Self-sensing Concrete Research Articles

A study on the structural behaviour of Self Sensing Concrete using Nanomaterial as Fillers

Abstract Concrete technology has recently advanced to the point that different sensors can be used to measure a building’s mechanical attributes, including stress, amount of crack formation, deflection, and in various applications across Civil engineering disciplines. This can be achieved by various techniques or methods to measure the stress and strain of concrete in real-time. One of the methods is self-sensing concrete. To measure the self-sensing characteristics, concrete should be prepared with materials that possess sensing properties. Fibers (Carbon fibers, Steel fibers etc.,) and nanoparticles (nano nickel powder, carbon black powder, graphene powder etc.) are the main sources in the preparation of sensing concrete. This paper reviews the study on various self-sensing materials and methods that can be adopted and the study on the piezoresistive characteristics of concrete. The carbon and steel fiber-based self-sensing concrete were examined for compressive, tensile, and flexural strength as well as the electrical resistivity of the concrete was discussed in this paper.

Long-term investigation of uniaxial compressive and self-sensing performances of ultra-high performance seawater sea-sand concrete incorporating superfine stainless wires: Insights into underlying mechanisms and theoretical models

Developing intrinsic self-sensing concrete is expected to provide a digital intelligence solution to address the infrastructure’s challenges in terms of safety, lifespan, resilience, and carbon emission reduction. Using seawater and sea-sand as well as corrosion-resistant conductive fillers to fabricate self-sensing ultra-high seawater sea-sand performance concrete (UHPSSC) with outstanding mechanical and durability performances is the prerequisite for realizing localized resource utilization and in-situ monitoring of marine infrastructure. However, the potential effect of ions from seawater and sea-sand on the long-term stability of mechanical and electrical performances cannot be ignored. This paper presents a long-term investigation of uniaxial compressive, electrical, and self-sensing performances of superfine stainless wires (SWs) reinforced UHPSSC under natural curing. The results show that incorporating 1.5% SWs improves the compressive strength, elastic modulus, peak strain, and toughness of UHPSSC by 25.0%, 11.7%, 33.8%, and 119.2%, respectively. The established statistical damage constitutive models based on Weibull strength theory highlight the roles of SWs in delaying crack initiation. The dense microstructure of SWs-reinforced UHPSSC inhibits the growth of expansive hydration products formed by corrosive ions, thus guaranteeing its long-term strength development. Additionally, due to incorporating 1.5% SWs, the electrical resistivity of UHPSSC is reduced by seven orders of magnitude, with a strain sensitivity of 119.1 under monotonic compressive loading and a monitoring stress range of 0-148.4 MPa, indicating that SWs-reinforced UHPSSC can sense its stress and strain while providing early warning of crack initiation and propagation. Benefiting from the rust-free property, micron diameter, and high aspect ratio of SWs, the primary conductive path of composites comprises the overlapping networks formed by low-content SWs, which are not influenced by the ion conduction of conductive ions. Hence, SWs-reinforced UHPSSC exhibits stable electrical resistivity and sensitivity during long-term curing, suggesting its considerable potential for long-term in-situ monitoring of marine infrastructure.

Research Progress on Electrical Properties of Self-sensing Concrete

In order to effectively avoid the different degrees of impact and damage to the existing buildings and structures, it is particularly important to strengthen the health detection of such structures and facilities, which is also an important research field in the development of green building discipline. Smart concrete is both structural and functional, and has the potential of self-monitoring of concrete structures. This paper reviews the basic concepts of self-sensing concrete, including the research progress of self-sensing concrete materials, and summarizes the classification of different conductive phase materials and their conductive properties. Secondly, the basic mechanical properties and electrical properties of self-sensing concrete are discussed. The factors affecting the perceptual performance of self-sensing concrete considered by different scholars are summarized. It is concluded that few scholars have studied the mechano-electric interaction evaluation mechanism that takes the electrical parameters into account the stress, strain, crack or damage of concrete, and evaluates mechanical properties and crack propagation length through the change of electrical signals. Finally, the importance of self-sensing performance of intelligent concrete is emphasized, and the prospect of future research is put forward.

