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Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents some principles of research done on the assessment of fiber-matrix adhesion and durability in cement-based and polymer-based composites reinforced with vegetable fibers. Natural vegetable fibers are light, biodegradable and low-cost; however, their compatibility with both matrices - which are generally hydrophobic- is poor, because of their hydrophilic character. This review presents the different strategies proposed in literature to improve (1) interfacial bonding between matrix and fibers and (2) sustainability of composite materials reinforced by vegetable fibers. In order to achieve these goals, searchers investigate chemical or/and physical treatments of fibers and/or matrix modification of composites materials. The impacts of these strategies are followed in terms of mechanical properties, thermal properties, morphology and water absorption of the composite materials. Authors proposed to focus on the influence of aging on these characteristics in order to estimate durability. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract The use of cement-based composites (CBC) with high thermal conductivity for geothermal well cementing is extremely important for the efficient development and use of geothermal energy. Accurate prediction of thermal conductivity can save a lot of experimental costs and time. At present, there is no specific calculation model for the thermal conductivity of CBC. In this study, the microstructure, thermal conductivity model and influencing factors of CBC were investigated by experimental tests, theoretical analysis and numerical simulation. The results showed that the cement-based material could be simplified into a two-layer structure of hydrated and unhydrated layers. Mathematical and numerical models based on the coupled Series model and the Maxwell–Eucken model were established to calculate the thermal conductivity for CBC. The mathematical and numerical models were found to be more accurate by comparison with the conventional models and experimental test results. The cubic packing was more favorable than the spherical packing to improve the thermal conductivity of CBC. The plate material had significant anisotropy. The thermal conductivity of CBC showed a rapid decrease followed by a slow decrease, a decrease followed by a slow increase and finally a rapid decrease, a rapid increase followed by an up and down fluctuation and finally a plateau, respectively, with the increase of filler particle diameter, spacing and curing temperature. Based on these results, the effective methods and future research directions were proposed to maximize the thermal conductivity of geothermal well cementing materials in actual engineering applications. The research findings can provide some technical references for the efficient development of geothermal energy and research on CBC with high thermal conductivity.

The use of cement-based composites (CBC) with high thermal conductivity for geothermal well cementing is extremely important for the efficient development and use of geothermal energy. Accurate prediction of thermal conductivity can save a lot of experimental costs and time. At present, there is no specific calculation model for the thermal conductivity of CBC. In this study, the microstructure, thermal conductivity model and influencing factors of CBC were investigated by experimental tests, theoretical analysis and numerical simulation. The results showed that the cement-based material could be simplified into a two-layer structure of hydrated and unhydrated layers. Mathematical and numerical models based on the coupled Series model and the Maxwell–Eucken model were established to calculate the thermal conductivity for CBC. The mathematical and numerical models were found to be more accurate by comparison with the conventional models and experimental test results. The cubic packing was more favorable than the spherical packing to improve the thermal conductivity of CBC. The plate material had significant anisotropy. The thermal conductivity of CBC showed a rapid decrease followed by a slow decrease, a decrease followed by a slow increase and finally a rapid decrease, a rapid increase followed by an up and down fluctuation and finally a plateau, respectively, with the increase of filler particle diameter, spacing and curing temperature. Based on these results, the effective methods and future research directions were proposed to maximize the thermal conductivity of geothermal well cementing materials in actual engineering applications. The research findings can provide some technical references for the efficient development of geothermal energy and research on CBC with high thermal conductivity. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Southeast University / Dongnan Daxue Xuebao is the property of Journal of Southeast University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the development of society, the demand for cement-based composites is increasing day by day. Cement production significantly increases CO2 emissions. These emissions are reduced when high volumes of cement are replaced. The consideration of sustainable development has prompted people to search for new cement substitutes. The lignocellulosic biomass ash obtained from burning lignocellulosic biomass contains a large number of active oxides. If lignocellulosic biomass ash is used as a partial cement substitute, it can effectively solve the high emissions problem of cement-based composites. This review summarizes the physicochemical properties of lignocellulosic biomass ashes and discusses their effects on the workability, mechanical properties, and durability (water absorption, acid resistance, etc.) of cement-based composites. It is found that appropriate treatments on lignocellulosic biomass ashes are beneficial to their application in cement-based composites. Meanwhile, the issues with their application are also pointed out. [ABSTRACT FROM AUTHOR]

Recycled carbon fiber, as a novel form of regenerated fiber, exhibits exceptional properties such as high strength, high modulus, excellent electrical conductivity, and corrosion resistance. Consequently, it has garnered significant attention in recent years, owing to its potential to confer unique intelligent characteristics to cement-based materials. However, the dispersion of recycled carbon fiber remains an inevitable concern. Building upon existing research, this paper meticulously categorizes different types of recycled carbon fiber based on their mechanical properties and surface characteristics, while also exploring the impact of additives on fiber dispersion. Furthermore, a thorough evaluation of fiber dispersion methods is provided, considering the dimensions of stability, uniformity, and morphology at various stages, including fiber suspension, fresh mixture, and hardened matrix. Additionally, this paper offers a comprehensive summary and comparison of fiber dispersion methods, taking into account fiber pretreatment and preparation processes. Extensive literature reviews unequivocally support the notion that achieving a uniform dispersion of recycled carbon fiber serves as a fundamental requirement for enhancing and optimizing the properties of composites. Consequently, the utilization of dispersion and evaluation methods based on carbon fiber enables the exploration of appropriate dispersion methods tailored to different types of recycled carbon fiber in cement-based materials.

