A novel type of confined recycled concrete pile and its construction method

Abstract

This invention discloses a novel type of confined recycled concrete pile and its construction method, belonging to the field of traffic engineering. The materials used to prepare the novel pile include a confining tube, a curing agent, recycled coarse aggregate, recycled fine aggregate, water, and admixtures. The mass ratio of the curing agent, recycled coarse aggregate, recycled fine aggregate, water, and admixtures ranges from 1 to 8.2: 3 to 8.8: 2 to 6.8: 0.3 to 4.2: 0.1 to 0.6. The ratio of the ultimate confining stress provided by the confining tube to the strength of the recycled concrete is >0.6. The curing agent consists of a cementing component and an expansion component. A rapidly hydrating and expanding material is used as the expansion component, and a slowly hydrating material is used as the cementing component. When the expansion component is fully hydrated, the hydration rate of the cementing component is ≤30%. The recycled aggregate is derived from continuously graded aggregate obtained by crushing and screening construction waste. The curing agent, recycled coarse aggregate, recycled fine aggregate, water, and admixtures are mixed evenly in the specified proportions and poured into the confining tube, which has been pre-embedded in the foundation, and then vibrated to compact it, forming a dense and high-strength confined recycled concrete novel pile.

Description

Technical Field

[0001] This invention relates to a novel type of confined recycled concrete pile and its construction method, belonging to the field of transportation engineering. Background Technology

[0002] With the development of industrialization and urbanization, construction waste is increasing daily. In my country, construction waste now accounts for more than one-third of total urban waste, mainly consisting of discarded concrete blocks, bricks, tiles, and gravel. The vast majority of construction waste is transported to the suburbs or countryside without any treatment, resulting in open dumping or landfilling. This consumes significant amounts of construction funds, including land acquisition fees and waste removal costs. Furthermore, the spillage, dust, and sand generated during transport and dumping cause serious environmental pollution. The indiscriminate dumping of construction waste poses safety hazards, and leachate from fermentation and rainwater leaching and soaking causes severe pollution of surface and groundwater. While crushing waste into recycled aggregate to prepare recycled concrete can achieve resource reuse, the crushing process easily creates numerous cracks and pores in the aggregate, leading to insufficient strength and durability in the recycled concrete, thus limiting its application and promotion. In addition, my country has nearly 10 billion tons of tailings from mines, and the comprehensive utilization rate needs to be improved. The large-scale dumping of tailings also occupies a lot of land, pollutes the environment, and consumes a lot of maintenance funds.

[0003] Currently, pile preparation mainly uses traditional building materials such as ordinary silicate cement, sand, and stone. However, the production of silicate cement causes a large amount of carbon emissions, and sand and gravel mining has been gradually restricted and halted due to its damage to natural resources and the ecological environment. This has led to a shortage and soaring prices of crushed stone and river sand resources. Therefore, the efficient resource recycling of construction waste and industrial slag, and the development of a new type of dense, high-strength, low-carbon, economical, and durable confined recycled concrete pile, has significant engineering value and social significance.

[0004] Constrained solidification technology is a novel soil reinforcement method proposed based on solidified soil piles. It uses a solidification agent containing an expansion component, organically combined with a confinement tube, to produce multiple reinforcement effects, as detailed in patents "Construction Method of Solidified Soil Piles" (ZL201610183422.6) and "Treatment Method of Contaminated Soil" (201610184702.9). However, constrained solidification technology uses silicate-based cement as a binder, resulting in significant carbon emissions. Moreover, under the condition that the content of binder and expansion component in the solidification agent remains constant, using solidification agents with different hydration rates for binder and expansion components will lead to significant differences in the strength of the solidified soil and the strength of the reinforced pile body, resulting in ineffective control of the solidification agent's expansion energy and low utilization efficiency of the solidification agent's expansion energy. The patent "A Steel Pipe Recycled Concrete Composite Carrier Pile and Its Preparation Method" (201510040277.1) employs a method of compacting construction waste in the pile bottom hole, then expanding it with hard recycled concrete to form dry-hard recycled concrete, and using sorted construction waste to form an expanded body. This method efficiently utilizes construction waste generated after the demolition of old buildings, but the core of this invention is still based on existing recycled concrete technology. The patent "A Combined Pile and Combined Pile Foundation Combined Construction Method and Application" (03126784.X) uses a combination of hollow piles, solid piles, enlarged piles, and telescopic piles to construct combined piles and a combined technology method. This method can significantly improve the bearing capacity of a single pile and reduce costs, but each individual pile is still prepared using traditional pile technology methods.

