A shaping optimization method for waste concrete recycled aggregate

Abstract

The application provides a shaping optimization method of waste concrete recycled aggregate, and belongs to the technical field of green building materials.The broken material of waste concrete is first placed in a saturated salt solution for first soaking to fully soak the surface old mortar of the broken material;when water evaporates, salt crystals are separated out, the crystals break or puff up the surface waste old mortar of the waste concrete, the waste old mortar is conveniently removed, and the stone material interface condition is improved;through grinding and shaping, particle shaping and surface old mortar removal are further realized;through chemical slurry soaking, the chemical slurry is fully absorbed, in the curing process, superfine cement, superfine silica ash and polymers are solidified on the surface cracks and surface of the stone material, the stone material interface performance is further improved, and higher performance concrete is prepared.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of green building materials, and particularly relates to a shaping optimization method of waste concrete recycled aggregate. BACKGROUND

[0002] With the attention of the state to the exploitation of mineral resources and environmental protection, the exploitation scale of natural stone for building is reduced, and the price gradually increases. In addition, a large amount of waste concrete in domestic building and infrastructure demolition engineering is difficult to utilize efficiently, which becomes a problem faced by the current engineering industry. In recent years, the state supports green building materials through various policies, and the recycling of waste concrete after crushing becomes the key to efficient utilization of building materials. Since the crushed stone formed after the waste concrete is crushed, there is still a large amount of waste mortar on the surface of the crushed stone, and a certain amount of cracks and poor morphology, which leads to the fact that the crushing value, abrasion value, water absorption rate and needle flakiness of the stone cannot meet the requirements of preparing high-grade or high-quality concrete. At the same time, part of the good treatment process still stays in the laboratory exploration stage, and an economic and efficient large-scale production process method has not been proposed. SUMMARY

[0003] The present application aims to provide a shaping optimization method of waste concrete recycled aggregate, which can solve the problem of poor stone quality after waste concrete is crushed and can realize large-scale production.

[0004] In order to achieve the above-mentioned application purpose, the present application provides the following technical scheme:

[0005] The present application provides a shaping optimization method of waste concrete recycled aggregate, comprising the following steps: placing the crushed material of waste concrete in a saturated salt solution for first soaking, and drying the soaked crushed material to obtain first crushed material;

[0006] Grinding and shaping the first crushed material, and screening to obtain second crushed material;

[0007] Washing the second crushed material to obtain third crushed material;

[0008] Placing the third crushed material in a chemical slurry for second soaking, and draining to obtain fourth crushed material;

[0009] The chemical slurry comprises, in mass fraction, 0.2-0.5 parts of methyl cellulose, 2-6 parts of ultra-fine mineral powder, 2-6 parts of ultra-fine silica fume, 1-3 parts of vinyl acetate-ethylene copolymer, 3-5 parts of ultra-fine cement and 79.5-91.8 parts of water;

[0010] Curing the fourth crushed material.

[0011] Preferably, the salt in the saturated salt solution comprises one or more of sodium chloride, ammonium carbonate, sodium carbonate and potassium carbonate.

[0012] Preferably, the first soaking time is 3-6 hours.

[0013] Preferably, the grinding shaping comprises: placing the first crushed material and grinding medium in a drum for grinding; the inner wall of the drum is corrugated or has fins, the volume of the first crushed material accounts for 40-60% of the internal volume of the drum, and the rotating grinding speed of the drum is 50-200 r / min.

[0014] Preferably, the shape of the grinding medium is spherical and / or polyhedral; the filling amount of the grinding medium is 5-15% of the first crushed material.

[0015] Preferably, the second soaking time is 6-12 hours.

[0016] Preferably, the viscosity of the methyl cellulose is 400 cp.

[0017] Preferably, the mesh number of the ultra-fine silica fume is greater than 1250 mesh.

[0018] Preferably, the particle size of the second crushed material is greater than 5 mm.

[0019] Preferably, the curing time is 12-24 hours.

