A deep foundation pit recycled aggregate backfill concrete and preparation method thereof

Abstract

The present invention relates to the field of construction technology, and specifically discloses a deep foundation pit recycled aggregate backfill concrete and a preparation method thereof. A deep foundation pit recycled aggregate backfill concrete, characterized in that, based on the mass parts of the deep foundation pit recycled aggregate backfill concrete, it includes 180 to 210 parts of cement, 400 to 500 parts of recycled powder, 500 to 600 parts of recycled fine aggregate, 1200 to 1300 parts of recycled coarse aggregate, 5.7 to 6.3 parts of water reducer, 17 to 23 parts of admixture, and 190 to 240 parts of water; the admixture includes agar, isopropyl trititanate, and vinyl triethoxysilane. A deep foundation pit recycled aggregate backfill concrete preparation method is to mix the various materials to obtain the deep foundation pit recycled aggregate backfill concrete. The present application not only improves the utilization rate of discarded construction waste, but also enhances the workability, impermeability, and compressive strength of the recycled aggregate backfill concrete.

Description

Technical Field

[0001] The invention relates to the technical field of construction, in particular to a deep foundation pit recycled aggregate backfill concrete and a preparation method thereof. Background Art

[0002] In order to pursue a larger usable area, today's buildings often expand the usable area of ​​the basement. With the continuous expansion of the usable area of ​​the basement, the space of the deep foundation pit of the building is constantly compressed and even developed into various special-shaped deep foundation pits. If such a deep foundation pit uses traditional plain soil, the quality of the building cannot be guaranteed due to the poor bearing capacity of the plain soil. If gray soil is used, it is often limited by the working surface and construction period. Many buildings currently use concrete as the backfill material for deep foundation pits to ensure the working period and building quality. When using backfill concrete to fill the deep foundation pit, due to the problem of high bulk density of the backfill concrete, filling it into the deep foundation pit will cause pressure on the deep foundation pit. In the long run, it may damage the deep foundation pit structure, reduce the quality of the building, and even cause engineering accidents.

[0003] Existing technology attempts to reduce the problem of excessive bulk density by adding recycled aggregate to backfill concrete. However, the recycled aggregate has numerous tiny cracks. During mixing, the recycled aggregate absorbs a large amount of mixing water into these cracks, increasing the amount of mixing water required. This not only affects the workability of the backfill concrete, but also, as the moisture in the recycled aggregate dries out, it can easily cause cracking and weaken the compressive strength of the backfill concrete. Using such backfill concrete for deep foundation pit filling can lead to deformation due to insufficient bearing capacity, thus reducing building quality. Therefore, backfill concrete containing recycled aggregate has room for further improvement. Summary of the Invention

[0004] To further improve the compressive strength of recycled aggregate backfill concrete, the present application provides a recycled aggregate backfill concrete for deep foundation pits and a preparation method thereof. Through the synergistic effect of recycled powder, cement, and an admixture consisting of agar, isopropyl trititanate, and vinyl triethoxysilane, the present application effectively fills the tiny gaps in the recycled aggregate, significantly reduces the recycled aggregate's absorption of mixing water, and further strengthens the bond between the old cementitious material attached to the surface of the recycled aggregate and the new cementitious material, further improving the compressive strength of the recycled aggregate backfill concrete.

[0005] In the first aspect, the deep foundation pit recycled aggregate backfill concrete provided by this application adopts the following technical solution:

[0006] A deep foundation pit recycled aggregate backfill concrete, comprising, based on the mass of the deep foundation pit recycled aggregate backfill concrete, 180-210 parts of cement, 400-500 parts of recycled powder, 500-600 parts of recycled fine aggregate, 1200-1300 parts of recycled coarse aggregate, 5.7-6.3 parts of water reducer, 10-12 parts of admixture, and 190-240 parts of water;

[0007] Wherein, the admixture comprises agar, isopropyl trititanate and vinyl triethoxysilane.

