High-strength and high-toughness concrete based on full-solid waste functional aggregate, and application and method of antibacterial self-healing in sewage environment

Abstract

This invention relates to high-strength, high-toughness concrete based on all-solid-waste functional aggregates, comprising cementitious materials, all-solid-waste functional aggregates, water, water-reducing agents, and toughening fibers. The all-solid-waste functional aggregates consist of a porous all-solid-waste matrix and an antibacterial agent loaded within its pores. The invention also relates to an antibacterial self-healing method and application of this high-strength, high-toughness concrete based on all-solid-waste functional aggregates in wastewater environments. This invention achieves a performance breakthrough in concrete under harsh underground pipe networks and biological acid corrosion environments through four core mechanisms: functional aggregate-induced cracking, in-situ release of antibacterial agents, fiber toughening to control cracking, and long-term self-healing of microcracks. It solves the problems of high brittleness and poor resistance to microbial erosion in traditional pipe concrete, and further reduces the ecological burden through the high-value utilization of multi-source solid waste such as urban sludge.

Description

Technical Field

[0001] This invention belongs to the field of municipal engineering and building materials technology, specifically relating to a high-strength and high-toughness concrete based on all-solid-waste functional aggregates and its antibacterial self-healing application and method in wastewater environments. Background Technology

[0002] As a lifeline project of urban infrastructure, underground drainage pipe networks directly affect the safe operation of cities and the health of the public environment through their structural safety and long-term service performance. However, with the increase in service life and the increasing complexity of the underground environment, traditional concrete pipes are prone to structural micro-cracks under complex mechanical loads such as uneven settlement, traffic dynamic loads, and soil lateral pressure. More seriously, in underground sewage environments, pipes are exposed to multiple corrosive media such as microbial metabolites, organic acids, and inorganic acids for extended periods, making them highly susceptible to bio-acid erosion. This is a key factor leading to severe degradation of the material's mechanical properties and a significant reduction in the pipe's service life.

[0003] During the specific erosion process, microorganisms such as sulfur-oxidizing bacteria (Acidithiobacillus thiooxidans) readily adhere to the surface of concrete pipes and form biofilms, continuously producing highly corrosive substances such as sulfuric acid through their metabolism. These bio-acids gradually penetrate downwards and dissolve the hydration products calcium hydroxide inside the concrete, severely damaging the integrity of the interface transition zone between aggregates and cement paste. This not only induces the formation of ettringite inside, generating huge expansion stress and leading to cracking, but also causes the hydrated calcium silicate gel to debond and fail. Under the long-term coupled damage of mechanical loads and bio-acid erosion, traditional concrete pipes often exhibit fatal defects such as high brittleness, easy crack penetration, and significant deterioration of impermeability, resulting in their actual service life being far below the design reference period.

[0004] To address the problem of brittle cracking in concrete, the engineering community has developed high-strength, high-ductility concrete in recent years. With its unique strain-hardening behavior and multi-crack characteristic, high-strength concrete can significantly delay structural failure of pipes caused by brittle fracture at the mechanical level. However, this type of concrete matrix lacks bioactivity inhibition capabilities. Under long-term exposure to bio-acidic environments, bacteria can still proliferate along microcracks, posing a significant bottleneck to its durability. To impart antibacterial properties to this type of concrete, existing technologies mainly rely on directly incorporating bactericidal additives (such as modifiers or quaternary ammonium compounds containing metal ions like silver, copper, and zinc) during the mixing stage. However, this traditional direct incorporation method has significant performance drawbacks: Firstly, the directly added antibacterial agents are often randomly and blindly distributed within the concrete matrix, with most of the effective agents deeply encapsulated by dense cement hydration products, making it impossible for them to contact microorganisms on the structural surface. This results in extremely low agent utilization and severe resource waste. Secondly, the small amount of antibacterial agent exposed only on the concrete surface is highly susceptible to rapid loss, early deactivation, or uncontrolled leaching under the combined effects of long-term wet-dry cycles of underground sewage, physical scouring by water flow, and continuous acidic chemical erosion. This makes it impossible to guarantee the long-term antibacterial stability of the concrete throughout its entire life cycle. Furthermore, with the accelerated urbanization process in my country, the annual discharge of municipal sludge and river silt is experiencing explosive growth. Traditional landfill disposal methods not only occupy a large amount of scarce land resources, but also pose serious ecological risks of secondary pollution from heavy metals and leachate.

[0005] Therefore, there is an urgent need to develop a multifunctional concrete material that utilizes a low water-cement ratio (0.18~0.22) and the close packing and activation of multi-source solid waste (such as slag and carbide slag) to construct a dense and high-strength cement matrix. Simultaneously, the synergistic effect of introducing toughening fibers and functional aggregates from all solid wastes will endow the concrete with high strength and ductility, long-lasting antibacterial properties, and self-healing ability for microcracks. This will enable it to maintain excellent mechanical and durability properties in complex underground environments over a long period, achieving high-value utilization of solid waste and reducing maintenance frequency and costs. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a high-strength, high-toughness concrete based on all-solid-waste functional aggregates and its preparation method.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a high-strength, high-toughness concrete based on all-solid-waste functional aggregate, comprising cementitious materials, all-solid-waste functional aggregate, water, water-reducing agent, and toughening fiber; the cementitious materials include PO42.5 or PO52.5 grade ordinary Portland cement; the all-solid-waste functional aggregate consists of porous all-solid-waste base material and an antibacterial agent loaded within its pores; the antibacterial agent is selected from calcium formate and / or sodium benzoate; wherein, based on 100 parts by weight of the cementitious materials, the dosage of the remaining raw materials is as follows: 30-150 parts of all-solid-waste functional aggregate, 18-22 parts of water, 1.5-2.5 parts of water-reducing agent, and 0.8-1.5 parts of toughening fiber.

[0008] Furthermore, by mass percentage, the raw material composition of the all-solid waste base material is: 40-60% sludge, 10-20% carbide slag, 15-25% desulfurized gypsum, and 10-20% slag, and the sum of the mass percentages of the above four components is 100%; the loading of the antibacterial agent is 0.2-1% of the mass of the all-solid waste base material.

