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This paper discusses the use of phase change materials (PCM) in concrete pavement as a method to store energy which can be used as a heat source during cooling events to melt ice/snow. The experimental program includes: (1) use of low-temperature differential scanning calorimetry to evaluate thermal properties of PCM, and (2) use of large-scale concrete slabs containing PCM to evaluate the ability of the PCM concrete to melt snow on the surface of the concrete pavement. The temperature in the concrete slabs and the snow melting rate were monitored as quantitative measurements of the efficiency of the PCM in the concrete. In addition, time-lapse images were taken. Two approaches were used to incorporate PCM in concrete: placing the PCM in lightweight aggregate (LWA) which was then mixed into the concrete, and placing the PCM in embedded metal pipes embedded in the slab during concrete casting. In this study, paraffin oil was use as a PCM that is effective in releasing heat near the freezing temperature of PCM when the PCM undergoes a phase transformation from liquid to solid. The heat released during the phase transformation can melt ice and snow on the concrete pavement surface. The results indicate that incorporating PCM in concrete pavement is not only feasible, but also practical.
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... Consequently, the temperature profile and associated heat flow within the specimen can be calculated by solving the heat transfer equation shown in equation (1) [22]. [12,15,22]. Equation (2c) describes a convection heat term that represents the heat dissipation to the surrounding using the convection coefficient, hconv-diss which is also obtained empirically [12,15]. ...
... [12,15,22]. Equation (2c) describes a convection heat term that represents the heat dissipation to the surrounding using the convection coefficient, hconv-diss which is also obtained empirically [12,15]. ...
... An LGCC test was conducted on a mortar specimen which was prepared using LWAs fully saturated with PCM and then maintained in a chamber with controlled relative humidity of 50 ± 1 % [15]. A slab test was performed on a concrete specimen which was prepared using LWAs fully saturated with PCM then moist cured for 14 days and air cured until the testing time [12]. Under these conditions, the internal relative humidity of the slab was reduced to 81 % [12,15]. ...
Article
We employ a numerical methodology to predict the freeze-thaw performance of cementitious composites containing lightweight aggregates (LWAs) impregnated with phase change material (PCM) as thermal energy storage (TES) agent. The governing equation for heat transfer is combined with homogenization techniques to predict the temperature and associated heat flow for cementitious materials during the phase transition of the PCM. The material properties of the cementitious composite and heat dissipation behavior during thermal cycling were characterized using a small-scale longitudinal guarded comparative calorimeter (LGCC) test. Phase transitions associated with freezing/melting of PCM occurs gradually over a narrow temperature range. Pore size effect of LWA on freezing and melting behavior of PCM was found to be relatively small. This approach is extended to the prediction of the thermal energy storage capacity of PCM on improving the freeze-thaw performance of concrete specimens exposed to realistic thermal conditions at various locations in the United States.
... As a novel solution, phase change materials (PCMs) have been introduced for antifreezing of asphalt pavements (Ma et al. 2019), melting ice and snow in concrete pavements (Farnam et al. 2017), thermal insulation of buildings (Ramakrishnan et al. 2015), and temperature control of mass concrete (Young et al. 2017). Paraffinbased PCMs are a potential media for heat storage because of their advantages of high enthalpy, small volume change, and reversibility during the phase-change process (Farnam et al. 2016). ...
... The feasibility of impregnating PCMs in lightweight aggregate (LWA) was investigated from the perspectives of leakage potential and frozen time at extreme low temperatures for extending the pavement life (Kheradmand et al. 2015). To reduce the need of using deicing chemicals or salts, PCMs have been incorporated into concrete pavements by means of embedded metal pipes and LWAs for melting snow and ice on the surface (Farnam et al. 2017). Considering the actual climatic conditions, a thermal analysis of a composite panel based on shape-stabilized PCMs was conducted to assess their potential value in building energy conservation (Wi et al. 2020). ...
... It is common that the impact depth in a low-temperature environment is relatively smaller than the ground-plane size of the workspace. Thus, based on the assumption of one-dimensional heat transfer (Farnam et al. 2017), the sides and bottom of samples were insulated using thermal insulation materials [thermal conductivity ¼ 0.0034 W=ðm ·°CÞ]. For each sample, the clay was divided into eight layers, and four type-T thermocouples (resolution ¼ 0.1°C) were placed in each layer. ...
Article
During earth-rock dam construction, temperature control to reduce the freeze-thaw impact on core-wall clay in cold regions is difficult. To address this challenge, this research developed a phase change material (PCM) incorporated into clay (PCM-clay) to improve the construction efficiency in a cold period. In the preparation of PCM-clay, considerable latent heat was stored by harvesting thermal energy from the environment, which was used for temperature control to extend the winter construction time. The feasibility of PCM-clay as core-wall clay was verified by an analysis of working performance. The results indicate that low-content PCM-clay (7%) is able to protect core-wall clay from freeze-thaw damage in a simulated environment (minimum temperature=-4.3 degrees C) in a 1-day cycle. The working performance (e.g., shear strength and impermeability) supports that PCM-clay is a promising solution for temperature control of core-wall clay during earth-rock dam construction in cold regions.
... Numerous researchers [25-27,45,47, 81,142,144,[146][147][148][149][150][151][152][153][154][155] have proposed several porous aggregates as PCM hosts, distinct impregnation processes and various coating and support materials. It was observed that porosity is not the only measurable parameter for the PCM absorption capacity of LWAs. ...
... Moreover, researchers have proposed adding supporting materials and other coatings (cement paste, silicone coating, bituminous emulsion, epoxy resin, graphite powder, silica fume) to moderate leakage molten PCM and make thermal and mechanical properties of the PCM better. In mixture proportioning with Portland cement, the gradual scape of PCM from pores of LWAs can make a difference to cement hydration reactions and consequently affect the compressive strength of concrete [25][26][27]45,47,81,142,144,[146][147][148][149][150][151][152][153][154][155]. ...
... Several investigations [25][26][27]142,144,[146][147][148][149][150][151][152][153][163][164][165][166] have already carried out microstructural analysis (SEM, DSC, TGA and FTIR) of PCM-LWA and analysis of the thermomechanical properties (thermal performance, thermal conductivity, compressive strength, shrinkage strain and effects of freezing and thawing cycles) of concretes and mortars incorporating PCM. No matter the method of mixing PCMs in concrete, most of the research argues that it lowers resistance to compression. ...
Article
Full-text available
The energy sector is one of the fields of interest for different nations around the world. Due to the current fossil fuel crisis, the scientific community develops new energy-saving experiences to address this concern. Buildings are one of the elements of higher energy consumption, so the generation of knowledge and technological development may offer solutions to this energy demand, which are more than welcome. Phase change materials (PCMs) included in building elements such as wall panels, blocks, panels or coatings, for heating and cooling applications have been shown, when heating, to increase the heat storage capacity by absorbing heat as latent heat. Therefore, the use of latent heat storage systems using phase change materials (PCMs) has been investigated within the last two decades. In the present review, the macro and micro encapsulation methods for construction materials are reviewed, the former being the most viable method of inclusion of PCMs in construction elements. In addition, based on the analysis of the existing papers on the encapsulation process of PCMs, the importance to pay more attention to the bio-based PCMs is shown, since more research is needed to process such PCMs. To determine its thermophysical and mechanical behavior at the micro and macro levels, in order to see the feasibility of substituting petroleum-based PCMs with a more environmentally friendly bio-based one, a section devoted to the excellent PCM with lightweight aggregate (PCM-LWA concrete) is presented due to the lack of description given in other reviews.
... Incorporation of liquid-solid PCM is an effective way of low temperature thermoregulation [27,28]. The heat released during the solid-liquid phase change of PCMs can be utilized to increase the pavement temperature and to melt snow from the pavement surface [27][28][29][30][31]. ...
... Furthermore, the incorporation of PCM in embedded pipes did not exhibit any chemical reaction. Later, Farnam et al. [29] replaced plastic pipes with metal pipes (22.4 mm inner diameter) of carbon steel with 0.5% carbon content and a thermal conductivity of 45 W/m.K. As the maximum size of aggregate used was 19 mm, a spacing of 25 mm was provided between the pipes. ...