[0005] Based on this, the present invention proposes a novel type of confined recycled concrete pile and its construction method. Summary of the Invention

[0006] This invention proposes a novel type of constrained recycled concrete pile and its construction method, aiming to provide a dense, high-strength, low-carbon, economical, and durable novel type of constrained recycled concrete pile. It solves the technical problem that the crushing of construction waste easily generates numerous cracks and pores in the aggregate, leading to insufficient strength and durability of recycled concrete. This invention gives the recycled concrete a dense structure, high strength, and good durability. It utilizes industrial waste residue to completely replace silicate-based cement as the binding component, achieving a highly efficient synergistic curing effect between the binding and expansion components under constrained conditions. This significantly improves the utilization efficiency of the curing agent and the comprehensive utilization efficiency of the industrial waste residue. It saves on the consumption of traditional building materials, reduces the engineering cost of pile preparation, and achieves low-carbon pile preparation.

[0007] This invention proposes a novel type of confined recycled concrete pile and its construction method. Specifically, the materials used to prepare the novel confined recycled concrete pile include a confining tube, a curing agent, recycled coarse aggregate, recycled fine aggregate, water, and admixtures. The confining tube is made of materials including, but not limited to, rigid materials, flexible materials, and combinations of both. The curing agent consists of a cementing component and an expansion component. A material with a slow hydration rate is used as the cementing component, while a material with rapid hydration and expansion is used as the expansion component. The cementing component is composed of industrial waste and an alkali activator. When the expansion component is fully hydrated, the hydration rate of the cementing component is ≤30%. The mass ratio of the cementing component to the expansion component in the curing agent is 25-80:20-75, respectively. The recycled coarse aggregate and recycled fine aggregate are continuously graded aggregates obtained by crushing and screening waste construction waste. The raw coarse aggregate has a particle size range of 4.75~25mm, and the recycled fine aggregate has a particle size range of 0.075~4.75mm. Construction waste includes, but is not limited to, waste concrete, waste sintered bricks, waste ceramic tiles, waste granite, and waste sand and gravel. Admixtures include, but are not limited to, water-reducing agents, pumping agents, air-entraining agents, waterproofing agents, rust inhibitors, and antifreeze agents. The mass ratio of curing agent, recycled coarse aggregate, recycled fine aggregate, water, and admixtures ranges from 1~8.2:3~8.8:2~6.8:0.3~4.2:0.1~0.6. The curing agent, recycled coarse aggregate, recycled fine aggregate, water, and admixtures are mixed evenly according to the mass ratio and poured into the confinement tubes pre-embedded in the foundation and vibrated to compact them, forming a new type of confined recycled concrete pile with dense, high-strength, and durable properties. The ratio of the ultimate confinement stress provided by the confinement tube to the strength of the recycled concrete is greater than 0.6.