[0008] In the above technical solution, by creatively adding recycled powder, recycled fine aggregate and recycled coarse aggregate into the recycled aggregate backfill concrete at the same time, on the one hand, the utilization rate of discarded construction waste is improved, the secondary utilization of construction waste is realized, and it is in line with the development concept of green environmental protection. On the other hand, the recycled powder with small particle size can replace part of the cement and enhance the adhesion between the various materials in the recycled aggregate backfill concrete. The recycled powder further interacts with cement, agar, isopropyl trititanate and vinyl triethoxysilane, and has a good filling and lubricating effect on the surface of the recycled aggregate. The agar combined with the recycled powder well fills and seals the tiny cracks in the recycled aggregate and reduces the absorption of mixing water by the recycled aggregate, while the isopropyl trititanate and vinyl triethoxysilane enhance the adhesion between the recycled powder and the recycled aggregate, and between the recycled powder and cement, that is, it plays a role in strengthening the adhesion between the old cementitious material attached to the surface of the recycled aggregate and the new cementitious material, significantly enhancing the compressive strength of the recycled aggregate backfill concrete in deep foundation pits. The interaction between the water reducer, agar and recycled powder in this application further lubricates the recycled aggregate, enhances the workability of the deep foundation pit recycled aggregate backfill concrete, and further promotes the full hydration of the cement. The cement and recycled powder work together to form a stable network microstructure in the deep foundation pit recycled aggregate backfill concrete, tightly bond the various materials in the deep foundation pit recycled aggregate backfill concrete, further compact the deep foundation pit recycled aggregate backfill concrete, and further enhance the anti-permeability of the deep foundation pit recycled aggregate backfill concrete.

[0009] Preferably, the mass ratio of agar, isopropyl trititanate and vinyl triethoxysilane is (10-15):(10-15):(7-9).

[0010] In the above technical solution, by limiting the mass ratio of agar, isopropyl trititanate and vinyl triethoxysilane to (10-15): (10-15): (7-9), the admixture formed by compounding agar, isopropyl trititanate and vinyl triethoxysilane can better cooperate with the recycled powder, further fill and seal the tiny cracks in the recycled aggregate, and further enhance the bonding force between the recycled aggregate, the old cementitious material attached to the surface of the recycled aggregate and the cement, so that the cementitious material in the recycled aggregate backfill concrete for deep foundation pits forms a stable and high-strength network micro-skeleton structure, further enhancing the compressive strength of the recycled aggregate backfill concrete for deep foundation pits.

[0011] Preferably, the particle size of the recycled coarse aggregate is 5 to 25 mm.

[0012] In the above technical solution, by selecting recycled coarse aggregate with a particle size of 5 to 25 mm to be specifically added to the recycled aggregate backfill concrete of the deep foundation pit, and by virtue of the fact that the density of the recycled coarse aggregate is lower than that of the natural coarse aggregate, the bulk density of the recycled aggregate backfill concrete of the deep foundation pit is effectively reduced, thereby further enhancing the integrity of the recycled aggregate backfill concrete of the deep foundation pit and the deep foundation pit, and further reducing the possibility of deformation of the deep foundation pit.

[0013] Preferably, the particle size of the recycled fine aggregate is 0.16 to 4.75 mm.

[0014] In the above technical solution, by selecting and adding recycled fine aggregate with a particle size of 0.16 to 4.75 mm to the recycled aggregate backfill concrete for deep foundation pits, such recycled fine aggregate can partially replace the role of natural sand in the recycled aggregate backfill concrete for deep foundation pits, further compact the recycled aggregate backfill concrete for deep foundation pits, and make the recycled aggregate backfill concrete have good impermeability and compressive strength.

[0015] Preferably, the particle size of the regenerated powder is less than 0.16 mm.

