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Fire performance of concrete containing nano-fibers and graphite nano-particles
Abstract
One of mankind's biggest achievements has been to harness fire which has quickened the pace of technological advancements. While we have benefitted greatly, we have suffered none the less. Structural fires have been a huge problem for the past few decades and the loss of property and life has been immense. Concrete structures are generally considered as potent against fire, given the intrinsic lower thermal conductivity of concrete and its enduring nature. However, irreversible physical and chemical changes occur in the cement matrix over long periods of fire exposure. Concrete is a multi-phase, multi-scale material, with each phase behaving differently under fire conditions. This difference of behavior often leads to deterioration of mechanical strength of concrete which can cause structural failures. Human population is on the rise and so is the need for its habitation, thus the building materials are being used today at a higher pace than ever. The advanced building materials are light, strong, durable and long lasting; however, the problem could be with their resistance to fire. This is where nano-technology offers innovative and effective solutions, by contributing to develop building materials that are not only durable and sustainable in nature, but at the same time are fire enduring.
... The heating process causes changes in the microstructure of building and construction industry, which in turn affects the structural characteristics of the material [181,182]. Structures may be efficiently protected by combining passive and active fire prevention systems with management systems like smoke exhaust systems and communication protocols [22,183]. Researchers are promoting the use of nano-materials as additives to improve thermal resistance in cementitious composites, as they offer superior reactivity compared to micro-scale materials, preventing structural failure [184,185]. ...
... The improvement in fire behavior is due to the formation of a surface layer during pyrolysis that acts as a heat barrier, preventing heat transfer and increasing surface radiation heat losses [189]. Fillers within the polymer matrix offer a protective clay-rich barrier, thereby reducing the polymer's mass loss rate (MLR) [181,[190][191][192][193][194]. Saraeian et al. [195] investigate the effect of nanoclay particles on the tensile strength and flame retardancy of polystyrene -nanoclay composite. ...
In construction engineering, there is currently a strong emphasis on finding construction materials, mainly the binder which plays a crucial role, that meet multiple criteria, including sustainability, cost-effectiveness, durability, and reduced environmental impact. However, there is a growing interest in exploring alternatives to traditional binders to address the limitations associated with their production and use. One such alternative is the use of naturally occurring materials like clay. Clay deposits are abundant and widely available, making them a sustainable resource for construction applications. Moreover, clay contains significant amounts of silica and alumina, which are key components for inducing pozzolanic reactions that contribute to the strength and durability of concrete. In recent studies, nanoclays (NCs) have emerged as a promising addition to construction materials as supplementary cementitious materials. These nanoparticles possess unique properties that can enhance the performance of concrete. Nanoclays significantly improve the compressive strength, sustainability, and durability of concrete structures. The high surface area and reactivity of nanoclays facilitate better bonding between cement particles, resulting in enhanced mechanical properties. This chapter aims to discuss the state of the art on performance enhancements of building materials that employ different types of nanoclays in place of conventional binders and the future trends.
... Furthermore, the presence of graphene derivatives may reduce temperature gradients in the concrete elements and therefore minimize thermal and shrinkage cracking [25]. Moreover, previous studies have shown that the improvement in thermal conductivity could contribute to thermal stress distribution and a reduction in the thermal inertia of CCs when exposed to fire [26,27]. Previous studies have also shown that GMs can improve the anti-spalling performance of CCs exposed to high temperatures, particularly in high-strength CCs [26,28]. ...
... Previous studies have also shown that GMs can improve the anti-spalling performance of CCs exposed to high temperatures, particularly in high-strength CCs [26,28]. The inclusion of GMs can therefore contribute to thermally conductive CCs that are multifunctional, durable, and fire-enduring [27]. ...
Graphene-based materials (GMs) have significant potential for enhancing the thermal conductivity of cementitious composites. This study uses both machine learning (ML) and computational micromechanics models (CMMs) through a hybrid modelling approach to investigate the thermal conductivity of GM-reinforced cementitious composites (GRCCs). Accordingly, validated CMMs were used to train the ML models, which were then employed to predict the thermal conductivity of GRCCs. The results show that, among the parameters investigated, the volume fraction of GMs is the most influential factor in predicting the thermal conductivity of GRCCs, followed by their aspect ratio.
... As such, various previous studies (e.g., [17][18][19][20]) have shown that in terms of thermal exposure, UHPC performs similarly to the Portland cement-based concrete structures. This similarity points to the deterioration of Portland cement-based binder that take place at the threshold of around 600 C -800 C [21][22][23]. In contrast, if another binder is considered for thermal exposure, they can have a considerably different performance (e.g., geopolymers are able to withstand high temperatures of around 1000 C -1200 C [24]). ...
This review paper presents a comparative evaluation of polymer, bacterial-based, alkali-activated, and geopolymer
binders in regard to their production methods, mechanical properties, their environmental/life cycle
assessment (LCA), and durability when exposed to deteriorating cycles (such as sulfates, acids, and high temperatures).
The significance of this study is to compare the results of over 400 journal papers, which present an
in-depth analysis of fresh and hardened state properties of various binders that are advocated in the literature.
Historically, Portland cement is generally considered a binder that plays a major role in any cementitious
composites because of its high availability, and relatively inexpensive cost. Despite its significant benefits, it is
known that the manufacturing process of Portland cement is energy and carbon intensive, and the resulted
material often has shortcomings when exposed to deteriorating causes such as sulfates, acids, and high temperatures.
However, recent movement toward net-zero as well as ultra-high-performance practices has increased
the need for a more sustainable and durable binding system. Based on the result of this paper, each binder
presents specific advantages when compared to Portland cement for specific applications that can be a better
choice for their ultra-high capabilities and ecological properties. This includes the significantly better performance
of alkali-activated binders (specifically geopolymers), under high temperatures, or very rapid strength
gain of polymer (e.g., epoxy, polyester, and vinyl ester) binders, making them great alternatives to Portland
cement, for rapid repair and rehabilitation purposes. Similarly, bacterial concrete also have certain capabilities
such as long term durability and the potential for a continued self-repair or self-healing. In terms of environmental
impacts, however, polymer binders are heavily dependent on their source of energy (e.g., petroleum vs.
bio-based resins) while alkali-activated concretes and geopolymers have activators’ large contributions to overall
LCA impact categories. For bacterial binders, the used urea and nutrition can play a key role in their LCA results.