... Further studies are needed to increase the quantity of PCM that can be incorporated without affecting the mechanical strength of these pavements significantly. [22] 6 _ Asphalt LWA Aqueous saline solution [111] À5 _ Asphalt Metallic containers RubithermÓ SP5 [111] 5-7 _ Asphalt Metallic containers Tetradecane [112] 6 _ Asphalt Melamine-formaldehyde shell Tetradecane [113] 6 _ Asphalt LWA coated with epoxy glue and OPC Tetradecane [11] 5.8 178 Concrete Carbon and silica carrier Paraffin oil and methyl laurate [28] 2-3 130-170 Concrete LWA and embedded plastic pipes Paraffin oil [29] 5.7 157.8 Concrete LWA and embedded metal pipes N-Tetradecane [24] 4.5 224.5 Concrete Microencapsulated with melamine-formaldehyde resin ...
Article
Elevated pavement temperature contributes to urban heat island effect and thermal distresses in pavements. The extreme low temperature in pavements causes freeze and thaw damage and low temperature cracking. Incorporation of phase change materials (PCMs) in pavements to restrict the temperature extremities is emerging as a field of research importance. Incorporation of PCM can restrict both the higher and lower temperature extremities in pavements. PCMs can store energy in the form of latent heat without any rise in temperature and with minimum change in volume. Encapsulated PCMs are used in pavements to minimize the PCM leakage. This paper provides a general outlook on different PCMs and their encapsulation techniques used for pavement applications. Moreover, a detailed review is included on the effect of incorporating PCMs in asphalt and concrete pavements. Being the first literature review in this area, discussing in detail about the incorporation of PCMs in both concrete and asphalt pavements, the current paper act as a firm foundation for future developments in this field.
... Phase change materials (PCMs) are substances with a high enthalpy of fusion that are capable of storing and releasing thermal energy thorough their phase transformation (i.e., from liquid to solid phase or vice versa) during thermal cycles [1][2][3]. Therefore, PCMs can be used as a passive thermal energy storage system to manage thermal energy in buildings where 20% of annual consumption of energy is related to this sector [4]. PCMs generally can be divided into categories of organic, inorganic and eutectic materials, among which organic PCMs attracted more attention for application in cementitious composites due to their suitability and compatibility with construction materials [5][6][7]. ...
... PCMs can be manufactured with phase transitions at various temperatures for different applications [8,9]. Previous studies have shown that PCM can be applied in applications such as buildings for thermal energy saving [10], in concrete pavements at warm locations to prevent thermal cracking originated from the heat of hydration [11], and in concrete pavements at cold locations to not only melt ice formed on the surface of concrete but to prevent crack and damaging [2]. Therefore, PCMs not only can be used for thermal energy saving purposes, but also can be incorporated in cementitious composites to increase their freeze-thaw durability by preventing thermal damage [12]. ...
... PCM leakage to the surface was observed when the direct incorporation and immersion methods were used, which can jeopardize PCM's long-term performance. Meanwhile, issues such as poor thermal conductivity and difficulty in incorporation are reported when the macroencapsulation method is used [2]. The use of lightweight aggregate, on the other hand, overcomes the issues of PCM sensitivity to mixing speed. ...
Article
Microencapsulated phase change materials (MCPM) have been shown to be a promising material that can be used in cementitious composites for thermal energy storage. This paper evaluates the thermal efficiency of MPCM incorporated in the cementitious composite and quantitatively identifies the influential mechanical and chemical damages that can lead to reductions in thermal efficiency of MPCM with melamine formaldehyde based shell. Longitudinal Guarded Comparative Calorimetry (LGCC) and Low Temperature Differential Scanning Calorimetry (LT-DSC) were used to quantitatively evaluate the thermal response of cementitious composite containing MPCM, in relatively large (10 − 2 m) and small (10 − 3 m) scale samples, respectively. The results indicated an average reduction of ~32%-34% in the effective thermal efficiency (i.e., the average ratio of measured over expected heat release/absorption) of cementitious composite containing MPCM due to mechanical as well as chemical damages to MPCM. Mixing speeds of various rate was also studied and it was found that sample preparation at slow mixing speed (i.e., 55 rpm) could cause minimal damage to the MPCM (i.e., ~5.5 %-7.5% reduction in thermal efficiency), while using fast mixing speed (i.e., 165 rpm) can reduce the thermal efficiency of MPCM by up to 50%. Exposure of plain MPCM to separate constitutes of synthesized pore solution indicated that the main cause of MPCM thermal efficiency reduction is its chemical reaction with the pore solution of the cementitious composite. It was found that the main constitute of pore solution that could chemically interacts with MPCM was SO 4 2-. Finally, it was observed that the incorporation of MPCM in the cementitious composite can reduce the compressive strength of mortars due to the soft nature of MPCM. To increase the thermal efficiency of MPCM, this work recommends potential solutions such as using a cement with low sulfate content or development of a shell material for MPCM which is unreactive when exposed to pore solution.
... Application of thermal energy storage capacity of microencapsulated paraffinic phase change materials (PCMs) towards enhanced energy efficiency of structures has been an active area of research in construction materials [1][2][3][4]. The ability of PCMs to store and release heat has been shown to introduce a thermal inertia in structural concretes thereby enhancing performance [2,[4][5][6]. ...
... Application of thermal energy storage capacity of microencapsulated paraffinic phase change materials (PCMs) towards enhanced energy efficiency of structures has been an active area of research in construction materials [1][2][3][4]. The ability of PCMs to store and release heat has been shown to introduce a thermal inertia in structural concretes thereby enhancing performance [2,[4][5][6]. Previous studies have shown the effectiveness of PCMs towards improving energy efficiency of buildings and indoor thermal comfort [6][7][8][9]. ...
... The modularity of PCMs in terms of availability of wide range of transition temperatures warrants various beneficial applications in infrastructure materials [1,13]. PCMs have been proposed for application in concrete pavements and bridges for improved performance under freeze-thaw cycles [4,13]. A common method of removing ice and snow from the surface of pavements and bridges is application of deicing salts [4,[13][14][15][16][17]. ...
Article
Full-text available
Use of phase change materials (PCMs) to tailor the thermal performance of concretes by efficient energy storage and transmission has gained traction in recent years. This study incorporates microencapsulated PCMs as sand-replacement in concrete bridge decks and performs numerical simulation involving multiple interactive length scales to elucidate the influence of PCM-incorporation in concretes subjected to combined freeze-thaw and chloride ingress-induced deterioration. The simulations show significant increase in durability against combined freeze-thaw and chloride ingress-induced deterioration in concretes when microencapsulated PCMs are incorporated. In addition, a reliability-based probabilistic analysis shows significant increase in life expectancy of bridge decks with PCM-incorporation. The numerical approach presented here provides efficient means to develop design strategies to tune dosage and transition temperature of PCMs to maximize durability of concrete structures in regions that experience significant winter weather conditions.
... The type of LWA and its absorption capacity, the impregnation method, the coating and supporting materials, and characterization and performance testing [54,[84][85][86][87][88][89][90]. Researchers proposed various porous aggregates as PCM host, different impregnation methods, and various coating and supporting materials. ...
... SEM, DSC, TGA, and FTIR have been used to investigate the morphology, thermal properties and chemical stability of PCM-LWAs, similar to the characterization of SSPCMs discussed earlier [54,84,85,88,92,93,[98][99][100][101]. Moreover, the thermal, mechanical, and durability properties of concrete incorporating PCM-LWA including thermal performance, thermal conductivity, compressive strength, shrinkage strain, and effects of freezing and thawing cycles have been investigated [54,[84][85][86][87][88][89][90][92][93][94]97,99,[102][103][104]. In terms of mechanical properties, while most studies in the literature argue that, regardless of their incorporation method, PCMs decrease the compressive strength, Memon et al. [84] reported that the compressive strength of concrete made with epoxy coated PCM-LWA was higher than that of lightweight concrete without coated PCM-LWA. ...