[0016] In the above technical solution, by selecting to specifically add recycled powder with a particle size of less than 0.16 mm to the recycled aggregate backfill concrete of deep foundation pits, the recycled powder can partially replace cement, thereby reducing the amount of cement used in the recycled aggregate backfill concrete of deep foundation pits and increasing the secondary utilization rate of building waste. The interaction between the recycled powder and the admixture composed of agar, isopropyl trititanate, and vinyl triethoxysilane can further improve the microstructure of the recycled powder, further enhance the bonding force between the recycled powder and cement, and further enhance the compressive strength of the recycled aggregate backfill concrete of deep foundation pits.

[0017] Preferably, the water reducer is a polycarboxylic acid water reducer.

[0018] In the above technical solution, by selecting to specifically add polycarboxylic acid water-reducing agent to the recycled aggregate backfill concrete for deep foundation pits, it helps to further promote the hydration of cement and further enhance the fluidity of the recycled aggregate backfill concrete for deep foundation pits, thereby enhancing the workability of the recycled aggregate backfill concrete for deep foundation pits, so that the recycled aggregate backfill concrete for deep foundation pits can better fill the deep foundation pits.

[0019] Preferably, the deep foundation pit recycled aggregate concrete further comprises 5 to 7 parts of coconut coir.

[0020] In the above technical solution, by further adding coconut husk on the basis of agar, isopropyl trititanate and vinyl triethoxysilane, on the one hand, coconut husk as production waste is used for secondary utilization in more ways, which is in line with the development concept of green environmental protection; on the other hand, coconut husk contains rich coconut shell fiber, which, combined with agar, isopropyl trititanate and vinyl triethoxysilane, can make part of isopropyl trititanate and vinyl triethoxysilane stably attached to coconut husk through the colloid formed by agar, and the coconut husk and the other adhesive materials are bonded to each other, further improving the reticular micro-skeleton of the recycled aggregate backfill concrete in the deep foundation pit. The step of building a denser and more stable network structure can further promote the bonding between the various materials of deep foundation pit recycled aggregate backfill concrete, reduce the shrinkage and deformation of deep foundation pit recycled aggregate backfill concrete during the drying process, further enhance the stability of the network micro-skeleton structure in deep foundation pit recycled aggregate backfill concrete, and further enhance the compressive strength of deep foundation pit recycled aggregate backfill concrete. At the same time, coconut coir can absorb part of the water, further promote the full hydration of the cementitious material, and absorb the hydration heat to promote the diffusion of heat, further reduce the cracking of deep foundation pit recycled aggregate backfill concrete, and enhance the anti-permeability of deep foundation pit recycled aggregate backfill concrete.

[0021] In a second aspect, the present application provides a method for preparing recycled aggregate backfill concrete for deep foundation pits using the following technical solutions:

[0022] A method for preparing recycled aggregate backfill concrete for a deep foundation pit, characterized by comprising the following steps:

[0023] Step 1: Mixing and stirring a water reducer and water to prepare a liquid mixture;

[0024] Step 2: Mix the liquid mixture, cement, and admixture to obtain a prefabricated mixture; mix the recycled powder, recycled fine aggregate, and recycled coarse aggregate to obtain a prefabricated dry material;

[0025] Step 3: Mix the prefabricated mixture and prefabricated dry materials to obtain deep foundation pit recycled aggregate backfill concrete.

[0026] In the above technical solution, by first mixing the water reducer and water, the water reducer can be fully dissolved in the water, thereby giving full play to its role in reducing the water consumption of concrete, promoting cement hydration and improving the fluidity of concrete. By mixing the recycled powder, recycled fine aggregate and recycled coarse aggregate to obtain prefabricated dry material, the recycled powder can first partially fill the microcracks of the recycled aggregate during the mixing process, and then can better interact with the admixture to fill and close the microcracks of the recycled aggregate. The deep foundation pit recycled aggregate backfill concrete prepared by the above preparation method is evenly mixed with each other and has better synergistic effect, which can further enhance the fluidity, compressive strength and anti-permeability of the deep foundation pit recycled aggregate backfill concrete.