Finally, based on the highlighted capabilities of each binder, recommendations on performance-based or hybrid
design methods and specifications for an optimized system are also provided. Novel areas in polymer, bacterial based,
alkali-activated, and geopolymer binders are also included.
... The development of macro-pores in PP strengthened HSC badly affects their durability characteristics under post-fire conditions. GFs are highly sensitive to alkaline conditions while the chemically inert carbon fibers and nanotubes owe the reservation of high cost and anisotropy [25,26]. ...
This research explores the effect of basalt fibers (BFs) added in high
strength concrete (HSC) to tailor its mechanical and microstructural response on being exposed to fire. Thermo-mechanical behavior of reference and modified formulations was monitored in ambiance alongside the exposed elevated temperatures till 100C, 200C, 400C, 600C, and 800C. The dose of BFs was maintained as 1% and 2% by weight of cement in modified HSC formulations. The specimens were subjected to the controlled heat ramp of 5C/min, to attain the desired temperature elevation with a hold time of 150 min. The heated specimens were then cooled by air till ambiance to test for residual properties. The test results revealed significant improvement in thermo-mechanical properties of BFs reinforced HSC formulations after being exposed to fire. Micro-forensics evidenced the homogenized distribution of BFs alongside their crack arresting actions throughout the matrix, contributing to the added residual performance. The matrix morphology of BFs reinforced HSC was also monitored to endorse any physical or chemical change in the hydration product. Moreover, numerical equations based on statistical analysis were formulated that can predict the fire behavior of modified HSC samples with BFs.
... The nano/micro platelets of graphite are closely packed and require surfactant for their dispersion in aqueous media. Surfactants have been used to undermine agglomeration and ensure the effective dispersion of nanomaterial in the concrete mixtures [18,43,44]. The chemical and mineral surfactants have been used to diffuse nanomaterials. ...
The graphite nano/micro platelets (GNMPs) offer distinct features for the effective reinforcement of cementitious matrices in the behaviors of concrete. The thoroughly dispersed and well-bonded nanomaterials provide effective control of the size and propagation of defects (microcracks) in the matrix and also act as closely spaced barriers against diffusion of moisture and aggressive solutions into the concrete. Graphite nanomaterials can play multi-faceted roles in enhancing the mechanical and physical attributes of concrete materials. The GNMPs have to exhibit enhanced mechanical and other functionalities to be suitable for emerging structural applications. Although GNMPs improved some of the mechanical performance of concrete but less information is available particular the influence of (GNMPs) in self-compacting concrete (SSC). Therefore, in this research an innovative nano-engineered self-compacting concrete was prepared using 0.1, 0.2, 0.3, 0.4 and 0.5% GNMPs. The rheological properties were assessed through slump flow, v funnel, v funnel at T5 minute, L box test while mechanical performance was assessed through compressive and tensile tests. The microstructural properties of the self-compacting concrete (SSC) with GNMPs were investigated through Scanning Electron Microscopy (SEM). The results indicate that the filling and passing ability of SCC improved with GNMPs. Furthermore, 0.3% addition of GNMPs shows 42 and 31% enhancement in compressive and tensile strength as compared to reference concrete respectively. Overall, the study demonstrated the effectiveness of GNMPs in SCC and may be applied in practical structural engineering applications.
... The thermal endurance of fiber-reinforced recycled concrete during fire is vital for its application in modern-day buildings and other infrastructures. It has been widely reported that the mechanical properties of conventional recycled aggregate concrete highly degrade at elevated temperatures [54,131]. To overcome this issue, the technique of fiber reinforcing in recycled aggregate concrete is used, which at present is one of the most promising and persuasive strengthening techniques that results in better thermal endurance of FRAC. ...
In recent times, the applications of fiber-reinforced recycled aggregate concrete (FRAC) in practical engineering have gained greater popularity due to its superior mechanical strength and fracture properties. To apply FRAC in buildings and other infrastructures, a thorough understanding of its residual mechanical properties and durability after exposure to fire is highly important. According to the established research, the properties and volume fractions of reinforcing fiber materials, replacement levels of recycled concrete aggregate (RCA), and heating condition would affect the thermal–mechanical properties of FRAC. This review paper aims to present a thorough and updated review of the mechanical performance at an elevated temperature and post-fire durability of FRAC reinforced with various types of fiber material, specifically steel fiber (SF), polypropylene (PP) fiber, and basalt fiber (BF). More explicitly, in this review article the residual mechanical properties of FRAC, such as compressive strength, splitting tensile capacity, modulus of elasticity, mass loss, spalling, and durability after exposure to elevated temperatures, are discussed. Furthermore, this study also encompasses the relationship among the dosages of fibers, replacement levels of recycled aggregate, and the relative residual mechanical properties of FRAC that would help in the optimum selection of the fiber content. Conclusively, this study elaborately reviews and summarizes the relevant and recent literature on recycled aggregate concrete containing SF, PP fiber, and BF. The study further provides a realistic comparison of these fibers in terms of the residual mechanical performance and durability of FRAC that would help in their future enhancements and applications in practical engineering.
... Many concrete materials tend to degrade themselves because of heat exposure and low thermal conductivity and resistivity (54). Thus, it is possible to change regular concrete materials to nanoadditives, improving thermal properties (55). ...
This review intends to show how nanotechnology is currently being applied in concrete. Both organic and inorganic species can be used as nanoagents, producing materials with improved properties, promoting economic and environmental gains by extending the materials' lifetime. Thus, this paper covers nanotechnology applications to improve mechanical, thermal, and corrosive properties of concrete and shows bibliometric results, proving the increase of interest in these fields. Results have shown that organic agents are more commonly used than inorganic ones, and that nanotechnology is applied mainly to improve mechanical and thermal properties.
... Many concrete materials tend to degrade themselves because of heat exposure and low thermal conductivity and resistivity (54). Thus, it is possible to change regular concrete materials to nanoadditives, improving thermal properties (55). ...