... Farnam et al. [90] evaluated the application of PCMs incorporated into LWAs in reducing the accumulation of ice and snow on concrete pavements. Accordingly, the heat released during the phase transition of such PCM composites could melt ice and snow on the surface of pavements [90,105,106]. Another study [16] explored the effects of such PCM-LWA composites on the freezing and thawing performance of concrete, suggesting that PCM-LWA cementitious materials are promising for enhancing the behavior of concrete pavements under freezing-thawing cycles. ...
Article
Applications of phase change materials (PCMs) have become of great interest in recent years owing to beneficial effects on the thermal, mechanical and durability properties of construction and pavement materials. PCMs can alter the thermal mass and thermal inertia of building materials, thus enhancing thermal energy storage. The effects of PCMs on cement hydration, thermal stress and shrinkage of concrete have stimulated further applications. Despite various virtues of PCMs in construction and pavement materials, their drawbacks still need concerted research efforts. Among the fundamental problems of PCMs is their risk of leakage in the melted state. Hence, several techniques have been proposed to mitigate this problem. The present study examines potential methods of incorporating PCMs into building materials, including microencapsulation, macro-encapsulation, shape-stabilization, and porous inclusion. A critical analysis of PCM applications and stabilization materials and methods in concrete is provided, hence identifying practical recommendations, research needs and current knowledge gaps.
... Use of Phase change materials (PCMs) in cementitious composites for enhanced energy efficiency is an active research area [1][2][3][4]. PCMs have been shown to be advantageous in structural concretes due to their ability to store and release heat [2,[4][5][6]. A large number of studies have focused on the use of PCMs towards indoor thermal comfort in buildings and enhancement of building energy efficiency [6][7][8][9]. ...
... Use of Phase change materials (PCMs) in cementitious composites for enhanced energy efficiency is an active research area [1][2][3][4]. PCMs have been shown to be advantageous in structural concretes due to their ability to store and release heat [2,[4][5][6]. A large number of studies have focused on the use of PCMs towards indoor thermal comfort in buildings and enhancement of building energy efficiency [6][7][8][9]. ...
... In addition to the above-mentioned applications, availability of these PCMs with a wide range of transition temperatures [1,13] opens up various innovative avenues towards beneficial utilization of these materials in infrastructure materials. For example, application of PCMs towards reduction in freeze-thaw cycles in concretes pavements has been proposed earlier [4,13]. ...
Article
Full-text available
The use of phase change materials in infrastructure has gained significant attention in the recent years owing to their robust thermal performance. This study implements a numerical simulation framework using finite element analysis to evaluate the influence of phase change materials (PCMs) on the thermal response of concrete pavements in geographical regions with significant winter weather conditions. The analysis is carried out at different length scales. The latent-heat associated with different PCMs is efficiently incorporated into the simulation framework. Besides, the numerical simulation framework employs continuum damage mechanics to evaluate the influence of PCMs on the freeze-thaw induced damage in concretes. The simulations show significant reductions in the freeze-thaw induced damage when PCMs are incorporated in concrete. The numerical simulation framework, developed here, provides efficient means of optimizing the material design of such durable PCM-incorporated concretes for pavements by tailoring the composition and material microstructure to maximize performance.
... In order to increase the heat capacity of the embedded pipe systems, it has been suggested to fill them with PCMs with an appropriate phase change temperature. In general, a closed pipe system is used [29,[31][32][33]. However, one study used a running system where water was replaced with PCM which was replaced every time a predetermined temperature was achieved, thereby increasing the rate of heat removal from the system [34]. ...
... Using the same approach, LWAs can be impregnated with suitable phase change materials, and then used in concrete ( Figure 4). Different types of LWAs have been used: expanded shale [23,29,32,[40][41][42], expanded clay [40,[43][44][45][46], perlite [42,47,48], and others such as diatomite and vermiculite [49][50][51][52]. These LWAs are impregnated with (liquid) PCMs using either immersion/direct impregnation (e.g., [23,[42][43][44][45]49]) or a vacuum impregnation procedure (e.g., [29,32,[46][47][48]). Schematic representation of the vacuum impregnation procedure is given in Figure 5. ...
... Different types of LWAs have been used: expanded shale [23,29,32,[40][41][42], expanded clay [40,[43][44][45][46], perlite [42,47,48], and others such as diatomite and vermiculite [49][50][51][52]. These LWAs are impregnated with (liquid) PCMs using either immersion/direct impregnation (e.g., [23,[42][43][44][45]49]) or a vacuum impregnation procedure (e.g., [29,32,[46][47][48]). Schematic representation of the vacuum impregnation procedure is given in Figure 5. ...
Article
Full-text available
Cracks in concrete structures present a threat to their durability. Therefore, numerous research studies have been devoted to reducing concrete cracking. In recent years, a new approach has been proposed for controlling temperature related cracking—utilization of phase change materials (PCMs) in concrete. Through their ability to capture heat, PCMs can offset temperature changes and reduce gradients in concrete structures. Nevertheless, they can also influence concrete properties. This paper presents a comprehensive overview of the literature devoted to using PCMs to control temperature related cracking in concrete. First, types of PCMs and ways of incorporation in concrete are discussed. Then, possible uses of PCMs in concrete technology are discussed. Further, the influences of PCMs on concrete properties (fresh, hardened, durability) are discussed in detail. This is followed by a discussion of modelling techniques for PCM-concrete composites and their performance. Finally, a summary and the possible research directions for future work are given. This overview aims to assure the researchers and asset owners of the potential of this maturing technology and bring it one step closer to practical application.
... Farnam and Haddock explored the feasibility of using paraffin-impregnated lightweight aggregates (LWAs) and paraffin-filled hollow steel tubes to melt snow and ice on concrete pavements. The PCM-impregnated LWAs and PCM-filled hollow steel tubes were able to melt the snow owing to the gradual heat released during a phase change [23]. ...
... The DSC results of the PCM-LWA and the macroencapsulated PCM-LWA are lower than those of the pure PCM owing to the pore size effect. The pore size effect alters the melting and crystallization behavior of PCM impregnated composite [23]. As the Gibbs-Thomson equations states that the crystallization temperature of a liquid inside porous material depends upon its pore radius. ...
Article
In this study, structural functional thermal energy storage concrete (TESC) containing Tetradecane which is a low-temperature phase change material (PCM) has been developed. The PCM was incorporated in the concrete using a porous lightweight aggregate (LWA). PCM–LWAs were fabricated using vacuum impregnation technique, and a dual–layer coating having high thermal conductivity. The epoxy of high thermal conductivity was applied on the surface of PCM impregnated LWAs to prevent leakage of PCM. Differential scanning calorimetry (DSC) and thermogravimetric analysis were used to evaluate the thermal performance of encapsulated PCM–LWA. The DSC results demonstrated that PCM–LWA had melting and freezing temperature 4.18 °C and 0.33 °C and corresponding enthalpies 18 J/g and 15 J/g, respectively. Thermal energy storing concrete was developed by replacing normal-weight aggregates with the PCM–LWAs in proportions of 50% and 100% by volume. The compression test results revealed that the strength of PCM–LWA concrete decreased significantly compared to normal concrete. The strength loss in the PCM–LWA concrete with replacement ratios of 50% and 100% were 29% and 39%, respectively. Due to porous nature and relatively low stiffness of LWAs, significant strength loss has been observed. To overcome the strength degradation, silica fume (SF) and multiwalled carbon nanotubes (MWCNTs) were added to the concrete mixture. The addition of SF/MWCNTs reduced the strength loss by 15% and 20%, respectively. The SEM results revealed that the SF/MWCNT addition in concrete resulted in denser microstructure. The XRD results confirmed that SF reacted with Ca(OH)2 to increase the growth of C-S-H. Therefore, the mechanical performance of TESC containing PCM–LWAs can be improved by adding SF/MWCNTs to the concrete mixture.
