Carbon Fiber Reinforced Concrete Research Articles

Electric Resistance and Curing Temperature Development of Carbon Fiber-Reinforced Conductive Concrete: A Comparative Study.

The development of electric resistance is a key factor affecting the performance of conductive concrete, especially the electrical-thermal performance. In this work, the effects of different influencing factors (including the water-to-binder ratio, coarse aggregate content and carbon fiber (CF) content) on the electric resistance of conductive concrete were systematically investigated. At the same time, ohmic heating (OH) curing was applied to fabricate CF-reinforced conductive concrete (CFRCC) under a negative temperature environment at -20 °C. The effects of different factors on the electrothermal properties (curing temperature and conductive stability) of the samples were studied. The mechanical strengths of the CFRCC cured by different curing conditions were also tested, and the feasibility of OH curing for preparing CFRCC in a negative-temperature environment was verified at various electric powers. This work aims to give new insights into the effects of multiple factors on the performance of CFRCC for improved concrete construction in winter.

Study on printability of 3D printing carbon fiber reinforced eco-friendly concrete: Characterized by fluidity and consistency

Carbon fibers have often been added to concrete as reinforcement. Eco-friendly concrete with industrial by-products has been widely studied and applied as green building materials. Studying the workability and printability of eco-friendly concrete with carbon fibers is worthwhile. The workability and printability of eco-friendly concrete are dominating factors that ensure that printing can be carried out smoothly. This study uses a combination of experiments and numerical simulations to study the printing performance of carbon fiber-reinforced eco-friendly concrete (CFREFC). The workability and printability of 9 mixes of 3D printing CFREFC under various combinations of different water-binder (w/b) ratio levels and superplasticizer (SP) dosages were tested. Two methods, namely the consistency and fluidity tests, were used to characterize the printability. After consistency and mortar fluidity tests, the 9 mixtures were printed to get the printing performance. Finally, the relationship between the workability and printability of 3D printing CFREFC was established. The condition numbered M7 (w/b = 0.4, SP = 0.5) in the selected experimental group was used as the source of its simulation parameter. The result shows that it is feasible to characterize printability using workability, i.e., consistency and fluidity, which increase with the increase of w/b and SP dosage. Under the printing parameters of the HC1008 printer were determined, i.e., 20 mm of nozzle size, 50 mm/s of printing speed, 30 rpm of material extrusion speed, and 14 mm layer height, the fresh CFREFC was not suitable for 3DP application when its consistency is less than 48.99 mm and more than 81.96 mm, or when its fluidity is less than 166.72 mm and more than 200.93 mm. When the consistency is from 56.34 to 65.61 mm, and the fluidity is from 172.18 to 183.30 mm, the printability of CFREFC is the best under the same printing parameters. The simulation results indicated that with the increased number of printing layers, the bottom of the printed model would be deformed by the gradual increase in pressure, and a specific height loss would occur, which was consistent with the experimental results.

Impact of Silica Sand on Mechanical Properties of Epoxy Resin Composites and Their Application in CFRP–Concrete Bonding

Premature debonding between carbon fiber-reinforced polymer (CFRP) and concrete is a critical issue in structural reinforcement applications, often leading to a significant reduction in the load-carrying capacity of the system. This failure mode is typically initiated by inadequate adhesion at the interface, compromising the effectiveness of CFRP in enhancing the structural performance of concrete elements. To address these issues, this study explores the impact of silica sand on the mechanical and adhesion properties of epoxy resin composites. Initially, this paper investigates the physical and mechanical properties of epoxy resin composites by varying the ratios of silica sand from 0% to 15% by volume. Subsequently, it examines the effectiveness of these composites as sealing materials to enhance the bond strength between CFRP and concrete. Incorporating a 10% silica content improves the mechanical properties of the epoxy resin, with the tensile strength increasing from 29.47 MPa to 35.52 MPa and an elastic modulus from 4.38 GPa to 5.83 GPa. Furthermore, silica sand enhances the adhesion strength between CFRP and concrete, as confirmed by the increase in the pull-out force from 14.21 kN to 18.79 kN. Silica particles improve surface roughness and interlocking, contributing to a better load distribution and stress transfer at the interface. Therefore, silica-filled epoxy resin is an efficient material for CFRP–concrete bonding applications.

