Cement-based Composites Research Articles

Identification of 2-d shape parameters for waste brick powders from varying milling methods: A discussion of quantitative image analysis

Quantitative characterisation of morphology and shape parameters of pozzolanic materials, as a fundamental problem of characterisation of pozzolanic materials, has received significant consideration in literature. Thus far, previous research works have not paid much attention to the circularity, roundness and solidity of pozzolanic materials including waste brick powder (WBP). This research makes a significant contribution on identification of circularity, roundness and solidity of WBP particles under milling conditions using quantitative image analysis. In particular, the goal was to interrogate the ball milling treatment variables for generating WBP using scanning electron microscopy (SEM) and image analysis. Under the milling conditions of changing sample masses introduced in ball mill, the average circularity values for the specimens were approximately 0.6 whilst the average solidity values for the specimens were approximately 0.71. Moreover, the average roundness values for the specimens were nearly 0.51. It was shown that the trends of shape parameters of WBP under changing fineness levels were not significant. The values of circularity, solidity and roundness in this study therefore collaborate to support the discoveries of hidden shape characteristics of WBP specimens and can tackle the overall behaviour of cement-based composites containing WBP. Quantitative image analysis was therefore observed to be capable of inheriting detailed information from SEM micrographs and remains one of the most outstanding approaches of generating shape parameters.

Calculation model and influence factors of thermal conductivity of composite cement-based materials for geothermal well

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.

Modification of in-situ polymerization of acrylamide and synergies with fiber in enhancing cement-based composite

Due to its inherent brittleness and heterogeneity, high performance cement-based materials continue to be a challenge. An enhancing cement-based composite is prepared based on polymer-fiber synergies, combining the structure design and toughening strategy of the dual organic networks. Crucially, the modification is performed by in-situ polymerization of acrylamide and synergies with fiber. The mechanical properties of the composite are significantly improved, such as flexural strength and toughness. Incorporating 4 wt% polymers and 1.75 vol% fibers, this approach shows that the remarkable flexural strength is increased by 151.7 %. And the brittle fracture of conventional cement-based materials is transformed into a distinct ductile fracture. The composite has obvious performance advantages over the single reinforcing material. Further, the dual network and synergistic modification mechanisms are revealed by microscopic characterizations. On the one hand, through structural design, in-situ polymers and fibers promote the formation of an interwoven dual network. On the other hand, the bonding interaction between polymers, fibers, and hydration products is confirmed by the experimental results, including hydrogen bonding and carboxyl-metal ion bonding, facilitating the formation of an interwoven and tightly integrated polymer-fiber ductile organic network. In addition, the bonding interaction establishes an efficient energy dissipation mechanism to enhance the bonding properties between fibers and hydration products significantly. Notably, in-situ polymerization can in-situ modify the fiber surface's interfacial structure, improving pore size distribution. The dual network structure and toughening strategy based on in-situ polymerization provide a viable and promising instance for manufacturing high-toughness cement-based composites and in-situ microstructure design.

Low Concentrations of Gold Nanoparticles as Electric Charge Carriers in Piezoelectric Cement-Based Materials.

Piezoelectric cement-based composites could serve to monitor the strain state of structural elements or act as self-powered materials in structural health monitoring (SHM) applications. The incorporation of piezoelectric materials as an active phase within cement matrices has presented a highly attractive avenue until today. However, their application is challenged by the low electrical conductivity of the hydrated cement matrix. Gold nanoparticles (Au NPs) possess substantial potential for elevating the free electrical charge within the matrix, increasing its electrical conductivity between the Au NPs and the cement matrix, thereby enhancing the piezoelectric response of the composite. In this sense, the objective of this study is to investigate the effects of incorporating low concentrations of gold nanoparticles (Au NPs) (442 and 658 ppm) on the electrical and piezoelectric properties of cement-based composites. Additionally, this study considers the effects of such properties when the material is cured under a constant electric field. Electrical impedance spectroscopy was used to evaluate the polarization resistance and piezoresistive properties of the material. Additionally, open-circuit potential measurements were taken alongside the application of mechanical loads to assess the piezoelectric activity of the composites. The findings revealed a notable decrease in the composite's total electrical resistance, reaching a value of 1.5 ± 0.2 kΩ, almost four times lower than the reference specimens. In the realm of piezoelectricity, the piezoelectric voltage parameter g33 exhibited a remarkable advancement, improving by a factor of 57 when compared to reference specimens. This significant enhancement can be attributed to both the concentration of Au NPs and the electrical curing process. In summary, the outcomes of this study underscore the feasibility of creating a highly electrically conductive cement-based matrix, using low concentrations of gold nanoparticles as electric charge carries, and indicate the possible piezoelectric behavior of the studied compposite.