This study investigates the piezoresistive (self-sensing) properties of short stainless-steel fiber-reinforced mortar under varying temperature conditions. Different reinforced mortars were produced by varying fiber and aggregate content. First, Electrical Impedance Spectroscopy (EIS) measurements were used to characterize the electrical properties of the mortar specimens. EIS measurements were performed at temperatures of 24 °C, 35 °C, and 50 °C. Second, to investigate the self-sensing capacity of the different composites, the fractional changes of electrical impedance at 1 kHz were monitored under two conditions: temperature variation alone (cooling down from 35 °C or 50 °C to room temperature), and temperature variation combined with cyclic compressive loading (up to 5 MPa). The results of the former were used to compensate for the effect of temperature variations in the latter. Both temperature and mechanical loading produced meaningful variations in the electrical impedance and piezoresistivity of the investigated composites. Conclusions are drawn with respect to the stress and temperature sensitivity of the composites. The real and imaginary parts of the electrical impedance of the mortar produced with the highest fiber volume fraction (0.01%) and higher aggregate content (volume fraction of 60%) were distinctly sensitive to temperature and stress, which suggests the possibility of using the same composite as a stress and temperature sensor.

Copyright of Journal of Materials Science & Engineering (1673-2812) is the property of Journal of Materials Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Graphene oxide (GO) is a two-dimensional derivative of graphene material, with carboxy, hydroxy group functional groups at the middle of the sheets, and oxygen-containing functional groups at sheet edges. It has multiple advantages, such as high strength, hydrophilicity, and strong reactivity. With the development of construction materials, GO has been widely used as a nano-reinforced material in cement-based composites (CBCs). Based on a large amount of relevant literature, the preparation and dispersion behavior of GO-reinforced CBC are summarized. Besides, the impact of GO on the workability, volume stability, mechanical performance, and durability of CBC are discussed. Moreover, the influencing mechanism of GO on the hydration of CBC is expounded. From the findings of this review, the following conclusions can be drawn: the fluidity of CBC will be decreased when GO is evenly dispersed in the cement slurry, which results in a loss of workability of CBC. Meanwhile, the addition of GO improves the volume stability of CBC, while the tensile, compressive, and flexural strengths are all improved to varying degrees. The improvement of GO on the durability of CBC is mainly reflected in the corrosion resistance and permeability resistance. In addition, problems existing in the current research are summarized and future perspectives are put forward. The review work in this article could offer important guidance for further research and implementation of GO-doped CBC in practical engineering.

This study investigates the piezoresistive (self-sensing) properties of short stainless-steel fiber-reinforced mortar under varying temperature conditions. Different reinforced mortars were produced by varying fiber and aggregate content. First, Electrical Impedance Spectroscopy (EIS) measurements were used to characterize the electrical properties of the mortar specimens. EIS measurements were performed at temperatures of 24 °C, 35 °C, and 50 °C. Second, to investigate the self-sensing capacity of the different composites, the fractional changes of electrical impedance at 1 kHz were monitored under two conditions: temperature variation alone (cooling down from 35 °C or 50 °C to room temperature), and temperature variation combined with cyclic compressive loading (up to 5 MPa). The results of the former were used to compensate for the effect of temperature variations in the latter. Both temperature and mechanical loading produced meaningful variations in the electrical impedance and piezoresistivity of the investigated composites. Conclusions are drawn with respect to the stress and temperature sensitivity of the composites. The real and imaginary parts of the electrical impedance of the mortar produced with the highest fiber volume fraction (0.01%) and higher aggregate content (volume fraction of 60%) were distinctly sensitive to temperature and stress, which suggests the possibility of using the same composite as a stress and temperature sensor. [ABSTRACT FROM AUTHOR]

This paper concerns the results of research into the influence of the composition of rock inclusions on the fracture response of cement-based composite specimens. Specially designed specimens of the nominal dimensions 40 � 40 � 160 mm with inclusions in the shape of prisms with nominal dimensions of 8 � 8 � 40 mm were provided with an initial central edge notch with a depth of 12 mm. These specimens, which were made of fine-grained cement-based composite with different types of rock inclusion � amphibolite, basalt, granite, and marble � were tested in the three-point bending configuration. Fracture surfaces were examined via scanning electron microscopy and local response in the vicinity of rock inclusions was characterized via the nanoindentation technique. The aim of this paper is to analyse the influence of the chemical/petrographic composition of rock inclusions on the effective mechanical fracture parameters of cement-based composites, as well as on the microstructural mechanical parameters of the interfacial transition zone. The results of this research indicate the significant dependence of the effective fracture parameters on the petrographic and related chemical composition of the rock inclusions.