Implementation of bio-inspired organic/inorganic layer structures as interphase in carbon fiber reinforced concrete

Biological materials found in nacre or glass sponges reveal specific layered organic and inorganic structures known for their fracture toughness caused by crack deflection and bridging. This work aims to bio-mimic the brick-and-mortar (BnM) structure from nacre and the layer-by-layer (LbL) structure from the glass sponge filaments to incorporate these effects into the contact zone of carbon fiber-reinforced concrete (CFRC) in order to prevent brittle composite failure. To build up BnM- and LbL-structure materials such as nanoclays, sodium water glass, and polymer dispersions were selected since they are well-established low-cost materials in building. Nanoclays were analyzed regarding their size, dispersibility and exfoliation. Montmorillonite (MMT) was used to be mixed with polymers to produce self-assembled BnM-structured films and coatings. Also, LbL-structures were formed by alternating layers of sodium water glass and polymer. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to verify the morphology. The MMT-containing coatings demonstrated enhanced nucleation potential when exposed to cementitious eluate. Micromechanical pull-out tests on single carbon fibers with BnM- and LbL-coatings embedded in concrete demonstrate the potential to increase composite toughness. The successful implementation of the bio-inspired structures using affordable materials lays the groundwork for their scalability and integration into composite structures for building.

Damage Model of Carbon-Fiber-Reinforced Concrete Based on Energy Conversion Principle

In order to enhance the practical application of carbon-fiber-reinforced concrete (CFRC) in engineering, it is necessary to study the damage mechanism of CFRC. Experimental research on the mechanical properties of CFRC under multiple strain rates was conducted. Five different fiber contents were analyzed to study the compressive strength and tensile strength of CFRC, and the damage characteristics of CFRC under multiple strain rates were analyzed based on failure modes and energy changes. An energy-based damage constitutive model was established. The results showed the following: (1) When the carbon fiber content was 0.4%, CFRC had the best comprehensive performance, with a 15.02% increase in compressive strength and a 51.12% increase in tensile strength. With the increase in strain rate, the compressive strength of the concrete increased. (2) Under high strain rates, carbon fiber significantly enhanced the compressive strength of the concrete, and the input energy, elastic strain energy, and dissipated energy increased. The peak value of the elastic strain energy conversion rate increased, and the minimum value of the dissipated energy conversion rate decreased. (3) Under the same strain rate, the CFRC had a larger inflection point of dissipated energy corresponding to the strain compared to the reference group of concrete during the loading process. A constitutive model for CFRC was established based on damage mechanics and probability statistics. The research results will provide theoretical references for the application of carbon-fiber-reinforced concrete.

Comparing Mechanical Characterization of Carbon, Kevlar, and Hybrid-Fiber-Reinforced Concrete under Quasistatic and Dynamic Loadings

Concrete is a brittle material due to its poor tensile strength; consequently, concrete tends to crack or peel under an applied external load. Previous studies have investigated the effect of incorporating fiber into concrete, which can improve its tensile strength. In this study, the static and dynamic mechanical characteristics of three types of fiber-reinforced concrete (FRC) were examined: carbon-fiber-reinforced concrete (CFRC); Kevlar-fiber-reinforced concrete (KFRC); and a combination of both, known as carbon/Kevlar-hybrid-fiber-reinforced concrete (HFRC). This study created concrete specimens by pneumatically dispersing carbon and Kevlar fibers and mixing them with cement to comprise 1% of the weight. The mixture was then combined with aggregates and water to form the concrete specimens. When compared with the benchmark concrete specimens, it was found that the compressive strength of the CFRC, KFRC, and HFRC specimens increased by about 19% to 50%, the bending strength increase by about 8% to 32%, and the splitting strength increased by about 4% to 36%. Specifically, the HFRC made with the 24 mm carbon and Kevlar fibers displayed the most significant mechanical strength in a static state. Furthermore, the HFRC showed superior resistance to impact compared to the benchmark concrete specimens across various impact energies, with the 24 mm carbon and Kevlar fiber HFRC showing the highest resistance. The inclusion of fibers in the split Hopkinson pressure bar (SHPB) test demonstrated a notable increase in the maximum strength, particularly in the case of the 12 mm carbon fiber combined with the 24 mm Kevlar fiber in the HFRC specimen.