... Farnam et al. embedded carbon steel pipes containing PCM in concrete slabs and performed a thermal cycling experiment with shaved ice (as a heat sink source) on the top of the slabs. They compared the piped-PCM with the impregnated PCM and found that the piped-PCM released heat more quickly, thus melting the snow at a higher rate [42]. However, the pipes were relatively wide (26.7 mm) and would adversely impact the mechanical strength of concrete [42]. ...
... They compared the piped-PCM with the impregnated PCM and found that the piped-PCM released heat more quickly, thus melting the snow at a higher rate [42]. However, the pipes were relatively wide (26.7 mm) and would adversely impact the mechanical strength of concrete [42]. Vascular channels of smaller diameters, as evidenced by Natural systems, are useful in maintaining the structural integrity of the materials [43][44][45]. ...
Article
Phase change materials (PCMs) have gained popularity as thermal energy storage (TES) materials because they reduce the active energy required to heat or cool a composite component. However, use of PCMs to manage heating/cooling faces two major challenges: their low thermal conductivity and their heterogeneous distribution within the depth of the composite component. This research considers Nature-inspired vascularization in designing PCM composite systems as a possible solution. In some animals, vascularization enhances thermal exchange by increasing surface area and temperature gradients of surfaces. To evaluate the effectiveness of vascularized composites, paraffin-based PCMs were incorporated in acrylic polymeric samples having 1D-mono discrete and 2D-square architected channels, incorporated using micro-machining, with different channel widths. PCM was then injected into the channels and the samples were placed in an environmental chamber that underwent thermal cycling. Infrared images were periodically taken to monitor and analyze thermal response of the samples. It was found that vascularization enhanced heat transfer/efficiency of PCM within the acrylic composite. The experimental analysis showed that doubling the channel width doubles the effective time for heat transfer while increases in the effective area and heat release were found to be small. The experiments also identified an optimal region near the channel where the effect of phase change on controlling heat loss/gain was the highest. The results of this study can be further used in the design optimization of PCM-filled vascular composites to increase the thermal efficiency of thermo-responsive composites.
... The performances of concrete mixtures containing PCM-LWAs have been investigated with experimental, analytical, and numerical approaches [3,4,11,[24][25][26]. In numerical modeling, the PCM-LWA particles are assumed to be homogeneous and isotropic. ...
... where α is the current hydration degree, p and p atm are the applied hydrostatic pressure and atmospheric pressure, respectively, and v T is the volume ratio between the hydration products and the reacted cement at temperature T. Once the hydration rate is obtained from Equation (21), the calculation of the current hydration degree is an initial value problem that can be solved using the forward finite difference method with a fourth-order Runge-Kutta scheme. The adiabatic hydration heat, Q(t), is represented as follows: (25) where Q max (kJ/kg) is the maximum heat output from the Bogue composition. Based on the cement properties presented in Section 2.3, the adiabatic heat output from cement was obtained and is plotted in Fig. 10. ...
Article
An image-based multi-level modeling method is proposed to estimate the effective bulk thermal conductivity of lightweight aggregate (LWA) impregnated with phase change material (PCM). The pore structure heterogeneity of the LWA and the uneven distribution of the PCM are considered by the model. The microstructure of the LWA is represented at two length scales (micro-level and macro-level), which are analyzed individually using imaging techniques. The reconstruction process is conducted on two-dimensional images to obtain three-dimensional digital representative volume element of the LWA, upon which multi-level numerical modeling of heat conduction is performed to estimate the effective bulk thermal conductivity of the PCM-LWA. The computed thermal conductivity of 0.34 W/(m∙K) is closed to experimental result and compared with estimates based on five traditional analytical methods for the sake of superiority analysis. Finally, the simulated thermal conductivity is used in a concrete level simulation to show its feasibility for modeling the thermal behaviors of PCM-LWA-incorporated concrete mixtures, in which PCM are employed to mitigate the hydration heat and prevent thermal cracking in mass concrete. The scale-up simulation manifests that the PCM-LWA not only reduced the peak temperature in the concrete by 3.18 °C but also changed the temperature distribution and gradient pattern inside the concrete.
... Their study assessed the effectiveness of two different PCM impregnation methods, i.e., lightweight aggregate filling and tube filling, by means of a differential scanning calorimeter (DSC). Another series of study by Farnam et al. cast large-scale concrete slabs incorporating PCM-impregnated lightweight aggregates (LWA) and tested them in an environmental chamber [21]. They concluded that the heat liberated during the phase change of embedded PCM can melt ice and snow on the concrete pavement surface. ...
Article
This study examines the effect of microencapsulated low-transition temperature phase change material (PCM) additions on the thermal response of concrete slabs subjected to long-term realistic environmental exposure. To prevent direct contact of PCM with cement hydration products and possible leakage upon liquefaction, an inert PCM was encapsulated with a melamine-formaldehyde resin via an emulsification process before being added in concrete mixtures. Temperature monitoring was performed on three 500 × 500 × 150 mm large-scale concrete slabs with and without PCM for about 14 months encompassing two cold winter seasons. Results indicated that the addition of microencapsulated PCM effectively reduced excessive temperature drop and the number of freeze-thaw cycles concrete slabs experience during winter seasons, which may lead to service life extension by up to 5.2%–35.9% based on a freeze-thaw deterioration model. In particular, the effectiveness of PCM was found to be pronounced when the ambient temperature varied around the transition temperature (mild-cold seasons) while it became insignificant under prolonged exposure to extreme climate conditions such as cold winter and summer. The result of a visual condition survey was consistent with that of the model predictions, which verified the potential benefits of low-transition temperature PCM technology in concrete applications. This study also investigated the influence of microencapsulated PCM pellet embedment on the compressive and flexural strength characteristics.
... Heat-harvesting pavement [77,78] Phase change material-impregnated pavement [79,80] and highconductive pavement [46] Reconstruction B. Zhou, et al. ...
... Ma, Li, Liu and Ma [10] added an organic solid-liquid PCM into asphalt mixture, and the material led to beneficial effects on pavement temperature, despite the mechanical properties of the mixture were negatively influenced. Farnam, Esmaeeli, Zavattieri, Haddock and Weiss [11] partially replaced lightweight aggregate with two PCMs https://doi.org/10.1016/j.conbuildmat.2020.118459 0950-0618/Ó 2020 Elsevier Ltd. ...
Article
The performance of porous asphalt concrete is highly sensitive to its internal temperature. During summer , the high temperature of the pavement could cause permanent deformation and subsequently leads to serious clogging issues for porous asphalt concrete. This study investigated the feasibility of using a phase change composite as an aggregate replacement to regulate porous asphalt concrete temperature. The mass stability of four commonly used phase change materials including myristic acid, stearic acid, palmityl alcohol, and polyethylene glycol (PEG) was evaluated using thermogravimetric analysis. The PEG was selected, and its chemical and mass stability subjected to the constant high temperature, high temperature cyclic conditioning, and low temperature cyclic conditioning was further examined using Fourier transform infrared spectroscopy and differential scanning calorimetry. A phase change composite material using SiO 2 as the shell and the PEG as the phase change material was fabricated and then mixed into porous asphalt concrete to replace the fine aggregate. The effect of the size and dosage of the PEG/ SiO 2 phase change composite on the internal temperature of porous asphalt concrete was experimentally investigated. It is found that the PEG/SiO 2 composite with a 70% PEG mass content could be a good candidate for the porous asphalt concrete application. The appropriate phase change composite particle size range was determined as 0.6-1.18 mm, and the optimum replacement level was 1.4% by the total weight of aggregate.
... Bentz and Turpin [10] theoretically analyzed the thermal responses of bridge decks in twelve different locations in the US by means of a CONTEMP model, which revealed that freeze-thaw cycles can be reduced by up to 30% with embedded PCM. Farnam et al. [11] investigated the thermal behavior of large-scale concrete slabs incorporating PCM-filled lightweight aggregates (LWA), demonstrating that the heat released upon solidification of PCM can melt ice and snow on concrete pavements. Esmaeeli et al. [12] numerically assessed the performance of cementitious composites incorporating PCM-impregnated LWA subjected to frost actions. ...