Comparative Evaluation of Stabilized Soil Properties Incorporating Bagasse Ash with Cement Vs Lime on Determination of Best Additive Combinations

This study investigated the use of bagasse ash from Custus arabicus L. as a pozzolanic admixture for stabilizing expansive black cotton soil alongside cement and lime. Samples of the problem soil were collected and treated with varying proportions (2.5-10% by dry weight) of bagasse ash in combination with a constant 8% content of cement or lime. The engineering properties of the treated composites such as maximum dry density, optimum moisture content, consistency limits, California bearing ratio and unconfined compressive strength were evaluated based on standard procedures. The results showed that both the cement-bagasse ash and lime-bagasse ash composites were effective in modifying the expansive behavior and improving the strength of the black cotton soil. Key indicators like liquid limit, plastic limit and plasticity index decreased with rising bagasse ash content, indicating a reduction in soil shrink-swell potential. Meanwhile, properties enhancing load-bearing capacity such as maximum dry density, optimum moisture content, CBR and UCS values increased upon treatment. Among the mixtures, soil stabilized with 8% cement and 7.5% bagasse ash composite exhibited the optimal performance. Compared to untreated soil, maximum improvements of 66.4% and 102.6% were recorded in the CBR and UCS values respectively for the optimal cement-bagasse ash blend. Overall, both lime and cement-based composites incorporating bagasse ash from Custus arabicus L. showed potential for modifying expansive subgrades and increasing their structural capacity. The study established the viability of utilizing agro-industrial waste alongside conventional stabilizers for ground improvement works.

Preparation and properties of pretreated jute fiber cement-based composites

In order to resolve the contradiction of poor compatibility between plant fiber and cement-based materials and improve the toughness and durability of cement-based composites, this paper takes jute fiber cement-based composites as the research object, and proposes the pretreatment method of jute fiber through mass loss rate and water absorption test. The influence of pretreated jute fiber on the properties of cement-based composites was investigated by means of mechanical properties and frost resistance tests. The strengthening mechanism of jute fiber in the pre-treatment of cement-based composite materials was revealed from a microscopic perspective using scanning electron microscopy and mercury porosimetry. The results indicate that the quality loss rate of jute fiber soaked in hot alkali solution ( 60 ℃, 4% NaOH solution) was the largest, which was 37.94%. After dipping in 10% chloroprene latex, the fiber water absorption was the smallest, which was 0.93%. Therefore, the jute fiber was pretreated by the combination of hot alkali solution soaking and chloroprene latex impregnation. The pretreatment of fibers will reduce the fluidity of the composites, but has little influence on the setting time of the composites. The flexural strength, splitting tensile strength, dry shrinkage and frost resistance of the composites are significantly improved by the pretreatment fiber, but the compressive strength is slightly insufficient. The jute fiber after pretreatment can achieve reinforcement, crack resistance and toughening, reduce the porosity of cement-based composites, and optimize the pore structure inside the cement-based composites.

