Fiber-reinforced concrete product with the possibility of continuous volumetric condition monitoring of the structure

Abstract

Fiber-reinforced concrete product with an integrated system for continuous volumetric condition monitoring, comprising a cement matrix and dispersed fibers, characterized in that the fibers consist of basalt or glass material and are coated with an electrically conductive layer based on graphene or thermally expanded graphite, wherein electrodes are arranged in the body of the product which are connected to a system for measuring electrical resistance or impedance.

Description

[0001] The utility model relates to the field of building materials and refers to the development of a fiber-reinforced concrete product with an integrated possibility of volumetric monitoring of the technical condition of the structure during operation, without the use of sensors or probes.

[0002] It serves to diagnose and detect defects early, to increase the strength and durability of concrete structures, and to improve reliability and environmental compatibility.

[0003] The product contains a cement matrix with uniformly distributed reinforcing fibers (made of basalt or glass), the surface of which is coated with an electrically conductive and alkali-resistant layer based on graphene dispersion or thermally expanded graphite. These fibers form a three-dimensional conductive network within the structure, enabling the detection of changes in electrical resistance or impedance in response to the formation of microcracks, deformations, and other defects.

[0004] Monitoring is carried out via integrated electrodes connected to an external measuring system that operates in pulse mode without affecting the concrete structure. The proposed technical solution enables long-term monitoring of structures under both wet and dry conditions, ensuring high sensitivity, reliability, and practical applicability.

[0005] The utility model can be used in the construction of objects with increased requirements for safety and durability - for example, bridges, dams, tunnels, high-rise buildings and strategic infrastructure projects.

[0006] The utility model relates to building materials, in particular fiber-reinforced concrete products with an integrated system for monitoring the technical condition of the structure. It can be used in the construction of buildings, bridges, tunnels, dams, and other civil engineering structures where long-term monitoring of strength and structural integrity is required.

[0007] It serves to diagnose and detect defects early, to increase the strength and durability of concrete structures, and to improve reliability and environmental compatibility.

[0008] The global fiber-reinforced concrete market is growing rapidly. Glass and basalt fibers are experiencing the largest increase in demand (up to 20%), with basalt fibers exhibiting the greatest growth potential. Sources: “Fiber Reinforced Concrete (FRC) Market Size, Potential, Market Insights & Forecast 2033”, Verified Market Reports, and “China Concrete Reinforcing Fiber Market Size & Outlook”, Grand View Research, Inc.

[0009] At the same time, the need for condition monitoring of concrete structures is growing to ensure safety and environmental compatibility. State of the art:

[0010] Conventional methods for monitoring concrete structures (visual inspection, ultrasound, acoustic emission analysis) are labor-intensive and do not always allow for early prediction of damage.

[0011] Several solutions for monitoring concrete are known, including: • Integrated strain sensors, • Acoustic systems (sound emission analysis, ultrasound testing), • Impedance diagnostic systems using carbon nanomaterials. Previous approaches to monitoring concrete structures: 1. Embedded sensors ◯ Point sensors (for strain, humidity, temperature, acoustics) that are placed in the concrete body. ◯ Technologies: ▪ String strain gauges, ▪ Vibration acoustic systems, ▪ Built-in RFID or NFC tags. Disadvantages: ▪ High costs, ▪ Difficult scalability, ▪ Local measurements, ▪ Complex exchange. 2. Fiber-reinforced concrete with metallic fibers ◯ Occasionally, steel or copper fibers are used for impedance monitoring. Disadvantages: ▪ Corrosion, ▪ Electrochemical instability, ▪ No shielding against electromagnetic interference. Main disadvantages of the current solutions: • Point-based or surface-related measurements, • Requirement for expensive separate sensors, • Reduced effectiveness when concrete dries or ages. New technologies and state of the art:

[0012] In recent years, there has been growing interest in materials and technologies that improve the reliability and longevity of structures. One promising approach is the use of nanomaterials (fullerenes, nanotubes, graphene) in concrete for intelligent monitoring systems. • US9828614B2: Uses carbon nanotubes, but without fiber-reinforcing properties. • US11549899B2 / US9638652B2: Describe non-contact corrosion diagnostics in reinforced concrete using impedance measurement, but without specific coating. • WO2021173730A1: Focuses on self-diagnosis, but with point-based measurement which is unreliable in the event of changes in humidity. • EP3838864B1: Electrically conductive cement mixture (graphite / graphene) for heating / monitoring, but without focus on reinforcing fibers. • CN108472047A: Concrete with conductive carbon fibers, but unstable conductivity during drying and no volumetric sensor network integration. The purpose of the utility model solution is:

[0013] Development of a fiber-reinforced concrete product with an integrated volumetric network for continuous condition monitoring through electrical resistance / impedance changes - without external sensors. Key features:

[0014] The fiber-reinforced concrete product includes: 1. A cement matrix (Portland cement or hydraulic binder), 2. Uniformly distributed fibers (basalt or glass) with conductive graphene or thermally expanded graphite coating, 3. Built-in electrodes connected to a resistance measurement system.

