produced by the hydration of slag powder, gypsum and calcium aluminate will undergo an alkali-induced reaction, consuming a large amount of Ca ²⁺ , Al(OH) ^4- , [SiO ₄ ] ^5- The rate of the hydration reaction. And with the dissolution of phosphogypsum, a large amount of low-concentration phosphate fertilizer enters the pores of vegetation concrete, which can provide trace elements for vegetation growth, continuously supply nutrients, and the utilization rate of steel slag reaches more than 80%. The reinforcing agent redispersible latex powder and modified polyacrylate can improve the interface bonding performance between the steel slag aggregate and the cementitious material, significantly improve the bonding strength, and ensure that the planted concrete will not be easily damaged under load with falling off. The addition of water reducer and retarder improves the workability of plant-grown concrete under the condition of low water-cement ratio, and provides great convenience for on-site construction.

The invention provides a steel slag-based low-alkali vegetable concrete and a preparation method thereof, which have the following beneficial effects:

1. The steel slag-based low-alkali plant-growing concrete and its preparation method use low-activity, long-term stockpiled steel slag powder and steel slag aggregate as raw materials for plant-growing concrete, and regulate the alkalinity coefficient of steel slag through slag to promote the production of steel slag. In the hydration of C ₂ S with low activity in the medium, the water reducer is used to reduce the water-cement ratio, and the mechanical properties of the new low-carbon cementitious material are improved. Steel slag with low alkalinity coefficient is used. When the new low-carbon cementitious material is hydrated, the free calcium oxide in the system is consumed, and the needle-shaped ettringite produced has a crack-resistance effect. Both of them can effectively inhibit expansion and solve the problem of steel slag stability. It provides a theoretical and technical reference for the large-scale, high-value-added utilization of steel slag and the engineering application of plant-grown concrete products.

2. The steel slag-based low-alkali plant-grown concrete and its preparation method cover the surface of steel slag particles by redispersible latex powder and/or modified polyacrylate particles to block the separation of steel slag aggregate and slurry in the initial stage of hydration contacts to improve work performance. The late stage of hydration improves the bonding performance between steel slag aggregate and steel slag-based cementitious materials. Compared with dihydrate gypsum, phosphogypsum is weakly acidic, which can effectively reduce the pH value in the pore solution of planting concrete, and after water dissolving, it can overflow a large amount of phosphate fertilizer and trace elements to provide nutrients for the growth of vegetation.

3. The steel slag-based low-alkali plant-growing concrete and its preparation method are simple in preparation and can be constructed on-site with a conventional concrete mixer. The process steps are relatively simple. Steel slag, slag, phosphogypsum, and water purifying agent calcium aluminate are all derived from Industrial by-products. Vegetative concrete can be used in slopes, roads, landscapes, central isolation belts, etc. It has high strength, a steel slag utilization rate of more than 80%, low alkalinity, and is rich in low-concentration fertilizers and trace elements.

Description of drawings

Fig. 1 is a process flow diagram of the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention.

Please refer to Fig. 1, the present invention provides a kind of technical scheme: a kind of low-alkali vegetable-growing concrete based on steel slag and preparation method thereof:

Example 1

A low-alkali vegetable-growing concrete (by mass parts) based on steel slag contains the following components:

Steel slag aggregate 300 parts

Steel slag powder 30 parts

Slag powder 55 parts

Phosphogypsum 15 parts

Calcium aluminate 5 parts

Polycarboxylate superplasticizer 0.2 parts

Redispersible latex powder 3 parts

Citric acid 0.05 parts

water 25 servings

300 parts of steel slag aggregate, 30 parts of steel slag powder, 55 parts of slag powder, 15 parts of phosphogypsum, 5 parts of calcium aluminate, 0.2 parts of polycarboxylate superplasticizer, 3 parts of redispersible latex powder, 0.05 parts of citric acid Mix evenly with 25 parts of water to prepare steel slag-based low-alkali vegetation concrete. A 100 mm×100 mm×100mm specimen was molded and cured for 28 days at a temperature of 20±2°C and a relative humidity of 95%. The compressive strength of the planted concrete was measured to be 15.6 MPa, the effective porosity was 25.4%, and the water permeability coefficient was 6.5 cm/ s, pH value 9.0.