Mechanical Performance of Hybrid Fibre Reinforced Magnesium Oxychloride Cement-Based Composites at Ambient and Elevated Temperature

Magnesium oxychloride cement (MOC) is often recognized as an eco-friendly cement and has found widespread application in various sectors. However, research on its resistance against elevated temperatures including fire is very limited. This paper thoroughly investigated the mechanical performance of fibre reinforced MOC-based cementitious composite (FRMOCC) at ambient and elevated temperatures. A recently developed water-resistant MOC was used as the base matrix which was further reinforced using hybrid basalt and polypropylene fibres at various proportions, and a systematic study on the effect of fibre dosage on compressive and tensile strength of FRMOCC was conducted. The specimens were exposed to elevated temperatures ranging from 200 to 800 °C; mechanical performance and phase composition from a microscale study were analysed. The findings revealed that compressive strength, with the increase in temperature, substantially decreased, with values of 30–87% at 400 °C and over 95% at 800 °C. Specimens with 1.5% basalt and 0.5% PP fibre showed the least reduction possibly due to the vacant channels created as a result of the melting effect of PP fibres. Tensile strength was also completely lost at 600 °C and the specimens suffered substantial mass loss exceeding 30% at this temperature, indicating significant matrix decomposition. Additional analysis using X-ray diffraction (XRD) and scanning electron microscope (SEM) revealed the decomposition stages of the matrix and highlighted the instability of the main hydration phases of FRMOCC at elevated temperatures.

Functional Bi2O3/Gd2O3 Silica-Coated Structures for Improvement of Early Age and Radiation Shielding Performance of Cement Pastes.

This study presents a new approach towards the production of sol-gel silica-coated Bi2O3/Gd2O3 cement additives towards the improvement of early mechanical performance and radiation attenuation. Two types of silica coatings, which varied in synthesis method and morphology, were used to coat Bi2O3/Gd2O3 structures and evaluated as a cement filler in Portland cement pastes. Isothermal calorimetry studies and early strength evaluations confirmed that both proposed coating types can overcome retarded cement hydration process, attributed to Bi2O3 presence, resulting in improved one day compressive strength by 300% and 251% (depending on coating method) when compared to paste containing pristine Bi2O3 and Gd2O3 particles. Moreover, depending on the type of chosen coating type, various rheological performances of cement pastes can be achieved. Thanks to the proposed combination of materials, both gamma-rays and slow neutron attenuation in cement pastes can be simultaneously improved. The introduction of silica coating resulted in an increment of the gamma-ray and neutron shielding thanks to the increased probability of radiation interaction. Along with the positive early age effects of the synthesized structures, the 28 day mechanical performance of cement pastes was not suppressed, and was found to be comparable to that of the control specimen. As an outcome, silica-coated structures can be successfully used in radiation-shielding cement-based composites, e.g. with demanding early age performances.

XGB Modeling Reveals Improvement of Compressive Strength of Cement-Based Composites with Addition of HPMC and Chitosan.

This study investigates the improvement in the compressive strength of cellulose/cement-based composites. Methyl cellulose (MC), carboxymethyl cellulose (CMC), and hydroxypropyl cellulose (HPMC) are separately used as the cellulose phase with different wt%. Graphene oxide (GO) and zoledronic acid (ZOL) are used as additives for bone regeneration for various formulations. Utilizing Extreme Gradient Boosting (XGB) modeling, this research demonstrates the roles of the choice of the cellulose phase, wt% of cement phase, % gelatin, % citric acid, degradation time, and concentration of GO and ZOL in influencing compressive strength. The XGB regression model, with an R2 value of 0.99 (~1), shows the predictive power of the model. Feature importance analysis demonstrates the significance of cellulose choice and the addition of chitosan in enhancing compressive strength. The correlation heatmap reveals positive associations, emphasizing the positive influence of HPMC and CMC compared with MC and the substantial impact of chitosan and citric acid on compressive strength. The model's predictive accuracy is validated through predicted compressive strength values with experimental observations, providing insights for optimizing cellulose-reinforced cements and enabling tailored material design for enhanced mechanical performance.

A Review on Chemical and Autogenous Shrinkage of Cementitious Systems.