[0027] Preferably, a method for preparing deep foundation pit recycled aggregate backfill concrete comprises the following steps:

[0028] Step 1: Mixing and stirring the water reducer and water to prepare a liquid mixture;

[0029] Step 2: Mix the liquid mixture, cement, and admixture to obtain a prefabricated mixture; mix the recycled powder, recycled fine aggregate, and recycled coarse aggregate to obtain a prefabricated dry material;

[0030] Step 3: Evenly mix the prefabricated mixture, prefabricated dry materials and coconut husk to obtain deep foundation pit recycled aggregate backfill concrete.

[0031] In the above technical solution, by mixing the prefabricated mixture, prefabricated dry material and coconut coir, and dispersing the coconut coir through the admixture, the coconut coir can be evenly dispersed in the deep foundation pit recycled aggregate backfill concrete, so that the coconut coir can better bridge the various materials in the deep foundation pit recycled aggregate backfill concrete, further enhancing the compressive strength of the deep foundation pit recycled aggregate backfill concrete.

[0032] In summary, this application includes at least one of the following beneficial technical effects:

[0033] 1. The present application creatively adds recycled powder, recycled fine aggregate and recycled coarse aggregate into the recycled aggregate backfill concrete at the same time. The recycled powder with small particle size can replace part of the cement, thereby enhancing the adhesion between the various materials in the recycled aggregate backfill concrete. The combination of agar, isopropyl trititanate and vinyl triethoxysilane enhances the adhesion between the old cementitious material attached to the surface of the recycled aggregate and the new cementitious material, significantly enhancing the compressive strength of the recycled aggregate backfill concrete for deep foundation pits. Through the interaction between the water reducer, agar and the recycled powder, a stable network microstructure is formed in the recycled aggregate backfill concrete for deep foundation pits, thereby further enhancing the workability and anti-permeability of the recycled aggregate backfill concrete for deep foundation pits.

[0034] 2. This application improves the utilization rate of construction waste by limiting the particle size of recycled coarse aggregate to 5-25 mm, the particle size of recycled fine aggregate to 0.16-4.75 mm, and the particle size of recycled powder to less than 0.16 mm. Since the density of recycled aggregate is lower than that of natural aggregate, the bulk density of recycled aggregate backfill concrete in deep foundation pits is effectively reduced, further enhancing the integrity of recycled aggregate backfill concrete in deep foundation pits and the deep foundation pit, and further reducing the possibility of deformation of deep foundation pits.

[0035] 3. This application further adds coconut pith to agar, isopropyl trititanate and vinyl triethoxysilane. Coconut pith contains rich coconut shell fiber. Combined with agar, isopropyl trititanate and vinyl triethoxysilane, it can further promote the adhesion between the various materials of deep foundation pit recycled aggregate backfill concrete, reduce the shrinkage and deformation of deep foundation pit recycled aggregate backfill concrete during the drying process, further enhance the stability of the network micro-skeleton structure in deep foundation pit recycled aggregate backfill concrete, and further enhance the compressive strength of deep foundation pit recycled aggregate backfill concrete. DETAILED DESCRIPTION

[0036] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0037] Example 1

[0038] A deep foundation pit recycled aggregate backfill concrete includes 180 kg of cement, 400 kg of recycled powder, 500 kg of recycled fine aggregate, 1200 kg of recycled coarse aggregate, 5.7 kg of water reducing agent, 17 kg of admixture, 5 kg of coconut coir, and 190 kg of water.

[0039] Among them, the admixtures include agar, isopropyl trititanate and vinyl triethoxysilane.

[0040] The mass ratio of agar, isopropyl trititanate and vinyl triethoxysilane is 10:10:7.

[0041] Among them, the particle size of the recycled coarse aggregate is 5 to 25 mm.

[0042] Among them, the particle size of the recycled fine aggregate is 0.16~4.75mm.

[0043] Among them, the particle size of the recycled powder is less than 0.16mm.

[0044] Among them, the water reducer is a polycarboxylic acid water reducer.

[0045] A method for preparing recycled aggregate backfill concrete for deep foundation pits comprises the following steps:

[0046] Step 1: Mix the water reducer and water and stir them evenly to prepare a liquid mixture.