[0009] Furthermore, the particle size of the solid waste functional aggregate is 0.1–2.5 mm.

[0010] Furthermore, the high-strength and high-toughness concrete has a compressive strength higher than 80 MPa, a uniaxial tensile strain of more than 2%, and exhibits multi-crack characteristics during uniaxial tension, with an average crack width of less than 150 μm.

[0011] Furthermore, the toughening fiber is selected from PE fiber and / or PVA fiber.

[0012] Furthermore, the toughening fiber is selected from polyethylene fiber, with a diameter of 15-25 μm, a nominal tensile strength ≥3000 MPa, a Young's modulus of 90-110 GPa, and an elongation at break of 2-3%.

[0013] Furthermore, the sludge is obtained from municipal sewage sludge or municipal river sludge treatment, with a moisture content ≤3%; the moisture content of the municipal sewage sludge or municipal river sludge is controlled between 35% and 70%.

[0014] Furthermore, the water-reducing agent is selected from polycarboxylate high-performance water-reducing agents with a water reduction rate of ≥25%.

[0015] Furthermore, the cementing material includes silicate cement and / or ultrafine slag powder.

[0016] This invention innovatively incorporates functional materials such as all-solid-waste functional aggregates and toughening fibers into concrete. Utilizing porous all-solid-waste functional aggregates as controllable "functional artificial defects" within the matrix, when concrete enters the strain-hardening stage under tensile load, it induces microcracks to preferentially propagate towards the aggregates, causing micro-fractures. This precisely triggers the in-situ release of antibacterial agents loaded within the pores. The released antibacterial ions target and disrupt the metabolism and enzyme activity of sulfur-oxidizing bacteria (Acidithiobacillus thiooxidans), blocking the generation of bio-acids at their source. Simultaneously, during crack propagation, the interfacial adhesion between the toughening fibers and the concrete matrix, along with the fiber pull-out effect, "bridges" the cracks, absorbing energy and confining macroscopic cracks into fine, steady-state microcracks. Combined with the secondary hydration of unhydrated particles in the all-solid-waste matrix and reactions such as calcium carbonate precipitation, long-term self-healing and sealing of the cracks are achieved. Ultimately, this results in the synergistic integration of multiple properties of high-strength, high-toughness concrete, including high ductility, high corrosion resistance, and long-term intelligent antimicrobial erosion.

[0017] This invention also provides a method for preparing the above-mentioned high-strength and high-toughness concrete based on all-solid-waste functional aggregate, comprising the following steps: mixing sludge, carbide slag, desulfurized gypsum and slag according to mass percentage, solidifying and molding, and sieving to control the particle size to 0.1-2.5 mm to obtain an all-solid-waste base material with mesoporous and macroporous structures; then loading an antibacterial agent into the pores of the all-solid-waste base material through a vacuum impregnation process, and drying to obtain all-solid-waste functional aggregate; mixing the cementitious material and the all-solid-waste functional aggregate at low speed to obtain a dry mixture; adding toughening fibers to the dry mixture in 2-3 batches, with an interval of 1-2 minutes between each addition, and dispersing by medium-speed stirring; finally adding water mixed with a water-reducing agent, controlling the water-cement ratio to 0.18-0.22, stirring at high speed, and then pouring and curing to obtain the high-strength and high-toughness concrete based on all-solid-waste functional aggregate.

[0018] Furthermore, the mechanical strength of the all-solid-waste functional aggregate is lower than the matrix strength of the cementitious material in the concrete after hydration and curing.

[0019] This invention also provides the application of high-strength and high-toughness concrete based on all-solid-waste functional aggregates in antibacterial and self-healing environments in wastewater environments.

[0020] The present invention also provides a method for antibacterial self-healing of high-strength and high-toughness concrete based on all-solid-waste functional aggregate in a sewage environment, including the following process: (1) the high-strength and high-toughness concrete based on all-solid-waste functional aggregate cracks under the coupling effect of tensile load and sewage ion erosion and deterioration; (2) the all-solid-waste functional aggregate induces microcracks to preferentially extend to the all-solid-waste functional aggregate and cause it to break, thereby triggering the in-situ release of antibacterial agent inside the pores of the all-solid-waste functional aggregate. The released antibacterial ions target and destroy the metabolism and enzyme activity of sulfur-oxidizing bacteria, block the generation of biological acid from the source, realize the antibacterial function, and reduce the biological acid erosion effect on the concrete surface; (3) when the cracks extend, the cracks are bridged by the interfacial bonding force between the toughening fiber and the concrete matrix and the fiber pull-out effect, absorb energy, and limit the macroscopic cracks to micro-fine steady-state cracks; (4) the all-solid-waste functional aggregate releases calcium ions, which react with sulfate ions or carbonate ions in sewage to generate precipitated minerals, repair the cracks of the high-strength and high-toughness concrete based on all-solid-waste functional aggregate, and realize the self-healing function.

[0021] Compared with the prior art, the present invention has the following advantages and technical effects: 1. This invention improves the performance of concrete in underground pipe networks and biological acid corrosion environments through four mechanisms: functional aggregate-induced cracking, in-situ release of antibacterial agents, fiber toughening to control cracking, and long-term self-healing of microcracks. Through multi-scale collaborative design of materials, structure, and environment, it solves the problems of high brittleness and poor resistance to microbial erosion of traditional pipe concrete, while realizing the high-value utilization of multi-source solid waste such as urban sludge, providing a safe and reliable material foundation for underground pipeline engineering.

[0022] 2. The core of this invention lies in achieving high strength and ductility, long-term resistance to bio-acid corrosion, and self-healing properties of underground space concrete through material composition optimization and multi-scale structural synergistic design. Its working principle can be broken down into the following three key synergistic mechanisms: (1) Synergistic mechanism of functional aggregate defect induction and in-situ drug release Mechanism of action: The compressive strength of the solid waste functional aggregate is lower than that of the hardened matrix, forming uniformly distributed "artificial defects" within the concrete. When the structure cracks under external force, the microcracks propagate directionally to the porous functional aggregate and induce microfractures, precisely triggering the release of antibacterial agents (such as calcium formate and sodium benzoate) that were originally sealed inside the pores.