This study aims to promote the valorization of agro-industrial waste and sustainability in the construction industry by evaluating the potential of bamboo leaf ash (BLA) as a partial replacement for Portland cement in extruded fiber cement. Squeeze flow, physical, mechanical, and microstructural analyses (Scanning Electron Microscopy and X-ray microtomography) were conducted. The results showed that the incorporation of fibers and BLA leads to an increased water demand and, consequently, an increase in porosity and pore connectivity. However, the mix design with 10 % replacement exhibited improved mechanical behavior for modulus of rupture (10.2 %) and limit of proportionality (4.5 %), when compared to a formulation without BLA. For the other parameters, the mix design with 10 % BLA showed mechanical behavior with no statical difference to the mix design without ash. Thus, the use of BLA as a partial replacement for Portland cement represents an alternative with technical and environmental improvements for fiber cement. • Extrudability was achieved when water/binder ratios were controlled. • The inclusion of BLA led to increased water absorption and porosity. • Replacement of 10 % OPC by BLA exhibited improved mechanical behavior. • The blended mix with 20 % BLA exhibited similar results to mixes with OPC. [ABSTRACT FROM AUTHOR]

Mortar sensors were fabricated as beams incorporating different amounts of carbon nanofibers (CNFs) synthesized in-situ on cement particles. Changes in electrical resistivity were measured and compared to recorded changes in compressive stress, temperature, and humidity. Sensing mechanisms and corresponding models were developed. The findings of the study indicate that the piezoresistive effect is influenced by the critical concentration of CNFs inside the composite matrix and the tunneling effect. In addition, water absorption and desorption, as well as the amount of chemically bound water played an important role in humidity sensing. Thermal fluctuation-induced tunneling conduction was dominant for the temperature sensitivity. [ABSTRACT FROM AUTHOR]

With the development of society, the demand for cement-based composites is increasing day by day. Cement production significantly increases CO2 emissions. These emissions are reduced when high volumes of cement are replaced. The consideration of sustainable development has prompted people to search for new cement substitutes. The lignocellulosic biomass ash obtained from burning lignocellulosic biomass contains a large number of active oxides. If lignocellulosic biomass ash is used as a partial cement substitute, it can effectively solve the high emissions problem of cement-based composites. This review summarizes the physicochemical properties of lignocellulosic biomass ashes and discusses their effects on the workability, mechanical properties, and durability (water absorption, acid resistance, etc.) of cement-based composites. It is found that appropriate treatments on lignocellulosic biomass ashes are beneficial to their application in cement-based composites. Meanwhile, the issues with their application are also pointed out.

Copyright of China Synthetic Fiber Industry is the property of Sinopec Baling Petrochemical Company and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study investigated the in-situ growth of carbon nanotubes (CNTs) in silica (SiO2) powder by polymer pyrolysis chemical vapor deposition with a polyethylene glycol (PEG) carbon source and cobalt nitrate catalyst. The mass ratio of PEG:citric acid:cobalt nitrate was determined to control the microstructures of the in-situ CNTs. Results indicated that with an increase in the mass ratio of PEG:citric acid:cobalt nitrate, the in-situ generated CNTs content in the SiO2 powder increased, the CNTs diameters (approximately 40 nm) did not significantly change, and the CNTs lengths decreased from 400–800 nm to 200–400 nm. Additionally, the in-situ CNTs that were anchored on the surfaces of SiO2 particles presented fewer defects and a high degree of graphitization. However, when the mass ratio of PEG:citric acid:cobalt nitrate exceeded the critical value, excessive amounts of amorphous carbon grown in situ on SiO2 particles were obtained. The suspension experiments showed that unlike the CNTs/SiO2 powders prepared by a combination of surfactant and ultrasonic methods with commercial CNTs, in-situ CNTs grown in SiO2 powders exhibited improved separation resistance in water. This would favor the uniform dispersion of CNTs within the matrix, improving the performance of nanocarbon-modified cement-based composites.

Diffusive behaviour is the fundamental mechanism of ionic-induced corrosion in cement–granular composites. Aggregate characteristics, including shape anisotropy, spatial orientation, and size distribution, significantly influence effective diffusivity. However, influences of all such types of aggregate irregularity have rarely been systematically quantified, and most of the representative aggregate shapes in numerical simulations are convex than realistic concave. In this study, we apply the finite element method (FEM) to investigate diffusion behaviour of 2D cement-based composites. Realistic multi-scale aggregate shapes, characterised by fractal dimension (Fd) and relative roughness (Rr), are generated to highlight the influence of aggregate morphology on the effective diffusivity. The spatial distribution is evaluated by the disorder index. From numerical results, samples with a larger disorder index, indicating a broader throat size distribution, show smaller effective diffusivities. Meanwhile, aggregate shape irregularity causes much smaller effective diffusivities, highlighting the necessity of the realistic concave particle shapes in numerical simulations. Sensitivity studies show Fd and Rr are more related to the effective diffusivity than other single-scale classical shape parameters. At last, a model with only these two shape parameters is proposed to predict effective diffusivity. This work further improves the understanding of the role of aggregate morphology on the effective diffusivity, towards applications in ionic-induced corrosion in two-phase composites. Highlights: Realistic grain shapes in composites are generated using Fourier transformation. Effects of aggregate characteristics on the effective diffusivity are investigated. Fd and Rr are key geometrical parameters influencing the effective diffusivity. [ABSTRACT FROM AUTHOR]

