A method for preparing paving bricks using steel slag

Abstract

This invention discloses a method for preparing paving bricks using steel slag, relating to the field of paving brick technology. The paving bricks of this invention are composed of modified steel slag, silica sol, composite fibers, cement, antifreeze agent, aggregate, silica fume, and other components. The modified steel slag, through the synergistic resource utilization of waste materials, achieves volume stability and surface strengthening of the steel slag aggregate. Combined with the porosity control of silica fume and aggregate, and the toughening and strengthening effect of composite fibers, the paving bricks possess high permeability, excellent mechanical properties, and freeze-thaw durability, significantly improving the overall performance of recycled concrete paving bricks in road paving.

Description

Technical Field

[0001] This invention relates to the field of paving brick technology, specifically a method for preparing paving bricks using steel slag. Background Technology

[0002] Steel slag, a major solid waste from the steel industry, not only occupies land resources when it is accumulated in large quantities, but its heavy metals and alkaline substances may also leach out with rainwater, polluting the soil and groundwater. However, using steel slag in building materials, especially as a substitute for natural aggregates in the preparation of concrete paving bricks, is a promising way to consume it.

[0003] Steel slag contains a certain amount of free calcium oxide and free magnesium oxide. These components undergo a slow dissolution reaction upon contact with water, leading to volume expansion and severely affecting the volume stability of concrete products. This can easily cause cracking, bulging, and even structural damage to paving bricks, thus restricting their long-term durability and safety. Secondly, the dense and smooth surface of steel slag results in poor adhesion to cement paste and a weak interfacial transition zone, making it difficult for the concrete to meet the mechanical strength requirements of high-load paving bricks. Simultaneously, steel slag aggregate itself is brittle and prone to fracture under impact loads. For permeable paving bricks, good freeze-thaw resistance is also necessary in addition to permeability. In cold regions, moisture easily penetrates the porous interior of the steel slag and the aggregate-paste interface. During freeze-thaw cycles, the expansion stress generated by water freezing exacerbates the propagation of internal microcracks, leading to surface spalling, a sharp drop in strength, and a significantly shortened service life. Current technologies often improve freeze-thaw resistance by adding organic fibers, air-entraining agents, or increasing cement content, but these methods often fail to balance strength, permeability, durability, and cost. In addition, although some existing steel slag modification methods can improve its volume stability to a certain extent, the processing technology is complex, which may introduce new environmental risks, or it is difficult to form a durable and effective reinforcing and protective layer on the aggregate surface, thus limiting the modification effect.

[0004] Therefore, developing a preparation method that can simultaneously improve the volume stability, interfacial adhesion, mechanical strength and freeze-thaw resistance of steel slag aggregate, and realize the high-value utilization of steel slag in conjunction with other solid wastes, is of great practical significance and environmental benefit for promoting the large-scale safe application of steel slag in building materials such as permeable paving bricks. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing paving bricks using steel slag, so as to solve the problems existing in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing paving bricks using steel slag, characterized in that it comprises the following components by weight: 100-150 parts modified steel slag, 8-10 parts silica sol, 4-7 parts composite fiber, 15-30 parts cement, 1-5 parts antifreeze agent, 20-50 parts aggregate, 20-50 parts silica fume, 0.8-1.2 parts water-reducing agent, and 10-20 parts water; the preparation method of the modified steel slag includes the following steps:

[0007] (1) Crush the waste animal bones to a particle size of 1-3 mm, then mix them with sludge and animal feces from the wastewater treatment plant, add 10-20 wt% sulfuric acid at 60℃ according to the material-liquid ratio of 1 g: 15 mL, soak for 20-120 min, separate the solid and liquid, and obtain solid residue and phosphate-containing composite solution.

[0008] (2) The phosphate-containing composite solution is mixed with steel slag with a particle size of 0.15-0.25 mm, the pH is adjusted to neutral, and the mixture is left to stand for 2-3 hours to allow the solution to enter the steel slag. After completion, the steel slag aggregate is taken out and steam cured to obtain pretreated steel slag.