[0008] The construction method of the novel confined recycled concrete pile described in this invention is as follows: First, based on the design values ​​of the strength of the recycled concrete and the strength of the pile body of the new type of confined recycled concrete, the material composition and size of the confining tube are determined, the mass ratio of curing agent, recycled coarse aggregate, recycled fine aggregate, water and admixture are determined, and the material composition and proportion of the cementing component and expansion component in the curing agent are determined. Secondly, the constraint tube is implanted into the foundation in advance. When the constraint tube is a rigid tube, it is directly implanted into the foundation after the pile tip is installed. When the constraint tube is a flexible tube, a recyclable rigid sleeve is needed to implant the constraint tube into the foundation. Finally, the curing agent, recycled coarse aggregate, recycled fine aggregate, water, and admixture are mixed evenly according to the mass ratio and poured into the confinement pipe that has been pre-embedded in the foundation. The mixture is then vibrated to compact the concrete and form a new type of confined recycled concrete pile. The performance of the new type of confined recycled concrete pile is then tested when it reaches the curing age.

[0009] The rigid materials described in this invention include, but are not limited to, steel pipes, polyvinyl chloride pipes, polyethylene pipes, reinforced high-density polyethylene pipes, polybutene pipes, polypropylene pipes, and fiber braided pultruded pipes, etc., while the flexible materials include, but are not limited to, fiber-reinforced composite fabrics, etc.

[0010] The cementing component of this invention is a material with a slow hydration rate, and the cementing hydrates produced by its hydration include, but are not limited to, hydrated calcium silicate, hydrated calcium aluminate, and hydrated calcium aluminosilicate. The cementing component is composed of industrial waste residue and an alkali activator, with the mass ratio of industrial waste residue to alkali activator in the cementing component being 75~100:0~25. The industrial waste residue includes, but is not limited to, one or more combinations of slag, copper slag, steel slag, phosphorus slag, fly ash, coal gangue, silica fume, red mud, bottom ash, rice husk ash, calcined ash, kiln ash, and desulfurization slag. The alkali activator includes, but is not limited to, one or more combinations of quicklime, hydrated lime, activated magnesium oxide, carbide slag, sodium hydroxide, and hydrated sodium silicate.

[0011] The expansion component of this invention is a rapidly hydrating expansion type material, and the expansion hydrates produced by its hydration include, but are not limited to, ettringite, monosulfide calcium sulfoaluminate, etc.; the expansion component includes, but is not limited to, a mixture composed of aluminum-containing waste residue, gypsum-based waste residue, sulfate waste residue, alkaline waste residue, etc.; the gypsum-based waste residue includes, but is not limited to, industrial waste gypsum such as phosphogypsum, titanium gypsum, flue gas desulfurization gypsum, organic gypsum, soda gypsum, salt gypsum, fluorogypsum, yellow gypsum, borosilicate gypsum, etc.

[0012] The curing agent described in this invention comprises industrial-grade materials, all of which have a specific surface area greater than 200 m². 2 / kg of powder.

[0013] The cementing component of this invention requires the selection of an alkali activator based on the hydration rate of the cementing component design, and the determination of the specific ratio of cementing material and alkali activator in the cementing component through preliminary experiments; the expansion component requires the determination of the specific ratio of each component material in the expansion component based on the chemical equation for the formation of expansion hydrates by hydration, and according to known calculation methods.

[0014] The water referred to in this invention refers to drinking water that meets the "Standards for Drinking Water Quality" (GB 5749-2022). When non-drinking water is used, a comparative test should be conducted with drinking water.

[0015] The novel confined recycled concrete pile of this invention is formed by drilling holes in the foundation using a known method. The application scope of the novel confined recycled concrete pile includes, but is not limited to, airport engineering, road engineering, and industrial building engineering.

[0016] The advantages of this invention are: 1. This invention solves the technical problem that construction waste easily generates a large number of cracks and pores in the aggregate during crushing, resulting in insufficient strength and durability of recycled concrete, thus giving recycled concrete the characteristics of dense structure, high strength and good durability.

[0017] 2. This invention achieves the technical effect of significantly improving the utilization efficiency of curing agents, thereby significantly improving the comprehensive utilization efficiency of industrial waste residue, and providing a new type of confined recycled concrete pile that is dense, high-strength, low-carbon, economical, and has good load-bearing capacity and durability for my country's infrastructure construction.