This paper concerns the results of research into the influence of the composition of rock inclusions on the fracture response of cement-based composite specimens. Specially designed specimens of the nominal dimensions 40 × 40 × 160 mm with inclusions in the shape of prisms with nominal dimensions of 8 × 8 × 40 mm were provided with an initial central edge notch with a depth of 12 mm. These specimens, which were made of fine-grained cement-based composite with different types of rock inclusion - amphibolite, basalt, granite, and marble - were tested in the three-point bending configuration. Fracture surfaces were examined via scanning electron microscopy and local response in the vicinity of rock inclusions was characterized via the nanoindentation technique. The aim of this paper is to analyse the influence of the chemical/petrographic composition of rock inclusions on the effective mechanical fracture parameters of cement-based composites, as well as on the microstructural mechanical parameters of the interfacial transition zone. The results of this research indicate the significant dependence of the effective fracture parameters on the petrographic and related chemical composition of the rock inclusions. [ABSTRACT FROM AUTHOR]

Tn order to understand the law of durability degradation of cement-based composite (CBC) in complex freezing-thawing environment, single side freezing-thawing test is used to evaluate the durability of cementbased composite in water and sodium sulfate solution. The macroscopic properties (spalling capacity, relative dynamic modulus of elasticity) and micropore structure parameters (gas content, bubble spacing coefficient, specific surface area and average chord length of bubbles) are measured. The grey correlation theory is used to calculate the correlation degree between the pore structure parameters and the relative dynamic elastic modulus for evaluating its influence on the macroscopic performance and a prediction model of the relative dynamic elastic modulus based on the pore structure parameters is established. [ABSTRACT FROM AUTHOR]

This paper concerns the results of research into the effect of the mechanical fracture parameters of inclusion material on the fracture response of specially designed cement-based composite specimens. These specimens of the nominal dimensions 40 × 40 × 160 mm with inclusion in the shape of prisms with nominal dimensions of 8 × 8 × 40 mm were provided with an initial central edge notch and tested in the threee-point bending configuration. The aim of this paper is to analyse the effect of the mechanical fracture parameters of inclusions material on the effective mechanical fracture parameters of cement-based composite. The results of this research indicate the dependence of the effective mechanical fracture parameters of cement-based composite on the Young's modulus of inclusion material. [ABSTRACT FROM AUTHOR]

In this study, physical and mechanical properties of non-structural composite panels used in buildings were determined experimentally. By evaluating the results obtained from the experimental study, the performances of these panels were revealed in terms of physical and mechanical properties. While evaluating the physical performance, its properties such as water absorption and expansion under moisture are taken into consideration. In terms of mechanical properties, four-point bending strengths, fracture energies, tensile strengths and modulus of elasticity values were obtained. The results of the water absorption and expansion tests were evaluated together and the relationships of these properties were revealed. Panels with optimum performance in terms of flexural strength and fracture energy have been determined. According to the results of the experimental study; While cellulose fiber reinforced cement matrix composite gives the highest strength values, cement-based textile reinforced composite panel exhibits the highest fracture energy. It has been concluded that glass fiber reinforced cement panels containing chopped glass fiber are the optimum solution in terms of flexural strength-fracture energy and expansion values. [ABSTRACT FROM AUTHOR]

Copyright of New Building Materials / Xinxing Jianzhu Cailiao is the property of New Building Materials Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper aims to investigate the feasibility of the incorporation of nanosilica (NS) in ultra-lightweight foamed concrete (ULFC), with an oven-dry density of 350 kg/m3, in regard to its fresh and hardened characteristics. The performance of various dosages of NS, up to 10 wt.-%, were examined. In addition, fly ash and silica fume were used as cement replacing materials, to compare their influence on the properties of foamed concrete. Mechanical and physical properties, drying shrinkage and the sorption of concrete were measured. Scanning electron microscopy (SEM) and X-ray microcomputed tomography (µ-CT) and a probabilistic approach were implemented to evaluate the microstructural changes associated with the incorporation of different additives, such as wall thickness and pore anisotropy of produced ULFCs. The experimental results confirmed that the use of NS in optimal dosage is an effective way to improve the stability of foam bubbles in the fresh state. Incorporation of NS decrease the pore anisotropy and allows to produce a foamed concrete with increased wall thickness. As a result more robust and homogenous microstructure is produced which translate to improved mechanical and transport related properties. It was found that replacement of cement with 5 wt.-% and 10 wt.-% NS increase the compressive strength of ULFC by 20% and 25%, respectively, when compared to control concrete. The drying shrinkage of the NS-incorporated mixes was higher than in the control mix at early ages, while decreasing at 28 d. In overall, it was found that NS is more effective than other conventional fine materials in improving the stability of fresh mixture as well as enhancing the strength of foamed concrete and reducing its porosity and sorption. [ABSTRACT FROM AUTHOR]