Piezoresistive response and self-sensing properties of UHPC reinforced with recycled carbon fibers

This research explores Ultra-High-Performance Concrete (UHPC) reinforced with recycled carbon fibers to verify its potential application in self-sensing concrete for structural health monitoring. The improved electrical conductivity due to the inclusion of carbon fibers enables the emergence of piezoresistivity, transforming UHPC into a sensitive sensor for detecting mechanical stresses. By incorporating various characterization tests alongside investigations into fiber type (loose versus fibrillated sheets) and content variations, the study aims to establish a correlation between the electrical properties and the resulting piezoresistive response. Resistivity will be measured using impedance scanning, while piezoresistivity will be determined through loading and unloading cycles with a datalogger recording the variations in electrical resistance. The inclusion of carbon fibers suggests an improvement in mechanical performance, up to 42 % in flexural strength and 26 % in compression compared to UHPC without fibers. Resistivity ranges from 1 to 2 Ω⋅m and gauge factor reach 38. These results are comparable to those reported in other studies on UHPC with carbonaceous additions, highlighting the potential of recycled carbon fibers as a sustainable and effective reinforcement strategy.

Effect of carbon fibers and graphite particles on mechanical properties and electrical conductivity of cement composite

The utilization of self-sensing concrete for structural monitoring is currently a significant research focus. This study involves fabricating self-sensing cement-based composites(SCC) with different carbon fiber contents; the graphite powder content remains fixed at 20 % by mass. The investigation focuses on assessing the influence of carbon fiber on the mechanical strength, electrical conductivity, and piezoresistive properties of cement-based composites incorporating graphite. Furthermore, the study examined the modification mechanisms of carbon fiber in SCC through Nuclear Magnetic Resonance (NMR) and Scanning Electron Microscopy (SEM). The compressive strength initially increases and then decreases with the addition of carbon fibers, reaching a peak of 43.01 MPa at a carbon fiber concentration of 0.6 vol%. SEM analysis revealed that the primary failure mode of carbon fibers is pull-out behavior, which enhances the damage pathway of SCC, thereby improving their mechanical properties. According to NMR results, the porosity of the SCC decreases to varying degrees with the inclusion of carbon fibers, showing an 11.36 % reduction at a carbon fiber concentration of 0.6 vol%. Under cyclic compressive loading within the elastic range, the change in resistivity can reach up to −76.8 %, with a strain sensitivity factor of 1300. Based on the results, it was determined that the addition of 0.6 vol% carbon fibers can significantly improve the mechanical, electrical conductivity, and piezoresistive properties of SCC with a graphite-modified cement matrix.

A Comparative Study of the Applications and Prospects of Self-healing Concrete / Biocrete and Self-Sensing Concrete

A Comparative Study of the Applications and Prospects of Self-healing Concrete / Biocrete and Self-Sensing Concrete