... Recent works investigated the effect of using by-products for modifying the residual strength after high temperature exposure [8][9][10]. Some works also highlight how the addition of (nano- [11], micro- [12] and macro- [13,14]) fibers can improve the residual strength of components and structures after high temperatures exposures. ...
High temperature effect on cement-based composites, such as concrete or mortars, represents one of the most important damaging process that may drastically affect the mechanical and durability characteristics of structures. In this paper, the results of an experimental campaign on cement mortars submitted to high temperatures are reported and discussed. Particularly, two mixtures (i.e., Normal (MNS) and High Strength Mortar (MHS)) having different water-to-binder ratios were designed and evaluated in order to investigate the incidence of both the mortar composition and the effects of thermal treatments on their physical and mechanical properties. Mortar specimens were thermally treated in an electrical furnace, being submitted to the action of temperatures ranging from 100 to 600 °C. After that and for each mortar quality and considered temperature, including the room temperature case of 20 °C, water absorption was measured by following a capillary water absorption test. Furthermore, uniaxial compression, splitting tensile and three-points bending tests were performed under residual conditions. A comparative analysis of the progressive damage caused by temperature on physical and mechanical properties of the considered mortars types is presented. On one hand, increasing temperatures produced increasing water absorption coefficients, evidencing the effect of thermal damages which may cause an increase in the mortars accessible porosity. However, under these circumstances, the internal porosity structure of lower w/b ratio mixtures results much more thermally-damaged than those of MNS. On the other hand, strengths suffered a progressive degradation due to temperature rises. While at low to medium temperatures, strength loss resulted similar for both mortar types, at higher temperature, MNS presented a relatively greater strength loss than that of MHS. The action of temperature also caused in all cases a decrease of Young’s Modulus and an increase in the strain corresponding to peak load. However, MHS showed a much more brittle behavior in comparison with that of MNS, for all temperature cases. Finally, the obtained results demonstrated that mortar quality cannot be neglected when the action of temperature is considered, being the final material performance dependent on the physical properties which, in turn, mainly depend on the mixture proportioning.
The use of Engineered Cementitious Composites (ECC) and ultra-high-performance concrete (UHPC) in combination with self-consolidating concrete (SCC) in a fresh state can improve the economical and sustainability benefits of modern concretes while increasing the structural properties of SCC-elements. However, it is important to determine if the resulted hot-jointed composite systems (CS) can resist the harsh environments-like fire conditions, especially with the presence of unknown proprieties interfacial bond layer. The goal of this study is to investigate and compare the flexural and bonding behavior of the SCC/ECC and SCC/UHPC composites at ambient and high temperatures up to 800 °C. In addition to the type of modern concrete in the tensile layer, the effect of fiber reinforcement on fire endurance of CSs was also investigated through the inclusion of PVA and steel fibers in ECC and UHPC. After cooling in air, fire-exposed samples were examined for visual, microstructural, tensile, and flexural bond properties. It was confirmed that, the applied ECC and UHPFRC in CSs significantly improved the mechanical properties of SCC elements at ambient and all fire exposure temperatures. In addition to the enhanced fire endurance and better residual performance for the UHPRFC-based CSs, steel fibers were shown to be essential for the physical anchorage and bond preservation between SCC/ECC and SCC/UHPFRC, particularly at 400 °C–800 °C.
The need for finding sustainable alternative sources of coarse aggregates as an ingredient for concrete has been increasing globally. Recycled and brick aggregates are two viable options in this regard. Many properties of recycled and brick aggregate concrete remain to be investigated to predict their behaviour accurately and to set proper code guidelines. In this study, a few properties of recycled and brick aggregate concrete and their behaviour in flexural members have been investigated. In particular, the stress–strain relationship, modulus of elasticity and splitting tensile strength of concrete made of brick, recycled and natural aggregate have been analysed. Using these properties, some of the flexural properties of reinforced concrete members made with these three types of aggregates have been determined and compared. To the best of our knowledge, for the first time, a comparative analysis of these properties of brick, recycled and natural aggregate concrete has been conducted in this study. Results from the study show that while the code equations for predicting some of the important mechanical properties of concrete are suitable for natural aggregate concrete, they are not appropriate for recycled or brick aggregate concrete. The moment–curvature response and deflection properties in flexural members made of recycled and brick aggregate concrete are affected by the difference in the properties of the aggregate. Finally, it is suggested that the utilization of recycled and brick aggregate in concrete is likely a feasible option without any significant degradation in the mechanical and flexural properties of the structural members.
This paper investigates the performance of composite systems combining self-consolidating concrete (SCC) and normal strength concrete (NSC) under fire exposure. SCC was used in the compression zone while NSC was overlaid in the tensile zone. The resulting systems were exposed to high temperatures ranging from 23 to 800 °C. Two types of cooling regimes have been considered i.e. water and air cooling. The primary objective of the study was to analyze the interfacial bond deterioration and the variation in mechanical strength. Test results indicated that the mechanical strength and mass decreases with rise in exposure temperature. The interface remained intact without excessive damage. Further, the thermal shock experienced during the water cooling negatively impacts the composite system.
Concrete is the second most globally consumed material in the world after water and the most used construction material. Yet, its benefits are masked with many ecological setbacks through the way it is produced, transported, or used. Concrete occurs in a brittle state characterized by low tensile strength, weak resistance to crack formation, and strain properties. Recent studies have focused on improving concrete properties by integrating it with innovative solutions such as fibers, admixtures, and supplementary cementitious components. The infrastructure of modern structures demands components with greater durability, and higher mechanical strength. This solution can only be achieved through the addition of nanomaterials to cement-based products, thus, enhancing their mechanical features. Examples of nanomaterials include carbon nanotubes (CNTs), nano-ferric oxide (nano - Fe2O3), and grapheme oxide. Nanomaterials can be added to cement with the addition of other reinforcements such as glass, steel fibers, fly ash and rice hull powder. With optimum dosages, the compressive, tensile, and flexural strength of cement-based materials, workability and water absorption are improved. The use of nanomaterials enhances the performance and life cycle of concrete structures. This study looks at some of the recent concrete improvisations, analyzing them on the spectrum of technical performance, durability, ecological sustainability, and economic benefits.