Article
This study examines the thermal behavior of cement mortar incorporating low-phase transition temperature phase change materials (PCM) (around the freezing point of concrete pore solutions) in an attempt to develop a novel strategy to reduce the expected number of freeze-thaw cycles concrete experiences and possibly to improve the frost resistance. To determine a viable inclusion method for PCM, thermal responses of mortars with two different PCM inclusion methods were tested under a 24-h sinusoidal temperature history, with the maximum and minimum ambient temperatures of 9 °C and −5°C, respectively, considering typical winter climate conditions in South Korea: (1) direct inclusion of non-treated raw PCM; and (2) inclusion of PCM-filled highly absorptive lightweight aggregates (LWA). In addition, another series of testing was conducted to identify the effect of phase transition temperature distribution on the thermal response of cement mortar: (1) inclusion of multi PCMs with three different transition temperatures (4.5 °C, 2.0–2.5 °C, and −0.5 °C); and (2) inclusion of single PCM with a phase transition temperature of 4.5 °C. Lastly, to see the effect of partial PCM embedment, thermal responses of cement mortars overlaid with three different PCM-embedment depths (20 mm, 30 mm, and 40 mm) were evaluated. Results have shown that the minimum specimen temperature was successfully raised by the addition of low-phase transition temperature PCMs. Also, it was revealed that the use of multi PCMs-filled LWA performed most effectively in terms of thermal and mechanical properties as compared to other incorporation methods. The partial PCM embedment improved the thermal performance, but there was no significant effect of PCM embedment depth.
... Concrete pavement is usually exposed to a combination of mechanical stresses and environmental impacts that accelerate its deterioration rate Al-Kheetan et al., 2019b). The presence of de-icing salts when in contact with the surface of concrete pavement during winter season can increase the damage of concrete, especially after their penetration in the pores with the absorbed water (Farnam et al., 2017;Farnam et al., 2015a;Farnam et al., 2015b;Al-Kheetan et al., 2019a;Sun et al., 2002). Add to that, the freezing and thawing cycles can produce a high pore pressure related to the water phase change inside the pores that work on initiating cracks within the concrete matrix (Li 2017). ...
Conference Paper
Full-text available
A new line of research is presented in this study where sodium acetate is used as a protective material for concrete. A newly developed freeze-thaw method that depends on the alteration of temperature and humidity is introduced in this research to investigate the efficacy of integrating sodium acetate with concrete with different water to cement ratios (w/c). Results from the introduced freeze-thaw method were compared with the outcomes of a standard freeze-thaw testing method. The distressed concrete was tested for water absorption and compressive strength after finishing six months of freeze-thaw testing. Results demonstrated the effectiveness of sodium acetate in protecting concrete
... Phase change materials can be introduced into concrete through four procedures: (1) by embedding PCM filled pipes/panels into concrete [11,12]; (2) by impregnating PCM in lightweight aggregate particles which are then used in the concrete mix [13]; (3) by using microencapsulated PCMs directly in the mix; and (4) by impregnating the liquid PCMs directly on the concrete surface [14]. ...
Article
Full-text available
Recent studies have shown that concrete containing Phase Change Materials (PCM) with low transition temperatures may reduce the number of freeze/thaw cycles suffered by the cementitious composite in temperate climates. Nevertheless, the positive influence of such admixtures on the frost resistance of cement-based materials has not been directly shown, nor the negative. In this study, mortars with different contents of microencapsulated PCM by volume of cement paste were studied with regard to the progression of their internal and salt scaling damages during freeze/thaw cycles. X-ray micro tomography was used to monitor damage development and spatial distribution in the mortars. Furthermore, the pore system and microstructure of the PCM-modified mortars were characterized to unveil the causes of the observed macroscopic behavior during frost weathering. The results show that limited amounts of PCM in mortar, namely 10% by volume of cement paste, results beneficial for the frost and scaling resistance of the composite. Whereas, for larger PCM additions, like 30% by volume of paste, the changes in microstructure, porosity and mechanical strength brought in by these admixtures resulted in worsened performance against freeze/thawing cycles.
... The phase-change snow melting method cleans snow by the thermal energy released from the phase change material (PCM) [6]. Its durability, reliability, and stability still need to be investigated [7]. The hydronic snow melting method melts snow through the delivered energy from circulating fluid (brine, water, oil, or ethylene glycol mixture). ...
Article
Snow on roads may cause serious problems such as increasing traffic fatalities, reducing road capacity, and expanding maintenance costs, therefore, snow melting systems are usually essential in this case. A ground source heat pump snow melting system was designed and implemented in the severely cold region of China (Harbin). The experimental conditions were at the snowfall of around 3 cm and the ambient temperatures of −5.9 ~ −4.8 °C. The heating characteristics, road surface temperature, snow free area ratio, and system performances were investigated. The results showed that the supplied fluid temperature could climb to the set value in 30 min, then fluctuated within 1.3 °C. The preheating stage, rapid heating stage, and slow heating stage illustrated the road heating process. The starting stage, rapid melting stage, and slow melting stage demonstrate the snow melting process. The critical value of the snow free area ratio between rapid and slow melting stages was around 0.60. The average COP (coefficient of performance) for the heat pump and the whole system in the whole process were 2.49 and 2.04, respectively. This study provided references for the further optimization and simulation of the hydronic snow melting system in severely cold regions.
... PCM has long been used in various industries, like solar power plants for thermal energy storage [2], buildings with cooling demand [3], heat dissipation of electric circuits [4], textile design for energy absorbing clothes [5], solar hot water heating system [6], pharmaceutical and food preservation [7], and space industry [8]. More recently, it has been used on concrete pavement for snow and ice melting [9], and crack control [10]. ...
... Concrete pavement is usually exposed to a combination of mechanical stresses and environmental impacts that accelerate its deterioration rate [1,2]. The presence of de-icing salts in contact with the surface of concrete pavement during winter season can increase the damage of concrete, especially after their penetration in the pores with the absorbed water [3][4][5][6][7]. Moreover, the cyclic freezing and thawing cycles can produce a high pore pressure related to the water phase change inside the pores that lead to initiating cracks within the concrete matrix [8]. ...
Article
Full-text available
The research carried out in this study presents the effectiveness of using sodium acetate as a protective material for concrete pavement. A newly developed freeze-thaw method that depends on the alteration of temperature and humidity is introduced in this research to investigate the efficacy of integrating sodium acetate with concrete with different water to cement ratios (w/c). Results from the introduced freeze-thaw method were compared with the outcomes of a standard freeze-thaw testing method. The distressed concrete was tested for water absorption and compressive strength after finishing six months of freeze-thaw testing. Additionally, the morphology of sodium acetate and its interaction with concrete were investigated by using Scanning Electron Microscope (SEM). Results demonstrated the effectiveness of sodium acetate in protecting concrete.
... Farnam et al. found that when the lightweight aggregates (a type of porous material) containing PCM were incorporated into the pavement, the maximum potential heat released during the phase change process was 12,111 ± 1,070 kJ/m 3, which can melt the ice of 36.3 ± 3.2 kg/m 3 [28]. They then conducted [29]. Results showed that the average snow melting velocity was about 42.86 g/h in 7 h when the ambient temperature dropped from 5 ℃ to 0 ℃. ...