Effect of coarse aggregate and carbon fiber content on ohmic heating curing of concrete slab in realistic severely cold weather

In this work, carbon fiber-reinforced high-performance concrete (CF-HPC) slabs with coarse aggregate content of 25 vol%/35 vol%/45 vol% and carbon fiber content of 0.6 vol%/0.8 vol%/1.0 vol% were cured by ohmic heating (OH) curing under realistic severely cold condition for practical on-site construction. Results indicated that the coarse aggregate content has a substantial influence on the electrical resistance and curing time of concrete slab. Higher and lower content of coarse aggregate will lead to insufficient ohmic heats and curing time. On the contrary, carbon fiber content only has a limited influence on OH curing feature, such as slight value difference of electrical resistance and curing temperature. Besides, the correlation between the curing temperature of concrete slab and the associated factors (OH curing power, ambient temperature) was quantitatively analyzed. It is found that the OH curing power had a strong correlation with the concrete temperature during the most time of curing period, while the snowfall weather enhanced the correlation between ambient temperature and concrete temperature. At last, a criterion of feasible resistance range based on the experimental results and theorical analysis was proposed to evaluate the feasibility of OH curing and assist the concrete mix design.

Mechanical Behaviors of Microwave-Assisted Pyrolysis Recycled Carbon Fiber-Reinforced Concrete with Early-Strength Cement

This study aimed to investigate the mechanical performance of early-strength carbon fiber-reinforced concrete (ECFRC) by incorporating original carbon fiber (OCF), recycled carbon fiber (RCF), and sizing-removed carbon fiber (SCF). Compressive, flexural, and splitting tensile strength were tested under three fiber-to-cement weight ratios (5‱, 10‱, and 15‱). The RCF was produced from waste bicycle parts made of carbon fiber-reinforced polymer (CFRP) through microwave-assisted pyrolysis (MAP). The sizing-removed fiber was obtained through a heat-treatment method applied to the OCF. The results of scanning electron microscopy (SEM) analysis with energy dispersive X-ray spectrometry (EDS) indicated the successful removal of sizing and impurities from the surface of the RCF and SCF. The mechanical test results showed that ECFRC with a 10‱ fiber-to-cement weight ratio of carbon fiber had the greatest improvement in its mechanical strengths. Moreover, the ECFRC with 10‱ RCF exhibited higher compressive, flexural, and splitting tensile strength than that of benchmark specimen by 14.2%, 56.5%, and 22.5%, respectively. The ECFRC specimens with a 10‱ fiber-to-cement weight ratio were used to analyze their impact resistance under various impact energies in the impact test. At 50 joules of impact energy, the impact number of the ECFRC with SCF was over 23 times that of the benchmark specimen (early-strength concrete without fiber) and was also greater than that of ECFRC with OCF and RCF.

Effects of sulfate and freeze–thaw cycles on the bond behavior of CFRP-concrete interface

The bonding performance of the interface between carbon fiber-reinforced polymer (CFRP) and concrete is crucial for the safety of concrete structures that are strengthened with CFRP. The reinforced structures in Northwest China are often affected by harsh environmental conditions. In this paper, by using the test method of sulfate and freeze–thaw cycles coupling erosion, the actual erosion environment that may be suffered in this area was simulated, and the bonding performance of CFRP reinforced concrete structures in this environment was studied. Combined with macro and micro experiments, the mechanism of coupled erosion was discussed, and the influence of the above environment on the interface failure mode, interface bearing capacity and interface characteristic values were analyzed. The experimental results show that under the coupling erosion, the failure mode of the CFRP-concrete interface has changed. And the bonding performance of the interface has been significantly reduced. The specific performance is that with the increase of erosion times, the interface bearing capacity is continuously reduced, and the maximum bond shear stress position is gradually moved to the free end. Through induction and analysis of the test data, the bond-slip model of the interface under this condition was established, and the accuracy of the model was evaluated by comparing it with the experimental data.