This paper presents the outcome of a project funded by Beni-suef University targeting the assessment of the addition of carbon nanotubes (CNTs) to reinforced concrete beams on exposure to elevated temperatures. Tests were carried out in compliance to ASTM E119-95a. Besides, pre and post their exposure to elevated temperature tests, the maximum bending capacity of the beams are evaluated. Standard reinforced concrete beams are cast- with and without Carbon Nanotube (CNT). Tests were performed at two temperature levels 400 °C and 600 °C working around temperature ranges expected to have significant effect on concrete endurance, using both one and two hours exposure. Results proved a positive effect for adding CNT to beams at room temperature. This improvement is slightly affected at 400 °C exposure for 2 hr. On the other hand, exposing CNT beams for 600 °C for two hours reduced the beams capacity by 14% compared to a similar reinforced beam without CNT. It is worth notice that CNT was not burnt but suffered de-bonding. Finally, this investigation implies that CNT can be used as an enhancing element to concrete ductility, with no deterioration in other mechanical characteristics on exposure to drastic thermal conditions.
The study of the application of nanotechnology in the construction industry and building structures is one of the most prominent priorities of the research community. The outstanding chemical and physical properties of nanomaterials enable several applications ranging from structural reinforcement to environmental pollution remediation and production of self-cleaning materials. It is known that concrete is the leading material in structural applications, where stiffness, strength and cost play a key role in the high attributes of concrete. This paper reviews the literature on the application of nanotechnology in the construction industry, more particularly in concrete production. The paper first presents general information and definitions of nanotechnology. Then, it focuses on the most effective nanoadditives that readily improve concrete properties, such as (i) nanosilica and silica fume, (ii) nanotitanium dioxide, (iii) iron oxide, (iv) chromium oxide, (v) nanoclay, (vi) CaCO3, (vii) Al2O3, (viii) carbon nanotubes and (ix) graphene oxide. Besides summarising the main nanomaterials used in concrete production as well as the results achieved with each addition, some future potential consequences of nanotechnology development and orientations to explore in construction are discussed.
In recent decades, the use of structural high performance concrete (HPC) sandwich panels made with thin plates has increased as a response to modern environmental challenges. Fire endurance is a requirement in structural HPC elements, as for most structural elements. This paper presents experimental investigations on the fire behaviour of HPC thin plates (20 or 30 mm thick) being used in lightweight structural sandwich elements. Tests were undertaken using a standard testing furnace and a novel heat-transfer rate inducing system (H-TRIS), recently developed at the University of Edinburgh. The parametric assessment of the specimen performance included: thickness of the specimen, testing apparatus, and concrete mix (both with and without polypropylene fibres). The results verified the ability of H-TRIS to impose an equivalent thermal boundary condition to that imposed during a standard furnace test, with good repeatability, and at comparatively low economic and temporal costs. The results demonstrated that heat induced concrete spalling occurred 1 to 5 min earlier, and in a more destructive manner, for thinner specimens. An analysis is presented combining the thermal material degradation, vapour pore pressure, stress concentrations, and thermo-mechanical energy accumulation in the tested specimens. Unexpectedly, spalling at the unexposed surface was observed during two of the tests, suggesting a potentially unusual, unwanted failure mode of very thin-plates during fire. On this basis it is recommended to favour 30 mm thick plates in these applications, since they appear to resist spalling better than those with 20 mm thickness.
High strength concrete (HSC) is a material often used in the construction of high rise buildings. In case of unexpected fire, building elements such as columns, slabs and walls will be subjected to extreme temperatures. In order to assess the performance of high-rise concrete members to such exposure, it is important to understand the changes in the concrete properties due to extreme temperature. This paper presents an experimental study undertaken to quantify the effect of elevated temperatures of 60, 75, 100, 200, 400 and 600°C with various exposure durations of 4, 8, 12, 72 hours and one month on HSC cylinders. HSC cylinders made of two strengths, namely 80 and 100 MPa are used. For comparing their performance with normal strength concrete, cylinders made with 40 MPa concrete are also investigated. Residual tensile and compressive strengths of concrete as well as weight loss values after high temperature exposures were determined. The detrimental effects of using silica fume for higher strength concrete mixtures are exhibited by the test results.
The knowledge of high temperature thermal properties is critical for evaluating the fire response of concrete structures. This paper presents the effect of temperature on the thermal properties of different types of high-strength concrete (HSC). Specific heat, thermal conductivity, and thermal expansion are measured for three concrete types, namely, HSC, self-consolidating concrete (SCC), and fly ash concrete (FAC), in the temperature range from 20–800°C. The effect of steel, polypropylene, and hybrid fibers on thermal properties of HSC and SCC is also investigated. Results from experiments show that SCC possesses higher thermal conductivity, specific heat, and thermal expansion than HSC and FAC in the 20–800°C temperature range. Data generated from tests is utilized to develop simplified relationships for expressing different thermal properties as a function of temperature. The proposed thermal property relationships can be used as input data for evaluating the response of concrete structures under fire conditions.
The paper presents the impact of high temperature on cement concrete. The presented data have been selected both from the author's most recent research and the published literature in order to provide a brief outline of the subject. The effect of a high temperature on concrete covers changes taking place in cement paste, aggregates, as well as the interaction of these two constituents, that result in changes of mechanical and physical characteristics of concrete. This paper presents the effects of a high temperature on selected physical properties of concrete, including colour change, thermal strain, thermal strains under load, and transient thermal strains. In addition, changes to mechanical properties are discussed: stress-strain relationship, compressive strength, and modulus of elasticity. Moreover, the phenomenon of explosive spalling and the main factors that affect its extent are analysed in light of the most recent research.