Waves, in general, can be characterised as a physical phenomenon. Mechanical waves occur in the environment, which is composed of particles between which there is a bond. In this material, the forced oscillation of one particle is progressively transferred to the other particles, with environmental particles not moving in the space but only oscillating around equilibrium positions and they are simultaneously deforming. The oscillation progresses at a certain speed from its source at some points, either in the plane or in space. In order to analyse the change of mechanical waves passing through fine-grained cement-based composite material during setting and hardening, a suitable experimental technique is needed. The main aim of this paper is a description of the non-destructive method, which will be used mainly to monitor the signal amplitude change during the setting and hardening of cement-based materials. The measuring set was composed for this purpose from the equipment of the Brno University of Technology. The form for the testing of composites is made in the same size as the Vicat´s ring. The own measurement of the signal will be done on the DAKEL XEDO acoustic analyser. The main advantage of the method is its non-destructive character. The first results show the obtained results could be used to determine the initial setting time of the cement-based composites. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Featured Application: Authors are encouraged to provide a concise description of the specific application or a potential application of the work. This section is not mandatory. The mechanical properties of cement-based composites reinforced with glass textile are strongly affected by the low ability of the inorganic matrix to penetrate within the single filaments, and by the low durability of the fibers in an alkaline environment. Over the last decades, different studies have investigated the possibility to improve the mechanical properties and the durability of this class of composites by modifying the surface of the reinforcement, mainly using different types of organic or inorganic coatings. Although different solutions have been proposed, the feasibility of applying these techniques strictly depend on the final application of the composite. This review aims to give an overview of the different methods that have been proposed in the literature and to highlight advantages and drawbacks. [ABSTRACT FROM AUTHOR]

Cement-based composites with periodic pyramidal surfaces were prepared, and its electromagnetic wave absorbing properties were measured with arch reflectivity test system in 1.7~18.0 GHz. The influence of the pyramid size and the matrix on the absorbing properties was discussed. The results were simulated with the software HFSS. The results showed the pyramidal structure improved the absorbing properties. Larger heights and electromagnetic parameters make better absorption properties. The absorption properties in lower frequency range were enhanced by larger scale in height, and the absorbing frequency band reached S band (2~4 GHz) as height increased. The reflectivity was better than -20 dB in 3.1~18.0 GHz when the pyramid height and carbon black content were 40 mm and 1.5%, respectively. The mechanism of the pyramid structure to improve the absorbing performance is that the pyramid structure can form impedance matching with free space and multiple reflections enhanced the attenuation, thereby increasing interference loss and internal dielectric loss, and introducing scattering and diffraction losses. [ABSTRACT FROM AUTHOR]

The physical and mechanical properties of cement-based materials can be improved by adding fiber. However, the influence of organic-inorganic hybrid fibers on the properties of cement materials is seldom studied. In this paper, mechanical properties of cement-based materials with single PVA fiber, single basalt fiber and two kinds of fiber were tested. The results showed that when only 1.6% short PVA fiber was added, the mechanical properties of cement-based materials were improved the best. The flexural strength of cement-based materials decreased by 7%, the compressive strength increased by 31% and the flexural ratio decreased by 24%. With only 0.3% basalt fiber staple, cement-based materials showed the best improvement in mechanical properties, with the flexural strength reduced by 8%, the compressive strength increased by 15.7% and the flexural strength decreased by 20%. When adding 0.3% short basalt fiber and 0.5% short PVA fiber, the flexural strength of cement-based composites had little effect, but the compressive strength was significantly improved, and the flexural compression ratio was relatively reduced, which showed the best comprehensive performance. [ABSTRACT FROM AUTHOR]

In this paper, non-ionic polyoxyethylene ether was used to modify the surface of poly(vinyl alcohol) (PVA) fibers and to improve their dispersion in cement mortar. The results showed that surface modification could apparently improve the dispersion of PVA fibers in cement mortar by weakening the original intermolecular hydrogen bonds between the adjacent hydroxyl groups on the surface of PVA fibers and increasing the formation of hydrogen bonds between PVA fibers and cement mortar. After modification, the advancing contact angle and the receding contact angle of the fibers were respectively reduced from 44.2° to 34.7° and from 38.8° to 33.1°, and the dispersion coefficient of the fibers was increased from 0.85 to 0.95. Owing to the improved interactions between modified PVA fibers and cement mortar and to the good dispersion of the fibers in the matrix, the fibers had a superior energy absorption capacity and showed a ductile fracture, leading to higher flexural strength, bending modulus and toughness of fiber-reinforced cementitious composites.