Multifunctional cementitious composite: Conductive and auxetic behavior

This research focused on developing an innovative multifunctional cementitious material with both conductive and auxetic properties simultaneously. This novel cement-based metamaterial has different applications, ranging from piezoresistivity to structural energy dissipation. The cementitious composite (CC) with an auxetic structure were produced using additive manufacturing techniques. The study involved analyzing different cementitious compositions, including Ultra High-Performance Concrete (UHPC) formulation tailored for both high strength and workability, and flexible mortar. Both types of composites were combined with two types of fibers: recycled carbon and Polyvinyl Alcohol (PVA). Uniaxial compression tests, conductivity, piezoresistivity by load cycles, and Digital Image Correlation (DIC) analysis were carried out on the auxetic cementitious composite (ACC). Among these tested cementitious composites (UHPC and flexible mortar) reinforced with PVA and recycled carbon fibers, only the flexible mortar with carbon fibers achieved the desired multifunctional properties. This success with flexible mortar and carbon fibers suggests promise for this combination. Conversely, UHPC composites with PVA fibers, with or without additional carbon fibers, failed to achieve the targeted functionality. As a result, both piezoresistivity and auxetic properties were achieved. From the auxetic behavior results, the Poisson’s ratio reached -67.5%. This implies that if compressed longitudinally, the specimen is shortened transversely (auxetic behavior) by up to 67.5%. This finding stands out compared to traditional construction materials like concrete and steel, which typically exhibit much lower strain recoveries (15–30%). On the other hand, the specific deformation energy absorption of the auxetic specimen reached 0.076 Jcm3. Moreover, the resistivity reached the small magnitude of 0.15 Ωm at 50 Hz, proving to be a conductive composite. The gauge factor of 4.26 indicates that it can be used as a self-sensing concrete. This innovative cementitious composite opens new possibilities for future applications that require materials with conductive and auxetic behaviors.

Improved conductive and self-sensing properties of cement concrete by PDMS/NCB-impregnated recycled fine aggregate

Polymer emulsion impregnation is a common method for strengthening recycled fine aggregate (RFA). By mixing Nano carbon black (NCB) into the polymer emulsion, highly conductive modified RFA (MRFA) can be simultaneously obtained. In this paper, highly conductive and self-sensing concrete was prepared by using the MRFA impregnated with the NCB and polydimethylsiloxane (PDMS) solution. The microstructure of MRFA and MRFA concrete physico-mechanical properties were studied. The effects of replacement ratio of MRFA, temperature, water content, and loading rate on the conductivity and self-sensing of prepared MRFA concrete was explored. The results show that the PDMS fills the pores of the RFA surface. The water absorption decreases by 2.53%, the apparent density and fineness modulus increased by 1.5% and 8.3%, respectively. With the increase of MRFA replacement ratio, the resistivity of concrete gradually decreases, and a sharp decline appears from 60% to 70%. The percolation threshold of concrete is calculated to be 3.37 vol% of NCB. Meanwhile, the MRFA concrete has good temperature sensitivity and humidity adaptability. Under the stress cycle loading, the stress sensitivity of the MRFA concrete with 70% replacement ratio MRFA is as high as 4.45%/MPa. Besides, the stress sensitivity of MRFA concrete decreases as the loading rate increases.

Research on factors affecting electrical conductive properties and applications of self-sensing concrete

Self-sensing concrete utilizes the electrical properties of concrete to predict the stress or deformation occurring within the material itself.. This study aims to provide an overview of the general properties as well as the factors influencing the electrical properties of self-sensing concrete. Based on analyses from previous studies, this study indicates that the electrical properties, specifically the electrical resistance, of concrete change with variations in the stress or strain. However, this change is influenced by numerous complex factors and can be categorized into three groups: (i) material composition and fabrication methods, (ii) specimen configuration and measurement conditions, and (iii) loading conditions and environment. Based on these principles, current applications of self-sensing concrete are primarily implemented in structural health monitoring, infrastructure management, and traffic surveillance.

A review of self-sensing ultra-high performance concrete: Towards next-generation smart structural materials

Today, the desired intelligent civil engineering structures urge the development of high-performance smart structural materials. Self-sensing ultra-high performance concrete (UHPC) emerged in 2014 based on the observation that the concrete structures rendered with randomly distributed conductive additives exhibit electromechanical effects under external loading, and the demand of UHPC from high-strength to sustainable, intelligent, and multifunctional. This smart structural material has since grown greatly and has been considered as one of the potential alternatives to ordinary self-sensing concrete. This paper presents a state-of-the-art review of self-sensing UHPC in terms of its raw materials, mixture design, manufacturing approaches, microstructural characteristics, mechanical properties, electrical resistivity, electromechanical properties, and applications, with a particular focus on stress-deformation/damage behaviour and changes in electrical conduction under external compression, tension, and bending. The novel uncertainties regarding electromechanical effects are thoroughly discussed from the perspective of the continuity of conductive network. Compared with ordinary self-sensing concrete, self-sensing UHPC exhibits significantly reduced porosity, exceptional strength, marginally lower stress/strain sensitivity, heightened damage sensitivity, insensitivity to humidity, and delayed cracking behaviour. In the end, this paper identifies research gaps, challenges, and recommendations in three aspects: (1) scale fabrication and cost control, (2) satisfactory and reliable properties, and (3) from smart structural materials to integrated components to civil engineering structures.