[0009] (3) Mix the silica sol with the solid slag obtained in step (1) according to the mass ratio, stir evenly, add 0.4-1 times the mass of the silica sol and pretreated steel slag, stir evenly, so that the surface of the pretreated steel slag is coated or covered with sol, dry at 180-200℃ for 3.5-4h, then calcine at 750-850℃ for 1-1.5h, and finally crush to a particle size of 2.25-4.75mm to obtain modified steel slag.

[0010] Furthermore, in step (1), the mass ratio of waste animal bones, sludge and animal feces is 1-3:4-6:5-10.

[0011] Furthermore, the total phosphorus content of the waste animal bones mentioned in step (1) is 6%-18% (dry basis), the total phosphorus content of the sludge is 1%-6% (dry basis), and the total phosphorus content of the animal feces is 0.5%-3.5% (dry basis).

[0012] Furthermore, the steam curing in step (2) is as follows: the temperature is increased to 75-78℃ at a rate of 10-15℃ / h and then kept at that temperature for 18-24 hours with a humidity of 90-95%.

[0013] Furthermore, the mass ratio of silica sol to solid slag in step (3) is 1:0.1-0.5.

[0014] Furthermore, the silica sol mentioned in step (3) is prepared in accordance with CN201410532394.5.

[0015] Furthermore, the composite fiber is a mixture of polypropylene fiber and carbon fiber in a mass ratio of 1-5:5-10; wherein the monofilament diameter of the polypropylene fiber is 18~48μm and the length is 12mm; and the diameter of the carbon fiber is 9~17μm and the length is 15mm.

[0016] Furthermore, the antifreeze is a mixture of ammonium chloride, ethylene glycol and formamide in a weight ratio of 1:(4-10):(3-7).

[0017] Furthermore, the water-reducing agent is a polycarboxylate water-reducing agent.

[0018] Furthermore, the particle size of the stone is 0.8-2.2 mm; the particle size of the silica fume is 0.15-1.5 mm.

[0019] Furthermore, the cement is type II silicate cement with a strength grade of 52.5.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0021] 1. This invention uses waste biomass materials, sludge, and steel slag as aggregate raw materials, realizing resource utilization and reducing environmental pollution caused by the outdoor accumulation of steel slag and waste.

[0022] 2. This invention involves acid leaching of biomass materials such as bones, feces, and sludge to dissolve a phosphoric acid solution and other solids. Then, utilizing the porous and cracked characteristics of steel slag aggregate, the phosphate solution is fully absorbed. The steel slag aggregate is cured under high temperature and humidity conditions to reduce CaO content, improving its volume stability and preventing later carbonation from causing cracking, bulging, or even detachment of the coating layer, which would affect the mechanical properties and freeze-thaw resistance of concrete. Next, the remaining solids are mixed with silica sol and coated onto the cured steel slag surface for co-carbonation. The resulting carbonized coating layer significantly enhances the concrete's properties. The strength and hardness of the aggregate reduce the brittleness of steel slag, thereby improving the mechanical properties of the paving bricks. The surface coating has a certain degree of hydrophobicity, which can effectively prevent water from penetrating into the internal pores of the aggregate, reducing the internal stress damage caused by water freezing and expansion during freeze-thaw cycles. Water can flow along the hydrophobic film inside the paving brick, thereby enhancing the permeability of the paving brick. The presence of the coating also improves the aggregate's resistance to freeze-thaw degradation, giving the concrete a long service life in cold regions. At the same time, the silica sol in the surface coating generates pores at high temperatures, achieving good permeability.

[0023] 3. This invention also incorporates silica fume and aggregate as concrete raw materials. Silica fume fills some of the voids in the paving brick raw materials, while aggregate increases the porosity of the concrete raw materials. Through the synergistic effect of silica fume and aggregate, not only are the mechanical properties of the concrete improved, but the permeability of the paving bricks is also enhanced. The addition of silica fume provides good bonding between the modified steel slag and cement, thus making the prepared permeable concrete paving bricks containing modified steel slag less prone to cracking and peeling, and improving their frost resistance.