In this study, structural light-weight concretes produced by Pumice (LWC) and concretes with normal-weight aggregate (NWC) were investigated. Compressive strength and weight loss of the concretes were determined after being exposed to high temperatures (20, 100, 400, 800, 1000 °C). To achieve these objectives, 12 different types of concrete mixtures were produced. In producing the mixtures, silica fume (SF) was used to replace the Portland cement in the ratios of 0%, 5% and 10% by weight. Half of the mixtures were obtained by adding superplasticizers (SP) to the above mixtures in the ratio of 2% by weight. In conclusion; unit weight of LWC was 23% lower than that of NWC. The LWC containing 2% SP could retain 38% of the initial compressive strength. Rate of deterioration was higher in NWC when compared to LWC. The loss of compressive strengths increased depending on the ratio of using SF at about 800 °C and over.
Graphene, a two-dimensional, single-layer sheet of sp(2) hybridized carbon atoms, has attracted tremendous attention and research interest, owing to its exceptional physical properties, such as high electronic conductivity, good thermal stability, and excellent mechanical strength. Other forms of graphene-related materials, including graphene oxide, reduced graphene oxide, and exfoliated graphite, have been reliably produced in large scale. The promising properties together with the ease of processibility and functionalization make graphene-based materials ideal candidates for incorporation into a variety of functional materials. Importantly, graphene and its derivatives have been explored in a wide range of applications, such as electronic and photonic devices, clean energy, and sensors. In this review, after a general introduction to graphene and its derivatives, the synthesis, characterization, properties, and applications of graphene-based materials are discussed.
An experimental program was developed to evaluate the effect of multi-walled carbon nanotubes (MWCNTs) inclusion on elevated temperature properties of normal weight concrete (NWC) and lightweight concrete (LWC). The mechanical performance was assessed by conducting material property tests namely compressive strength (f’c ,T ), tensile strength (f’t,T ), mass loss (MT ), elastic modulus (ET ), compressive toughness (Tc ) and stress–strain response under unstressed and residual conditions in the range of 23°C to 800°C. The mechanical properties were measured by heating 100 × 200 mm cylindrical specimens to 200°C, 400°C, 600°C and 800°C at a heating rate of 5°C/min. Results show that the inclusion MWCNTs in cementitious matrices enhanced the fire endurance. The relative retention of mechanical strength and mass of concretes modified with MWCNTs was higher. The stress–strain response of specimens modified with MWCNTs was more ductile. Microstructural study of cyrofractured samples evidenced the homogenous dispersion of nano-reinforcements in host matrix. Furthermore, the data obtained from high temperature material property tests was utilized to develop mathematical relationships for expressing mechanical properties of modified mixes as a function of temperature.
Addition of nanomaterials to Portland cement mortars could potentially enhance their properties. It has been previously reported that addition of multi-walled carbon nanotubes (MWCNTs) to mortars can lead to considerable improvement in the mechanical properties of the binder paste. In this study, the effect of the addition of MWCNTs at the ratios of 0–0.15 wt% of Portland cement on the compressive, tensile, and flexural strength; and resistance to the elevated temperature of Portland cement mortar was evaluated. The specimens were heated up at the elevated temperatures (200–800 °C) and accordingly, the mass loss and compressive strength were determined. The microstructure of the samples was analyzed by petrography. The obtained results showed that the mortar samples containing MWCNT acquired higher mechanical strength and resistance to the elevated temperatures, in comparison with the ordinary mortar samples. The mortar containing solely 0.1 wt% MWCNT showed an increase in the compressive, tensile, and flexure strength by 35, 8 and 11.2%, respectively. Moreover, the residual compressive strength after heating showed significant improvement. Petrography image analyses also indicated that the porosity of the cement paste was reduced, whereas the cement paste became denser and more stable due to the addition of MWCNT.
Thermal performance and fire resistance of nanoclay modified cement mortar were evaluated in this study. To prepare the modified mortar mix, part of the cement was replaced by montmorillonite nanoclay in a range of 0–2% by weight of cement. After a curing period of 28 days, the hardened mortar specimens were exposed to high temperatures of 200 °C, 400 °C, and 600 °C for 2 h. DSC and TGA tests were conducted to examine the thermal performance of the nanoclay modified specimens. The fire resistance was evaluated by comparing the residual mechanical strengths of heated specimens with the strengths of control specimens. The effect of nanoclay on the chemical composition and microstructure of heat-damaged specimens were evaluated using XRD and SEM tests, respectively. Experimental results revealed that the nanoclay modified cement mortar exhibits higher compressive, tensile, and flexural strengths than control specimens, especially at higher temperatures. The addition of nanoclay significantly reduced the degradation in the tensile and flexural strengths of cement mortar due to elevated temperatures exposure. SEM images showed that the presence of nanoclay decreased the density and the width of the hairline cracks that appeared along the cement matrix due to elevated temperature exposure.
Effects of incorporation of graphene oxide (GO) in normal and high strength concrete at high temperatures were experimentally investigated. The behaviour of concrete specimens was examined by comprehensive thermal analyses of heat transfer, residual mechanical strength, pore structure, mass loss and dilatometery. The results showed significant improvement of mechanical strength of the specimens with GO; the residual compressive strength was about 70% compared to 35% for the reference specimens. This can be attributed to the modification of pore structure of GO specimens, which increased gel porosity and reduced capillary porosity. Hence, thermal deformation of specimens with GO was compatible and shows no early negative expansion. As a result, better resistance for cracks was observed in GO mixes and led to maintaining the mechanical strengths. Effective anti-spalling behaviour was observed for GO high strength specimens, whereas the reference specimens exhibited high spalling. This could be due to the reinforcing effect of GO and the influence of GO on creating networks of micro channels that assisted in releasing the vapour pressure.