[0023] Synergistic effect: This "crack-and-release" intelligent response mechanism allows the released effective antibacterial ions to accumulate in a high concentration at the microcracks, interfering with and disrupting the metabolism and cell membrane stability of sulfur-oxidizing bacteria (Acidithiobacillus thiooxidans). This solves the shortcomings of traditional admixtures, which are easily lost, easily encapsulated in deep layers, and have extremely low utilization rates when directly incorporated.

[0024] (2) Synergistic mechanism of fiber toughening and strain hardening crack control Mechanism of action: High-strength polyethylene fibers are uniformly dispersed in the concrete matrix. When cracks initiate and propagate, they absorb a large amount of structural deformation energy through the "bridging" effect between the fibers and the matrix, causing the concrete to transform from brittle fracture to significant multi-crack cracking and strain hardening failure.

[0025] Synergistic effect: Through fiber bridging, macroscopic harmful wide cracks were successfully confined into micro-cracks with extremely small widths (average crack width ≤ 90 μm). This ability to transform "large cracks" into "multiple micro-cracks" cuts off the direct channel for corrosive media, providing an environment for subsequent self-healing reactions.

[0026] (3) Synergistic mechanism of chemical activation and microcrack self-healing in multi-source solid waste Mechanism of action: Multi-source solid waste particles that are not fully hydrated in the solid waste matrix and inside the micro-cracks will spontaneously undergo secondary hydration under the induction of environmental moisture; at the same time, free calcium ions dissolved in the matrix can react with carbonate ions in the environment to generate crystalline precipitates such as calcium carbonate, which are rapidly deposited and filled into the cracks.

[0027] Synergistic effect: The in-situ released antibacterial agent blocks the bio-acid erosion at the microcracks, protecting self-healing products such as calcium carbonate from secondary dissolution and destruction, thus significantly improving the closure rate of the microcracks. The healed cracks further lock in the internal antibacterial ions, significantly reducing permeability and forming a long-term synergistic stable state.

[0028] 3. The high-strength, high-toughness concrete based on all-solid-waste functional aggregates provided by this invention has the following advantages: (1) Mechanical and toughness properties: Under the conditions of low water-cement ratio (0.18-0.22) and dense accumulation of multi-source solid waste, the concrete has excellent compressive strength; the uniaxial direct tensile ultimate strain stably reaches more than 4.2%, showing significant multi-crack characteristics, and the deformation capacity is greatly improved compared with traditional pipe concrete.

[0029] (2) Antibacterial and anti-corrosion durability: It has a precise killing effect on typical sulfur oxidizing bacteria, with an inhibition zone diameter of more than 15 mm and an inhibition rate of ≥92%; Under the accelerated corrosion environment of biological acid, the material's mass loss rate and strength deterioration are greatly reduced, significantly extending the full life anti-corrosion cycle.

[0030] (3) Solid waste resource utilization rate: A large amount of municipal sludge, carbide slag and other industrial solid wastes are utilized to effectively eliminate the toxicity of heavy metal leaching, significantly reduce the cost of raw material procurement and solid waste disposal, and conform to the green building materials carbon reduction and emission reduction orientation. Attached Figure Description

[0031] Figure 1 These are multi-crack diagrams of concrete in Examples 1-3.

[0032] Figure 2 These are the self-healing evolution diagrams of cracks in Examples 1-3.

[0033] Figure 3 These are diagrams illustrating the antibacterial effect of the antibacterial aggregate in concrete in Examples 1-3.

[0034] Figure 4 This is a backscattering diagram of the aggregate interface in Examples 1-2.

[0035] Figure 5 This is the backscattering diagram of the aggregate interface in Example 3. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to specific embodiments.

[0038] This invention provides a high-strength and high-toughness concrete based on all-solid-waste functional aggregate, comprising the following raw materials in parts by weight: 100 parts of cementitious material, 30-150 parts of all-solid-waste functional aggregate, 18-22 parts of water, 1.5-2.5 parts of water-reducing agent, and 0.8-1.5 parts of toughening fiber.

[0039] In a preferred embodiment, the amount of cementitious material in the high-strength, high-toughness concrete based on all-solid-waste functional aggregate is 100 parts by weight; the cementitious material is selected from PO42.5 or PO52.5 grade ordinary Portland cement. The cementitious material in this invention provides the initial cementitious strength and a dense hydration product network of the concrete matrix, ensuring the high load-bearing capacity of the structure.

[0040] In a preferred embodiment, the amount of the all-solid-waste functional aggregate in the high-strength and high-toughness concrete based on all-solid-waste functional aggregate is 30-150 parts by weight. This invention breaks through the traditional design concept of "high strength and density" aggregates, utilizing porous functional aggregates to introduce controllable "functional micro-defects" into the matrix. This allows micro-cracks to be directionally induced to the aggregate during propagation, causing them to fracture, thus achieving the first layer of synergistic effect in "stress-induced cracking".

[0041] In a preferred embodiment, the all-solid-waste functional aggregate consists of a porous all-solid-waste base material and an antibacterial agent loaded within its pores. By mass percentage, the raw material composition of the all-solid-waste base material is: 45-55% sludge, 10-20% carbide slag, 15-25% desulfurized gypsum, and 10-20% slag. In a preferred embodiment, the raw material composition is: 50% sludge, 15% carbide slag, 20% desulfurized gypsum, and 15% slag. This invention cleverly utilizes the highly alkaline environment provided by carbide slag and the sulfate ions provided by desulfurized gypsum to form an "alkali-sulfate" composite system, synergistically enhancing the potential cementitious activity of the slag. This system not only effectively solidifies the heavy metals in the sludge but also develops a mesoporous and macroporous network with pore sizes between 10 nm and 50 μm during crystal bonding, reducing the risk of macroscopic cracking of the matrix while providing ample internal reservoir space for the antibacterial agent.