[0024] 4. This invention incorporates elastic fibers, rigid fibers, and silica sol to form a ternary system, which intertwines with each other, thereby improving the frost resistance of concrete paving bricks. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1; A method for preparing paving bricks using steel slag, comprising the following components by weight: 100 parts modified steel slag, 8 parts silica sol, 4 parts composite fiber, 15 parts cement, 1 part antifreeze agent, 20 parts sepiolite with a particle size of 0.8 mm, 20 parts silica fume with a particle size of 0.15 mm, 0.8 parts polycarboxylate superplasticizer, and 10 parts water; the method for preparing the modified steel slag is as follows:

[0027] (1) The waste animal bones were crushed to a particle size of 1 mm, and then mixed with sludge and animal feces from the wastewater treatment plant at a mass ratio of 1:4:5. 10 wt% sulfuric acid at 60℃ was added at a material-liquid ratio of 1 g:15 mL. The mixture was soaked for 20 min, and the solid and liquid were separated to obtain solid residue and a phosphate-containing composite solution.

[0028] (2) Mix the phosphate-containing composite solution with steel slag with a particle size of 0.15 mm, adjust the pH to neutral, let stand for 2 hours to allow the solution to enter the steel slag, and after completion, take out the steel slag aggregate for steam curing. Heat the mixture to 75°C at 10°C / h and keep it at 90% humidity for 18 hours to obtain pretreated steel slag.

[0029] (3) Mix silica sol and solid slag at a mass ratio of 1:0.1, stir evenly, add 0.4 times the mass of pretreated steel slag, stir evenly, so that the surface of the pretreated steel slag is coated or covered with sol, dry at 180℃ for 3.5h, calcine at 750℃ for 1h, and crush to a particle size of 2.25mm to obtain modified steel slag;

[0030] The method for preparing the silica sol is as follows: distilled water is heated to boiling, and a 35% (w / w) trimethylsiloxysilicate solution is slowly added dropwise at a speed of 300 r / min, with the dropping rate controlled at 1 ml / min. The volume ratio of distilled water to trimethylsiloxysilicate solution is 16:1. After the addition is complete, the mixture is stirred at the same speed for 30 min. Nano-silica is then added, and the pH is adjusted to 9 with an 8% (w / w) sodium hydroxide aqueous solution. The mixture is then heated and kept at this temperature for 3 h to obtain the silica sol.

[0031] The composite fiber is a mixture of polypropylene fiber and carbon fiber in a mass ratio of 1:3. The polypropylene fiber has a single filament diameter of 18μm and a length of 12mm, and the carbon fiber has a diameter of 9μm and a length of 15mm.

[0032] The antifreeze agent comprises ammonium chloride, ethylene glycol, and formamide in a weight ratio of 1:4:3.

[0033] Example 2; A method for preparing paving bricks using steel slag, comprising the following components by weight: 150 parts modified steel slag, 10 parts silica sol, 7 parts composite fiber, 30 parts cement, 5 parts antifreeze agent, 50 parts sepiolite with a particle size of 2.2 mm, 50 parts silica fume with a particle size of 1.5 mm, 1.2 parts polycarboxylate superplasticizer, and 20 parts water; the method for preparing the modified steel slag is as follows:

[0034] (1) The waste animal bones were crushed to a particle size of 3 mm, and then mixed with sludge and animal feces from the wastewater treatment plant at a mass ratio of 3:6:10. 20 wt% sulfuric acid at 60°C was added at a material-liquid ratio of 1 g:15 mL. The mixture was soaked for 120 min and then separated into solid and liquid to obtain solid residue and a phosphate-containing composite solution.

[0035] (2) Mix the phosphate-containing composite solution with steel slag with a particle size of 0.25 mm, adjust the pH to neutral, let stand for 3 h to allow the solution to enter the steel slag, and after completion, take out the steel slag aggregate for steam curing. Heat the mixture to 78 °C at 15 °C / h and keep it at 95 °C for 24 hours to obtain pretreated steel slag.

[0036] (3) Mix silica sol and solid slag at a mass ratio of 1:0.5, stir evenly, add pretreated steel slag with a mass of 1 times that of silica sol, stir evenly, so that the surface of the pretreated steel slag is coated or covered with sol, dry at 200℃ for 4 hours, calcine at 850℃ for 1.5 hours, and crush to a particle size of 4.75 mm to obtain modified steel slag;

[0037] The method for preparing the silica sol is as follows: distilled water is heated to boiling, and a 45% (w / w) trimethylsiloxysilicate solution is slowly added dropwise at a speed of 400 r / min, with the dropping rate controlled at 1.5 ml / min. The volume ratio of distilled water to trimethylsiloxysilicate solution is 20:1. After the addition is complete, the mixture is stirred at the same speed for 40 min. Nano-silica is then added, and the pH is adjusted to 10 with a 12% (w / w) sodium hydroxide aqueous solution. The mixture is heated and kept at this temperature for 4 h to obtain the silica sol.