Chemical shrinkage (CS) is an intrinsic parameter that may affect the early age cracking of paste, mortar and concrete. It is well known as the driving force of self-desiccation, autogenous shrinkage (AGS) and drying shrinkage. During the first stage of cement hydration (at the initial setting time), the CS and AGS are equal. In the hardened stages, there is a difference in values between the two shrinkage parameters. This paper is a comprehensive review on CS and AGS, measurement techniques, modeling and prediction of different cementitious systems. Based on the various experimental studies, chemical shrinkage depends on the water to binder ratio (w/b) and is proportional to the degree of hydration. A low w/b ratio leads to high CS and AGS. The composition of cement has an effect on both CS and AGS. Also, incorporating supplementary cementitious materials (SCMs) affects both shrinkage parameters. It is concluded that adding fly ash (FA) to concrete contributes to CS and AGS reductions. However, this is not the case when concrete contains slag. More than 170 references were consulted including 35 which were published after 2020. According to the authors knowledge, there is no published work on the effect of fibers, especially bio-fibers, on the chemical shrinkage of cement-based composites. Therefore, in addition to traditional chemical shrinkage of cementitious systems, this review includes a section on recent papers conducted by the authors on the effect of bio-fibers on the chemical shrinkage of cement composites.

Effect of CTBN and Nano-SiO2 modified epoxy resin powder on the mechanical properties of cement-based composites

The high brittleness of oil well cement seriously affects the cementing quality. In order to maintain the safe and effective production of oil and gas wells, it is crucial to employ solid flexible fillers to reduce the brittleness of cement. In this study, a new type of flexible resin material (C-ER) was prepared by modifying epoxy resin with liquid nitrile butadiene rubber (CTBN) and nano-SiO2. The chemical composition, hydrophilicity, dispersibility, microstructure, and mechanical properties of C-ER were studied by FT-IR, XPS, contact angle, UV spectroscopy, SEM, DMA, and uniaxial compression. The results show that CTBN reacted with the epoxy group successfully. Due to the presence of SiO2, C-ER has good hydrophilicity and dispersion properties. The introduction of flexible segments makes C-ER have a lower modulus and crosslinking density, and its compressive elastic modulus is reduced by 47.4 % compared with pure resin. In addition, the effect of C-ER on the performance of oil well cement was tested. The results show that the addition of C-ER does not affect the fluidity of cement slurry and can improve the strain capacity of cement stone under load. Compared with blank cement and unmodified resin cement, the flexural strength of cement sample containing 4 % C-ER particles increased by 9.0 % and 25.1 %, respectively, and the elastic modulus of cement stone decreased by 31.2 % and 25.0 %, respectively. SEM images show that C-ER maintains good dispersion and bonding properties in cement matrix. C-ER can reduce the brittleness of cement effectively through its own elastic deformation and debonding to the cement matrix.

Calculation and manufacture of multilayer composite structures

A brief overview of the work done to solve the problems of bending of composite plates and shells is presented. A mathematical model has been developed that takes into account the physically nonlinear properties of the layer’s material. The seams between the layers have finite longitudinal stiffness. Seams can be continuous or discrete (anchors). The proposed mathematical model makes it possible to take into account the creep properties of the aging material. The reliability of calculations is substantiated by comparison with experimental data and known calculations. Taking into account the temperature mode made it possible to develop a technology for manufacturing multilayer structures with predicted properties of the material of the layers. Based on the results presented, methods for calculating multilayer structures and technologies for their manufacture have been developed. It is proposed to create products from cement-based composites with unique planned characteristics, oriented to the intended purpose of the manufactured structures. The intended purpose of products can be achieved by using a material with special characteristics in each layer. To protect against rodents and microorganisms, light antiseptics can be used in the process of making the composite. The solution of these issues in thin-walled structures is associated with the development of technologies for creating multilayer composite systems. The results of the creation of composites are presented.