Performance of silica fume slurry treated recycled aggregate concrete reinforced with carbon fibers

The utilization of recycled concrete aggregate (RCA) is a sustainable way to produce concrete. However, using recycled aggregate in concrete results in inferior mechanical performance and durability, mainly due to the weak interfacial transition zone (ITZ) and attached mortar. The research aims to overcome the inferior properties of recycled aggregate concrete (RAC) by treating recycled aggregate with silica fume (SF) slurry and carbon fibers (CF) as reinforcement. A total of thirteen mixes were prepared and tested for workability, water absorption, mechanical strength, elastic modulus and performance against acid attack. To optimize the performance of recycled concrete, carbon fiber and silica fume were employed at 0.5% and 10%, respectively, with 25%, 50%, and 100% substitution levels of recycled aggregates. The aggregate was pre-soaked in SF slurry for 24 h before mixing in concrete to ensure its absorption or adherence to aggregate. Compressive, split tensile, and flexure strengths of recycled aggregate concrete were evaluated at 7, 28, and 56 days. Elastic modulus was examined under axial compression at 28 days of curing age. Experimental results showed that SF improves the microstructure of cement paste and the bonding between binder matrix and carbon fibers. Compressive, split tensile and flexural strength results of 45.2 MPa, 5.4 MPa and 7.8 MPa, respectively were observed by combined utilization of carbon fiber and silica fume at 28-day curing age in 100% recycled concrete i.e., for recycled concrete mix CFSF-RC100, which is 20%, 34%, and 46% more than their corresponding control mix i.e., RC100. Elastic modulus for RC mixes were found to vary between 22 GPa for RC100 mix and 35.6 GPa for CFSF-RC25 mix respectively. Silica fume also contributed to the water absorption reduction of up to 14% in recycled concrete. Carbon fiber-reinforced recycled concrete was more acid attack resistant having only 6.3% mass loss after acid attack and hence 40% reduced mass loss was observed compared to that of recycled aggregate concrete. Hence, strong, durable, and environment friendly concrete was produced.

Effect of coarse aggregate grading optimization on temperature, thermal stress and compressive strength of carbon fiber-reinforced concrete by ohmic heating curing

The ohmic heating (OH) method is demonstrated to be promising for the curing of carbon fiber-reinforced mortar under ultra-low temperature condition. For the large-scale application in engineering and the reduction of carbon emission, the addition of coarse aggregates is necessary. However, coarse aggregates also influence on the temperature distribution and mechanical strength of OH cured concrete. This study proposed an optimization process of coarse aggregate gradation by combining particle packing theory with thermal simulation. The gradation was firstly decided by modified Andreasen & Andersen curve, and then optimized by the numerical simulation of temperature and thermal stress, in order to relieve the high thermal stress gradient in cold condition. The experimental results showed that the compressive strength of the samples with coarse aggregates of both 5–10 mm and 10–16 mm cured by 2 days OH curing at −20 °C reached 51.94 MPa, which was higher than samples including single aggregate diameter level, presenting a comparable strength value with 7 days room temperature (RT) curing. In addition, the microstructure and hydration products of concrete with OH and RT curing were compared and analyzed. This work will provide better guidance on the optimization design of mix proportion of carbon fiber-reinforced concrete for promoting the development of OH curing of concrete in large-scale practical applications.