[0020] The application provides a shaping optimization method of waste concrete recycled aggregate, comprising the following steps: placing the crushed material of waste concrete in a saturated salt solution for first soaking, drying the soaked crushed material to obtain first crushed material; grinding and shaping the first crushed material, screening to obtain second crushed material; cleaning the second crushed material to obtain third crushed material; placing the third crushed material in a chemical slurry for second soaking and leaching to obtain fourth crushed material; the chemical slurry comprises, in mass fraction, 0.2-0.5 parts of methyl cellulose, 2-6 parts of ultra-fine mineral powder, 2-6 parts of ultra-fine silica fume, 1-3 parts of vinyl acetate-ethylene copolymer, 3-5 parts of ultra-fine cement and 79.5-91.8 parts of water; and curing the fourth crushed material.

[0021] The application first puts the broken material of waste and old concrete into saturated salt solution for first soaking to fully soak the surface old mortar of the broken material, and when water evaporates, salt crystals are separated out, which will break or puff the surface waste and old mortar of the waste and old concrete, so as to facilitate the removal of the waste and old mortar and improve the stone material interface condition; through grinding and shaping, further particle shaping and surface old mortar removal are achieved; through chemical slurry soaking, the chemical slurry is fully absorbed, and in the curing process, the superfine cement, superfine silica ash and polymer are solidified on the stone material surface cracks and surface, so as to further improve the stone material interface performance, thereby preparing higher performance concrete. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The flow chart of the shaping optimization method of the waste and old concrete recycled aggregate of the application. DETAILED DESCRIPTION

[0023] The application provides a shaping optimization method of waste and old concrete recycled aggregate, which comprises the following steps: putting the broken material of waste and old concrete into saturated salt solution for first soaking, drying the soaked broken material to obtain first broken material;

[0024] Grinding and shaping the first broken material, and screening to obtain second broken material;

[0025] Washing the second broken material to obtain third broken material;

[0026] Putting the third broken material into chemical slurry for second soaking, and draining to obtain fourth broken material;

[0027] The chemical slurry comprises 0.2-0.5 parts of methyl cellulose, 2-6 parts of superfine mineral powder, 2-6 parts of superfine silica ash, 1-3 parts of vinyl acetate-ethylene copolymer, 3-5 parts of superfine cement and 79.5-91.8 parts of water in terms of mass fraction;

[0028] Curing the fourth broken material.

[0029] In the application, the raw materials used are all commercially available goods well known in the art without special instructions.

[0030] The application puts the broken material of waste and old concrete into saturated salt solution for first soaking, and dries the soaked broken material to obtain first broken material.

[0031] The present application does not have special requirements for the particle size of the broken material of the waste concrete, and the particle size known in the art can be used. In the present application, the salt in the saturated salt solution preferably includes one or more of sodium chloride, ammonium carbonate, sodium carbonate and potassium carbonate. The present application does not have special requirements for the amount of the saturated salt solution, and the broken material of the waste concrete can be completely immersed. In the present application, the first soaking time is preferably 3-6h, and more preferably 4-5h. The present application makes the salt solution fully infiltrate the surface of the broken material.

[0032] The present application does not have special requirements for the drying, and the soaked broken material can be taken out and dried layer by layer. In the drying process of the present application, salt crystals are precipitated and expanded, and then the surface of the waste concrete is broken or puffed.

[0033] After obtaining the first broken material, the present application grinds and shapes the first broken material to obtain the second broken material.

[0034] In the present application, the grinding and shaping preferably includes placing the first broken material and the grinding medium in a roller for grinding.

[0035] In the present application, the inner wall of the roller is preferably corrugated or has fins, the volume of the first broken material preferably accounts for 40-60% of the internal volume of the roller, and more preferably 45-55%; the rotation grinding speed of the roller is preferably 50-200r / min, and more preferably 100-150r / min.

[0036] In the present application, the shape of the grinding medium is preferably spherical and / or polyhedral, and more preferably spherical; the present application does not have special requirements for the polyhedron, and the polyhedron known in the art can be used, such as cube and tetrahedron. In the present application, the size of the grinding medium is preferably 10-15 times the maximum diameter of the broken material, and more preferably 12-13 times; the filling amount of the grinding medium is preferably 5-15% of the first broken material, and more preferably 7-12%. The present application does not have special requirements for the material of the grinding medium, and the material known in the art can be used. The present application realizes particle shaping and surface old mortar removal through grinding and shaping.

[0037] In the present application, the mesh size of the screen used for screening is preferably 5mm, and the part above the screen is used as the second broken material.