Concrete with nanoclay is utilized to replace cement of 0.1%–0.5% by weight, observing the compressive strength and thermal conductivity coefficients under 25–1000 °C for one hour. Results show that nanoclay concrete exhibits increased strength when temperature is not higher than 300 °C; strength is significantly reduced at a temperature range of 440–580 °C; and strength is lower than 10% of the original strength when temperature reaches 1000 °C. The thermal conductivity coefficient is reduced with increased temperature. When cement is replaced by 0.3% and 0.5% nanoclay, and the compressive strength and thermal conductivity coefficients of concrete increase.
h i g h l i g h t s Enhancing mechanical properties of oil well cement (OWC) pastes using different nanomaterials. Increasing curing temperature causes a notable increase in the compressive strength. 0.1% CNTs causes a good enhancement in the mechanical properties of the hardened OWC pastes. Optimum addition of NS to hardened OWC pastes is 1% at 25 and 90 °C. a b s t r a c t Nanotechnology has shown great potential in different applications and presents solutions to some of the upstream and downstream challenges in the oil and gas industry. This research work aimed to improve the mechanical properties of oil well cement (OWC) pastes using multiwall carbon nanotubes (CNTs), nano-silica (NS) and nano-metakaolin (NMK). The effect of different curing temperatures, namely; room temperature and elevated temperature (90 °C) on the hydration reaction of OWC pastes admixed with different nano materials was investigated. XRD, TG/DTG, and SEM techniques were used to investigate the phase composition and the microstructure of some selected hardened specimens. The obtained results indicated that all of the nano materials used in this study cause a notable improvement in the mechanical properties of hardened OWC pastes at both curing temperatures. In addition, NMK – OWC hardened pastes present the highest improvement in the mechanical properties among all of other tested mixes.
AbstractIn this contribution the effect of nanosilica (NS) on the behavior of cement mortars containing quartz aggregate and two types of heavyweight aggregates (magnetite and barite) exposed to elevated temperature will be investigated. The cement mortars have been modified with nanosilica in quantities of 1%, 2%, 3%, 4% and 5% (by weight of cement). The samples were exposed to the elevated temperatures of 200 °C, 400 °C, 600 °C and 800 °C, respectively. The mass loss, flexural and compressive strength of the cooled specimens were determined. Additionally, by means of scanning electron microscopy (SEM) and optical microscopy the structure defects have been determined.
The results clearly demonstrate that there is an optimal nanosilica content, in the cement mortar containing quartz and magnetite aggregate, improving the thermal resistance and preventing the crack extension (especially in the range of 200–400 °C). However, the study has also shown that cement mortars containing barite aggregate tend to crack and exhibit spalling as a result of low thermal resistance of the aggregate.
The paper is an extended summary of the state-of-the-art report on Application of Nanotechnology in Construction, which is one of the main tasks of a European project Towards the setting up of a Network of Excellence in Nanotechnology in Construction (NANOCONEX). The paper first presents background information and current developments of nanotechnology in general. Then, the current activities and awareness of nanotechnology in the construction industry are examined by analysing results of a survey of construction professionals and leading researchers in the field. This is followed by results of a desk study of nanotechnology development and activities focussing on key areas relevant to construction and the built environment. Examples of nanotechnology-enabled materials and products that are either on the market or ready to be adopted in the construction industry are provided. Finally, the future trend/potential and implications of nanotechnology development in construction are discussed.
Recently, nanosilica has been widely suggested as an excellent supplementary cementitious material due to its superior reactivity in comparison to other types of siliceous materials. Nanosilica is reported to increase the residual compressive strength of mortar after exposure to high temperatures. The addition of nanosilica has also been reported to cause fundamental changes in hydration products, increasing the average chain length of calcium silicate hydrate (C-S-H) and volume fraction of high-density C-S-H in cement paste in addition to decreasing calcium hydroxide content. However, it is not well understood exactly how nanosilica addition increases thermal stability of cement-based composites. In this study, the effects of replacement of a small amount of cement with nanosilica on the degradation of cement paste exposed to various heating and cooling regimes were investigated. Following heat treatment of cement paste samples with and without nanosilica up to 500°C (935°F), two different cooling regimes (cooling down to room temperature of 23± 2°C [73.4 ± 3.6°F] and prolonged heat treatment at 50°C [122°F] for 3 days) were followed. The residual states of each sample were analyzed by compression test, X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The experimental results show that replacing 5% cement by weight with nanosilica leads to a 7 to 20% higher residual compressive strength after exposure to elevated temperatures. Furthermore, maintained exposure at above ambient temperature for long periods of time after exposure to high temperatures caused severe damage only to paste samples that did not contain nanosilica. This damage was not seen in samples containing nanosilica. Reduction in calcium hydroxide content due to the pozzolanic activity of nanosilica seems to be the primary reason for the minimized level of damage by reducing the degree of carbonation of hydration products immediately following heat treatment.
High temperature is well known for seriously damaging concrete micro- and meso-structure, which brings in a generalised mechanical decay of the concrete and even detrimental effects at the structural level, due to concrete spalling and bar exposure to the flames, in case of fire. Because of the relevance of concrete behaviour at high temperature and in fire, many studies have been carried out, even very recently, on cementitious composites at high temperature, and the most relevant parameters have been identified and investigated. Within this framework, the authors provide a comprehensive and updated report on the temperature dependency of such parameters as the compressive strength, modulus of elasticity, strength in indirect tension (bending and splitting tests), stress–strain curves and spalling, but the roles played by the water–binder ratio (w/b), aggregate type, supplementary cementitious materials (SCMs) and fibres are investigated as well. Among the objectives of the paper, the approaches currently adopted to improve concrete mechanical properties at high temperature are treated as well. Meanwhile, the influence of test modalities on the mechanical properties of concrete at high temperature is also discussed in the paper.
This paper investigates the effects of nano-kaolinite clay (NKC) on the freezing and thawing (F-T) behavior of concrete. In our experiments, we substituted NKC for 0, 1, 3, and 5% of mixtures of ordinary Portland, cement, by weight. The blended concrete was prepared using w/c ratio as 0.5. A rapid freeze-thaw Cabinet was then used to measure the resistance of ordinary Portland cement concrete, as opposed to the concrete/NKC mixture, to examine deterioration caused by repeated F-T actions. We regularly measured the properties of the concrete specimens, including the pore structure, mass, electrical resistivity, chloride diffusion coefficient, compressive strength and dynamic modulus of elasticity. A computed tomography scan test evaluated the porosity characteristics of the concrete. This paper also applied scanning electron microscopy and X-ray diffraction tests in order to investigate the micro morphology and chemical element distributions inside of the concrete. The experimental results and visual comparisons revealed that the introduction of NKC improves the F-T resistivity values, as compared to the control concrete. The samples with 5% NKC exhibited the highest compressive strength, chloride diffusion resistivity, relative dynamic modulus of elasticity, and the most electrical resistivity after 125 F-T cycles. We designated the anti-freezing durability coefficient (DF) as the index to assess the F-T resistivity of concrete. The following research discusses the relationship between the concrete’s DF and the number of F-T cycles, compressive strength, chloride diffusion coefficient, and the electrical resistivity of the concrete samples.
