All-solid-waste high-performance conductive concrete and preparation method thereof

Abstract

The invention relates to the related technical field of building materials, in particular to full-solid-waste high-performance conductive concrete and a preparation method thereof.The full-solid-waste high-performance conductive concrete is prepared from 600 kg of sulphoaluminate cement, 200 kg of superfine mineral powder, 150 kg of silica fume, 50 kg of desulfurized gypsum, 800 kg of iron tailing sand, 78-124.8 kg of steel fibers, 7.2-18 kg of carbon fibers, 200 kg of water and 15 kg of a water reducing agent according to the dosage per cubic meter. According to the all-solid-waste high-performance conductive concrete and the preparation method thereof, sulphoaluminate cement is used as a gelling main body, superfine mineral powder, silica fume and desulfurized gypsum are used for synergistically exciting the activity of a gelling system, and iron tailing sand is used for replacing natural sand to realize all-solid waste of aggregate and provide an iron element for a matrix to enhance the conductivity; a high-efficiency conductive network is constructed, the mechanical property is enhanced, and the working performance is guaranteed by matching with a water reducing agent.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, and in particular to a high-performance conductive concrete made entirely from solid waste and its preparation method. Background Technology

[0002] With the rapid development of industrialized and intelligent construction, the demand for concrete materials with excellent mechanical properties and functional characteristics (such as conductivity) is becoming increasingly urgent in fields such as intelligent buildings (e.g., self-sensing structures), electromagnetic shielding engineering (e.g., electronic equipment protection), and structural health monitoring (e.g., crack self-diagnosis). Among these, high-performance concrete, due to its high compressive strength and good durability (impermeability, frost resistance, and erosion resistance), has become a key material for major infrastructure and special buildings. Conductive concrete, as an important branch of functional concrete, can achieve structural-functional integration through its conductivity, further expanding the application boundaries of concrete materials. However, existing technologies still have significant pain points when balancing the three core requirements of "high performance," "conductivity," and "green environmental protection": The dependence on raw materials and resource consumption in traditional high-performance concrete: Currently, most high-performance concrete uses high-purity cement and natural sand as core raw materials. Although some formulas incorporate small amounts of mineral admixtures (such as ordinary mineral powder), the over-exploitation of natural aggregates (such as river sand) can easily lead to ecological damage. Moreover, the use of high-purity raw materials drives up production costs, which is inconsistent with the development direction of green building materials. At the same time, a large amount of solid waste generated in the industrial sector (such as desulfurization gypsum, iron tailings sand, ultrafine mineral powder, etc.) has long faced the problem of accumulation. Such solid waste not only occupies land resources, but may also cause soil and air pollution due to leaching, dust and other problems. Its high-value utilization has become a core issue in the fields of environmental protection and resource recycling.

[0003] The performance imbalance of conductive concrete: Existing conductive concretes mostly construct conductive pathways by adding single carbon-based materials (such as carbon fiber and carbon black) or metallic materials (such as steel fiber and metal powder), but this has obvious drawbacks: If only carbon fiber is added, its single filament diameter is small and its surface energy is high, making it prone to agglomeration, resulting in an uneven distribution of the conductive network, and the effect of carbon fiber alone on enhancing the mechanical strength of concrete is limited; if only steel fiber is added, although it can improve mechanical strength and conductivity, the high density of steel fibers makes them prone to settling, making it difficult to form a uniform conductive network, and high dosage can easily lead to a decrease in the workability (such as fluidity) of concrete. In addition, existing conductive concretes rarely incorporate "all-solid-waste raw materials" in their design, making it difficult to simultaneously meet the synergistic requirements of "functionality (conductivity), mechanical properties (high performance), and environmental protection (solid waste utilization)".