Comparative study on the static and dynamic mechanical properties and micro-mechanism of carbon fiber and carbon nanofiber reinforced concrete

In order to compare the effects of carbon fiber and carbon nanofiber on the static and dynamic mechanical properties of concrete, the static mechanical tests, dynamic compression test and dynamic splitting tensile test were carried out on carbon fiber reinforced concrete (CFRC) and carbon nanofiber reinforced concrete (CNFRC). Meanwhile, relevant micro-mechanism was analyzed through the MIP test and SEM test. The results showed that both carbon fiber and carbon nanofiber could improve the mechanical properties of concrete and refine the pore size distribution of concrete. In terms of the static mechanical properties, the ductility of CFRC was better, while the strength performance and deformation performance of CNFRC were better. In terms of the dynamic compression mechanical properties, the energy consumption performance of CFRC was better, while the strength performance of CNFRC was better. In terms of the dynamic splitting tensile properties, the strength performance, deformation performance and energy consumption performance of CFRC were better. Under a load, carbon fiber exerted a more obvious “crack resistance effect”, while carbon nanofiber exerted a more obvious “filling effect”. Carbon nanofiber had a better optimization effect on the pore structure of concrete than carbon fiber. The research results could provide reference for the selection of CFRC and CNFRC under different engineering requirements.

An Investigation of Mechanical Properties of Recycled Carbon Fiber Reinforced Ultra-High-Performance Concrete.

Carbon fiber-reinforced concrete as a structural material is attractive for civil infrastructure because of its light weight, high strength, and resistance to corrosion. Ultra-high performance concrete, possessing excellent mechanical properties, utilizes randomly oriented one-inch long steel fibers that are 200 microns in diameter, increasing the concrete's strength and durability, where steel fibers carry the tensile stress within the concrete similar to traditional rebar reinforcement and provide ductility. Virgin carbon fiber remains a market entry barrier for the high-volume production of fiber-reinforced concrete mix designs. In this research, the use of recycled carbon fiber to produce ultra-high-performance concrete is demonstrated for the first time. Recycled carbon fibers are a promising solution to mitigate costs and increase sustainability while retaining attractive mechanical properties as a reinforcement for concrete. A comprehensive study of process structure-properties relationships is conducted in this study for the use of recycled carbon fibers in ultra-high performance concrete. Factors such as pore formation and poor fiber distribution that can significantly affect its mechanical properties are evaluated. A mix design consisting of recycled carbon fiber and ultra-high-performance concrete was evaluated for mechanical properties and compared to an aerospace-grade and low-cost commercial carbon fiber with the same mix design. Additionally, the microstructure of concrete samples is evaluated non-destructively using high-resolution micro X-ray computed tomography to obtain 3D quantitative spatial pore size distribution information and fiber clumping. This study examines the compression, tension, and flexural properties of recycled carbon fibers reinforced concrete considering the microstructure of the concrete resulting from fiber dispersion.

Mechanical behavior of different fiber lengths mix-proportions carbon fiber reinforced concrete subjected to static, impact, and blast loading

Impact and blast wave loadings act as high instant energy and might cause damage to reinforced concrete infrastructures. This research aims to investigate the effect of using different length proportions of carbon fiber on the mechanical behaviors of concrete. Moreover, in this study, original carbon fiber and sizing-removed carbon fiber were added into concrete with different mix-proportions. The sizing on the carbon fiber surface was removed by using heat-treated method. In addition, the carbon fiber was dispersed by a high-pressure air compressor. Lengths of 12 mm and 24 mm carbon fibers were used in different mix-proportions to find the highest mechanical strength of carbon fiber reinforced concrete (CFRC) under a 1% fiber-to-cement weight ratio. Compressive, flexural, and impact tests were conducted on CFRC specimens. The CFRC specimen with 50% 12 mm and 50% 24 mm sizing-removed carbon fiber attained the highest impact resistance, and it also had the best performance under blast wave loading compared with the other CFRC specimens. The broken CFRC specimens were examined by an optical microscope to identify the failure mode of the carbon fibers in CFRC specimens. The addition of 50% 12 mm and 50% 24 mm sizing-removed carbon fiber can significantly improve the compressive and flexural strength of reinforced concrete.