A novel multiscale reinforcement was prepared by the fast growth of carbon nanospheres (CNSs) onto the surface of carbon fiber (CF) under mildly hydrothermal reaction. The uniform layer of CNS with an average diameter of 85 nm produced on the fiber surface. Further, the structural analysis, surface morphology, and thermal decomposition behavior of CNS–CF reinforcement were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy combined with Fourier transform infrared spectroscopy and thermogravimetric analysis, respectively. Cement-based composites based on the multiscale CNS–CF reinforcement have been fabricated to evaluate their high-temperature resistance. CNS–CF/cement composites have a better resistance to the degradation resulted from exposure to elevated temperature up to 600 °C than CF/cement composites and pristine hardened pastes, since their relative residual compressive strength is superior. The degrading mechanisms due to exposure to elevated temperatures were discussed and confirmed by using SEM and XRD. Results indicated that enhanced high-temperature resistance was attributed to the effective interlocking between CF and matrix due to (1) the presence of nanoscale CNS on the surface of CF and (2) the formation of microchannels in the matrix since CNS collapsed prior to CF after exposure to elevated temperatures.
To extend the beneficial reuse of waterworks sludge, nano-SiO 2 was considered as an additive to improve the engineering properties of waterworks sludge ash cement paste. Waterworks sludge was first incinerated to ash at 800°C. Different amounts of nano-SiO 2 were added to the sludge ash and then mixed with cement to make a paste. The benefits of using sludge ash as a replacement for cement were assessed. Tests of the fresh paste properties (including flowability and setting time), hardened paste properties (compressive strength), and microstructure analysis (SEM) were performed to assess the influences of the different proportions of nano-SiO 2 and sludge ash added to the paste. Both added admixtures could reduce the flowability and shorten the setting time of the cement paste. Furthermore, the cement paste became denser, more uniform, and exhibited improved early and later compressive strengths after the addition of nano-SiO 2. However, because of the late development of pozzolanic effects, the compressive strengths of the cement paste were reduced with increased amounts of ash replaced. This study indicates that, because Portland cement is well compatible with nano-SiO 2, the performance of silicate cement is improved and the strength of the hardened cement paste is raised, especially for the early strength.
An experimental investigation was conducted to evaluate the performance of mortars with and without Metakaolin (MK) exposed to elevated temperatures , , and for two hours. The binder to sand ratio was kept constant (1:5.23). The ordinary Portland cement (OPC) was replaced with MK at 0%, 5%, 10% 20% and 30%. All mixtures were designed to have a flow of . The compressive strength of mortars before and after exposure to elevated temperature was determined. The formation of various decomposition phases were identified using X-ray diffractometry (XRD) and differential thermal analysis (DTA). The microstructure of the mortars was examined using scanning electron microscope (SEM). Test results indicated that MK improves the compressive strength before and after exposure to elevated temperature and that the 20% cement replacement of MK is the optimum percentage.
Intercalation phenomena of gas molecules in the interlayer of graphene oxide have been investigated using CO2, CH4, H2, and N2 gases. Intercalation of gas molecules is highly affected by the affinity between the hydrophilic surface of GO and target molecules. Among tested gases, CO2 can only be intercalated. Furthermore, the swelling of interlayer changed the intercalation phenomena. Amounts of intercalated gases are significantly enhanced, and all the gases can be intercalated by retarded dynamics of intercalated water.
This is a review of cement-matrix composites containing short carbon fibers. These composites exhibit attractive tensile and flexural properties, low drying shrinkage, high specific heat, low thermal conductivity, high electrical conductivity, high corrosion resistance and weak thermoelectric behavior. Moreover, they facilitate the cathodic protection of steel reinforcement in concrete, and have the ability to sense their own strain, damage and temperature. Fiber surface treatment can improve numerous properties of the composites. Conventional carbon fibers of diameter 15 μm are more effective than 0.1 μm diameter carbon filaments as a reinforcement, but are much less effective for radio wave reflection (EMI shielding). Carbon fiber composites are superior to steel fiber composites for strain sensing, but are inferior to steel fiber composites in the thermoelectric behavior.
This review summarizes research conducted on concrete containing recycled materials after exposure to fire. Discarded products consist of brick and concrete demolition from the construction and building industries, in addition to supplementary cementing materials from industrial waste such as fly ash, blast furnace slag, silica fume and biomass/volcanic ashes. To understand the effects with and without aggregates, researchers have conducted a variety of tests on cement pastes, cement mortars, and concrete. Three heating and loading conditions have been used by researchers in this area: preloaded and tested hot, unloaded and tested hot, and unloaded and tested at room temperature. Of the many possible material property measurements, the most common was the compression strength and is reported here. The literature suggests a great deal of work is needed in this area to understand the performance in fire of structures constructed with sustainable concretes.
High-volume fly ash has been widely used in concrete to reduce the cost and environmental impact of producing cements. However, the effect of high temperature on cement-based materials containing fly ash and nanosilica has not been well characterized. In this study, cement was replaced by high-volume fly ash combined with colloidal nanosilica to produce high strength mortars with high residual strength after exposure to high temperatures of 400 °C and 700 °C. Heated and unheated specimens were subjected to flexural and compression tests. The samples were evaluated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) tests; and their porosity were determined using BET (Brunauer, Emmett, and Teller) technique to study the specimens’ behavior after exposure to high temperatures. High strength mortars can be produced using nanosilica and fly ash with resultant high residual strength, as confirmed by the porosity, XRD and TGA tests results.