[0042] In a preferred embodiment, the sludge is selected from urban sewage treatment plant sludge or river dredging sludge, with a moisture content of ≤3%; the moisture content of the original urban sewage treatment plant sludge or river dredging sludge is controlled at 35%~70%, and the sludge is naturally sun-dried or low-temperature dried to a moisture content of ≤3% by the original urban sewage treatment plant sludge or river dredging sludge.

[0043] In a preferred embodiment, the particle size of the all-solid-waste functional aggregate is 0.1–2.5 mm, preferably 0.15–0.45 mm. Strictly controlling the aggregate particle size within this fine range ensures that its size as an "artificial defect" does not excessively weaken the macroscopic compressive strength of the concrete (maintaining it above 80 MPa), while also ensuring a high-density distribution of the aggregate, allowing microcracks to hit the aggregate with a very high probability along their propagation path, triggering the release of the active ingredient.

[0044] In a preferred embodiment, the antibacterial agent is calcium formate and / or sodium benzoate. This invention utilizes an antibacterial agent encapsulated within the pores of the aggregate, achieving in-situ release upon micro-fracture of the aggregate under stress. The released antibacterial ions (such as formate) form an extremely high concentration of "antibacterial enrichment zone" in the localized cracks, precisely targeting and disrupting the cell membranes and enzyme activity of sulfur-oxidizing bacteria (SOB), thus blocking the generation of bio-acids (sulfuric acid) at its source. The long-lasting antibacterial effect can reach over 10 years.

[0045] In a preferred embodiment, the preparation method of the all-solid-waste functional aggregate includes the following steps (vacuum impregnation method): A. Sludge, carbide slag, desulfurized gypsum and slag are mixed with water in proportion at room temperature, and then extruded and granulated to obtain primary solid waste granules. B. The primary solid waste particles are placed in a standard curing chamber for solidification, followed by crushing and sieving to obtain a porous all-solid waste base material; C. The solid waste base material is immersed in an antibacterial solution for vacuum impregnation, then removed and dried to obtain the solid waste functional aggregate.

[0046] In a preferred embodiment, in step A, the amount of water added is 15-25% of the total weight of the solid waste mixture; in step B, the curing temperature is 20±2℃, the relative humidity is ≥90%, and the curing time is 3-7 days; the crushing equipment is selected from jaw crusher or ball mill, and after crushing, particles with D90≤2.5 mm are cut through a standard sieve.

[0047] In a preferred embodiment, in step C, the mass concentration of the antibacterial solution is 2–5 wt%; the vacuum impregnation conditions are: vacuum degree -0.08 to -0.1 MPa, and impregnation time of 30–60 min. This invention uses negative pressure to expel air from the deep pores of the aggregate, forcibly pressing the antibacterial solution into and penetrating the micropores inside the aggregate.

[0048] In a preferred embodiment, in step C, the drying temperature is 60–80 °C, the drying time is 12–24 h, until the aggregate moisture content is ≤1%.

[0049] In a preferred embodiment, the amount of toughening fiber in the high-strength, high-toughness concrete based on all-solid-waste functional aggregate is 0.8–1.5 parts by weight, more preferably 1.0–1.2 parts; the length of the toughening fiber is 8–15 mm. The toughening fiber in this invention is used to improve the ductility and multi-crack resistance of concrete. Through fiber pull-out action, it absorbs a large amount of deformation energy, stabilizing the ultimate tensile strain of the concrete at above 4.0%.

[0050] In a preferred embodiment, the toughening fiber is selected from polyethylene fiber (PE fiber) and / or polyvinyl alcohol fiber (PVA fiber); more preferably, it is polyethylene fiber with a diameter of 15-25 μm, a nominal tensile strength ≥3000 MPa, a Young's modulus of 90-110 GPa, and an elongation at break of 2-3%. The extremely fine diameter and ultra-high modulus PE fibers form a dense three-dimensional bridging network in the matrix, successfully dispersing and confining macroscopic wide cracks into steady-state microcracks with a width ≤90 μm. Combined with the in-situ release of antibacterial agents to block bio-acid erosion, the unhydrated gel particles within the microcracks spontaneously undergo secondary hydration and calcium carbonate precipitation, rapidly achieving physical self-healing and sealing of the cracks.

[0051] In a preferred embodiment, the amount of water in the high-strength and high-toughness concrete based on all-solid-waste functional aggregate is 18 to 22 parts by weight; the amount of water-reducing agent is 1.5 to 2.5 parts, more preferably 1.8 to 2.2 parts.

[0052] In a preferred embodiment, the water-reducing agent is selected from polycarboxylate high-performance water-reducing agents (water reduction rate ≥ 25%).

[0053] The present invention also provides a method for preparing high-strength and high-toughness concrete based on all-solid-waste functional aggregates as described in the above technical solution, comprising the following steps: mixing cementitious materials and all-solid-waste functional aggregates at low speed to obtain a dry mixture; adding toughening fibers in batches to the dry mixture for medium-speed mixing and dispersion; then adding water and water-reducing agent after mixing evenly, performing high-speed wet mixing, and after pouring and curing, obtaining the high-strength and high-toughness concrete based on all-solid-waste functional aggregates.

[0054] In a preferred embodiment, the low-speed stirring speed is 30–50 rpm for 3–5 minutes. This invention utilizes low-speed mechanical shear force to ensure that the dry powder cementitious material fully and uniformly coats the surface of the fine porous aggregate.

[0055] In a preferred embodiment, the toughening fiber is added in 2 to 3 batches, with an interval of 1 to 2 minutes between each addition. This batch addition process effectively prevents the high aspect ratio and ultra-high strength PE fibers from agglomerating or entangled in the dry material.

[0056] In a preferred embodiment, the medium-speed stirring speed is 60-80 rpm, and the cumulative dispersion time is 3-5 min.

[0057] In a preferred embodiment, the water and water-reducing agent must be premixed evenly before addition, and the water temperature must be controlled at 20±2℃. The water-cement ratio of the system after adding water and water-reducing agent is strictly controlled between 0.18 and 0.22.