[0038] The present application preferably puts the particles below the screen into an evaporation pond to form a high-concentration salt solution or a saturated salt solution, so as to realize the recycling of salt.

[0039] After obtaining the second crushed material, the present application carries out cleaning on the second crushed material to obtain a third crushed material. The present application does not have special requirements for the cleaning process, and the cleaning process known in the art can be used. The present application removes the salt in the second crushed material by cleaning, and the salt solution after cleaning enters the evaporation pool to be used for preparing a high-concentration salt solution or a saturated salt solution.

[0040] After obtaining the third crushed material, the present application places the third crushed material in a chemical slurry for a second soaking, and then leaches to obtain a fourth crushed material.

[0041] The chemical slurry of the present application includes, in mass fraction, 0.2-0.5 parts of methyl cellulose, 2-6 parts of superfine mineral powder, 2-6 parts of superfine silica ash, 1-3 parts of vinyl acetate-ethylene copolymer, 3-5 parts of superfine cement, and 79.5-91.8 parts of water.

[0042] Further, the methyl cellulose is more preferably 0.3-0.4 parts, the superfine mineral powder is more preferably 3-5 parts, the superfine silica ash is more preferably 4-5 parts, the vinyl acetate-ethylene copolymer is more preferably 1.5-2.5 parts, and the superfine cement is more preferably 3.5-4.5 parts.

[0043] In the present application, the viscosity of the methyl cellulose is preferably 400 cp, and the mesh number of the superfine silica ash is preferably greater than 1250 mesh.

[0044] In the present application, the time of the second soaking is preferably 6-12 h, and more preferably 8-10 h. The present application fully absorbs the chemical slurry through the second soaking.

[0045] After obtaining the fourth crushed material, the present application carries out maintenance on the fourth crushed material.

[0046] The present application does not have special requirements for the maintenance process, and the maintenance process known in the art can be used. In the embodiments of the present application, the leached stone is stacked and covered with a plastic film for maintenance. In the present application, the time of the maintenance is preferably 12-24 h, and more preferably 15-20 h; and the maintenance is preferably carried out at room temperature. In the maintenance process, the superfine cement, the superfine silica ash, and the polymer are solidified on the surface cracks and the surface of the stone, which improves the interface performance of the stone, thereby preparing a higher-performance concrete.

[0047] After the maintenance is completed, the plastic film is removed and naturally air-dried for use.

[0048] Figure 1 The flowchart of the shaping and optimizing method of the waste and old concrete recycled aggregate of the present application is shown in FIG. 1. Figure 1As shown, this invention involves immersing crushed waste concrete in a saturated salt solution for a first soaking, then drying the soaked crushed material to obtain a first crushed material; the first crushed material is then ground, shaped, and sieved to obtain a second crushed material. Figure 1 Medium and coarse aggregate); the second crushed material is washed to obtain the third crushed material; the mortar debris and salt crystals obtained by screening are dissolved in the evaporation tank and the waste liquid generated from washing the second crushed material is used to prepare high-concentration salt or saturated salt solution; the third crushed material (i.e. clean aggregate) is placed in a chemical slurry for a second soaking and drained to obtain the fourth crushed material; the fourth crushed material is cured to obtain high-quality recycled aggregate.

[0049] The following detailed description of the shaping and optimization method for recycled aggregates from waste concrete provided by the present invention, in conjunction with specific embodiments, should not be construed as limiting the scope of protection of the present invention.

[0050] Example 1

[0051] Soak the old concrete fragments in a saturated potassium carbonate solution for 3 hours, then remove and air dry.

[0052] After drying, the stones are placed in a drum, with the stone volume occupying 50% of the drum's volume. Then, 15cm diameter steel balls are added, occupying 10% of the stone volume. The drum is started and rotated at 100 rpm for 60 minutes. After stopping, the stones are sieved using 22mm, 11mm, and 5mm screens to separate 0-5mm mortar stone chips, 5-10mm crushed stone, and 10-20mm crushed stone, respectively.

[0053] The 5-10mm and 10-20mm gravel were soaked and rinsed with clean water. The rinsing waste liquid was kept for later use. The 0-5mm mortar stone chips with crystalline salt were put into the rinsing waste liquid to prepare a saturated salt solution for recycling.