Despite great recent progress with carbon nanotubes and other nanoscale fillers, the development of strong, durable, and cost-efficient multifunctional nanocomposite materials has yet to be achieved. The challenges are to achieve molecule-level dispersion and maximum interfacial interaction between the nanofiller and the matrix at low loading. Here, the preparation of poly(vinyl alcohol) (PVA) nanocomposites with graphene oxide (GO) using a simple water solution processing method is reported. Efficient load transfer is found between the nanofiller graphene and matrix PVA and the mechanical properties of the graphene-based nanocomposite with molecule-level dispersion are significantly improved. A 76% increase in tensile strength and a 62% improvement of Young's modulus are achieved by addition of only 0.7 wt% of GO. The experimentally determined Young's modulus is in excellent agreement with theoretical simulation.
The nano-montmorillonite, which has characteristics of high aspect ratio and interaction between polymer chains and dispersed
nanolayers, has been widely used in the development of new reinforced nanocomposite polymers to improve their mechanical properties.
Since a potential pozzolanic reaction may occur between Portland cement paste and high amount of silicon dioxide (SiO2) in nano-montmorillonite, the effects of introduction of montmorillonite to Portland cement-based material on the improvement
of matrix properties of cement paste is of great interest in the construction industry. In this study, a liquid-form of nano-montmorillonite
particle with a planar diameter of about 100nm were incorporated into the Portland cement paste at five different dosages
and analyzed at four different ages to identify the nanosizing effects on material properties of such cement-based composite.
Experimental results show that the composite with 0.60% and 0.40% of added nano-montmorillonite by weight of cement have the
optimum compressive strength and permeability coefficient, respectively, in which the increase of compressive strength is
about 13.24%, and the decrease of permeability coefficient about 49.95%. Microstructural properties through the analyses of
XRD, DSC, NMR, and MIP also indicate that the microstructures of cement paste with nano-montmorillonite contain more dense
solid material and more stable bonding framework.
Supplementary cementing materials (SCM) have become an integral part of high strength and high performance concrete mix design. These may be naturally occurring materials, industrial wastes, or byproducts or the ones requiring less energy to manufacture. Some of the commonly used supplementary cementing materials are fly ash, silica fume (SF), granulated blast furnace slag (GGBS), rice husk ash (RHA) and metakaolin (MK), etc. Metakaolin is obtained by the calcination of kaolinite. It is being used very commonly as pozzolanic material in mortar and concrete, and has exhibited considerable influence in enhancing the mechanical and durability properties of mortar and concrete. This paper presents an overview of the work carried out on the use of MK as partial replacement of cement in mortar and concrete. Properties reported in this paper are the fresh mortar/concrete properties, mechanical and durability properties.
High-reactivity metakaolin (HRM) is a manufactured pozzolan produced by thermal processing of purified kaolinitic clay. Field performance and laboratory research of concrete containing HRM have demonstrated its value for bridge decks, bridge deck overlays, industrial flooring, high-strength concrete and masonry products. This paper discusses laboratory evaluations to assess the long-term performance of concrete containing HRM produced in North America for resistance to chloride penetration and reduction in expansion due to alkali-silica reactivity. Bulk diffusion testing indicated that HRM substantially reduced chloride ion penetration in concrete with w/cm of 0.30 or 0.40. Reductions in diffusion coefficients compared to control specimens were of the order of 50% and 60% for concrete with 8% and 12% HRM, respectively. Also, the performance of the concrete containing 8% or 12% cement replacement with HRM showed improved performance versus merely reducing the w/c from 0.4 to 0.3. Such reductions can be expected to have a substantial impact on the service life of reinforced concrete in chloride environments. Expansion tests on concrete prisms containing reactive aggregates showed that 15% HRM can prevent deleterious expansion due to alkali-silica reactivity (ASR). The mechanism of control is likely linked to the substantial reduction in pore solution alkalinity seen in pastes containing 20% HRM in comparison to the control specimen which contained no supplementary cementing materials. However, the reduction was not large enough to depassivate steel reinforcement.
The effects on the microstructural development of adding silica fume to cements and concretes during cement hydration have been studied using small-angle neutron scattering and ultrasmall-angle X-ray scattering. A previously developed fractal based microstructural model has been applied to extract representative microstructural parameters from the small-angle scattering data. A link has been established between the existence of coarse or agglomerated particles in the silica fume particle size distribution and possible deleterious microstructural evolution during cement hydration.
The quantitative scanning electron microscope-backscattered electron (SEM-BSE) image analysis was used to evaluate capillary porosity and pore size distributions in high-strength concretes at early ages. The Powers model for the hydration of cement was applied to the interpretation of the results of image analysis. The image analysis revealed that pore size distributions in concretes with an extremely low water/binder ratio of 0.25 at early ages were discontinuous in the range of finer capillary pores. However, silica-fume-containing concretes with a water/binder ratio of 0.25 had larger amounts of fine pores than did concretes without silica fume. The presence of larger amounts of fine capillary pores in the concretes with silica fume may be responsible for greater autogenous shrinkage in the silica-fume-containing concretes at early ages.
There is intense interest in graphene in fields such as physics, chemistry, and materials science, among others. Interest in graphene's exceptional physical properties, chemical tunability, and potential for applications has generated thousands of publications and an accelerating pace of research, making review of such research timely. Here is an overview of the synthesis, properties, and applications of graphene and related materials (primarily, graphite oxide and its colloidal suspensions and materials made from them), from a materials science perspective.
The concept of storing radioactive waste in geological formations calls for large quantities of concrete that will be in contact with the clay material of the engineered barriers as well as with the geological formation. France, Switzerland and Belgium are studying the option of clayey geological formations. The clay and cement media have very contrasted chemistries that will interact and lead to a degradation of both types of material. The purpose of this review is to establish an exhaustive list of laboratory experiments so as to identify the reaction sequences in the evolution of both the clay minerals and accessory minerals during their alteration in an alkaline environment. We review the data on clay dissolution kinetics in this environment, and include an invaluable study of natural analogues that allow one to correlate the phenomena in time. The available data and experiments make it possible to construct predictive numerical models. However, as the quality of the data is inhomogeneous, we recommend a continuation of the thermodynamic and kinetic data acquisition. It is obvious that the numerical modeling of the alkaline disturbance will be more relevant if it can combine the advantages of the different detailed models: mineralogical completeness, combined modeling of the clay and cement media, evolution of the porosity, consideration of the pCO2 and all the surface reactions.
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