[0058] In a preferred embodiment, the high-speed wet mixing speed is 100–150 rpm, and the time is 5–8 min. This invention utilizes strong high-speed shearing to thoroughly destroy the flocculation structure of the cementitious system, fully utilize the water-reducing agent, and enable the slurry with an extremely low water-cement ratio to quickly reach a suitable viscoplastic state for casting (spread ≥200 mm).

[0059] In a preferred embodiment, the pouring process is combined with vibration table compaction, with a vibration frequency of 50 Hz and a vibration time of 30-60s; after the pouring is completed, the surface needs to be covered with a waterproof membrane.

[0060] In a preferred embodiment, the curing is divided into early mold curing and later standard curing; the early mold curing is carried out by standing for 24 hours at a temperature of 20±2℃ and a relative humidity of ≥95%; after demolding, the later standard curing is carried out for 28 days at a temperature of 20±2℃ and a relative humidity of ≥95%.

[0061] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels.

[0062] Example 1

[0063] A high-strength, high-toughness concrete based on all-solid-waste functional aggregates is composed of the following raw materials in parts by weight: All-solid-waste functional aggregate: 120 parts, particle size controlled between 0.15 and 0.45 mm, compressive strength of approximately 22 MPa; Cementitious material: 100 parts, using PO42.5 grade ordinary Portland cement, with a specific surface area ≥350 m² 2 / kg; Toughening fiber: 1.2 parts, selected from PE fiber (polyethylene fiber), 12 mm in length, 20 μm in diameter, tensile strength ≥3000 MPa, and elongation at break 2.5%; Water-reducing agent: 2.0 parts, selected polycarboxylate high-performance water-reducing agent, water reduction rate ≥25%, solid content 40%; Water: 20 parts, water-to-gel ratio: 0.20, water temperature controlled at 20±1℃.

[0064] The preparation process of the functional aggregate from all solid waste is as follows: First, weigh out 50% of dewatered sludge from urban sewage treatment plants (dried at 105℃ to a moisture content ≤3% and then pulverized), 15% of calcium carbide slag, 20% of desulfurized gypsum, and 15% of slag powder by mass percentage; mix them evenly at room temperature and add 20% of the total mass of the mixture with clean water for extrusion granulation; place the granules in a standard curing room at 20℃ and 95% relative humidity for 5 days to solidify; then crush them using a jaw crusher and sieve them to obtain porous all solid waste base material with a diameter of 0.1~0.45 mm. Prepare a 3wt% (mass ratio of 1:1) composite antibacterial aqueous solution of calcium formate and sodium benzoate, immerse the all solid waste base material in it, place it in a vacuum drying oven, evacuate it to -0.09 MPa and hold it under pressure for 45 min, remove it and place it in a 70℃ forced-air drying oven to dry it to a moisture content ≤1%, thus obtaining the functional aggregate from all solid waste.

[0065] The preparation method of high-strength and high-toughness concrete based on all-solid-waste functional aggregates includes the following specific steps: (1) Put PO42.5 grade ordinary Portland cement and solid waste functional aggregate into a forced mixer and mix at low speed of 40 rpm for 4 min until the dry powder evenly coats the surface of the aggregate to obtain dry material.

[0066] (2) Add PE fiber to the dry material in two batches, each batch being 0.6 parts, with a time interval of 1.5 min between the two batches. Stir at a medium speed of 70 rpm during the addition to prevent fiber clumping. The total dispersion time is 4 min.

[0067] (3) Dissolve the polycarboxylate superplasticizer completely in water, slowly add it to the mixer, and stir at 120 rpm for 6 minutes until the slurry expansion reaches 220 mm. Pour the slurry into the dog bone mold and the 100 mm³ cubic steel mold, vibrate it on the vibrating table (frequency 50 Hz, time 40s), cover the surface with a geomembrane, cure under standard conditions (20℃, humidity 95%), let it stand for 24 hours, then demold and continue standard curing for 28 days.

[0068] The concrete in Example 1 was tested for 28-day compressive strength according to GB / T50081-2019; uniaxial direct tensile tests were conducted using dog bone specimens according to JC / T2461-2018, and the ultimate tensile strain was tested using DIC (Digital Image Correlation Technology); and the inhibition rate was tested after 14 days of inoculation with sulfur-oxidizing bacteria (Acidithiobacillus thiooxidans) using the patch method according to JC / T897-2014. The measured 28-day compressive strength was 92.5 MPa, the ultimate tensile strain was 4.5%, the average crack width was 65 μm, and the inhibition rate against sulfur-oxidizing bacteria (Acidithiobacillus thiooxidans) was as high as 96.2%.

[0069] Example 2

[0070] A high-strength, high-toughness concrete based on all-solid-waste functional aggregates is composed of the following raw materials in parts by weight: All solid waste functional aggregate: 100 parts, particle size controlled between 0.1 and 2.5 mm; Cementitious material: 100 parts, using PO52.5 grade ordinary Portland cement; Toughening fiber: 0.8 parts, selected from PE fiber, 12 mm in length, 15 μm in diameter, tensile strength ≥3000 MPa; Water-reducing agent: 1.5 parts, using polycarboxylate high-performance water-reducing agent; Water: 18 parts, water-to-gel ratio is 0.18, water temperature is controlled at 20±1℃.

[0071] The preparation process of the solid waste functional aggregate is as follows: the solid waste raw material composition is 45% river dredging sludge, 20% carbide slag, 25% desulfurized gypsum, and 10% slag powder; after granulation and solidification, it is crushed and screened; the antibacterial solution used for impregnation is a 2wt% calcium formate solution, the pressure is maintained at -0.08 MPa for 30 min under vacuum, and then dried at 80℃.

[0072] The preparation method of high-strength and high-toughness concrete based on all-solid-waste functional aggregates includes the following specific steps: Step (1) is the same as in Example 1, except that the low-speed stirring speed is 30 rpm and the time is 3 min; (2) Add PE fiber to the dry material in two batches, with an interval of 1 min, and stir at medium speed of 60 rpm for 3 min. (3) Add water and water-reducing agent mixture, stir at 150 rpm for 5 min; vibrate on a vibrating table for 30 s, and then cure as in Example 1.