[0038] The composite fiber is a mixture of polypropylene fiber and carbon fiber in a mass ratio of 5:5. The polypropylene fiber has a single filament diameter of 48μm and a length of 12mm, and the carbon fiber has a diameter of 17μm and a length of 15mm.

[0039] The antifreeze agent comprises ammonium chloride, ethylene glycol, and formamide in a weight ratio of 1:10:7.

[0040] Example 3; A method for preparing paving bricks using steel slag, comprising the following components by weight: 125 parts modified steel slag, 9 parts silica sol, 5.5 parts composite fiber, 22 parts cement, 3 parts antifreeze agent, 35 parts sepiolite with a particle size of 1.5 mm, 35 parts silica fume with a particle size of 0.8 mm, 1.0 part polycarboxylate superplasticizer, and 15 parts water; the method for preparing the modified steel slag is as follows:

[0041] (1) The waste animal bones were crushed to a particle size of 2 mm, and then mixed with sludge and animal feces from the wastewater treatment plant at a mass ratio of 2:5:7. 15 wt% sulfuric acid at 60℃ was added at a material-liquid ratio of 1 g:15 mL. The mixture was soaked for 70 min and then separated into solid and liquid to obtain solid residue and a phosphate-containing composite solution.

[0042] (2) Mix the phosphate-containing composite solution with steel slag with a particle size of 0.20 mm, adjust the pH to neutral, let stand for 2.5 h to allow the solution to enter the steel slag, and after completion, take out the steel slag aggregate for steam curing. Heat the mixture to 76 °C at 12 °C / h and keep it at 92 °C for 21 hours to obtain pretreated steel slag.

[0043] (3) Mix silica sol and solid slag at a mass ratio of 1:0.3, stir evenly, add 0.7 times the mass of pretreated steel slag, stir evenly, so that the surface of the pretreated steel slag is coated or covered with sol, dry at 190℃ for 3.8h, calcine at 800℃ for 1.2h, and crush to a particle size of 3.5mm to obtain modified steel slag;

[0044] The method for preparing the silica sol is as follows: distilled water is heated to boiling, and a 40% (w / w) trimethylsiloxysilicate solution is slowly added dropwise at a speed of 350 r / min, with the dropping rate controlled at 1.2 ml / min. The volume ratio of distilled water to trimethylsiloxysilicate solution is 18:1. After the addition is complete, the mixture is stirred at the same speed for 35 min. Nano-silica is then added, and the pH is adjusted to 9.5 with a 10% (w / w) sodium hydroxide aqueous solution. The mixture is then heated and kept at this temperature for 3.5 h to obtain the silica sol.

[0045] The composite fiber is a mixture of polypropylene fiber and carbon fiber in a mass ratio of 3:7. The polypropylene fiber has a single filament diameter of 30μm and a length of 12mm, and the carbon fiber has a diameter of 13μm and a length of 15mm.

[0046] The antifreeze agent comprises ammonium chloride, ethylene glycol, and formamide in a weight ratio of 1:7:5.

[0047] Example 4; A method for preparing paving bricks using steel slag, comprising the following components by weight: 110 parts modified steel slag, 8.5 parts silica sol, 4.5 parts composite fiber, 18 parts cement, 2 parts antifreeze agent, 25 parts sepiolite with a particle size of 1.0 mm, 25 parts silica fume with a particle size of 0.3 mm, 0.9 parts polycarboxylate superplasticizer, and 12 parts water; the method for preparing the modified steel slag is as follows:

[0048] (1) The waste animal bones were crushed to a particle size of 1.5 mm, and then mixed with sludge and animal feces from the wastewater treatment plant at a mass ratio of 1.5:4.5:6. 12 wt% sulfuric acid at 60°C was added at a material-liquid ratio of 1 g:15 mL. The mixture was soaked for 50 min and then separated into solid and liquid to obtain solid residue and a phosphate-containing composite solution.