Interfacial modification: The dynamic compression properties and enhancement mechanism of concrete added with micro-nano hierarchical carbon-based fiber

The modification of interfacial characteristics between carbon fiber and matrix (F/M) is one of the most pressing issues in the research related to carbon fiber reinforced concrete (CFRC). Herein, carbon nanotubes were grafted onto the surface of carbon fiber using an ultrasonic-assisted electrophoretic deposition technique to create a carbon-based fiber with micro-nano hierarchical structure (CNTs-CF) for concrete modification. The impact test of concrete (CCMC) added with micro-nano hierarchical carbon-based fiber was carried out by using split Hopkinson pressure bar (SHPB), and the effects of CNTs-CF and strain rate on the dynamic compression mechanical properties of concrete specimens were investigated. The microstructures and interfacial characteristics of CNTs-CF and CCMC were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results indicate that the CNTs-CF improves the internal F/M interface toughness due to its synergistic filling, bridging, and crack arresting effects, thus effectively relieving the local stress concentration and enhancing the dynamic compression properties of concrete. In the strain rate range of 50–120 s−1, as compared to CFRC, when the volume content of CNTs-CF is 0.3%, the dynamic compressive strength and peak strain of CCMC increase by 11.98% and 7.16%, respectively. When the volume content of CNTs-CF is 0.4%, the dynamic ultimate strain of CCMC increases by 5.52%.

Evaluating performance of carbon fiber-reinforced pavement with embedded sensors using destructive and non-destructive testing

Installation of concrete pavement at the curb travel lane at the bus stop is a common way to improve the resistance of bus pads to environmental and petroleum deterioration in Canada. The Satisfactory condition of concrete pavements remains a key consideration in the development of infrastructure, especially in countries with an aggressive environment. Innovative materials that could remarkably increase the service life of infrastructure are being researched and developed over decades. This paper aggregates the real-time comparison between the performance of a carbon fiber-reinforced concrete (CFRC) bus pad and a normal concrete bus pad. A series of wireless sensors such as temperature and humidity sensors, thermocouples and strain gauges were embedded in both pavements during the construction. Additionally, a series of six piezoelectric patches were embedded in the concrete in each bus pad. Visual monitoring exhibited that the carbon fiber-reinforced bus-pad remained cracked free while exhibiting some balling of carbon fibers on the surface of pavement whereas the normal concrete bus pads exhibited several hairline cracks in the first 10 days of construction. Along with the visual monitoring using a thermal imaging camera (FLIR), data was acquired regularly from both bus-pads at regular intervals. After 28 days of construction, Non-destructive tests (NDT) including Schmidt Hammer (SH), Electrical Resistivity (ER) and Ultrasonic Pulse Velocity (UPV) were conducted on both the bus pads. When compared to normal concrete bus pads, which have electrical resistivities of roughly 30 kΩ-cm, CFRC bus pads showed extremely low electrical resistivity. Schmidt hammer and UPV both revealed degradation in the normal concrete bus pad in comparison to the CFRC bus pad. Several clusters of very low UPV values were observed in the location of bus pad cracks. The lesser values in the CFRC bus pad are indicative of the scatter in the wave energy due to the presence of carbon fibers.

Finite Element of Nanoscale Carbon Fiber-Reinforced Concrete Bridge Engineering Monitoring Based on Data Mining Technology

The finite element method divides the existing solid structure into a finite number of elements. It integrates and analyzes the divided elements according to preset criteria, and then solves the equilibrium equation of the overall structure according to the corresponding boundary conditions. The problem is analyzed through a finite element model. A large amount of data from the experiment are derived, and then data mining technique is used to find out the data that are useful for the experiment. The purpose of this paper is to test bridge engineering through data mining technology, and then simulate different fiber-reinforced concrete models through finite element method. In this paper, three kinds of nanofibers, carbon fiber (CFRP), glass fiber (GFRP), and aramid fiber (AFRP) are used to make concrete bridges. Loading experiments are also carried out with different degrees of load on the bridge and 100 experiments on the error interval. The experimental results show that the displacement is proportional to the load to a certain extent. The carbon fiber concrete has a stronger positive correlation than the other two materials. Its finite element simulation experimental data have 78% error difference between 0 and 10, while the other two are around 40%.