[0073] According to the test specifications, precast concrete specimens with initial microcracks of 50 μm were prepared from the concrete of Example 2 and immersed in a simulated bioacid environment (containing SOB bacterial solution, sulfuric acid medium with initial pH=2) for 90 days of cyclic erosion. The results showed that the mass loss rate was only 1.8%, and after being placed in an underground simulated humidity environment for 28 days, the self-healing closure rate of the microcracks reached 88.5% as determined by ultrasonic wave velocity.

[0074] Example 3

[0075] A high-strength, high-toughness concrete based on all-solid-waste functional aggregates is composed of the following raw materials in parts by weight: All solid waste functional aggregate: 150 parts, particle size controlled between 0.1 and 0.6 mm; Cementitious materials: 100 parts cementitious materials, including 95 parts cement and 5 parts ultrafine slag powder; Toughening fiber: 1.5 parts, selected from a blend of PE fiber and PVA fiber (mass ratio 2:1). Water-reducing agent: 2.5 parts, polycarboxylate high-performance water-reducing agent is selected; Water: 22 parts, water-to-gel ratio: 0.22, water temperature controlled at 20±1℃.

[0076] The preparation process of the solid waste functional aggregate is as follows: the solid waste raw material composition is 55% municipal sludge, 10% carbide slag, 15% desulfurized gypsum, and 20% slag powder; the antibacterial solution used for impregnation is a sodium benzoate solution with a mass concentration of 5wt%, the pressure is maintained at -0.1 MPa for 60 min, and the material is dried at 60℃.

[0077] The preparation method of high-strength and high-toughness concrete based on all-solid-waste functional aggregates includes the following specific steps: Step (1) is the same as in Example 1, except that the low-speed stirring speed is 50 rpm and the time is 5 min; (2) Add the mixed fiber to the dry material in three batches, with a 2-minute interval between each batch, and stir at medium speed of 80 rpm for 5 minutes. (3) Add water and water-reducing agent after mixing, stir at 100 rpm for 8 min; vibrate on a vibrating table for 50 s, and then cure as in Example 1.

[0078] The specimens from Example 3 were subjected to the same tensile and bio-acid erosion tests. The ultimate tensile strain was 4.8%, the mass loss rate after 90 days of bio-acid erosion was as low as 1.3%, and it exhibited an extremely dense micro-crack pattern (average crack width of about 50 μm).

[0079] Multi-crack formation in concrete in Examples 1-3, such as Figure 1 As shown.

[0080] The properties of various concrete materials in Examples 1-3 and traditional pipe concrete are statistically analyzed, and the results are shown in Table 1: Table 1 Comparison of concrete performance between the examples and traditional pipe materials. .

[0081] The following tests were conducted: 28-day compressive strength was tested according to GB / T50081-2019; ultimate tensile strain and ultimate average crack width were tested according to JC / T2461-2018; the inhibition rate of sulfur-oxidizing bacteria (Acidithiobacillus thiooxidans) (SOB) was tested using the patch method according to JC / T897-2014; the mass loss rate was tested using a 90-day accelerated bio-acid erosion test; and the 20-day crack self-healing closure rate was tested using microscopic morphology combined with ultrasonic wave velocity method. Examples 1-3 are as follows. Figure 2 As shown. In Examples 1-3, the concrete exhibits multi-crack formation (e.g. Figure 1 ).

[0082] Figure 1 From left to right, the images show the crack morphology of concrete prepared in Examples 1, 2, and 3 under load. As can be clearly observed from the images, the concrete surface does not exhibit penetrating macroscopic cracks, but rather multiple fine and uniformly distributed microcracks. The crack width was measured to be mainly controlled within the range of 70–90 μm. This confirms that the high-strength polyethylene fibers play a significant bridging and toughening role in the matrix, successfully transforming harmful macroscopic cracks into stable microcracks.

[0083] Figure 2This reflects the self-healing evolution of cracks in Examples 1-3 over time. The top three images horizontally represent the self-healing evolution of cracks in Example 1, the middle three horizontally represent the self-healing evolution of cracks in Example 2, and the bottom three horizontally represent the self-healing evolution of cracks in Example 3. Furthermore, the leftmost three vertically images, from top to bottom, represent the initial state of Examples 1-3, the middle three vertically images, from top to bottom, represent the healing process of Examples 1-3, and the rightmost three vertically images, from top to bottom, represent the final state of Examples 1-3. Initial state (day 0): Cracks are clearly visible with sharp edges; Healing process (days 7-14): White flocculent or crystalline products begin to form at the crack edges, and the crack width significantly narrows; Final state (day 28): Cracks are basically completely filled and closed by newly formed crystalline products such as calcium carbonate, and the surface tends to be smooth. This evolution process intuitively demonstrates that the unhydrated multi-source solid waste particles in the matrix underwent a secondary hydration reaction induced by environmental moisture, achieving in-situ self-healing of microcracks, and all three examples showed a consistent healing pattern.

[0084] Figure 3 This reflects the antibacterial effect of the concrete aggregate in Examples 1-3.

[0085] like Figure 3 As shown in the left figure, the pH value of the control group of carbide slag aggregate without antibacterial loading remained at a low level of approximately 3.2-3.4 throughout the entire test period, indicating that sulfur-oxidizing bacteria maintained vigorous metabolic activity and continued to produce acid. In contrast, the experimental group of functional aggregate loaded with calcium formate, copper acetate, and DDBAC antibacterial agents showed a completely different trend. In the early stage of cultivation (0-5 days), the pH value decreased slightly due to the initial metabolism of bacteria. However, as the antibacterial agents were released from the porous aggregate, bacterial metabolism was significantly inhibited, and the acid production capacity decreased. In particular, the pH value of the calcium formate and copper acetate loading groups began to rise significantly after 10 days of cultivation, reaching above 5.0 by day 30. This upward trend directly proves that the acid production metabolism of bacteria was effectively blocked, and even caused them to die and dissolve due to unsuitable environment, thus achieving the antibacterial effect of inhibiting the production of biological acids from the source.