[0018] 3. This invention uses industrial waste residue as a cementing material to completely replace silicate cement, uses recycled coarse aggregate to completely replace natural coarse aggregate, and uses recycled fine aggregate to completely replace natural fine aggregate, thus achieving low-carbon preparation of piles, saving traditional building material consumption, protecting the natural ecological environment, and significantly reducing engineering costs. Detailed Implementation

[0019] The following detailed description of the novel constrained recycled concrete pile and its construction method according to the present invention uses specific embodiments. However, the application forms and scope of the novel constrained recycled concrete pile provided by the present invention are not limited to this.

[0020] Example 1 A highway project plans to use the novel confined recycled concrete pile and its construction method described in this invention for foundation reinforcement. The designed pile length is 20m, the pile diameter is 350mm, the strength of recycled concrete and the strength of the novel confined recycled concrete pile body are 35MPa and 62MPa, respectively.

[0021] The constraint tube was determined to be a combination of PVC pipe and BFRP fabric, specifically a 13mm thick PVC pipe with 6 layers of BFRP fabric adhered to its outer surface. The recycled coarse and fine aggregates were determined to be waste bricks, and the admixture was an antifreeze agent. The mass ratio of curing agent, recycled coarse aggregate, recycled fine aggregate, water, and admixture was 5.2:8.3:6.4:2.7:0.16. The curing agent composition, calculated by weight, was as follows: 5.5 parts slag, 2.0 parts calcined ash, and 2.5 parts quicklime as the binder; and 3.4 parts aluminum-containing waste residue, 2.4 parts alkaline waste residue, and 9.2 parts soda ash. The constraint tube was pre-installed in the foundation. The curing agent, recycled coarse aggregate, recycled fine aggregate, water, and admixture were mixed evenly according to the mass ratio and poured into the constraint tube, then vibrated to compact it, forming a new type of constrained recycled concrete pile. Testing showed that all performance characteristics of the new type of constrained recycled concrete pile met the requirements at 28 days of age.

[0022] Example 2 An airport project plans to use the novel confined recycled concrete pile and its construction method described in this invention for foundation reinforcement. The designed pile length is 18m, the pile diameter is 500mm, the strength of recycled concrete and the strength of the novel confined recycled concrete pile body are 56MPa and 98MPa, respectively.

[0023] The constraint tube was determined to be a combination of steel pipe and GFRP fabric, specifically a 15mm thick steel pipe with 8 layers of GFRP fabric bonded to its outer surface. The recycled coarse and fine aggregates were determined to be waste granite, and the admixture was a water-reducing agent. The mass ratio of curing agent, recycled coarse aggregate, recycled fine aggregate, water, and admixture was 3.5:5.6:4.3:1.7:0.1. The curing agent composition, calculated by weight, was as follows: cementing component: 6.5 parts silica fume, 2.0 parts desulfurization slag, 1.5 parts calcium carbide slag; expansion component: 2.8 parts aluminum-containing waste slag, 1.5 parts alkaline waste slag, 5.3 parts sulfate waste slag. The constraint tube was pre-installed in the foundation. The curing agent, recycled coarse aggregate, recycled fine aggregate, water, and admixture were mixed evenly according to the mass ratio and poured into the constraint tube, then vibrated to compact, forming a new type of constrained recycled concrete pile. Testing showed that all performance characteristics of the new type of constrained recycled concrete pile met the requirements at 28 days of age.

[0024] Example 3 A high-speed railway project plans to use the novel confined recycled concrete pile and its construction method described in this invention for foundation reinforcement. The designed pile length is 15m, the pile diameter is 400mm, the strength of recycled concrete and the strength of the novel confined recycled concrete pile body are 45MPa and 88MPa, respectively.