A Numerical Model for Electrical Properties of Self-Sensing Concrete with Carbon Fibers

A Numerical Model for Electrical Properties of Self-Sensing Concrete with Carbon Fibers

Compression self-sensibility of the concrete using high content carbon black with various measurement conditions

Self-sensing concrete (SSC) is a smart material created by dispersing a conductive filler into the concrete. This helps to increase the resistivity variation of concrete when the microstructure of the material changes under the effect of load. Thus, the stress, strain or damage of the concrete can be sensed by resistivity measurements of the concrete itself. This study aims to clarify the effects of parameters related to the measurement method on the self-sensibility of SSC. SSC specimens were prepared using carbon black with 7% volumetric content. A series of compression tests were conducted to investigate the relationship between the resistivity variation and the applied load of different test specimens in terms of excitation voltage, electrode distance and specimen size. The results show that the excitation voltage need to be large enough to generate a current of suitable stability when measuring the self-sensibility of SSC. The resistivity of all specimens decreased with increasing compressive load on the SSC specimen. The larger the specimen size and the smaller the electrode distance, the more pronounced the resistivity variation.

Measurement techniques for self-sensing cementitious composites under flexure

Intrinsic self-sensing concrete has gained substantial interest recently as a promising construction material for smart structures. Most of the research focuses on testing their sensing behaviour under pure compression, but in practice, damage to concrete structures due to bending is more commonly seen. It is thus necessary to also test the sensing performance of the composites under flexural loading. Due to the variation of the stress distribution in a concrete element subject to bending, the influence of the geometry of electrodes on measured results is more complex. This study investigated the self-sensing behaviour of prismatic graphite-cementitious specimens under three- and four-point bending with different electrode placements. Composites were tested both in the elastic and plastic range by applying cyclic and monotonic flexural loading. Prisms with different sample depth, sample width, electrode penetration and electrode diameter were further modelled numerically using Finite Element Analysis (FEA) to study the electrical behaviour. Experimental results show that to obtain accurate measurements for composites under flexure, the electrodes need to be at close spacings with shallow penetration at the tensile side of the specimen in order to measure behaviour in the tensile zone. An equation for the relationship between the measured resistance and the geometry variables has been found through numerical simulation that can estimate the influence zone within the sample and hence enable optimisation of the electrode placement for self-sensing cementitious composites under flexure.

Characterization and piezo-resistivity studies on graphite-enabled self-sensing cementitious composites with high stress and strain sensitivity

Carbon-based conductive fillers have recently been incorporated into a cement matrix to develop an intrinsic self-sensing concrete for data monitoring without the need for embedded, attached, or remote sensors while maintaining or improving its mechanical properties and durability. This paper studies cementitious composites filled with graphite as a novel self-sensing construction material. Experiments were systematically conducted to investigate the dispersion, chemical, mechanical, electroconductivity and piezo-resistivity properties of the composites. Experimental results showed an effective mixing with uniform dispersion of the graphite which acted as an inert filler in the mix and did not alter the microstructure of cement hydration products. Isothermal calorimetry, TGA and rheology tests showed good hydration and adequate workability of the composites with low graphite concentration (≤ 10%), while the effect of adding graphite on the compressive strength is insignificant for graphite concentrations of up to 10%. Monotonic and cyclic compressive test results indicated a repeatable piezo-resistivity performance for low graphite concentration cementitious composites whose stress sensitivity values vary from 0.75 to 7.25%/MPa, and strain sensitivity/gauge factor (GF) 150–1250 with some hysteresis. These combinations showed a stable and reliable piezo-resistivity and the ability to detect damage upon failure.