[0086] like Figure 3As shown in the right figure, the OD value of the Ref control group decreased from approximately 0.78 to approximately 0.48 in the early stage of the experiment, and then fluctuated within the range of 0.35–0.48, indicating that the sulfur-oxidizing bacteria maintained a high survival level and growth activity. In contrast, the OD values ​​of Examples 1–3 all showed a continuous decreasing trend with the extension of culture time: the decrease was more significant in Examples 1 and 2 after about 15 days of culture, and dropped to approximately 0.07–0.08 at 30 days; the rate of decrease in Example 3 was relatively slower, but the OD value also dropped to approximately 0.10 at 30 days. The above results indicate that the solid waste functional aggregate loaded with antibacterial agents can effectively inhibit the growth and reproduction of sulfur-oxidizing bacteria, and the antibacterial effect of Examples 1 and 2 is more significant. Figure 3 As shown in the left figure, the increasing trend of pH value in the systems of each embodiment indicates that the antibacterial effect of functional aggregates helps to reduce the acid-producing activity of sulfur-oxidizing bacteria, thereby mitigating the risk of bio-acid erosion of concrete.

[0087] Figure 4 and Figure 5 These are backscattered images of the aggregate interface in Examples 1-3, where... Figure 4 From left to right are backscattering images of Examples 1 and 2. Figure 5 This is the backscattering diagram of Example 3. Figure 4 and Figure 5 The study clearly revealed that cracks preferentially penetrate aggregate particles rather than bypass the interface transition zone, confirming that the strength of the functional aggregate is lower than that of the concrete matrix. A large amount of high-brightness, dense hydration products were observed filling the aggregate fracture surface and cracks, indicating that the active calcium ions released after aggregate fracture generated healing products such as calcium carbonate in situ at the cracks, effectively repairing the microcracks.

[0088] Among them, the testing and performance standards for traditional pipe concrete are as follows: 1.28-day compressive strength (40–50 MPa) "Concrete and Reinforced Concrete Drainage Pipes" (GB / T11836-2009): specifies that the concrete strength grade of conventional underground drainage pipes is usually C40 to C50.

[0089] 2. Ultimate tensile strain (0.01~0.02%) The Technical Specification for Fiber Reinforced Concrete Structures (CECS38:2004) states that ordinary pipe concrete without the addition of high elastic modulus microfibers exhibits typical brittle fracture under tension, with extremely low ultimate tensile strain.

[0090] 3. Antibacterial rate of sulfur-oxidizing bacteria (Acidithiobacillus thiooxidans) and bioacid erosion Based on relevant literature and field measurements on environmental microbial erosion, ordinary silicate cement concrete does not have antibacterial properties (the antibacterial rate is close to the natural fluctuation ≤5%). Under the accelerated environment of biological acid (sulfuric acid) at pH=2, the mass loss rate is usually as high as 15-20% after 90 days, and the surface peels off severely.

[0091] 4. Crack self-healing closure rate Traditional concrete, once it cracks, is usually a macroscopic through crack with a width of more than 200μm, which exceeds the limit of physical crystallization self-healing (usually required to be ≤100μm), and is therefore considered unhealable.

[0092] As can be seen from Table 1, compared with traditional pipe concrete, the high-strength and high-toughness concrete based on all-solid waste functional aggregate provided by the present invention has significant strain hardening characteristics, ultra-high ultimate tensile strain, long-term precise targeted antibacterial ability and extremely high microcrack self-healing rate, and can serve for a long time in harsh underground biological acid and complex load coupling environment.

[0093] Table 2 shows the applicable environment and some core process mechanisms of the concrete used in Examples 1-3.

[0094] Table 2 Applicable Environment and Mechanism Matching Table .

[0095] As can be seen from Examples 1-3 in Table 2, this invention can provide high-performance concrete that meets different underground and marine corrosion prevention needs by adjusting the percentage of solid waste mass, the type of antibacterial agent, and fiber parameters. While ensuring the core properties of high strength, high toughness, and resistance to biological erosion, it realizes the resource utilization of large quantities of urban sewage sludge, providing a customized solution for municipal lifeline engineering.

[0096] Examples 4-10 The specific raw material ratios and composition of the solid waste base material in Examples 4-10 are shown in Table 3 (based on 100 parts of cementitious material, the remaining components are weighed according to the corresponding proportions; each component of the solid waste base material is a mass percentage, and the sum of the four is 100%).

[0097] Table 3. Raw material ratios and composition of solid waste base material in Examples 4-10 .

[0098] The high-strength and high-toughness concretes based on all-solid-waste functional aggregates prepared in Examples 4 to 10 were subjected to conventional basic performance tests (28-day compressive strength was tested according to GB / T50081-2019; uniaxial tensile properties and average crack width were tested according to JC / T2461-2018; and antibacterial rate was tested according to JC / T897-2014). The performance indicators are shown in Table 4.

[0099] Table 4. Main performance test results of Examples 4-10

[0100] Comparative Example 1 The difference from Example 1 is that the solid waste functional aggregate is replaced with an equal weight proportion of natural quartz sand (particle size 0.15-0.45mm), and no PE toughening fibers are added; that is, it degenerates into traditional ordinary concrete. Other process steps are the same as in Example 1.

[0101] Comparative Example 2 The difference from Example 1 is that the "preparation of antibacterial aqueous solution and vacuum impregnation" step was omitted in the preparation of the solid waste sludge aggregate (i.e., only blank porous solid waste aggregate was used). Other raw material ratios and steps are the same as in Example 1.

[0102] Comparative Example 3 The difference from Example 1 is that the solid waste functional aggregate is replaced with an equal weight proportion of natural quartz sand; at the same time, the same dosage of calcium formate and sodium benzoate antibacterial agents as in Example 1 are directly dissolved in water required for the water-cement ratio and incorporated into the matrix during the wet mixing stage. Other steps are the same as in Example 1.

[0103] Comparative Example 4 The difference from Example 1 is that the toughening fiber (PE fiber) is omitted. The other raw material ratios and steps are the same as in Example 1.