Article
Steel slag is a solid waste which originates frrom the steelmaking industry. Its improper disposal can cause serious environmental pollution and land encroachment. Currently, recycling steel slag as aggregate for asphalt paving has been identified as an emerging sustainable way to promote the secondary reuse of solid waste. However, the functional use of steel slag aggregates still needs further exploration to maximize its utilization efficiency. This study aimed to develop a novel steel slag-based composite phase change aggregate (SS-CPCA) for snow/ice melting of asphalt pavements. Firstly, a binary n-alkane eutectic system was established to determine the binary eutectic composite of PCMs. In combination with the DSC test results, the n-tetradecane and n-octadecane were screened out as the best binary eutectic composite, of which eutectic mass ratio, phase change temperature, and enthalpy were 84.4: 15.6, 2.87 °C, and 179.60 J/g, respectively. The SS-CPCA was then developed by using the coarse steel slag aggregate to adsorb the PCM composite while using the cement mortar as a coating. A type of SMA-13 asphalt mixture was subsequently selected and used for fabricating the SS-CPCA asphalt mixture. Finally, the pavement performance and temperature regulation performance of the SS-CPCA based asphalt mixture were tested and compared with those of the steel slag-based asphalt mixture. The test results indicated that the pavement performance properties of SS-CPCA asphalt mixture satisfied the specification requirements, verifying the feasibility of utilization of the SS-CPCA for asphalt paving. Moreover, it showed that the incorporation of SS-CPCA has the capability to increase the surface temperature of SMA-13 asphalt mixture as high as 3.4 ℃, while extending the cooling time to 780 s when the asphalt mixture surface temperature reaches 0 ℃. These findings demonstrate that the developed SS-CPCA has a promising snow/ice melting performance for asphalt pavements.
... Not only has the thermal performance of PCM-integrated concretes been evaluated but also the effect of PCMs on the thermal stress and thermal shrinkage of cementitious composites has been of great interest. Consequently, several unique applications of PCMs in concrete research have emerged, such as temperature control in mass concrete, snow-melting pavements, etc. [6][7][8][9]. ...
Article
Phase change materials (PCMs) have been widely proven to provide thermal energy storage (TES) capacity in building systems. However, some potential problems associated with the incorporation of PCMs in building materials may cause uncertainty about their real performance. Among such problems, the leakage possibility of PCMs in the molten state has been greatly addressed in the literature. In this regard, this study is aimed to evaluate the mechanical and thermal behavior of a shape-stabilized PCM (SSPCM) as a TES component in the conventional wall system of buildings in Iran. For this purpose, PEG 600 was shape-stabilized in the porous structure of the silica fume as the supporting material using the vacuum impreg-nation method. The SSPCM was further employed to prepare cement mortars for plastering masonry brick wall specimens. The mechanical experiments on the SSPCM-incorporated mortars indicated satisfactory results to be used as the finishing plaster for masonry walls. Moreover, a novel experimental setup was utilized to perform thermal performance test on the wall specimens plastered with SSPCM-incorporated mortar under ambient temperature conditions of two different cities. Accordingly, the developed SSPCM exhibited the promising potential to provide TES capacity in external masonry wall systems by reducing the peak temperature as well as mitigating indoor temperature fluctuations.
... It was reported that PCM containing G/C panel had reduced peak temperature with lagged time and pronounced impact was observed in the case of n-octadecane PCM. Farnam et al. [17] used low transition temperature paraffin oil in his study, by applying two different techniques; a) Impregnation into a lightweight aggregate (LWA) b) Using metal tubes filled with paraffin. Taking the advantage of the heat generated during the phase changing process of PCM to melt snow on the surfaces of rigid pavements, the added that quantity of deicing salt can be reduced that modify the properties of concrete. ...
Article
Structural thermocrete was developed by the incorporation of novel non-encapsulated paraffin-aggregate (NE-PA) into the cement matrix. The preparation of NE-PA follows the intrusion of liquid paraffin into porous expanded clay lightweight aggregate (EC-LWA), tailed by subsequent exposure to heat (50 °C) to ooze-out surface paraffin until an appreciable amount (29.13%) was retained. Flow characteristics, microstructure, thermal properties, chemical characterization, and thermal stability were determined using hangerman’s cone, scanning electron microscope (SEM), differential scanning calorimeter (DSC), fourier transform infrared spectroscope (FT-IR), and thermo-gravimetric analyzer (TGA) respectively. Moreover, to evaluate the mechanical characteristics in terms of compressive and flexural response three mixes were formulated via 0%, 50%, and 100% replacement of EC-LWA by NE-PA, and tested at 7 and 28 days of curing age. Results showed that a self-flowable and non-segregating mix was achieved for all the thermocrete compositions. Omission of the encapsulation layer (in NE-PA) resulted in an ameliorate interfacial transition zone (ITZ) that was enriched with nano-silica fume (NSF) inclusion, providing a substantial increase in mechanical properties. At 28 day curing age, compressive strength was increased by 47.26% and 26.58% for both the respective compositions. Moreover, 100% replacement by NE-PA resulted a maximum of 44 MPa compressive strength and rupture modulus of 4.03 MPa at 28 day, confirming its applicability in sustainable structures. Load–deflection also curve showed rational improvement (14%) in overall fracture toughness. The retained thermal energy storage capacity of structural thermocrete via DSC analyses was determined to be 20.48 J/g. Achievement of thermal stable and superior structural thermocrete with thermal properties as good as the available literature provided the opportunity that the encapsulation layer can be eliminated for practical application practices in sustainable construction.
... Other than reducing high temperature of DGAC in summer, PCM can also regulate pavement temperature in winter. Farnam et al. [22] used paraffin oil as a PCM in concrete. They found that paraffin oil can effectively release thermal energy near the freezing temperature by undergoing a phase transition process from liquid to solid, and thus melting snow and ice on concrete pavement surface. ...
Article
Open-graded friction course (OGFC) is prone to deformation-related clogging during summer owing to high internal temperature. Reducing OGFC temperature during summer has significant benefits in relation to mitigation of rutting and clogging problems. A phase change composite material with PEG-4000 serving as the core and SiO2 as the shell (PEG/SiO2) was used to modify OGFC. Different mechanical performance tests were conducted, and the results showed that the addition of the PEG/SiO2 only has slight negative impacts. The effectiveness of the PEG/SiO2 modified OGFC for pavement temperature regulation was subsequently demonstrated through a lab-scale, indoor heating test using slab specimens with different PEG/SiO 2 dosages and moisture conditions. Finally, a 3-D heat transfer modeling technique was applied to model the temperature field of the slab during the heating test. The results from the numerical simulation were generally in close agreement with the lab test results. Based on this study, using PEG/SiO2 phase change composite to modify OGFC can be considered as an effective approach to reducing porous pavement temperature during summer.
... It was discovered that, by using phase change energy storage materials, the temperature fluctuation range in summer could be reduced by more than 20 • C, but the inside temperature may also be enhanced by around 6 • C [18]. Similarly, a pipe filled with PCMs was utilized in the building of mass concrete to lower the temperature increase during the hydration phase of the concrete [19][20][21]. As a result, several researchers have concluded that the direct application of PCMs to building walls or the construction sector is a worthwhile endeavor. ...
Article
Full-text available
The use of phase change materials (PCMs) in the construction industry is one of the primary strategies for addressing the building industry’s present excessive energy usage. However, since PCMs must be enclosed before being used in construction, their efficiency is limited and their compatibility with concrete is poor. Thus, polyethylene glycol (PEG), a sequence of PCMs that may be put directly into concrete, is the target of this research. The fluidity, mechanical properties, thermal properties, hydration process, and hydration products of PEG-600 cement slurry were examined by TAM, XRD, FTIR, DSC, MALDI, etc., methods in this study. Furthermore, we tested the thermal properties of PEG-800 to confirm that the same depolymerization of PEG occurred in an alkaline environment. When PEG, with a molecular weight of 600 (PEG-600), dose was increased to 10%, both compressive and flexural strength fell by 19% and 18%, respectively. The phase change points of both PEG-600 cement paste and PEG-800 cement paste decreased to 10~15 °C, and the enthalpy of the phase change was about 6 J/g. Additionally, it was discovered that PEG entered the reaction during the hydration step. PEG underwent depolymerization and subsequently formed a complex with Ca2+. However, due to the large dose of PEG used in this investigation, a self-curing effect of PEG in concrete was not seen. The findings of this research suggest a novel use for PCMs: PEG may be directly applied to concrete to fulfill both mechanical and thermal requirements. Additionally, the number of hydration products and phase compositions remained almost constant.