• A novel bio-inspired cement-based composite system is proposed. • The self-retardant mechanism of APP-PER-EN composite is introduced in detail. • The thermal behavior of APP-PER-EN composite is characterized. • One-side heating tests are conducted to reveal the interaction of novel system. The mechanical properties of concrete can degrade significantly under high temperature, posing a threat to the safety of structures. In this work, a novel bio-inspired cement-based composite material that can improve the fire resistance of engineering structures is put forward. This bio-inspired cementitious system, which functions in a manner similar to that of sweat glands and skin in the human body, consists of APP-PER-EN composite, synthetic reinforcing fibers, and concrete binder. The APP-PER-EN composite is mainly composed of ammonium polyphosphate, pentaerythritol, and melamine, with low-density polyethylene as the base material, which is prepared by melt compounding in a twin-screw extruder followed by grain cutting molding technique. At the micro level, multiple analysis methods are used, including X-ray diffraction, Fourier transform infrared ray, thermo-gravimetric analysis, differential scanning calorimeter, and scanning electron microscopy, to characterize the thermal and flame retardant behavior of this novel composite. At the macro level, the one-side heating tests indicate that the thermally triggered fire-resistant system can exhibit significant thermal insulation effect through melting, connecting, foaming, and overflowing. Therefore, the novel composite system is expected to exhibit a promising prospect in the fire resistance of engineering structures. [ABSTRACT FROM AUTHOR]

The present work focused on growth of in-situ CNTs on slag through polymer pyrolysis chemical vapor deposition method (PP-CVD) for improving the electromagnetic interference shielding effectiveness of cement-based composite. The results indicated that numbers of in-situ CNTs were uniformly anchored on the slag particles after PP-CVD treatment, the density and aspect ratio of in-situ CNTs were increased, as the mass ratio of melamine to nickel acetylacetonate increased. However, when the mass ratios exceeded the critical value, amorphous carbons, in contrast to CNTs, were generated on slag particles. The EMI shielding effectiveness (SE) results showed that the EMI SE total of the in-situ CNT/slag cement-based composite reach up to 55 dB, much higher than that of the composite with addition of CNTs/slag powder (which were prepared by a combination of surfactant and ultrasonic methods with commercial CNTs), due to the higher electrical conductivity of the former resulted from the improved dispersion of CNTs within the cement-based composite. • In-situ CNTs/slag were prepared through polymer pyrolysis chemical vapor deposition method for improving the electromagnetic interference shielding effectiveness of cement-based composites. • The CNTs incorporated into the cement-based composite through in-situ CNTs/slag had excellent dispersion, resulting in an increase of 31.8% in electrical conductivity of cement-based composite. • An EMI SE of 55 dB was achieved for in-situ CNTs/slag modified cement-based composite. [ABSTRACT FROM AUTHOR]

The mechanical properties of cement-based composites reinforced with glass textile are strongly affected by the low ability of the inorganic matrix to penetrate within the single filaments, and by the low durability of the fibers in an alkaline environment. Over the last decades, different studies have investigated the possibility to improve the mechanical properties and the durability of this class of composites by modifying the surface of the reinforcement, mainly using different types of organic or inorganic coatings. Although different solutions have been proposed, the feasibility of applying these techniques strictly depend on the final application of the composite. This review aims to give an overview of the different methods that have been proposed in the literature and to highlight advantages and drawbacks.

Strength and toughness of cement-based composite has been a hot topic in this field. Graphene oxide which added in cement-based composites can modify hydration products and the defects in microstructure, so as to improve the strength and toughness of cement-base composites. In view of the structure and defects of cement-based composites, this paper review the progress on modifying structural defects of cement-based composites by graphene oxide, and mainly introduces the effect and mechanism of strengthening and toughening, and prospects the future development. [ABSTRACT FROM AUTHOR]

Abstract The pullout behavior of single filament jute fibers and yarns from a low calcium hydroxide cement matrix were studied. Pullout tests were performed in the micro and meso scales. In the micro scale, the tests were conducted inside an environmental SEM. The fibers were treated with styrene butadiene polymer to improve the fiber-matrix bond and a double-sided pullout configuration was used for the meso scale tests. An analytical model was used to calculate the parameters related to adhesional, frictional, and dynamic bond slip mechanisms between jute fiber and matrix. Results showed that the polymer coating increased the bond up to 130%. The fiber matrix bond at the meso scale also yielded higher values for the polymer-coated fibers. The analytical model is observed to fit the experimental results with the parameters of the maximum shear and frictional stresses that correlate well with the nominal interface strength. [ABSTRACT FROM AUTHOR]