[0104] Comparative Example 5 The difference from Example 1 is that the all-solid waste functional aggregate was prepared using a high-temperature (1000°C) ultra-high-temperature sintering process, which completely densified it and achieved a compressive strength of up to 80 MPa. Subsequently, only a surface antibacterial agent was applied (vacuum impregnation was not possible due to the loss of internal pores). Other raw material ratios and steps were the same as in Example 1.

[0105] The properties of concrete in Comparative Examples 1-5 were tested using the same test methods as in Example 1, and the results are shown in Table 5.

[0106] Table 5 Comparison of Performance Test Results (Comparative Example)

[0107] As shown in Table 5, Comparative Example 1, by completely omitting the solid waste aggregate and fiber system, exhibited typical brittle fracture and severe acid corrosion, verifying the necessity of the synergistic system of this invention; Comparative Example 2, by omitting antibacterial agent impregnation, had a mass loss rate as high as 16.2% and a self-healing rate reduced to 45.6%, indicating that the lack of an "antibacterial and acid-inhibiting" mechanism would lead to the secondary dissolution and destruction of the self-healing products; Comparative Example 3, by freely incorporating the antibacterial agent into the matrix, resulted in a large amount of the agent being deeply encapsulated by the hydration products and losing its activity, with an antibacterial rate of only 42.5%, highlighting the "aggregate pores" The invention demonstrates the targeted drug release advantage of "crack encapsulation-stress release"; Comparative Example 4 omitted PE fibers, resulting in the loss of microcrack control capabilities, and the generation of wide cracks accelerated the large-volume intrusion of acid, which could not be closed; Comparative Example 5 made the aggregate strength too high and dense, causing cracks to extend directly around the aggregate at the interface during expansion, completely losing the triggering mechanism of "artificial defect-induced aggregate fracture", and the antibacterial agent could not be released in a targeted manner (the antibacterial rate was only 25.4%), which, from the opposite perspective, confirms the importance of the present invention in deliberately reducing the aggregate strength to achieve the synergistic design of "stress-induced drug release".

[0108] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A high-strength, high-toughness concrete based on all-solid-waste functional aggregates, characterized in that, The product comprises cementitious materials, functional aggregates from solid waste, water, water-reducing agents, and toughening fibers. The functional aggregates from solid waste consist of a porous solid waste matrix and an antibacterial agent loaded within its pores. Specifically, 40-60% sludge, 10-20% carbide slag, 15-25% desulfurized gypsum, and 10-20% slag are mixed and granulated at a total mass percentage of 100%, with a particle size controlled at 0.1-2.5 mm. After curing, a porous solid waste matrix with mesoporous and macroporous structures is obtained. An antibacterial agent is then loaded into the pores of the porous solid waste matrix, with the antibacterial agent loading amount being 0.2-1% of the mass of the solid waste matrix. After drying, a porous functional aggregate with the antibacterial agent loaded within its pores is obtained. The antibacterial agent is selected from calcium formate and / or sodium benzoate. Based on a mass of 100 parts of the cementitious material, the amounts of the remaining raw materials are as follows: 30-150 parts of solid waste functional aggregate; 18-22 parts of water; 1.5-2.5 parts of water-reducing agent; 0.8-1.5 parts of toughening fiber.

2. The high-strength, high-toughness concrete based on all-solid-waste functional aggregates according to claim 1, characterized in that, The toughening fiber is selected from PE fiber and / or PVA fiber.

3. The high-strength, high-toughness concrete based on all-solid-waste functional aggregates according to claim 2, characterized in that, The toughening fiber is a PE fiber with a diameter of 15~25 μm, a nominal tensile strength ≥3000 MPa, a Young's modulus of 90~110 GPa, and an elongation at break of 2~3%.

4. The high-strength, high-toughness concrete based on all-solid-waste functional aggregates according to claim 1, characterized in that, The sludge is obtained from municipal sewage sludge or municipal river sludge treatment, with a moisture content of ≤3%; the moisture content of municipal sewage sludge or municipal river sludge is controlled between 35% and 70%.

5. A method for preparing high-strength, high-toughness concrete based on all-solid-waste functional aggregates as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Prepare all-solid-waste functional aggregates according to claim 1; (2) High-strength and high-toughness concrete dry material premixing and fiber dispersion: The cementitious material and the all-solid waste functional aggregate obtained in step (1) are uniformly mixed according to the mass parts of the raw materials described in claim 1 to obtain a dry mixture. Then, the toughening fiber is added to the dry mixture in 2 to 3 batches and stirred and dispersed. (3) Wet mixing and molding: Water and water-reducing agent are mixed according to the mass fraction of the raw materials described in claim 1 and then added to the dry mixture. The water-cement ratio is controlled at 0.18~0.

22. After stirring evenly until it has good fluidity, it is poured and molded. After curing, the high-strength and high-toughness concrete based on all solid waste functional aggregate is obtained.

6. The application of high-strength and high-toughness concrete based on all-solid-waste functional aggregates in antibacterial and self-healing environments according to any one of claims 1-4.

7. A method for antibacterial self-healing of high-strength, high-toughness concrete based on all-solid-waste functional aggregates in a wastewater environment, as described in any one of claims 1-4, characterized in that... The process includes the following steps: (1) High-strength and high-toughness concrete based on all-solid-waste functional aggregate cracks under the coupling effect of tensile load and sewage ion erosion and deterioration; (2) Microcracks induced by all-solid-waste functional aggregate preferentially extend to the all-solid-waste functional aggregate and cause it to break, thereby triggering the in-situ release of antibacterial agents inside the pores of the all-solid-waste functional aggregate. The released antibacterial ions target and destroy the metabolism and enzyme activity of sulfur-oxidizing bacteria, block the generation of biological acids from the source, realize the antibacterial function, and reduce the biological acid erosion effect on the concrete surface; (3) When the cracks extend, the interface bonding force between the toughening fiber and the concrete matrix and the fiber pull-out effect bridge the cracks, absorb energy, and limit the macroscopic cracks to micro-fine steady-state cracks; (4) All-solid-waste functional aggregate releases calcium ions, which react with sulfate ions or carbonate ions in sewage to generate precipitated minerals, repair the cracks of high-strength and high-toughness concrete based on all-solid-waste functional aggregate, and realize the self-healing function.

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