[0049] (2) Mix the phosphate-containing composite solution with steel slag with a particle size of 0.18 mm, adjust the pH to neutral, let stand for 2.2 h to allow the solution to enter the steel slag, and after completion, take out the steel slag aggregate for steam curing. Heat the mixture to 75.5 °C at 11 °C / h and keep it at 91 °C for 19 hours to obtain pretreated steel slag.

[0050] (3) Mix silica sol and solid slag at a mass ratio of 1:0.2, stir evenly, add 0.5 times the mass of pretreated steel slag, stir evenly, so that the surface of the pretreated steel slag is coated or covered with sol, dry at 185℃ for 3.6h, calcine at 770℃ for 1.1h, and crush to a particle size of 2.8mm to obtain modified steel slag;

[0051] The method for preparing the silica sol is as follows: distilled water is heated to boiling, and a 38% (w / w) trimethylsiloxysilicate solution is slowly added dropwise at a speed of 320 r / min, with the dropping rate controlled at 1.1 ml / min. The volume ratio of distilled water to trimethylsiloxysilicate solution is 17:1. After the addition is complete, the mixture is stirred at the same speed for 32 min. Nano-silica is then added, and the pH is adjusted to 9.2 with a 9% (w / w) sodium hydroxide aqueous solution. The mixture is then heated and kept at this temperature for 3.2 h to obtain the silica sol.

[0052] The composite fiber is a mixture of polypropylene fiber and carbon fiber in a mass ratio of 2:8. The polypropylene fiber has a single filament diameter of 22μm and a length of 12mm, and the carbon fiber has a diameter of 11μm and a length of 15mm.

[0053] The antifreeze agent comprises ammonium chloride, ethylene glycol, and formamide in a weight ratio of 1:5:4.

[0054] Example 5; A method for preparing paving bricks using steel slag, comprising the following components by weight: 140 parts modified steel slag, 9.5 parts silica sol, 6.5 parts composite fiber, 28 parts cement, 4 parts antifreeze agent, 45 parts sepiolite with a particle size of 2.0 mm, 45 parts silica fume with a particle size of 1.2 mm, 1.1 parts polycarboxylate superplasticizer, and 18 parts water; the method for preparing the modified steel slag is as follows:

[0055] (1) The waste animal bones were crushed to a particle size of 2.5 mm, and then mixed with sludge and animal feces from the wastewater treatment plant at a mass ratio of 2.5:5.5:9. 18 wt% sulfuric acid at 60℃ was added at a material-liquid ratio of 1 g:15 mL. The mixture was soaked for 100 min and then separated into solid and liquid to obtain solid residue and phosphate-containing composite solution.

[0056] (2) Mix the phosphate-containing composite solution with steel slag with a particle size of 0.22 mm, adjust the pH to neutral, let stand for 2.8 h to allow the solution to enter the steel slag, and after completion, take out the steel slag aggregate for steam curing. Heat the mixture to 77.5 °C at 14 °C / h and keep it at 94 °C for 23 hours to obtain pretreated steel slag.

[0057] (3) Mix silica sol and solid slag at a mass ratio of 1:0.4, stir evenly, add 0.9 times the mass of pretreated steel slag, stir evenly, so that the surface of the pretreated steel slag is coated or covered with sol, dry at 195℃ for 3.9h, calcine at 820℃ for 1.4h, and crush to a particle size of 4.2mm to obtain modified steel slag;

[0058] The method for preparing the silica sol is as follows: distilled water is heated to boiling, and a 42% (w / w) trimethylsiloxysilicate solution is slowly added dropwise at a speed of 380 r / min, with the dropping rate controlled at 1.4 ml / min. The volume ratio of distilled water to trimethylsiloxysilicate solution is 19:1. After the addition is complete, the mixture is stirred at the same speed for 38 min. Nano-silica is then added, and the pH is adjusted to 9.8 with an 11% (w / w) sodium hydroxide aqueous solution. The mixture is then heated and kept at this temperature for 3.8 h to obtain the silica sol.

[0059] The composite fiber is a mixture of polypropylene fiber and carbon fiber in a mass ratio of 4:6. The polypropylene fiber has a single filament diameter of 40μm and a length of 12mm, and the carbon fiber has a diameter of 15μm and a length of 15mm.