Reinforcement Effect of Recycled CFRP on Cement-Based Composites: With a Comparison to Commercial Carbon Fiber Powder

Reinforcement Effect of Recycled CFRP on Cement-Based Composites: With a Comparison to Commercial Carbon Fiber Powder

Employing Piezoelectricity to Generate Sustainable Energy with Green Harmonics

This paper examines the potential of piezoelectric substances in presenting sustainable and renewable energy solutions, that specialize in energy harvesting and self-maintaining smart sensing mechanisms inside numerous systems. Highlighting the inefficacy of conventional construction substances like simple cement paste in energy capture, this study delves into current methodologies that expand the piezoelectric abilities of cement-based composites through innovative admixtures and physical treatments. Additionally, the research explores the broader utilization of piezoelectric materials across various sectors together with healthcare, environmental tracking, and consumer electronics, propelled by using the need for wireless sensing nodes and embedded microsystems to have a reliable power source. Emphasizing the environmental advantages, this paper affords a comparative analysis of cutting-edge developments, challenges, and future possibilities within the area of piezoelectric power harvesting (PEH), which include the exploration of lead-free substances and the advancement in hybrid energy harvesting devices.

Comparative analysis of the effects of waste shell aggregates on the material properties of cement mortars

This study investigates the effects of different waste shells on the material characteristics and properties of cement-based composites. The accumulation of large quantities of waste shells poses significant environmental concerns, leading to soil pollution and odors. Furthermore, the construction industry contributes to global environmental issues through high energy consumption and CO2 emissions during aggregate production. Recycling different waste shells, including cockles, oysters, and murex, after cleaning them using an ultrasonic device, and incorporating them as partial substitutes for fine aggregates, can potentially tackle both environmental challenges. The physical and mechanical properties, including freeze–thaw resistance, of mortar specimens with different types and amounts of waste shell aggregates were measured, to examine the effect of each shell aggregate on the specimens. The microstructural characteristics of the specimens were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and micro-computed tomography (micro-CT) and correlated with the material properties. The results demonstrate that mortars incorporating waste shells, with appropriate treatments such as 30% replacement and washing of the particles, exhibit compressive strength up to 90% of that observed in the normal case. Therefore, these shells can be effectively used as substitutes for fine aggregates.

Investigation of cementitious composites reinforced with metallic nanomaterials, boric acid, and lime for infrastructure enhancement

<abstract> <p>Nanomaterials integration within construction materials could promote the generation of more sophisticated structural materials, as it imbues reinforcement at the nanoscale. This research adopted experimental approaches to assess the influence of metallic nanomaterials on the performance of cementitious composites with various ratios of boric acid (1%, 3%, and 5% by sand's weight) and lime (0.5%, 1.5%, and 2.5% by sand's weight), respectively, for use in construction infrastructure facilities. This research provides valuable insight into the potential of using boric acid and lime as well as metallic nanomaterials to strengthen cement-based composites. Initial curing stages revealed a notable decrease in compressive strength attributed to the inhibitory effects of boric acid and lime on cement hydration. However, the introduction of TiO<sub>2</sub> nanoparticles demonstrated significant enhancements in compressive strength and durability. Statistical analysis emphasized the significance of nanomaterials in augmenting compressive strength, with implications for long-term performance. This study has shown that the addition of nano-titanium dioxide TiO<sub>2</sub> can significantly enhance the compressive strength of Portland cement mortars, particularly when used in conjunction with appropriate ratios of boric acid and lime. The results of the 7 days test indicated that the inclusion of boric acid and lime in the cement mortars significantly decreased the compressive strength. However, the addition of nano-TiO<sub>2</sub> to cement mortars containing 1% boric acid and 0.5% lime resulted in a 31-fold increase in compressive strength compared to cementitious composites without nano-TiO<sub>2</sub>. In contrast, the compressive strength significantly increased by 1.2 times, 85.3 times, and 65.1 times, respectively, after 56 days for the addition of boric acid (1%, 3%, and 5%) with lime (0.5%, 1.5%, and 2.5%), respectively, in the presence of nano-TiO<sub>2</sub>, compared to the 7 days strength. The results also illustrated that, in general, the incorporation of various types of nano-TiO<sub>2</sub> into cementitious composites containing boric acid and lime increases their compressive strength as the ratios of boric acid and lime increase, as long as sufficient curing time is allowed.</p> </abstract>

Preparation and mechanical characterization of multi-functional high-ductility engineered magnesium oxysulfate cement-based composites