[0025] The constraint tube was determined to be an 18mm thick GFRP pipe, the recycled coarse and fine aggregates were all waste concrete, and the admixture was a water-reducing agent. The mass ratio of curing agent, recycled coarse aggregate, recycled fine aggregate, water, and admixture was determined to be 4.5:6.6:5.2:2.1:0.4. The curing agent composition, calculated by weight, was determined as follows: the binder component consisted of 5.0 parts silica fume, 4.0 parts red mud, and 1.0 part hydrated sodium silicate; the expansion component consisted of 3.8 parts aluminum-containing waste residue, 2.2 parts salt gypsum, and 7.5 parts alkaline waste residue. The constraint tube was pre-installed in the foundation. The curing agent, recycled coarse aggregate, recycled fine aggregate, water, and admixture were mixed evenly according to the mass ratio, poured into the constraint tube, and vibrated to compact, forming a new type of constrained recycled concrete pile. After testing, all performance characteristics of the new type of constrained recycled concrete pile met the requirements at 28 days of age.

[0026] Example 4 An industrial building project plans to use the novel confined recycled concrete pile and its construction method described in this invention for foundation reinforcement. The designed pile length is 13m, the pile diameter is 300mm, the strength of recycled concrete and the strength of the novel confined recycled concrete pile body are 25MPa and 58MPa, respectively.

[0027] The constraint tube was determined to be a combination of polypropylene pipe and GFRP fabric, specifically a 12mm thick polypropylene pipe with 5 layers of GFRP fabric adhered to its outer surface. The recycled coarse and fine aggregates were determined to be waste sand and gravel, and the admixture was a pumping agent. The mass ratio of curing agent, recycled coarse aggregate, recycled fine aggregate, water, and admixture was 2.8:4.5:3.5:1.4:0.3. The curing agent composition, calculated by weight, was as follows: binder: 5.0 parts slag, 4.0 parts rice husk ash, 1.0 part quicklime; expansion component: 2.2 parts aluminum-containing waste residue, 1.2 parts alkaline waste residue, and 5.0 parts gypsum-based waste residue. The constraint tube was pre-installed in the foundation. The curing agent, recycled coarse aggregate, recycled fine aggregate, water, and admixture were mixed evenly according to the mass ratio and poured into the constraint tube, then vibrated to compact, forming a new type of constrained recycled concrete pile. Testing showed that all performance characteristics of the new type of constrained recycled concrete pile met the requirements at 28 days of age.

Claims

1. A novel type of confined recycled concrete pile and its construction method, characterized in that: The materials for preparing the new type of confined recycled concrete piles include confining tubes, curing agents, recycled coarse aggregate, recycled fine aggregate, water, and admixtures. The mass ratio of curing agent, recycled coarse aggregate, recycled fine aggregate, water, and admixtures ranges from 1 to 8.2: 3 to 8.8: 2 to 6.8: 0.3 to 4.2: 0.1 to 0.

6. The ratio of the ultimate confining stress provided by the confining tube to the strength of the recycled concrete is >0.

6. The materials of the confining tubes include, but are not limited to, rigid materials, flexible materials, and combinations of both types. The curing agent consists of a cementing component and an expansion component. A fast-hydrating and expanding material is used as the expansion component, and a slow-hydrating material is used as the cementing component. The cementing component consists of industrial waste residue and an alkali activator. When the expansion component is fully hydrated, the hydration rate of the cementing component is ≤30%. The cementing component and the expansion component are in the curing... The mass ratio of the additives is 25~80:20~75; both recycled coarse aggregate and recycled fine aggregate are continuous graded aggregates obtained by crushing and screening waste construction waste. The particle size range of recycled coarse aggregate is 4.75~25mm, and the particle size range of recycled fine aggregate is 0.075~4.75mm. Construction waste includes, but is not limited to, waste concrete, waste sintered bricks, waste ceramic tiles, waste granite, waste sand and gravel, etc.; the additives include, but are not limited to, water-reducing agents, pumping agents, air-entraining agents, waterproofing agents, rust inhibitors, antifreeze agents, etc.; the curing agent, recycled coarse aggregate, recycled fine aggregate, water, and additives are mixed evenly according to the mass ratio and poured into the confinement tubes pre-embedded in the foundation and vibrated to compact them, forming a new type of confined recycled concrete pile with dense, high-strength, and durable properties; the specific construction process of the confined recycled concrete pile is as follows: First, based on the strength of the recycled concrete and the design value of the pile body strength of the new type of confined recycled concrete pile, the material composition and size of the confining tube are determined, the mass ratio of curing agent, recycled coarse aggregate, recycled fine aggregate, water and admixture are determined, and the material composition and proportion of the cementing component and expansion component in the curing agent are determined. Secondly, the constraint tube is implanted into the foundation in advance. When the constraint tube is a rigid tube, it is directly implanted into the foundation after the pile tip is installed. When the constraint tube is a flexible tube, a recyclable rigid sleeve is needed to implant the constraint tube into the foundation. Finally, the curing agent, recycled coarse aggregate, recycled fine aggregate, water, and admixture are mixed evenly according to the mass ratio and poured into the confinement pipe that has been pre-embedded in the foundation. The mixture is then vibrated to compact the concrete and form a new type of confined recycled concrete pile. The performance of the new type of confined recycled concrete pile is then tested when it reaches the curing age.