[0060] The antifreeze agent comprises ammonium chloride, ethylene glycol, and formamide in a weight ratio of 1:9:6.

[0061] Example 6; A method for preparing paving bricks using steel slag, comprising the following components by weight: 105 parts modified steel slag, 8.8 parts silica sol, 5.0 parts composite fiber, 20 parts cement, 1.5 parts antifreeze agent, 30 parts sepiolite with a particle size of 1.2 mm, 28 parts silica fume with a particle size of 0.5 mm, 0.85 parts polycarboxylate superplasticizer, and 14 parts water; the method for preparing the modified steel slag is as follows:

[0062] (1) The waste animal bones were crushed to a particle size of 1.2 mm, and then mixed with sludge and animal feces from the wastewater treatment plant at a mass ratio of 1.2:4.2:5.5. 11 wt% sulfuric acid at 60℃ was added at a material-liquid ratio of 1 g:15 mL. The mixture was soaked for 40 min and then separated into solid and liquid to obtain solid residue and a phosphate-containing composite solution.

[0063] (2) Mix the phosphate-containing composite solution with steel slag with a particle size of 0.16 mm, adjust the pH to neutral, let stand for 2.1 h to allow the solution to enter the steel slag, and after completion, take out the steel slag aggregate for steam curing. Heat the mixture to 75.2 °C at 10.5 °C / h and keep it at 75.2 °C for 18.5 h with a humidity of 90.5% to obtain pretreated steel slag.

[0064] (3) Mix silica sol and solid slag at a mass ratio of 1:0.15, stir evenly, add 0.45 times the mass of pretreated steel slag, stir evenly, so that the surface of the pretreated steel slag is coated or covered with sol, dry at 182℃ for 3.55h, calcine at 760℃ for 1.05h, and crush to a particle size of 2.5mm to obtain modified steel slag;

[0065] The method for preparing the silica sol is as follows: distilled water is heated to boiling, and a 36% (w / w) trimethylsiloxysilicate solution is slowly added dropwise at a speed of 310 r / min, with the dropping rate controlled at 1.05 ml / min. The volume ratio of distilled water to trimethylsiloxysilicate solution is 16.5:1. After the addition is complete, the mixture is stirred at the same speed for 31 min. Nano-silica is then added, and the pH is adjusted to 9.1 with an 8.5% (w / w) sodium hydroxide aqueous solution. The mixture is then heated and kept at this temperature for 3.1 h to obtain the silica sol.

[0066] The composite fiber is a mixture of polypropylene fiber and carbon fiber in a mass ratio of 1.5:8.5. The polypropylene fiber has a single filament diameter of 20μm and a length of 12mm, and the carbon fiber has a diameter of 10μm and a length of 15mm.

[0067] The antifreeze agent comprises ammonium chloride, ethylene glycol, and formamide in a weight ratio of 1:6:3.5.

[0068] Comparative Example 1; The difference between Comparative Example 1 and Example 4 is that the preparation method of the modified steel slag is different. The preparation method of the modified steel slag is as follows: (1) Waste animal bones are crushed to a particle size of 1.5 mm, and then mixed with sludge and animal feces from the wastewater treatment plant at a mass ratio of 1.5:4.5:6. 12 wt% sulfuric acid at 60°C is added at a material-liquid ratio of 1 g:15 mL. The mixture is soaked for 50 min, and the solid and liquid are separated to obtain solid slag; (2) Silica sol and solid slag are mixed at a mass ratio of 1:0.2. After stirring evenly, steel slag with a particle size of 0.18 mm, which is 0.5 times the mass of silica sol, is added and stirred evenly so that the surface of the pretreated steel slag is coated or covered with sol. The mixture is dried at 185°C for 3.6 h, calcined at 770°C for 1.1 h, and crushed to a particle size of 2.8 mm to obtain modified steel slag; The rest of the formula and preparation method are the same as in Example 4.