[0054] Rinse the cleaned 5-10mm and 10-20mm gravel and soak them in a chemical slurry for 6 hours. The chemical slurry consists of 0.3 parts methylcellulose, 3 parts ultrafine mineral powder, 3 parts ultrafine silica fume, 1 part vinyl acetate-ethylene copolymer, 2 parts ultrafine cement, and 90.7 parts water.

[0055] After soaking, remove 5-10mm and 10-20mm gravel, wrap them in plastic film for curing for 12 hours, and then let them air dry naturally. Test the gravel index and use them for concrete preparation.

[0056] Concrete was prepared using shaped and optimized 5-10mm and 10-20mm crushed stone, and its performance was tested after 28 days of curing. The concrete mix proportions are shown in Table 1 below.

[0057] Table 1 Concrete mix proportions (unit: kg)

[0058]

[0059] Comparative Example 1

[0060] The old concrete broken stone is sieved by 22mm, 11mm and 5mm screen, and 5-10mm broken stone and 10-20mm broken stone are separated, and the broken stone indexes are tested respectively, and the results are shown in Table 3. The concrete is prepared by the same method as in Example 1, and the performance test is carried out after 28d curing. The concrete proportioning is shown in Table 2, and the performance is shown in Table 4.

[0061] Table 2 Concrete proportioning (unit: kg)

[0062]

[0063] Table 3 Stone performance test comparison

[0064] Name Crushing value Abrasion value Needle-like Water absorption (%) 5-10 mm stone (Example 1) - 13.9 5.5 1.34 10-20 mm stone (Example 1) 12.6 11.3 7.8 0.92 5-10 mm stone (Comparative Example 1) - 36.2 13.2 3.11 10-20 mm stone (Comparative Example 1) 24.5 29.4 16.4 2.85

[0065] Table 4 Concrete performance test comparison

[0066]

[0067] As shown by the results in Tables 3-4, the broken stone of the old concrete treated by the waste old concrete recycled aggregate shaping and optimizing process (Example 1) has a significantly improved crushing value and abrasion value, and a significantly reduced needle flakiness and water absorption rate, among which the water absorption rate and abrasion value are most obviously improved. The concrete prepared by the broken stone after shaping and optimizing (Example 1) has improved concrete performance indexes, such as compressive strength, flexural strength and flexural fatigue performance, and the most obviously improved indexes are flexural strength and slump.

[0068] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make some improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method for sizing optimization of recycled aggregate from waste concrete, characterized by, The method comprises the following steps: The broken material of waste concrete is placed in a saturated salt solution for first soaking, and the soaked broken material is dried to obtain first broken material; the salt in the saturated salt solution comprises one or more of sodium chloride, ammonium carbonate, sodium carbonate and potassium carbonate; the first soaking time is 3-6h; The first broken material is ground and shaped, and screened to obtain second broken material; The second broken material is cleaned to obtain third broken material; The cleaning is water washing; The third broken material is placed in a chemical slurry for second soaking, and then drained to obtain fourth broken material; The chemical slurry comprises, in mass fraction, 0.2-0.5 parts of methyl cellulose, 2-6 parts of superfine mineral powder, 2-6 parts of superfine silica fume, 1-3 parts of vinyl acetate-ethylene copolymer, 3-5 parts of superfine cement and 79.5-91.8 parts of water; The fourth broken material is maintained.

2. The shape optimization method of claim 1, wherein, The grinding and shaping comprises placing the first broken material and grinding medium in a roller for grinding; the inner wall of the roller is corrugated or has fins; the volume of the first broken material accounts for 40-60% of the internal volume of the roller; and the rotating grinding speed of the roller is 50-200r / min.

3. The shape optimization method of claim 2, wherein, The shape of the grinding medium is spherical and / or polyhedral; and the filling amount of the grinding medium is 5-15% of the first broken material.

4. The shape optimization method of claim 1, wherein, The second soaking time is 6-12h.

5. The shape optimization method of claim 1, wherein, The viscosity of the methyl cellulose is 400cP.

6. The shape optimization method of claim 1, wherein, The mesh number of the superfine silica fume is greater than 1250 mesh.

7. The shape optimization method of claim 1, 2 or 3, wherein, The particle size of the second broken material is greater than 5mm.

8. The shape optimization method of claim 1, wherein, The maintenance time is 12-24h.

Images