2. The novel confined recycled concrete pile and its construction method according to claim 1, characterized in that: The rigid material includes, but is not limited to, steel pipes, polyvinyl chloride pipes, polyethylene pipes, reinforced high-density polyethylene pipes, polybutene pipes, polypropylene pipes, and fiber-braided pultruded pipes, etc.; the flexible material includes, but is not limited to, fiber-reinforced composite fabrics, etc.; the cementing component is a material with a slow hydration rate, and the cementing hydrates produced by its hydration include, but are not limited to, hydrated calcium silicate, hydrated calcium aluminate, hydrated calcium aluminosilicate, etc.; the mass ratio of industrial waste residue and alkali activator in the cementing component is 75~100:0~25, respectively; the industrial waste residue includes, but is not limited to, one or more of the following: slag, copper slag, steel slag, phosphorus slag, fly ash, coal gangue, silica fume, red mud, bottom ash, rice husk ash, calcined ash, kiln ash, and desulfurization slag, etc. The composition includes, but is not limited to, quicklime, hydrated lime, activated magnesium oxide, carbide slag, sodium hydroxide, hydrated sodium silicate, etc.; the expansion component is a rapid hydration expansion type material, and the expanded hydrates produced by its hydration include, but are not limited to, ettringite, monosulfide calcium sulfoaluminate, etc.; the expansion component includes, but is not limited to, a mixture composed of aluminum-containing waste residue, gypsum-based waste residue or sulfate waste residue, alkaline waste residue, etc.; the gypsum-based waste residue includes, but is not limited to, industrial waste gypsum such as phosphogypsum, titanium gypsum, flue gas desulfurization gypsum, organic gypsum, soda gypsum, salt gypsum, fluorogypsum, yellow gypsum, borosilicate gypsum, etc.; the components of the curing agent are all industrial grade, and the curing agent materials all have a specific surface area greater than 200 m². 2 / kg of powder.

3. The novel confined recycled concrete pile and its construction method according to claim 1, characterized in that: The cementing component requires the selection of an alkali activator based on the hydration rate of the cementing component design, and the specific ratio of cementing material and alkali activator in the cementing component is determined through preliminary experiments; the expansion component requires the determination of the specific ratio of each component material in the expansion component based on the chemical equation for the formation of expansion hydrates by hydration and according to known calculation methods.

4. The novel confined recycled concrete pile and its construction method according to claim 1, characterized in that: The water referred to is drinking water that meets the "Standards for Drinking Water Quality" (GB 5749-2022). When non-drinking water is used, a comparative test should be conducted with drinking water.

5. The novel confined recycled concrete pile and its construction method according to claim 1, characterized in that: The novel constrained recycled concrete piles are drilled in the foundation using known methods. The application scope of the novel constrained recycled concrete piles includes, but is not limited to, airport engineering, road engineering, and industrial building engineering.