[0047] Step 2: Mix the liquid mixture, cement and admixture and stir them evenly to obtain a prefabricated mixture; mix the recycled powder, recycled fine aggregate and recycled coarse aggregate and stir them evenly to obtain a prefabricated dry material.

[0048] Step 3: Mix the prefabricated mixture, prefabricated dry material and coconut coir, and stir them evenly to obtain deep foundation pit recycled aggregate backfill concrete.

[0049] Example 2

[0050] A deep foundation pit recycled aggregate backfill concrete, which is different from Example 1 in that it includes 210 kg of cement, 500 kg of recycled powder, 600 kg of recycled fine aggregate, 1300 kg of recycled coarse aggregate, 6.3 kg of water reducer, 23 kg of admixture, 7 kg of coconut coir, and 240 kg of water.

[0051] Among them, the admixtures include agar, isopropyl trititanate and vinyl triethoxysilane.

[0052] The mass ratio of agar, isopropyl trititanate and vinyl triethoxysilane is 15:15:9.

[0053] Example 3

[0054] A deep foundation pit recycled aggregate backfill concrete, which is different from Example 1 in that it includes 200 kg of cement, 430 kg of recycled powder, 545 kg of recycled fine aggregate, 1280 kg of recycled coarse aggregate, 5.9 kg of water reducer, 21 kg of admixture, 6 kg of coconut coir, and 210 kg of water.

[0055] Among them, the admixtures include agar, isopropyl trititanate and vinyl triethoxysilane.

[0056] Among them, the mass ratio of agar, isopropyl trititanate and vinyl triethoxysilane is 13:12:8.

[0057] Example 4

[0058] A deep foundation pit recycled aggregate backfill concrete, which differs from Example 3 in that an equal amount of coconut husks is replaced with carbon fibers.

[0059] Comparative Example 1

[0060] A deep foundation pit recycled aggregate backfill concrete, which is different from Example 3 in that an equal amount of agar is replaced by starch.

[0061] Comparative Example 2

[0062] A deep foundation pit recycled aggregate backfill concrete, which is different from Example 3 in that an equal amount of isopropyl trititanate is replaced by vinyl triethoxysilane.

[0063] Comparative Example 3

[0064] A deep foundation pit recycled aggregate backfill concrete, which is different from Example 3 in that an equal amount of vinyltriethoxysilane is replaced by isopropyl trititanate.

[0065] Comparative Example 4

[0066] A deep foundation pit recycled aggregate backfill concrete, which is different from Example 3 in that it does not include an admixture.

[0067] Performance testing:

[0068] 1. Slump test: Refer to 4.1 Slump test in GB / T50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures", measure the slump (mm) and record it in Table 1.

[0069] 2. Shrinkage test: Refer to 8.2 Contact method of shrinkage test in GB / T50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete". The specimen is a prismatic specimen with a size of 100mm*100mm*515mm. Standard curing is carried out for 28 days. The shrinkage rate (%) is measured and calculated and recorded in Table 1.

[0070] 3 Water penetration resistance test: refer to the water seepage height method in GB / T 50082-2009 "Standard for test methods of long-term performance and durability of ordinary concrete". The test piece is a truncated cone with a height of 150mm, a lower diameter of 180mm and an upper diameter of 175mm. The standard curing time is 28 days. The water pressure during the test is 1MPa and the test time is 24h. The water seepage height (mm) is measured and recorded in Table 1. 1.28

[0071] 4. Compressive strength test: Refer to the compressive strength test in GB / T50081-2019 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete". The specimen is a cube of 100mm*100mm*100mm. Standard curing is 28d. The compressive strength (MPa) is measured and recorded in Table 1.

[0072] Table 1:

[0073]

[0074]

[0075] In combination with Examples 1-4, Comparative Examples 1-4 and Table 1, it is not difficult to see that the deep foundation pit recycled aggregate backfill concrete of the present application has good workability, shrinkage resistance, permeability resistance and compressive strength.