[0069] Comparative Example 2; The difference between Comparative Example 2 and Example 4 is that the preparation method of the modified steel slag is different. The preparation method of the modified steel slag is as follows: (1) Waste animal bones are crushed to a particle size of 1.5 mm, and then mixed with sludge and animal feces from a wastewater treatment plant at a mass ratio of 1.5:4.5:6 to obtain solid slag; (2) Silica sol and solid slag are mixed at a mass ratio of 1:0.2, stirred evenly, and then steel slag with a particle size of 0.18 mm, which is 0.5 times the mass of silica sol, is added and stirred evenly so that the surface of the pretreated steel slag is coated or covered with sol. It is dried at 185°C for 3.6 h, calcined at 770°C for 1.1 h, and crushed to a particle size of 2.8 mm to obtain modified steel slag; The rest of the formula and preparation method are the same as in Example 4.

[0070] Comparative Example 3; The difference between Comparative Example 3 and Example 4 lies in the different preparation methods of the modified steel slag. The preparation method of the modified steel slag is as follows: (1) Waste animal bones are crushed to a particle size of 1.5 mm, and then mixed with sludge and animal feces from a wastewater treatment plant at a mass ratio of 1.5:4.5:6. 12 wt% sulfuric acid at 60°C is added at a material-to-liquid ratio of 1 g:15 mL. The mixture is soaked for 50 min, and the solid and liquid are separated to obtain solid slag and a phosphate-containing composite solution; (2) The phosphate-containing composite solution is mixed with... Steel slag with a particle size of 0.18 mm was mixed, pH was adjusted to neutral, and the mixture was left to stand for 2.2 h to allow the solution to enter the steel slag. After completion, the steel slag aggregate was taken out and steam cured. The temperature was raised to 75.5 °C at 11 °C / h and kept at 91 °C for 19 hours to obtain pretreated steel slag. (3) Solid slag and pretreated steel slag were mixed at a mass ratio of 0.2:0.5, calcined at 770 °C for 1.1 hours, and crushed to a particle size of 2.8 mm to obtain modified steel slag. The remaining formula and preparation method are the same as in Example 4.

[0071] Comparative Example 4; The difference between Comparative Example 4 and Example 4 lies in the different preparation methods of the modified steel slag. The preparation method of the modified steel slag is as follows: (1) Waste animal bones are crushed to a particle size of 1.5 mm, and then mixed with sludge and animal feces from a wastewater treatment plant at a mass ratio of 1.5:4.5:6. 12 wt% sulfuric acid at 60°C is added at a material-to-liquid ratio of 1 g:15 mL. The mixture is soaked for 50 min, and the solid and liquid are separated to obtain solid slag and a phosphate-containing composite solution; (2) The phosphate-containing composite solution is mixed with a particle size of 0.18 mm. Steel slag is mixed, pH is adjusted to neutral, and it is left to stand for 2.2 hours to allow the solution to enter the steel slag. After completion, the steel slag aggregate is taken out and steam cured. The temperature is raised to 75.5℃ at 11℃ / h and kept at 91% humidity for 19 hours to obtain pretreated steel slag. (3) Silica sol and solid slag are mixed at a mass ratio of 1:0.2, dried at 185℃ for 3.6 hours, calcined at 770℃ for 1.1 hours, and then 0.5 times the mass of pretreated steel slag is added to mix to obtain modified steel slag. The remaining formula and preparation method are the same as in Example 4.

[0072] Comparative Example 5; The difference between Comparative Example 5 and Example 4 is that no silica sol is added, but the rest of the preparation method and formulation are the same as in Example 4.

[0073] Comparative Example 6; The difference between Comparative Example 6 and Example 4 is that no silica fume is added, but the rest of the preparation method and formulation are the same as in Example 4.

[0074] Comparative Example 7; The difference between Comparative Example 7 and Example 4 is that sepiolite is not added, but the rest of the preparation method and formula are the same as in Example 4.

[0075] Comparative Example 8; The difference between Comparative Example 8 and Example 4 is that no composite fiber is added, but the rest of the preparation method and formula are the same as in Example 4.

[0076] Performance testing

[0077] The permeability and mechanical properties of the highly permeable concrete obtained in Examples 1-6 and Comparative Examples 1-8 were tested using the following methods:

[0078] (1) Permeability

[0079] The permeability coefficient was tested according to the specifications in GB / T25993-2010.