Investigation of mechanical behavior and fracture energy of fiber-reinforced concrete beams and panels

This study quantifies the role of carbon fibers as micro-reinforcement in round panels to prevent and slow the formation of cracks. While carbon fiber-reinforced concrete (CFRC) has drawn considerable attention for use in pavements, the majority of CFRC performance assessment is limited to laboratory-scale samples which do not conform to the predominant failure mechanism, yield-line theory, for concrete pavements. In this study, the effects of carbon fiber content and length on flowability, fiber-matrix bond, and mechanical properties were studied and compared to polypropylene fiber. Analysis of the quadratic polynomial fitted surface plot helped to find the most effective fiber content and length. Composite theory was used to predict the flexural strength, and the result were compared to that of experimental results. The last phase consisted of concrete round panels tested under center-point bending in which the failure mechanism under yield line theory was analyzed. Analysis of Variance (ANOVA) model was finally adopted to compare the calculated modulus of rupture in beams and panels. The results showed beneficial effect of CFRC on pre-crack energy absorption, and their role as crack retarders was justified when the absorbed energy was compared to non-fibrous mixes. The residual flexural strength was also improved in beams and round panels reinforced with carbon fibers. Using the composite theory, the experimental-to-predicted flexural strength ratios in PAN-based carbon fibers were in the range of 1.11–1.34. However, the predicted strengths of mixtures with polypropylene and pitch-based carbon fibers were significantly higher than the experimental values.

Research Progress in Environmental Response of Fiber Concrete and Its Functional Mechanisms

Smart fiber reinforced concretes (FRC) are good in intelligent environmental response. With the smart FRC being used in buildings such as bridges and tunnels, the real-time online distributed monitoring of concrete state can be realized. It provides an excellent solution to reduce the emergencies caused by the accumulation of damages, resistance attenuation, etc. This paper analyzes smart FRC’s self-sensing and self-healing response characteristics under different environmental response fields. Furthermore, the intelligent response mechanism of smart carbon fiber reinforced concrete (CFRC), optical fiber reinforced concrete (OFRC), glass fiber reinforced concrete (GFRC), and nanofiber reinforced concrete (NFRC) would be summarized. The response fields include the stress field, temperature field, electromagnetic field, chemical field, and humidity field, among which the field response mechanism of smart NFRC is classified and summarized. Finally, the advantages and disadvantages, the intelligent response parameters, and the applications of smart FRC under different environmental fields are compared.

Impact of Thermal Stress on Abrasive Dust from a Carbon Fiber-Reinforced Concrete Composite

Recently, a novel corrosion-resistant construction material, Carbon Concrete Composite (C3), consisting of coated carbon fibers embedded in a concrete matrix, was introduced. However, thermal exposure during domestic fires may impact the release of organic pollutants and fibers during abrasive processing and/or demolition. Consequently, the objective of this study was to explore the emission characteristics of toxic compounds and harmful fibers during the dry-cutting after exposure to 25–600 °C (3 h, air). These parameters mimic the abrasive machining and dismantling after a domestic fire event. Mass spectrometry and chromatography served as analytical methodologies, and no organic pollutants for exposure temperatures ≥ 400 °C were found. In contrast, significant amounts of pyrolysis products from the organic fiber coating were released at lower temperatures. Studying the morphology of the released fibers by electron microscopy revealed a decrease in fiber diameter for temperatures exceeding 450 °C. At ≥550 °C, harmful fibers, according to the World Health Organization (WHO) definition, occurred (28–41 × 103 WHO fibers/m3 at 550–600 °C). This leads to the conclusion that there is a demand for restraining and protection measures, such as the use of wet cutting processes, suction devices, particle filtering masks and protective clothing, to handle thermally stressed C3.