[0004] The lack of integrated technology: Currently, the industry lacks a technological solution that deeply integrates "the application of all solid waste raw materials," "high-performance mechanical assurance," and "excellent conductivity." Some solid waste-admixed concrete focuses only on solid waste disposal, neglecting mechanical properties and functional characteristics; while some high-performance conductive concretes can meet performance requirements, they rely on natural raw materials and high-cost conductive fillers, resulting in insufficient environmental friendliness and economic efficiency. This technological gap makes it difficult for existing products to adapt to the comprehensive requirements of "green, high-performance, and functional" in fields such as intelligent buildings and electromagnetic shielding, limiting the functional upgrading and industrial transformation of concrete materials. Summary of the Invention

[0005] The purpose of this invention is to provide a high-performance conductive concrete made entirely from solid waste and its preparation method, so as to solve the problems of insufficient utilization of solid waste, imbalance between high performance and conductivity, and high resource and environmental costs mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a high-performance conductive concrete made entirely from solid waste, comprising the following components per cubic meter: 600 kg of sulfoaluminate cement, 200 kg of ultrafine mineral powder, 150 kg of silica fume, 50 kg of desulfurized gypsum, 800 kg of iron tailings sand, 78-124.8 kg of steel fiber, 7.2-18 kg of carbon fiber, 200 kg of water, and 15 kg of water-reducing agent; The steel fiber content accounts for 1%-1.6% of the total concrete volume, the carbon fiber is chopped carbon fiber, the chopped carbon fiber content accounts for 0.4%-1% of the total concrete volume, and the total content of steel fiber and chopped carbon fiber is 2% of the total concrete volume. The concrete has a 28-day compressive strength exceeding 80 MPa and a conductivity ≥ 0.02 S / m.

[0007] Preferably, the strength grade of the sulfoaluminate cement is 52.5 or higher.

[0008] Preferably, the steel fiber has a length of 13 mm and a diameter of 0.2 mm.

[0009] Preferably, the chopped carbon fiber has a length of 9 mm, a diameter of 10 μm, and a tensile strength ≥3000 MPa.

[0010] A method for preparing high-performance conductive concrete made entirely from solid waste includes the following steps: (1) Sulfoaluminate cement, ultrafine mineral powder, silica fume, desulfurized gypsum and 50% of the total amount of chopped carbon fiber are put into a mixer and stirred at a low speed of 62.5 r / min for 3 min to obtain mixture A. (2) Keep the stirring rate at 62.5 r / min, add the mixture of water and water-reducing agent premixed into the mixture A obtained in step (1), and add the remaining 50% of short-cut carbon fiber to the mixer in small amounts several times, and continue stirring for 3-6 min to obtain mixture B; (3) Keep the stirring rate at 62.5 r / min, add iron tailings sand to the mixture B obtained in step (2), and then add steel fiber to the mixer in small amounts several times. Continue stirring for 3-6 minutes to obtain the final mixture C. (4) Pour the mixture C obtained in step (3) into a 40mm×40mm×160mm triple concrete mold, vibrate it to make it dense, cover it with plastic wrap, and demold it after curing in a constant temperature and humidity environment for 24 hours. (5) Place the demolded specimen in a constant temperature and humidity curing chamber at 20℃ and 95%RH for 28 days to obtain the finished product.

[0011] Preferably, in step (4), two electrodes with a aperture of 4 mesh are preset in the mold. The electrodes are brass mesh electrodes with an electrode size of 30mm×60mm. The distance between the two electrodes is 120mm, and the distance between each electrode and the side end face of the test block is 20mm.

[0012] Compared with the prior art, the beneficial effects of the present invention are: 1. Achieve efficient utilization of all solid waste resources: Using industrial solid waste as the core raw material, desulfurized gypsum (byproduct of industrial flue gas desulfurization), iron tailings (byproduct of mineral mining), and ultrafine mineral powder (byproduct of the iron and steel industry) are used as components and aggregates of the cementitious system, respectively, to replace natural gypsum, natural sand, and some high-purity admixtures in traditional high-performance concrete. This achieves the complete solid waste utilization of "cementing auxiliary components-aggregates" in concrete raw materials, effectively disposing of industrial solid waste (each cubic meter of a single formula can dispose of 800 kg of iron tailings, 50 kg of desulfurized gypsum, and 200 kg of ultrafine mineral powder), reducing dependence on natural resources, reducing environmental pollution caused by solid waste accumulation, and simultaneously reducing raw material costs, thereby improving the environmental benefits and economic competitiveness of the product.