[0080] (2) Mechanical properties

[0081] The compressive strength test was conducted after 28 days in accordance with the provisions of GB 28635-2012 "Concrete Pavement Bricks";

[0082] (3) Freeze resistance

[0083] According to the provisions of GB 28635-2012, the freeze resistance test is conducted, mainly measuring the mass loss rate and strength loss after 50 freeze-thaw cycles.

[0084] Table 1

[0085]

[0086] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing paving bricks using steel slag, characterized in that, The composition by weight is as follows: 100-150 parts modified steel slag, 8-10 parts silica sol, 4-7 parts composite fiber, 15-30 parts cement, 1-5 parts antifreeze agent, 20-50 parts aggregate, 20-50 parts silica fume, 0.8-1.2 parts water-reducing agent, and 10-20 parts water. The method for preparing the modified steel slag includes the following steps: (1) Crush the waste animal bones to a particle size of 1-3 mm, then mix them with sludge and animal feces from the wastewater treatment plant, add 10-20 wt% sulfuric acid at 60℃ according to the material-liquid ratio of 1 g: 15 mL, soak for 20-120 min, separate the solid and liquid, and obtain solid residue and phosphate-containing composite solution. (2) The phosphate-containing composite solution is mixed with steel slag with a particle size of 0.15-0.25 mm, the pH is adjusted to neutral, and the mixture is left to stand for 2-3 hours to allow the solution to enter the steel slag. After completion, the steel slag aggregate is taken out and steam cured to obtain pretreated steel slag. (3) Mix the silica sol with the solid slag obtained in step (1) according to the mass ratio, stir evenly, add 0.4-1 times the mass of the silica sol and pretreated steel slag, stir evenly, so that the surface of the pretreated steel slag is coated or covered with sol, dry at 180-200℃ for 3.5-4h, then calcine at 750-850℃ for 1-1.5h, and finally crush to a particle size of 2.25-4.75mm to obtain modified steel slag.

2. The method for preparing paving bricks using steel slag according to claim 1, characterized in that, In step (1), the mass ratio of waste animal bones, sludge and animal feces is 1-3:4-6:5-10.

3. The method for preparing paving bricks using steel slag according to claim 1, characterized in that, The total phosphorus content of the waste animal bones mentioned in step (1) is 6%-18% (dry basis), the total phosphorus content of the sludge is 1%-6% (dry basis), and the total phosphorus content of the animal feces is 0.5%-3.5% (dry basis).

4. The method for preparing paving bricks using steel slag according to claim 1, characterized in that, The steam curing in step (2) is as follows: heat the temperature to 75-78℃ at a rate of 10-15℃ / h and keep it at that temperature for 18-24 hours with a humidity of 90-95%.

5. The method for preparing paving bricks using steel slag according to claim 1, characterized in that, The mass ratio of silica sol to solid slag in step (3) is 1:0.1-0.

5.

6. The method for preparing paving bricks using steel slag according to claim 1, characterized in that, The composite fiber is a mixture of polypropylene fiber and carbon fiber in a mass ratio of 1-5:5-10; wherein the monofilament diameter of the polypropylene fiber is 18~48μm and the length is 12mm; and the diameter of the carbon fiber is 9~17μm and the length is 15mm.

7. The method for preparing paving bricks using steel slag according to claim 1, characterized in that, The antifreeze is a mixture of ammonium chloride, ethylene glycol and formamide in a weight ratio of 1:(4-10):(3-7).

8. The method for preparing paving bricks using steel slag according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate water-reducing agent.

9. A method for preparing paving bricks using steel slag according to claim 1, characterized in that, The stone has a particle size of 0.8-2.2 mm; the silica fume has a particle size of 0.15-1.5 mm.

10. A method for preparing paving bricks using steel slag as described in any one of claims 1-9, characterized in that, Includes the following steps: According to the stated weight proportions, add the modified steel slag, stone, silica fume, cement, and composite fiber into a mixer and dry mix evenly. Then add silica sol, antifreeze, water-reducing agent, and water, and continue mixing until uniform. Quickly pour the mixture into the resin mold for permeable pavement bricks, spread it evenly, and gently tamp the lower layer of material with a rubber mallet for 20-40 seconds. After molding, leave the green body in the mold and cure it in a humid environment and at room temperature above 10°C for 1-3 days before demolding. The demolded green body should be left in a humid environment and at room temperature above 10°C for more than 27 days.

Images