Aiming at the integrated requirements of building energy saving and thermal insulation reinforcement in reinforcement engineering, the technology of preparing multi-functional high-ductility engineered magnesium oxysulfate cement-based composites (MOSC-ECC) by magnesium oxysulfate cement (MOSC) was proposed; the mechanism of industrial waste fly ash (FA) to improve the ductility of MOSC-ECC was explored; the effects of FA on the density, thermal conductivity and water resistance of MOSC-ECC were studied; the phase composition and microstructure of the hydration products of MOSC-ECC were analyzed. The results show that the incorporation of FA instead of light-burned magnesium oxide (LB-MgO) powder of equal mass can effectively reduce the cracking strength, fracture toughness, density and thermal conductivity of the matrix, and improve the ductility and multiple cracking ability of MOSC-ECC. The incorporation of hydrophobic agent made MOSC-ECC have excellent water resistance. The findings of this study provide useful knowledge for realizing the integrated design of thermal insulation and reinforcement of structures, which is of great significance for promoting the engineering application of ECC and the promotion of energy-saving green building materials.

Experimental Study on Mechanical Properties of Nano-Alumina-Modified Cement Composites Exposed to High Temperatures

Due to improved mechanical properties, nano-alumina (NA) addition has been considered as an interesting method to promote the performance of cement composites. To investigate the enhancing effect of NA on the fire resistance of cement-based composites, the physical and mechanical properties of NA-modified cement composites (NAMCCs) were experimentally measured after exposure to high temperatures (up to 800 °C). The variation mechanism of the physical properties of NAMCCs with increasing temperature was explored using X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods. Increasing temperature leads to a gradual decrease in density and ultrasonic wave velocity but an overall increase in mass loss. The addition of NA particles effectively improved the mechanical properties of hardened cement pastes after heat treatment at all the temperatures studied. The compressive strength, elastic modulus and flexural strength all gradually decrease with increasing temperature. Combined with the changes in XRD and SEM, three regions are identified for the variation in mechanical performance in the temperature range of 20~400 °C, 400~600 °C and 600~800 °C. Finally, the relation between the physical and mechanical parameters of these regions was evaluated.

Optimization of mix proportion and strength prediction of magnesium phosphate cement-based composites based on machine learning

In order to optimize the mix ratio design of magnesium phosphate cementitious composites (MPCC) to obtain excellent workability and strength, this study investigated the effects of MgO-phosphate ratio, water-binder ratio, aggregate-binder ratio, the mass ratio of coarse and fine aggregates, mineral admixture content and steel fiber content on the flowability, setting time and cubic compressive strength (CCS) of MPCC using orthogonal design of experiments with a total of 32 sets of mix ratios. The experimental results were also analyzed utilizing range and variance analysis to determine the main influencing parameters and the optimal dosage of each factor, and the optimal MPCC mix ratio was obtained. In addition, the prediction of CCS for MPCC using five machine learning models was first introduced, and the predicted results were interpreted and analyzed regarding the SHAP (Shapley Additive exPlanations) features importance. The results showed that the effect of steel fiber volume content and water-binder ratio on the flowability was significant, and M/P significantly affected the setting time of MPCC. The CCS of MPCC increased with the age of curing, and MPCC exhibited high early strength, with 1-day CCS accounting for 55%～85% of the 28-day CCS. The effect of M/P on the 1-day, 3-day and 28-day CCS was highly significant, with M/P contribution rate as high as 76.3%, 80.3% and 83.6% of the CCS at 1, 3 and 28 days, respectively. Besides, the effect of steel fiber volume content on 28-day CCS was also significant. In summary, the optimal mix ratio of MPCC was A4B1C4D1E4F4G1 (M/P = 3, w/b=0.11, a/b=1.4, c/f=3, FA content =15%, MK content= 15%, steel fiber volume content= 0%). Furthermore, random forest (RF) and particle swarm optimization of back propagation artificial neural network (PSO-BP-ANN) models have a higher prediction accuracy, and the results of SHAP feature significance further confirmed the above test results.

The growth of in-situ CNTs on slag to enhance electromagnetic interference shielding effectiveness of cement-based composite

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 SEtotal 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.