... In recent years, apart from energy storage for building applications, there have been a rising number of studies focusing on the applications of PCMs in mitigation of thermal damages of concrete (e.g., in pavement and urban engineering). These efforts include: (1) thermal cracking control of mass concrete [15,16]; (2) thermal fatigue mitigation [17]; (3) ice/snow melting [18]; and (4) mitigation of urban heat island effect [19]. ...
Article
In this study, the effects of phase change material (PCM) on the thermo-mechanical behaviors of concrete pavement slabs are investigated so as to test the feasibility of utilizing PCM for mitigation of thermal curling of pavement. The PCM is elaborately stabilized in porous lightweight aggregate then loaded into concrete, without compromising strength associated with PCM incorporation. Thermal analysis indicates that the PCM introduces a latent heat capacity of about 21 J/g to the pavement slab. Two emerging fiber-optic monitoring techniques, i.e., truly distributed strain/temperature sensors and a high-resolution inclinometer, are employed to continuously monitor distributions of the temperature, strain, and tilting angle of the slabs subjected to heating and cooling, respectively. Validated by the obtained experimental results, a finite element simulation framework is established to further investigate the temperature gradient distributions, slab deformations/curvatures, and thermal strain and stress inside the slabs. The results suggest that the PCM-incorporated slab has a higher top surface temperature, a larger top-vs-bottom surface temperature difference, and thereof a larger curvature. However, the temeprature gradient reveals that heat accumulates at the upper layer before PCM melts completely, thus accounting for most of the temerpature difference. Moreover, regardless of the larger top-vs-bottom strain difference and stress nonlinearity, the linear strain of the PCM slab is smaller due to its lower coefficient of thermal expansion, and the later stage stress at the middle of the PCM slab center is smaller. Based on the findings, strategies of using PCM to control thermal curling of pavement slabs are proposed.
... In addition, the NaCl and CaCl 2based road salts cause corrosion in both the concrete and steel structures on bridges, roadways, and sidewalks (Tang and Lindvall 2012;Gode and Paeglitis 2014) leading to risk of failure and potential for injuries and fatalities. Interestingly, self-heating concrete mixtures are being tested as an alternative to applying road salts for deicing (Farnam et al. 2017). Another experimental approach is the use of Sporosarcina pasteuria bacteria to reduce the formation of calcium oxychloride when CaCl in road salt reacts with the calcium hydroxide (Ca(OH) 2 in concrete (Jones et al. 2020). ...
Article
Full-text available
Freshwater salinization is an emerging global problem impacting safe drinking water, ecosystem health and biodiversity, infrastructure corrosion, and food production. Freshwater salinization originates from diverse anthropogenic and geologic sources including road salts, human-accelerated weathering, sewage, urban construction, fertilizer, mine drainage, resource extraction, water softeners, saltwater intrusion, and evaporative concentration of ions due to hydrologic alterations and climate change. The complex interrelationships between salt ions and chemical, biological, and geologic parameters and consequences on the natural, social, and built environment are called Freshwater Salinization Syndrome (FSS). Here, we provide a comprehensive overview of salinization issues (past, present, and future), and we investigate drivers and solutions. We analyze the expanding global magnitude and scope of FSS including its discovery in humid regions, connections to human-accelerated weathering and mobilization of ‘chemical cocktails.’ We also present data illustrating: (1) increasing trends in salt ion concentrations in some of the world’s major freshwaters, including critical drinking water supplies; (2) decreasing trends in nutrient concentrations in rivers due to regulations but increasing trends in salinization, which have been due to lack of adequate management and regulations; (3) regional trends in atmospheric deposition of salt ions and storage of salt ions in soils and groundwater, and (4) applications of specific conductance as a proxy for tracking sources and concentrations of groups of elements in freshwaters. We prioritize FSS research needs related to better understanding: (1) effects of saltwater intrusion on ecosystem processes, (2) potential health risks from groundwater contamination of home wells, (3) potential risks to clean and safe drinking water sources, (4) economic and safety impacts of infrastructure corrosion, (5) alteration of biodiversity and ecosystem functions, and (6) application of high-frequency sensors in state-of-the art monitoring and management. We evaluate management solutions using a watershed approach spanning air, land, and water to explore variations in sources, fate and transport of different salt ions ( e.g. monitoring of atmospheric deposition of ions, stormwater management, groundwater remediation, and managing road runoff). We also identify tradeoffs in management approaches such as unanticipated retention and release of chemical cocktails from urban stormwater management best management practices (BMPs) and unintended consequences of alternative deicers on water quality. Overall, we show that FSS has direct and indirect effects on mobilization of diverse chemical cocktails of ions, metals, nutrients, organics, and radionuclides in freshwaters with mounting impacts. Our comprehensive review suggests what could happen if FSS were not managed into the future and evaluates strategies for reducing increasing risks to clean and safe drinking water, human health, costly infrastructure, biodiversity, and critical ecosystem services.
... These materials can be incorporated into other systems to improve the overall energy performance of the system. For instance, PCMs have been incorporated into various construction materials and components including: asphalt [4][5][6][7] and concrete [8][9][10][11] pavements for de-icing purposes; bricks [12][13][14][15][16], masonry [17] and concrete [18][19][20][21] walls, plasters/mortars [22][23][24], ceiling [25][26][27] and plaster [28] boards, glass [29], roofs [27,30] etc. ...
Article
This study assesses the feasibility of the impregnation/encasement of phase change materials (PCM) into lightweight aggregates (LWAs) for engineering applications. Four types of plant-based PCMs (PCM1 – unrefined palm oil, PCM2 – unrefined shea butter, PCM3 – unrefined coconut oil, and PCM4 – Crodatherm PCM) are investigated at material level. Similarly, two types of LWAs are used in the investigations, namely, fly–ash aggregates (FA) and glass aggregates (GA). The aggregates are by-products of the fly-ash and glass wastes generated from the construction and demolition activities. The wastes generated are recycled into various forms to reduce/eliminate the need for landfill disposal, thereby, lowering carbon-based emissions, and minimise resource extraction activities within the construction sector. In the initial investigations of this study, PCM4 was found to be the most energy efficient of all the PCMs. PCM4 had a thermal energy storage value of 33.5 kJ/kg per pound sterling (£) in comparison to 21.43 kJ/kg/£, 27.6 kJ/kg/£ and 20.71 kJ/kg/£ for PCM1, PCM2 and PCM3, respectively. PCM4 was adopted and used for impregnation into the pulverised FA and GA LWAs. Maximum absorption capacities of about 18.56% and 30.66% for the FAs and GAs were observed via vacuum impregnation technique in comparison to 5.78% and 12.86% measured using simple immersion method for the FAs and GAs, respectively. To prevent leakage and avoid coalescing of the aggregates, the PCM impregnated LWAs were coated, first, with primer epoxy resin, followed by graphite powder. Two layers of coating were applied to arrive at a durable product that can withstand abrasive forces (abrasive value of 6 and 21% for the double and single coating), heating and cooling temperatures, salt attack and a combination of thermal load and salt attack that are expected during buildings’ construction or infrastructural development in the industry.
Article
Concrete structures in cold regions are often damaged by freeze-thaw action, which can seriously reduce their service life. How to actively reduce the freeze-thaw cycles suffered by the structures is key to enhance their freeze-thaw durability. In this paper, a composite pier protective technique with microencapsulated phase change material concrete (MPCMC) was proposed, including the MPCMC layer, the pure microencapsulated phase change material (MPCM) layer, the insulation layer, and the structure concrete (SC). To analyze the thermal control performance of the composite MPCMC pier, a 3-D heat transfer model with phase change were established. Combing the laboratory and field tests, a series of numerical simulations were conducted. The results indicated that the key parameters, including the thickness, phase change range, and thermal conductivity of the MPCMC layer and MPCM layer, and the thickness and thermal conductivity of the insulation layer, can determine the thermal control performance of the composite pier. An optimal composite structure was obtained considering the engineering cost. The optimal structure can effectively reduce the freeze-thaw cycles and extend its service life. Compared to the ordinary concrete pier, the maximum degree of reduction for freeze-thaw cycles can reach 94% and the maximum extension for service life can be 1470% at the freezing point of 0 °C. The study can provide some theoretical basis for the design of the freeze-thaw resistance of the concrete structure in cold regions and related researches.