Example 2

A low-alkali vegetable-growing concrete (by mass parts) based on steel slag contains the following components:

Steel slag aggregate 450 parts

Steel slag powder 40 parts

Slag powder 40 parts

Phosphogypsum 20 parts

Calcium aluminate 5 parts

Polycarboxylate superplasticizer 0.2 parts

Redispersible latex powder 5 parts

Citric acid 0.15 parts

35 servings of water

450 parts of steel slag aggregate, 40 parts of steel slag powder, 40 parts of slag powder, 20 parts of phosphogypsum, 5 parts of calcium aluminate, 0.2 parts of polycarboxylate superplasticizer, 5 parts of redispersible latex powder, 0.15 parts of citric acid Mix evenly with 35 parts of water to prepare steel slag-based low-alkali vegetation concrete. A 100 mm×100 mm×100mm specimen was molded and cured for 28 days at a temperature of 20±2°C and a relative humidity of 95%. The compressive strength of the planted concrete was measured to be 10.8 MPa, the effective porosity was 25.6%, and the water permeability coefficient was 7.4 cm/ s, pH value 8.6.

Example 3

A low-alkali vegetable-growing concrete (by mass parts) based on steel slag contains the following components:

Steel slag aggregate 300 parts

Steel slag powder 30 parts

Slag powder 55 parts

Phosphogypsum 15 parts

Calcium aluminate 5 parts

Naphthalene-based water reducer 0.2 parts

Modified polyacrylate 3 parts

Sodium gluconate 0.05 parts

water 25 servings

300 parts of steel slag aggregate, 30 parts of steel slag powder, 55 parts of slag powder, 15 parts of phosphogypsum, 5 parts of calcium aluminate, 0.2 parts of naphthalene-based water reducer, 3 parts of modified polyacrylate, 0.05 parts of sodium gluconate Mix evenly with 25 parts of water to prepare steel slag-based low-alkali vegetation concrete. A 100 mm×100 mm×100mm specimen was molded and cured for 28 days at a temperature of 20±2°C and a relative humidity of 95%. The compressive strength of the planted concrete was measured to be 21.2 MPa, the effective porosity was 24.4%, and the water permeability coefficient was 6.6 cm/ s, pH value 8.8.

Example 4

A low-alkali vegetable-growing concrete (by mass parts) based on steel slag contains the following components:

Steel slag aggregate 450 parts

Steel slag powder 40 parts

Slag powder 40 parts

Phosphogypsum 20 parts

Calcium aluminate 5 parts

Naphthalene-based water reducer 0.5 parts

Modified polyacrylate 5 parts

Sodium gluconate 0.15 parts

35 servings of water

450 parts of steel slag aggregate, 40 parts of steel slag powder, 40 parts of slag powder, 20 parts of phosphogypsum, 5 parts of calcium aluminate, 0.5 parts of naphthalene-based water reducer, 5 parts of modified polyacrylate, 0.15 parts of sodium gluconate Mix evenly with 35 parts of water to prepare steel slag-based low-alkali plant-growing concrete. A 100 mm×100 mm×100mm specimen was molded and cured for 28 days at a temperature of 20±2°C and a relative humidity of 95%. The compressive strength of the planted concrete was measured to be 12.4 MPa, the effective porosity was 23.2%, and the water permeability coefficient was 8.2 cm/ s, pH value 8.0.

Comparative example 1

A low-alkali vegetable-growing concrete (by mass parts) based on steel slag contains the following components:

Steel slag aggregate 450 parts

Steel slag powder (alkalinity coefficient 2.3) 40 parts

Slag powder 40 parts

Phosphogypsum 20 parts

Calcium aluminate 5 parts

Polycarboxylate superplasticizer 0.5 parts

Modified polyacrylate 5 parts

Citric acid 0.15 parts

35 servings of water

450 parts of steel slag aggregate, 40 parts of steel slag powder with an alkalinity coefficient of 2.3, 40 parts of slag powder, 20 parts of phosphogypsum, 5 parts of calcium aluminate, 0.5 parts of polycarboxylate superplasticizer, and 5 parts of modified polyacrylate , 0.15 parts of citric acid and 35 parts of water were uniformly mixed to prepare steel slag-based low-alkali vegetation concrete. A 100 mm×100 mm×100mm specimen was molded and cured for 28 days at a temperature of 20±2°C and a relative humidity of 95%. The compressive strength of the planted concrete was measured to be 8.2 MPa, the effective porosity was 20.2%, and the water permeability coefficient was 7.2cm/ s, pH value 12.5.