Self-sensing GFRP-reinforced concrete beams containing carbon nanotube-nano carbon black composite fillers

This study investigated the self-sensing behavior of nonconductive glass fiber reinforced polymer (GFRP) reinforced concrete beam incorporated with electrostatic self-assembly carbon nanotube-nano carbon black (CNT-NCB) composite fillers (CNCFs) under monotonic and cyclic flexural loadings. The CNCFs feature synergistic effect of long-range conduction for fibrous CNTs and short-range conduction for granular NCBs, as well as their good dispersibility. Self-sensing signals in the compression and tension zones of the concrete beams were synchronously recorded through embedding stainless steel gauze electrodes in these sensing zones. Experimental results showed that incorporating CNCFs can achieve low and stable electrical resistivity (ranging from 33 to 76 Ω‧cm) for the concrete beams. Under monotonic flexural loading, the largest resistivity variation was observed in the case of concrete beam with 1.8 vol.% CNCFs, and the magnitude of fractional changes in resistivity (FCR) reached nearly 286%. Moreover, FCR in tension zone was more pronounced than that in compression zone. Under cyclic flexural loading, high self-sensing repeatability and stability of FCR variation with strain were obtained for all the concrete beams, and concrete beam with 2.0 vol.% CNCFs demonstrated the optimum self-sensing capability for its highest strain sensitivity of 322.7. Consequently, by measuring FCR of concrete beams with CNCFs and replacing metallic steel reinforcement with nonconductive GFRP bars which have the benefits of avoiding short circuit or electric field disturbance inside self-sensing concrete, in-situ monitoring the strain and damage accumulation of concrete components can be achieved.

Enhancement of the piezoresistive and mechanical properties of cement-based composites filled with CNTs/GO and nano-SiO2 sprayed steel fibers

Steel fibers (SFs) are one of the most suitable functional fillers for the preparation of large-volume self-sensing concrete due to their good dispersion and toughness, whereas it has poor sensing performance. In this paper, a CNTs/GO-sprayed method was proposed to modify the surface of SFs as well as nano-SiO2 was used to enhance the interface between SFs and matrix, in which the content of carbon-based materials could be precisely quantified. Then, self-sensing performance, pull-out test, and macro stable mechanical performance were carried out. The results revealed that the specimens filled with straight smooth (SS) SFs sprayed with GO and nano-SiO2 had the highest self-sensing ability. Compared to unmodified SFs, the degree of improvement reached 225% and 270% within 0 ∼ 60 kN and 0 ∼ 90 kN, respectively, and the addition of nano-SiO2 increased the pull-out energy. In addition, the macro mechanical properties of the specimens filled with the modified SS SFs were better than that of the hooked end (HE) SFs.

Influence of carbon nanotube on the mechanical and electrical characteristics of concrete – A review

Conventional concrete, which is composed of cement, coarse aggregate, fine aggregate, water, and superplasticizer, has the disadvantages of low maximum split tensile strength and low ductility, which can lead to sudden failure. However, the use of carbon nanotubes (CNT) can improve the binding to detect cracks in the structure before it collapses, as well as increase the maximum split tensile strength and ductility. The CNT is utilized to improve the mechanical characteristics of concrete, including its compressive strength, split tensile strength, and flexural strength. In addition to self-sensing, researchers examined the impact of carbon fiber and CNT particles on the mechanical characteristics of beam specimens with the suggested reinforcement arrangement. In this review, mechanical tests such as compressive strength, split tensile strength, and flexural strength are examined to determine the impact percentage of CNT that is beneficial for enhancing the strength of concrete. The study also further reviewed the resistivity of self-sensing CNT concrete. The review explored that CNT also improves electrical properties, such as resistivity and conductivity, and thermal conductivity of cement composites. To increase the electrical conductivity of beams, CNT and chopped carbon fibers (CF) were utilized. As a Nano-material, CNT may be widely distributed in the concrete through a proper mixing strategy. Due to their high modulus of elasticity, tensile strength, and yield strain, CNTs are an appealing material for concrete reinforcement. Using ultrasonication and a superplasticizer, a solution of dispersed CNTs with exceptional workability in concrete was made because the accumulation of CNTs significantly decreased the electrical resistance. The purpose of adding CNT to concrete for the Structure Health Monitoring technique is to detect building fractures using self-sensing concrete (SHM). The research finally concludes that CNT is highly beneficial to enhance compressive strength, flexure strength, and split tensile strength.