[0013] 2. Ensuring high-performance mechanical properties of concrete: By optimizing the cementitious system and aggregate gradation design, using sulfoaluminate cement as the main cementitious material, and utilizing the synergistic effect of ultrafine mineral powder, silica fume, and desulfurized gypsum to activate the cementitious system, while replacing natural sand with iron tailings sand (after gradation optimization) to improve the interfacial bonding strength between aggregate and cement paste; combined with the synergistic reinforcement effect of steel fiber and carbon fiber, ensuring that the 28-day compressive strength of concrete stably reaches 80MPa.

[0014] 3. Constructing a highly efficient and synergistic conductive network to achieve excellent conductivity: Addressing the shortcomings of single conductive fillers, a synergistic admixture scheme of "steel fiber + carbon fiber" is adopted. Steel fibers (13mm long, 0.2mm in diameter) possess high conductivity and strong mechanical reinforcement, serving as the "main pathway" of the conductive network. Short-cut carbon fibers, with high conductivity and crack-resistant dispersibility, serve as the "auxiliary pathway," filling the gaps between steel fibers and avoiding conductive blind spots. By controlling the steel fiber content (1%-1.6% of total volume) and the carbon fiber content (0.4%-1% of total volume), with the total fiber content fixed at 2% of the total volume, a uniform and continuous synergistic conductive network is ensured, resulting in a stable concrete conductivity of over 0.02 S / m, meeting the conductivity requirements of intelligent building structural health monitoring and electromagnetic shielding projects.

[0015] 4. Optimize the preparation process to ensure industrial feasibility: Using conventional concrete mixing equipment and curing processes, the problem of carbon fiber agglomeration and steel fiber settling is solved by "staged feeding" (first dry mixing of cementitious raw materials and part of carbon fiber, then adding water-water reducing agent mixture and the remaining carbon fiber, and finally adding aggregate and steel fiber), thus ensuring the workability of concrete. The curing process adopts "24-hour constant temperature and humidity initial curing and 28-day standard curing", which does not require special equipment and is easy for existing concrete production enterprises to directly adapt, reducing the technical threshold and equipment investment cost for industrialization.

[0016] 5. Achieving synergy among environmental protection, technology, and economy: By achieving the above goals, the product will simultaneously possess the comprehensive advantages of solid waste disposal, high performance with conductivity, and low cost, meeting the functional requirements of special construction fields, promoting the transformation of concrete materials from "structural materials" to "integrated structural-functional materials," and providing the industry with replicable and scalable technical solutions. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the preparation process of high-performance conductive concrete made entirely from solid waste according to the present invention. Figure 2 This is a schematic diagram of the copper mesh arrangement in the high-performance conductive concrete made entirely from solid waste, according to the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0019] Please see Figure 1-2The present invention provides a technical solution: a high-performance conductive concrete made entirely from solid waste, comprising the following components per cubic meter: 600 kg of sulfoaluminate cement, 200 kg of ultrafine mineral powder, 150 kg of silica fume, 50 kg of desulfurized gypsum, 800 kg of iron tailings sand, 78-124.8 kg of steel fiber, 7.2-18 kg of carbon fiber, 200 kg of water, and 15 kg of water-reducing agent; The steel fiber content accounts for 1%-1.6% of the total concrete volume, and the carbon fiber is short-cut carbon fiber, accounting for 0.4%-1% of the total concrete volume. The total content of steel fiber and short-cut carbon fiber is 2% of the total concrete volume. The concrete has a 28-day compressive strength exceeding 80 MPa and a conductivity ≥ 0.02 S / m.