Highlights • Studying the combined effect of GO content and w/c ratio on GO-cement composites. • Exploring the influence of GO on the optimal water/cement ratio. • Studying the governing mechanism for the improvements in GO-cement composites. • Investigating the composition-microstructure-strength relationship for GO-cement. Abstract Aiming to improve the flexural and compressive strength of cement, graphene oxide (GO) was incorporated into the production of cement-based composites in this study. The effects of the GO content and water/cement (w/c) ratio on the mechanical properties and microstructure of GO–cement composites were systematically investigated through experimental tests. Testing results show that with a constant w/c ratio, the flexural and compressive strengths of the developed GO–cement composites increased first and then declined with respect to the increase in GO content. Specifically, the increase in flexural strength was more significant than that in compressive strength, indicating that the addition of GO could help improve the toughness of cement composites. Additionally, a combination of a w/c ratio of 0.35 and a GO content of 0.05 wt% led to both the highest flexural and compressive strengths. The investigation of the composition–microstructure–strength relationship shows that the introduction of GO could help improve the macroscopic properties for the cement-based composites via improving the microstructure of cement hydration products, refining the crystal size, and forming a denser and more uniform network structure. The filling effect, hydration effect and nucleation effect of GO could be optimized with an appropriate combination of w/c ratio and GO content. [ABSTRACT FROM AUTHOR]

The proper use of renewable or recycled source materials can contribute significantly to reducing the environmental impact of construction industry. In this work, cement-based composites reinforced with natural fibres were developed and their mechanical behaviour was characterised. To ensure the composite sustainability and durability, the ordinary Portland cement matrix was modified by adding metakaolin and the natural aggregate was substituted by 10 and 20% of recycled concrete aggregate. Compression and splitting tensile tests indicated that mechanical strength did not seem to be affected by recycled content. Flat sheets were cast in a self-compacted cement matrix and bending tests were performed to determine the first crack, postpeak strength and cracking behaviour of the composites. The use of short sisal fibre as reinforcement of recycled cement matrices results in a composite with multiple cracking and increment in strength after first crack. The modelling of composites using the finite-element method allowed to determine the tensile stress−strain behaviour of material and to design possible applications of this new sustainable material. [ABSTRACT FROM AUTHOR]

Abstract A novel electric induced curing method is introduced in this paper in order to solve the problem of cold region construction. This method applies alternating voltage (AC) to the fresh graphene/cement-based composite to generate ohmic heating, which can helps to accelerate the hydration reaction and form the structural strength of cement-based materials in deep-freeze low temperature. Graphene nanoplatelets (GNPs) were utilized to form conductive path in the fresh cement-based composite, thus reducing electrical resistivity. Numerical and experimental study was conducted to quantify the bridging behavior of GNPs and an optimum amount of GNPs of 2.0 vol% is determined as the global GNPs connection threshold. The graphene/cement-based composite by electric induced curing at −20 °C experiences an internal temperature rise and has superior mechanical properties. Further, the structural homogeneity of the hardened cement-based composite was confirmed using the nondestructive ultrasonic evaluation and microhardness measurement by one-way analysis of variance. Moreover, SEM, Raman spectra and MIP results show that the electric induced curing can accelerate the cement hydration leading to denser microstructure at low temperatures. This work provides insights into the quality control of cement-based materials for cold weather construction by means of the convenient and energy-efficient electric induced curing. Graphical abstract Unlabelled Image Highlights • Experimental measurement and numerical simulation give an optimum graphene content in the fresh cement-based composite • Graphene/cement-based composite cured under alternating current experience an internal temperature rise due to Joule heat • Electric induced curing of graphene/cement-based composites at -20℃ accelerates the hydration thus improving the strength • No significant differences in Vickers hardness and ultrasonic velocities of sample indicate the structural homogeneity [ABSTRACT FROM AUTHOR]

• The effect of clinoptilolite content on the mechanical properties is tested. • The microstructure of matrix is compared and analyzed by XRD, SEM and MIP. • Adding clinoptilolite can improve the strength and compactness of the matrix. • The fractal characteristic of pore structure is indicated by fractal dimension. • A relationship model between property and pore fractal characteristics is proposed. To further analyze the effect mechanism of clinoptilolite on the macro-mechanics and microstructure of polypropylene fiber-reinforced cement-based composite, the samples with 0, 5%, 10%, 15%, 20% and 25% clinoptilolite contents were investigated by compression test, flexural test, X-ray diffraction (XRD), scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP), and the pore structure characteristics were quantitatively analyzed by fractal theory. Results showed that: With the increase of clinoptilolite content, the compressive strength, flexural strength and porosity of samples first increased and then decreased. The addition of clinoptilolite reduced the 7-day strength but increased the 28-day compressive strength, 60-day compressive strength, 28-day flexural strength and 60-day flexural strength of the samples by about 6%, 14.3%, 13.9% and 19.1%. It was recommended that the clinoptilolite content should not exceed 15%. Due to the filling effect and pozzolanic effect of clinoptilolite, adding clinoptilolite into the matrix could promote a hydration reaction to produce more C-S-H gels and reduce the proportion of more harmful pores and harmful pores, effectively improving the internal pore structure of the matrix. Meantime, it was found that the evolution law of pore structure based on fractal dimension calculated by the thermodynamic fractal model was consistent with the variation law of the pore size distribution curves and pore volume measured by MIP. Furthermore, a polynomial relationship model between clinoptilolite content, the quantitative fractal characteristic of pore structure and the macroscopic mechanical behaviors was established, which indicated that the pore fractal dimension could quantitatively describe the effect of clinoptilolite content on the pore microstructure. [ABSTRACT FROM AUTHOR]