Study of the Behavior of Self-Sensing Concrete under the Influence of Different Mechanical Loads: A Review

Self-sensing concrete is an intelligent application of scientific knowledge for practical purposes and new concrete structures, which can feel the damage, stress and strain in the body of concrete. It has been widely used because of its possibility of getting efficient cost solution for controlling the structural sustainability of concrete structures, which indicate, that it is very impressive during the design life of the facilities. This review contains universal behavior and global information about different conditions of loading for self-sensing concrete. Also, the definitions and applications of intrinsic and non-intrinsic self-sensing concretes are mentioned. Moreover, a major confirmation is stated on the application of scientific knowledge for practical purposes and new concrete structures. The characteristics of self-sensing concrete provide an ability to reveal small cracks before they begin to become significant. During unchanging compression, firstly, the values of electrical resistivity decrease through an increase in load, subsequently become stable and then increased suddenly. While, during impact loading, the electrical resistivity decreases suddenly, but it regresses then to 0 after loading. However under tensile stress, the electrical resistivity increases as the tensile stress increases. Nevertheless, since the flexural is a component of compression and tension, the comparison between sensitivity for compression part is much smaller than in tension part.

Book Review of Self-Sensing Concrete in Smart Structures

Self-Sensing Concrete in Smart Structures, published by Elsevier, is the first English monograph in the field of self-sensing concrete and its smart structures. The monograph contains 11 chapters in 3 parts. The first part describes in detail the structure, composition, preparations, testing methods, sensing properties, sensing mechanisms, and smart structures of self-sensing concrete. The second part gives the results of the authors’ systematic research in the field of self-sensing concrete materials and smart structures from 2000 to 2014, including the self-sensing concrete with carbon fiber, nickel powder, and carbon nanotubes. The third part discusses the future challenges and countermeasures for the development of self-sensing concrete and its smart structures. The monograph not only provides a comprehensive introduction to the basic principles of self-sensing concrete and the research cases of self-sensing concrete-based smart structures applications, but also presents a series of representative innovative researches results of selfsensing concrete and its smart structures, as well as plans and deploys the future research and applications of self-sensing concrete and its smart structures. This monograph can provide guidance and reference for scientific researchers and engineers in the field of concrete materials and structures as well as smart materials and structures.

Piezoresistivity and AC Impedance Spectroscopy of Cement-Based Sensors: Basic Concepts, Interpretation, and Perspective.

Cement-based sensors include conductive fillers to achieve a sensing capability based on the piezoresistivity phenomenon, in which the electrical resistivity changes with strain. The microstructural characterisation of cement-based sensors can be obtained using a promising non-destructive technique, such as AC impedance spectroscopy (ACIS), which has been recently used by many researchers. This paper reviews the fundamental concepts of piezoresistivity and ACIS in addition to the comparison of equivalent circuit models of cement-based sensors found in the literature. These concepts include piezoresistivity theory, factors affecting piezoresistivity measurement, resistance measurement methodology, strain/damage sensing, causes of piezoresistivity, theories of conduction, AC impedance spectroscopy theory, and the equivalent circuit model. This review aims to provide a comprehensive guide for researchers and practitioners interested in exploring and applying different techniques to self-sensing concrete.