[0020] Furthermore, the strength grade of sulfoaluminate cement is 52.5 or higher.

[0021] Furthermore, the steel fibers are 13mm long and 0.2mm in diameter.

[0022] Furthermore, the chopped carbon fibers have a length of 9 mm, a diameter of 10 μm, and a tensile strength of ≥3000 MPa.

[0023] A method for preparing high-performance conductive concrete made entirely from solid waste includes the following steps: (1) Sulfoaluminate cement, ultrafine mineral powder, silica fume, desulfurized gypsum and 50% of the total amount of chopped carbon fiber are put into a mixer and stirred at a low speed of 62.5 r / min for 3 min to obtain mixture A. (2) Keep the stirring rate at 62.5 r / min, add the mixture of water and water-reducing agent premixed into the mixture A obtained in step (1), and add the remaining 50% of short-cut carbon fiber to the mixer in small amounts several times, and continue stirring for 3-6 min to obtain mixture B; (3) Keep the stirring rate at 62.5 r / min, add iron tailings sand to the mixture B obtained in step (2), and then add steel fiber to the mixer in small amounts several times. Continue stirring for 3-6 minutes to obtain the final mixture C. (4) Pour the mixture C obtained in step (3) into a 40mm×40mm×160mm triple concrete mold, vibrate it to make it dense, cover it with plastic wrap, and demold it after curing in a constant temperature and humidity environment for 24 hours. (5) Place the demolded specimen in a constant temperature and humidity curing chamber at 20℃ and 95%RH for 28 days to obtain the finished product.

[0024] Furthermore, in step (4), two electrodes with a aperture of 4 mesh are preset in the mold. The electrodes are brass mesh electrodes with an electrode size of 30mm×60mm. The distance between the two electrodes is 120mm, and the distance between each electrode and the side end face of the test block is 20mm. Example

[0025] Experimental groups 1 to 4 and a control group were provided for comparative experiments. The raw material ratios (kg / m3) for the five groups are as follows: All five groups had a volume of 1L. The amounts of sulfoaluminate cement, ultrafine mineral powder, silica fume, desulfurized gypsum, iron tailings sand, and water were fixed at 0.6kg, 0.2kg, 0.15kg, 0.05kg, 0.8kg, and 0.2kg, respectively. The water-cement ratio was 0.2 and the amount of water-reducing agent was 0.015kg. The only difference was the amount of steel fiber and carbon fiber. The control group did not add carbon fiber (0% amount) and the amount of steel fiber was 0.156kg. The amounts of steel fiber in experimental groups 1 to 4 were 0.1248kg, 0.1092kg, 0.0936kg, and 0.078kg, respectively, and the amounts of carbon fiber were 0.0072kg, 0.0108kg, 0.0144kg, and 0.018kg, respectively.

[0026] Preparation method: (1) Add sulfoaluminate cement, ultrafine mineral powder, silica fume, desulfurized gypsum and 50% carbon fiber to a mixer and dry mix for 3 minutes until uniform so that the short-cut carbon fiber is initially dispersed. (2) Add water, water-reducing agent, and 50% short-cut carbon fiber, and stir for 3-6 minutes to disperse the short-cut carbon fiber again; (3) Add iron tailings sand and steel fibers to a mixer and stir for 3-6 minutes to obtain a uniform mixture; (4) Pour into a triple 40mm×40mm×160mm casting mold. After casting, electrodes need to be pre-set inside the specimen: use two 4-mesh brass meshes as electrodes, with an electrode size of 30mm×60mm, a 120mm interval between the two electrodes, and a distance of 20mm between each electrode and the side end face of the specimen. After vibration compaction, place in a constant temperature and humidity (20℃, 95%RH) curing room for 24 hours before demolding and continue curing for 28 days.