Comparative example 2

A low-alkali vegetable-growing concrete (by mass parts) based on steel slag contains the following components:

Steel slag aggregate 350 parts

Steel slag powder 30 parts

Slag powder 40 parts

Dihydrate gypsum 20 parts

Calcium aluminate 5 parts

Polycarboxylate superplasticizer 0.2 parts

Modified polyacrylate 3 parts

Citric acid 0.15 parts

water 25 servings

350 parts of steel slag aggregate, 30 parts of steel slag powder, 40 parts of slag powder, 20 parts of phosphogypsum, 5 parts of calcium aluminate, 0.2 parts of polycarboxylate superplasticizer, 3 parts of modified polyacrylate, 0.05 parts of citric acid Mix evenly with 25 parts of water to prepare steel slag-based low-alkali vegetation concrete. A 100 mm×100 mm×100mm specimen was molded and cured for 28 days at a temperature of 20±2°C and a relative humidity of 95%. The compressive strength of the planted concrete was measured to be 8.8 MPa, the effective porosity was 18.2%, and the water permeability coefficient was 4.2 cm/ s, pH value 12.0.

Comparative example 3

A low-alkali vegetable-growing concrete (by mass parts) based on steel slag contains the following components:

Steel slag aggregate 350 parts

Steel slag powder 30 parts

Slag powder 40 parts

Phosphogypsum 20 parts

Polycarboxylate superplasticizer 0.2 parts

Redispersible latex powder 3 parts

Sodium gluconate 0.15 parts

water 25 servings

Mix 350 parts of steel slag aggregate, 30 parts of steel slag powder, 40 parts of slag powder, 20 parts of phosphogypsum, 0.2 parts of polycarboxylate superplasticizer, 3 parts of redispersible latex powder, 0.05 parts of sodium gluconate and 25 parts of water Mixing to prepare steel slag-based low-alkali vegetative concrete. A 100mm×100mm×100mm specimen was molded and cured for 28 days at a temperature of 20±2°C and a relative humidity of 95%. The compressive strength of the planted concrete was measured to be 1.8 MPa and the pH value to be 11.0.

With reference to the national standard JC/tT2557-2020 "Plant Concrete" and GB/T 50107-2010 "Concrete Strength Inspection and Evaluation Standard", the performance of the low-alkali plant concrete based on steel slag of Examples 1-4 and Comparative Examples 1-3 was tested, The measurement results are shown in Table 1 below.

Table 1 Performance test results of low-alkali plant-grown concrete based on steel slag

Shown by the result of table 1, the compressive strength of embodiment 1-4 improves more than 50% than comparative example 1-3, and effective porosity improves more than 20%, and water permeability coefficient improves more than 40%, and pH value is all at 9 the following.

As can be seen from Examples 1, 2, 3, 4 of the present invention and Comparative Examples 1, 2, 3, the excitation of slag and phosphogypsum has accelerated the hydration reaction of calcium aluminate and low-alkalinity steel slag powder, breaking the solution The balance of ion concentration improves the strength of planting concrete, reduces the consumption of Ca (OH) ₂ , and reduces the pH value in the pore solution. Therefore, the combination of steel slag powder, slag powder, phosphogypsum and calcium aluminate can improve the strength of plant-grown concrete, solve the problem of steel slag stability, reduce the effect of plant-grown concrete pH, and form low-alkali plant-grown concrete.

The basicity coefficient of the steel slag powder in the plant-growing concrete of Comparative Example 1 is 2.3>1.8. Although ettringite and calcium hydroxide are formed in the system, the stable formation of ettringite is hindered due to the high content of calcium oxide, and the strength is low. High pH. Finally, it also affects the water permeability of planting concrete.