[0076] Combining Example 3 with Comparative Examples 1-4 and Table 1, it is not difficult to see that the deep foundation pit recycled aggregate backfill concrete with the addition of agar, isopropyl trititanate and vinyl triethoxysilane has good shrinkage resistance, permeability resistance and compressive strength. The applicant further analyzed that only by adding agar to the deep foundation pit recycled aggregate backfill concrete can it be well coordinated with other materials to make the deep foundation pit recycled aggregate backfill concrete have better workability, and agar can better cooperate with cement and recycled powder to better fill the deep foundation pit recycled aggregate. Backfill the pores in the concrete to avoid the expansion and contraction reaction of the concrete during the solidification process, which may lead to deformation of the deep foundation pit. Isopropyl trititanate and vinyl triethoxysilane can better cooperate with agar, not only making the agar evenly dispersed in the deep foundation pit recycled aggregate backfill concrete, but also cooperating to enhance the bonding force between the old cementitious material attached to the surface of the recycled aggregate and the new cementitious material, so that the deep foundation pit recycled aggregate backfill concrete forms a stable network microstructure to enhance the workability, shrinkage resistance, permeability resistance and compressive strength of the deep foundation pit recycled aggregate backfill concrete.

[0077] In combination with Example 3, Example 4 and Table 1, it is not difficult to see that the present application further adds coconut husk on the basis of agar, isopropyl trititanate, and vinyl triethoxysilane, which can further enhance the shrinkage resistance, permeability resistance, and compressive strength of the deep foundation pit recycled aggregate backfill concrete. The applicant further analyzed and believed that only coconut husk can better cooperate with agar, isopropyl trititanate, and vinyl triethoxysilane. Only simple mixing can make part of the isopropyl trititanate and vinyl triethoxysilane stably attached to the coconut husk. The process is simple and can further promote the bonding between the various materials of the deep foundation pit recycled aggregate backfill concrete, reduce the shrinkage deformation of the deep foundation pit recycled aggregate backfill concrete during the drying process, further enhance the stability of the network micro-skeleton structure in the deep foundation pit recycled aggregate backfill concrete, and further enhance the compressive strength of the deep foundation pit recycled aggregate backfill concrete.

[0078] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A deep foundation pit recycled aggregate backfill concrete, characterized in that: Calculated by mass proportions of recycled aggregate backfill concrete for deep foundation pits, it includes 180-210 parts of cement, 400-500 parts of recycled powder, 500-600 parts of recycled fine aggregate, 1200-1300 parts of recycled coarse aggregate, 5.7-6.3 parts of water reducer, 17-23 parts of admixture, 190-240 parts of water, and 5-7 parts of coconut coir. The admixture comprises agar, isopropyl trititanate and vinyl triethoxysilane; the mass ratio of agar, isopropyl trititanate and vinyl triethoxysilane is 10:10:

7.

2. The deep foundation pit recycled aggregate backfill concrete according to claim 1, characterized in that: The particle size of the recycled coarse aggregate is 5-25 mm.

3. The deep foundation pit recycled aggregate backfill concrete according to claim 1, characterized in that: The particle size of the recycled fine aggregate is 0.16-4.75 mm.

4. The deep foundation pit recycled aggregate backfill concrete according to claim 1, characterized in that: The particle size of the regenerated powder is less than 0.16 mm.

5. The deep foundation pit recycled aggregate backfill concrete according to claim 1, characterized in that: The water reducer is a polycarboxylic acid water reducer.

6. A method for preparing recycled aggregate backfill concrete for deep foundation pits according to any one of claims 1 to 5, characterized in that: The process includes the following steps: Step 1: mixing and stirring a water reducer and water to obtain a liquid mixture; Step 2: Mix the liquid mixture, cement, and admixture to obtain a prefabricated mixture; mix the recycled powder, recycled fine aggregate, and recycled coarse aggregate to obtain a prefabricated dry material; Step 3: Evenly mix the prefabricated mixture, prefabricated dry material and coconut husk to obtain deep foundation pit recycled aggregate backfill concrete.

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