[Display omitted] Heat accumulation on cement pavement will deteriorate traffic safety and aggravate the urban heat island effect in summer so that efficient heat transfer methods become the key to road heat dissipation. However, traditional heat dissipation attempts tended to focus on utilizing water evaporation and pavement heat convection, which led to unsustainable heat transfer and reduced pavement strength. In this work, lowering the water-cement ratio and increasing the carbon fiber (CF) content were applied consecutively on the basis of the standard pouring method in order to achieve the highest thermal conductivity of the cement-based composites. Heat transfer behavior was determined by measurements of thermal conductivity and porosity, and demonstrated by microscopic topography and temperature change image characterization. According to the results, by lowering the water-cement ratio and raising the CF content, composites' thermal conductivity improved by 26.7 %, and their cold side temperature rose by 14.7 °C after the same heating period, a 26.5 % increase. Moreover, in order to characterize the stability of heat transfer, each group of samples was subjected to freeze–thaw cycles and then added to the previous test methods. Test results demonstrated that a low water-cement ratio and appropriate CF content reduced the sensitivity of thermal conductivity to freeze–thaw cycles. [ABSTRACT FROM AUTHOR]

• Expanded graphite improves the thermal conductivity of cement-based composites. • Diamond/ZnO optimizes the expanded graphite network and improves the thermal conductivity. • Diamond/ZnO reduces damage to thermal conductivity from freeze-thaw cycle treatment. • Pressed cement has lower porosity and higher thermal conductivity than poured cement. • Diamond and expanded graphite can hinder crack development during freeze–thaw cycles. In recent years, the deterioration of traffic safety due to high road temperatures and the increase in transport costs have led to an urgent need for road users to reduce the temperature of the road surface. In this paper, high thermal conductivity diamond/ZnO/expanded graphite (D/ZnO/EG) 1 1 Diamond: D; Expanded graphite: EG. cement-based composites were prepared by constructing and optimizing a thermal conductivity network in a cement matrix to achieve road cooling. Thermal network structure and porosity's impact on thermal conductivity had both been investigated, and the mechanism governing thermal conductivity had also been analyzed. With a thermal conductivity of 6.338 W/(m·K), 732 % of the cement matrix, the result showed that the expanded graphite (EG) thermal conductivity network and D/ZnO significantly enhanced heat transfer. The excellent thermal transfer capacity of D/ZnO/EG cement-based composites was also shown to be beneficial in reducing pavement temperatures in the temperature distribution simulations at the road surface under solar irradiation. The above results illustrated the EG network thermal's conductivity, the impact of D in shortening the EG spacing, and the impact of ZnO in filling the gaps, all of which were effective in enhancing thermal conductivity. In addition, D/ZnO/EG prevented crack extension and thus attenuated the damage to thermal conductivity caused by freeze–thaw cycles. This work confirms that the D/ZnO/EG cement-based composite can achieve effective heat dissipation from pavements, thereby improving traffic safety and reducing the long-term costs of road traffic. [ABSTRACT FROM AUTHOR]

It is researched, in this study, the strengthening technique known as Near Surface Mounted (NSM), which consists of the insertion of laminates of Carbon Fiber Reinforced Polymer (CFRP) into notches in the covering concrete structures. In the strengthening in beams, the tensile zone is found damaged for several reasons (cracking and corrosion, for instance), which demands, in the practice of engineering, its preliminary retrofitting. It should be considered that the good performance of the material used in this retrofitting is fundamental for a higher efficiency of the strengthening. Therefore, it is proposed a methodology that consists of the reconstitution of the tensile zone of the beams with a cement-based composite of high performance (CCAD), which acts as a substrate for the application of CFRP and as an element for the transfer of efforts to the part strengthened. The retrofitting of this tensile zone was performed only in the shear span, as well as throughout of the zone with a view to evaluating the influence of this aspect on the performance of the beams. The CCAD, produced from Portland cement, steel fibers and microfibers, was evaluated using the Rilem (2002), showed to be able to delay the cracking. Tests performed in the beams with the tensile zone retrofitting by CCAD and strengthening using the technique NSM showed the efficiency of the proposed methodology.

This Special Issue on “Cement-Based Composites: Advancements in Development and Characterization” presents the latest research and advances in the field of cement-based composites. This special issue covers a variety of experimental studies related to fibre-reinforced, photocatalytic, lightweight, and sustainable cement-based composites. Moreover, simulation studies are present in this special issue to provide the fundamental knowledge on designing and optimizing the properties of cementitious composites. The presented publications in this special issue show the most recent technology in the cement-based composite field.