In the planting concrete of Comparative Example 2, the type of gypsum was changed from phosphogypsum to dihydrate gypsum. Although the hydration reaction in the system did not change, calcium hydroxide and ettringite were also formed, but because dihydrate gypsum had no phosphate fertilizer and trace amounts Elements have no promoting effect on vegetation growth, and the excitation intensity is weak, so it cannot achieve the effect of high strength and low alkali.

The plant-growing concrete of Comparative Example 3 lacks calcium aluminate, and the system only relies on gypsum to stimulate slag powder and steel slag powder to generate strength, forming an alkali excitation effect to generate aluminosilicate gel products. Due to the lack of ettringite and calcium hydroxide, the strength is relatively low. Low, can't form cementation, so can't form type planting concrete. Within the technical scope disclosed by the invention, any equivalent replacement or change according to the technical solution and the inventive concept of the present invention shall be covered by the protection scope of the present invention.

Claims (10)

1. The low-alkali plant-growing concrete based on the steel slag comprises the following components: the slag aggregate, the slag powder, the granulated blast furnace slag powder, the gypsum, the calcium aluminate, the reinforcing agent, the water reducing agent, the retarder and the water, and is characterized in that: the regenerated micro-powder composite expanding agent comprises the following components in parts by mass: 300-450 parts of steel slag aggregate, 20-30 parts of steel slag powder, 30-40 parts of granulated blast furnace slag powder, 15-20 parts of gypsum, 3-5 parts of calcium aluminate, 3-5 parts of reinforcing agent, 0.2-0.5 part of water reducing agent, 0.05-0.15 part of retarder and 25-35 parts of water.

2. The steel slag-based low-alkali plant-growing concrete as claimed in claim 1, wherein: the steel slag aggregate is granular steel slag discharged from a steel mill, the particle size of the steel slag is 5-20 mm, the crushing value is less than or equal to 15%, and the water-soaking expansion rate is less than or equal to 1.0%.

3. The steel slag-based low-alkali plant-growing concrete as claimed in claim 1, wherein: the steel slag powder is obtained by grinding 0-5 mm steel slag aggregate, and the specific surface area is more than or equal to 350 m ² The steel slag has a grain size of 28 microns or less and a basicity coefficient of 1.8 or less, and belongs to low-basicity steel slag.

4. The steel slag-based low-alkali plant-growing concrete as claimed in claim 1, wherein: the calcium aluminate is water purifying agent calcium aluminate powder, and the specific surface area is more than or equal to 400 m ² /kg。

5. The steel slag-based low-alkali plant-growing concrete as claimed in claim 1, wherein: the gypsum is phosphogypsum with weak acidity, the content of calcium sulfate dihydrate is more than or equal to 80 percent, and the specific surface area is more than or equal to 300 m ² /kg。

6. The steel slag-based low-alkali plant-growing concrete as claimed in claim 1, wherein: the granulated blast furnace slag powder is S95 grade.

7. The steel slag-based low-alkali plant-growing concrete as claimed in claim 1, wherein: the water reducing agent is a polycarboxylic acid high-efficiency water reducing agent and/or a naphthalene high-efficiency water reducing agent, and the water reducing rate is more than or equal to 30%.

8. The steel slag-based low-alkali plant-growing concrete as claimed in claim 1, wherein: the reinforcing agent is re-dispersible latex powder and/or modified polyacrylate.

9. The steel slag-based low-alkali plant-growing concrete as claimed in claim 1, wherein: the retarder is citric acid and/or sodium gluconate, and the water-cement ratio is 0.25-0.35.

10. The method for preparing low-alkali steel slag-based green concrete for plant according to any one of claims 1 to 9, wherein the method comprises the following steps: the method comprises the following steps:

the first step is as follows: sieving the steel slag, taking the steel slag with the grain size of 5-20 mm as aggregate of the plant-growing concrete, and grinding the steel slag with the grain size of 0-5 mm until the specific surface area is more than or equal to 350 m ² /kg；

The second step: uniformly mixing the steel slag powder, the phosphogypsum and the calcium aluminate according to a proportion to prepare a low-carbon cementing material;

the third step: uniformly mixing the steel slag aggregate, the low-carbon cementing material, the reinforcing agent, the water reducing agent, the retarder and water according to a proportion to obtain the plant-growing concrete.

Images