[0027] Conductivity test method: After the specimen has been cured to the specified age of 28 days, the resistance R (unit: Ω) of the concrete specimen is measured by using the "two-electrode method" and connecting to an AC power supply; the resistivity ρ (unit: Ω·m) of the concrete is calculated according to formula (1), and then the conductivity is obtained by converting the resistivity to the reciprocal relationship between the conductivity and the resistivity: In Equation 1: ρ is the concrete resistivity (unit: Ω·m); R is the concrete resistance (unit: Ω); s is the effective area of ​​a single brass mesh electrode inserted into the concrete (unit: m²); L is the distance between the two electrodes (unit: m).

[0028] In Equation 2: σ Concrete conductivity (unit: S / m, 1S=1 / Ω). ρ The concrete resistivity calculated above is given in Ω·m.

[0029] The performance test results are shown in the table below: Table 1 Compressive Strength (MPa)

[0030] Table 2 Conductivity (S / m)

[0031] This invention significantly improves the synergistic effect between materials by optimizing the ratio of all-solid waste raw materials, steel fiber and carbon fiber. Test results show that experimental groups 1 and 2 have both ultra-high performance and excellent conductivity, demonstrating significant technological advancement.

[0032] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-performance conductive concrete made entirely from solid waste, characterized in that, The following components are included per cubic meter: 600 kg of sulfoaluminate cement, 200 kg of ultrafine mineral powder, 150 kg of silica fume, 50 kg of desulfurized gypsum, 800 kg of iron tailings sand, 78-124.8 kg of steel fiber, 7.2-18 kg of carbon fiber, 200 kg of water, and 15 kg of water-reducing agent. The steel fiber content accounts for 1%-1.6% of the total concrete volume, the carbon fiber is chopped carbon fiber, the chopped carbon fiber content accounts for 0.4%-1% of the total concrete volume, and the total content of steel fiber and chopped carbon fiber is 2% of the total concrete volume. The concrete has a 28-day compressive strength exceeding 80 MPa and a conductivity ≥ 0.02 S / m.

2. The high-performance conductive concrete made entirely from solid waste according to claim 1, characterized in that, The strength grade of the sulfoaluminate cement is 52.5 or higher.

3. The high-performance conductive concrete made entirely from solid waste according to claim 1, characterized in that, The steel fiber is 13 mm long and 0.2 mm in diameter.

4. The high-performance conductive concrete made entirely from solid waste according to claim 1, characterized in that, The chopped carbon fiber has a length of 9 mm, a diameter of 10 μm, and a tensile strength of ≥3000 MPa.

5. A method for preparing a high-performance conductive concrete made entirely from solid waste as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Sulfoaluminate cement, ultrafine mineral powder, silica fume, desulfurized gypsum and 50% of the total amount of chopped carbon fiber are put into a mixer and stirred at a low speed of 62.5 r / min for 3 min to obtain mixture A. (2) Keep the stirring rate at 62.5 r / min, add the mixture of water and water-reducing agent premixed into the mixture A obtained in step (1), and add the remaining 50% of short-cut carbon fiber to the mixer in small amounts several times, and continue stirring for 3-6 min to obtain mixture B; (3) Keep the stirring rate at 62.5 r / min, add iron tailings sand to the mixture B obtained in step (2), and then add steel fiber to the mixer in small amounts several times. Continue stirring for 3-6 minutes to obtain the final mixture C. (4) Pour the mixture C obtained in step (3) into a 40mm×40mm×160mm triple concrete mold, vibrate it to make it dense, cover it with plastic wrap, and demold it after curing in a constant temperature and humidity environment for 24 hours. (5) Place the demolded specimen in a constant temperature and humidity curing chamber at 20℃ and 95%RH for 28 days to obtain the finished product.

6. The method for preparing high-performance conductive concrete from all solid waste according to claim 5, characterized in that, In step (4), two electrodes with a 4-mesh aperture are preset in the mold. The electrodes are brass mesh electrodes with a size of 30mm×60mm. The distance between the two electrodes is 120mm, and the distance between each electrode and the side end face of the test block is 20mm.

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