[0015] The coated fibers form a 3D sensor network that detects microcracks and deformations through changes in resistance. Example of an embodiment: 1. Concrete implementation: As a practical example, a concrete slab with dimensions of 1 × 1 m was produced, which: • Contains 1.2 wt% basalt fibers, • These fibers are coated with a conductive layer based on graphene or thermally expanded graphite, • Stainless steel electrodes (AISI 304 / 316) are installed along the edge of the plate and connected to an impedance spectroscopy controller. 2. Measurement methods: • Simple resistance measurement: A standard ohmmeter (1.5 V) detects changes in the power grid. • Precise location of damage: In the case of microcracks in the center of the plate, a sudden increase in resistance (e.g. from 37 Ω to 15 kΩ) is measured - even without visible cracks. 3. Manufacturing details: • Shape: Square (22 × 22 cm, thickness 5 cm), • Binder: Portland cement, • Fibers: Staple fibers (length 12 mm, diameter 10-12 µm) made of coated basalt filament, • Electrodes: Embedded over 70% of the plate thickness, spacing 20-25 cm. 4. Measurement results (time dependence): Age (days) Resistance (Ω) 1 2,2 × 10 6 3 13 × 10 3 7 680 28 37 (stable state) 5. Key test: • Stress test: After an impact without visible cracks, the resistance rose to 15 kΩ - a clear signal for internal micro-damage. • Surface vs. volume: Surface measurements show no conductivity (insulator behavior), while volume measurements confirm the 3D wiring network.

[0016] Additionally, it should be noted that when measuring with a simple ohmmeter (e.g., a portable multimeter with a 1.5V battery), the resistance values ​​remain unstable, especially during the early setting stages of the concrete. This is due to the capacitive properties of the material and the incompletely developed conductive structure. In contrast, when using an impedance meter, stable values ​​for ohmic resistance (R) and reactive component (X) can be determined as early as the first day, enabling reliable monitoring of the spatial conductivity network. Particularly stable and low impedance values ​​were achieved using glass fibers coated with a water-based polymer emulsion and a graphene dispersion. This is attributable to the improved distribution of the conductive components and the overall higher graphene content.The proposed method is therefore suitable for both scientific and technical applications as well as for cost-effective condition monitoring directly on the construction site.

[0017] In one embodiment, a method is used in which the glass fiber is treated with a water-based polymer emulsion before being incorporated into the mix to improve adhesion and surface wettability. Graphene is then dispersed in water, and the treated fibers are introduced into this dispersion, uniformly wetted, and filtered. The fibers prepared in this way are then added to the mixing water of the concrete mix and evenly distributed within it. This method results in a uniform conductive coating of the fibers and contributes to the formation of a three-dimensional conductive network within the concrete.

[0018] In another embodiment, the water-based polymer emulsion and the graphene dispersion can be premixed to obtain a homogeneous functional liquid that is added directly to the mixing water. This solution enables simple and reproducible integration of the conductive coating directly during the mixing process of the concrete mix, without requiring separate treatment of the fibers. The prepared suspension is introduced into the mix, uniformly wetting and coating the fibers during mixing, thus creating a continuous three-dimensional conductive network within the concrete. Technical illustrations: • Fig. 1: Fracture surface of the fiber-reinforced concrete slab (visible fibers). • Fig. 2: Schematic structure: 1. Cement matrix, 2. Coated basalt / glass fibers, 3. Stainless steel electrodes, 4. Measurement controller. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 9828614B2

[0012] US 11549899B2

[0012] US 9638652B2

[0012] WO 2021173730A1

[0012] EP 3838864B1

[0012] CN 108472047A

[0012]

Claims

[1] Fiber-reinforced concrete product with a built-in system for continuous volumetric condition monitoring, containing a cement matrix and dispersed fibers, characterized by that the fibers consist of basalt or glass material and are coated with an electrically conductive layer based on graphene or thermally expanded graphite, wherein electrodes are arranged in the body of the product which are connected to a system for measuring electrical resistance or impedance. [2] Fiber-reinforced concrete product according to claim 1, characterized by that the fibers have a coating that was applied by adding it to the concrete mixture, the coating retaining its conductivity in the cement matrix. [3] Fiber-reinforced concrete product according to claim 1, characterized by that the resistance measurement is carried out in short pulse mode with a predetermined periodicity, without disturbing the concrete structure. [4] Fiber-reinforced concrete product according to claim 1, characterized by that the coated fibers form a volumetric network within the concrete matrix, enabling the detection of microcracks and defects by changing the electrical properties. [5] Fiber-reinforced concrete product according to claim 1, characterized by , ensuring that the electrical conductivity is maintained in both dry and wet conditions of the structure, thus guaranteeing monitoring throughout its entire service life. [6] Fiber-reinforced concrete product according to claim 1, characterized by that the coated fibers have an alkali resistance that is at least 2 times higher than that of uncoated fibers of the same material.

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