Article
Low-temperature phase change material (PCM) is a material that stores additional heat at elevated temperatures and releases energy when the temperature is below the limit. A way to solve the low-temperature disaster of asphalt pavement is desired to be developed. In this article, a two-component organic low-temperature PCM was encapsulated by melamine-urea-formaldehyde resin and finally reinforced with polypropylene. The reinforced PCM microcapsules were mixed with 70# SBS (Styrene-Butadiene-Styrene) modified asphalt in SMA-10 (Stone Matrix Asphalt-10) to form aggregates. The results showed that after adding 6.0% (w/w) reinforced PCM microcapsules, there was a significant delay compared to a blank sample with a maximum temperature difference of 1.8 °C when the temperature dropped to 0 °C, which proved that this method has a good potential in resisting low temperature disasters on asphalt pavement and deserves further improvement.
Article
A soft magnetic layer in the airport pavement can shape magnetic field and improve the induction heating efficiency. During the preparation of soft magnetic material, binder matrix material is mixed with magnetic susceptible inclusions such as iron powders, resulting in the high magnetic and mechanical performances of the soft magnetic layer. Geopolymer, which shows high cohesion strength as well as little environmental impact, appears to be a promising binder candidate. The motivation of this work is to unveil the formation mechanisms of electromagnetic and mechanical properties of FA-GBFS geopolymer composite from the perspective of initial SiO2/Al2O3 molar ratio, so as to provide a theoretical basis for the design of geopolymer-based soft magnetic layer. Results show that the magnetic properties of FA-GBFS geopolymer composite are mainly generated by the Na⁺ movement. Both geopolymer reaction and calcium silicate hydration reaction exist within the FA-GBFS geopolymer composite, and the synergy of the two chemical reactions determines the electromagnetic and mechanical properties of the FA-GBFS geopolymer composite. Besides, the optimized FA-GBFS geopolymer composite can not only present a saturation magnetization intensity up to 25 times that of cement, but also meet the mechanical requirement of airport pavement.
Article
Building construction deserves many attentions due to its huge energy consumption, while Phase Change Materials (PCMs) provide positive solutions for improving energy efficiency and enhancing the thermal properties of construction materials. However, PCMs also present some negative impacts, such as weakening mechanical properties and increasing costs, chemical instability and so on. In this paper, the main characteristics of PCMs, researching and incorporating methods, influences on energy consumption and construction reliability are reviewed and discussed. Although plentiful materials have the capacity of phase change, some organic PCMs are more suitable due to the higher latent heat and favourable phase change point in buildings, when eutectic PCMs present greater potential to become the optimal one but much effort is required. Current incorporation methods and application in construction materials can meet the essential requirements, but the effectiveness is inadequate, including low efficiency of phase changing leading to low energy storage. Subsequently, some promising research direction and critical areas deserved optimization are also proposed accordingly. Future development of PCMs, including novel PCM and efficient incorporation, as well as its application and function in buildings are proposed. Additionally, multifunctional construction materials combining PCM deserve much attention and possess promising prospect for energy saving in future building construction.
Article
In cold weather, the outer surface of stay cable sheaths easily freezes. When the ambient temperature increases, the ice on the surface melts easily, and there is a risk of falling ice at high altitudes. In this paper, a simple design method is proposed that uses carbon fiber heating wires to prevent the icing of stay cables. Conventional indoor tests and numerical simulations of heat conduction are carried out for a sheath with a single diameter, and the number of heating wires required for different diameter sheaths is obtained. Taking the stay cable sheath of the Qingshan Bridge in Wuhan as an example, when the diameters of the heating wire and the stay cable sheath are 6 mm and 200 mm, respectively, the temperature rise rule of the heating wire, the calibrated heating power and the convective coefficients are obtained through tests and numerical simulations. At an ambient temperature of 4 °C, thread-like ice formed in the arc range of 0.314 m on the surface of the sheath. The critical non-icing temperature required by the heating wire during preheating to ensure that the sheath surface does not freeze is 1.5 °C.
Article
Full-text available
Nano-refined epoxy paste is formulated using the optimum fractions of nano-silica fume and graphite powder to effectively encapsulate the aggregate storing phase change materials. The refined recipe offered delays in setting by 3–3.5 hrs accompanied with 15 times reduction in the thickness of coated layer, contributing in added workability, reduced consumption and strong adhesion to the established interfacial bond. The developed macro encapsulated phase change materials were found to be thermally stable, chemically compatible and thermally reliable. The melting and freezing temperatures were determined as 17.12 °C and 32.90 °C respectively with the latent heat storage capacity of 12.6 J/g. The developed thermocrete via 100% integration of macro-encapsulated aggregates showed compressive strength of more than 15 MPa and owed the potential to conserve energy by lowering the internal temperature (6.4 °C), resistance to high fluctuation in temperature while maintaining a narrow range (22 °C−30.2 °C) and by shifting the energy loads during peak periods (15-min).
Article
Black ice is a type of thin ice sheet that forms on roads and pavements forms easily generated in moist areas with subzero temperatures, especially in shade. In cold region, a high-efficiency black-ice removal system is required because of the environmental nature of easily generated black-ice. In this study, a new type of black-ice removal system using latent heat thermal energy storage (LHTES) with a solar thermal collector is firstly introduced and was tested in the field. A concrete pavement was made for the test with a surface area of 0.4 m² with heat pipes were embedded a depth of 0.05 m, with 0.15 m intervals. The solar thermal collector was used to store heat energy in the LHTES, which was dissipated through the concrete pavement by passing the embedded pipes. One centimeter of thin ice sheet, which was assumed to be black-ice, was formed on the surface of the concrete pavement. The LHTES charging and discharging flow rates were 5 and 7 L/min, respectively. The results were that the black-ice with 0.4 m² area and a thickness of 1 cm at −15 °C ambient temperature was heated to 8 °C and completely melted in 2 h.
Article
Reinforced concrete (RC) structures in cold regions are subjected to double attacks of chloride erosion and freeze–thaw cycles (FTCs), accelerating the deterioration of concrete performance. Here, a multi-phase mesoscopic numerical model is proposed to systematic study the diffusion mechanism of chloride under the FTCs. Unlike most of existing models, the interface transition zone (ITZ) with random thickness is taken into account in the proposed concrete meso-structure. Moreover, the relationship between FTCs damage and chloride diffusion coefficient of concrete is deduced from the classical Aas-Jakobsen S-N equation. The reliability of the proposed model is further verified by compared with the third-party experiments data. It is evident from the proposed model that FTCs can promote the chloride diffusion. More importantly, this promoting effect is obvious when the number of FTCs is close to the limit number of FTCs. Specially, the mechanism of ITZ promoting the chloride diffusion is revealed by simulating the chloride diffusion trajectories in concrete meso-structure. Interestingly, despite the existence of FTCs in cold regions, chloride is diffused more rapidly in the tropical regions. Our findings reveal previously ignored fundamental aspects of the chloride diffusion mechanism under FTCs, and provide insights for the durability prediction of RC structures.
Conference Paper
Concrete pavements suffer from deicing salt attack and freeze-thaw damage to different degrees. These damages reduce the service life of pavement systems and consequently increase the life-cycle cost of pavements and environmental footprints associated with transportation infrastructure. Salt erosion and environmental condition are common causes of damage to pavements due to adverse impact on concrete durability. This paper examines the impact of sodium chloride (NaCl) solution and freeze-thaw cycles on the performance of concrete made with water-to-cementitious-materials ratios of 0.4. The experimental investigation includes three different saline environments with salt-to-water ratios of 0%, 10%, and 20%, in presence and absence of saline solution. Results include the 28-day compressive strength and weight loss of 22 specimens. Results show that the concrete specimens subjected to freeze-thaw cycles were peeled more severely in saline solution than those in the absence of chloride salt solution. However, the amount of peeling exhibited a decrease when the NaCl percentage rose from 10% to 20%. Further, observations revealed that the presence of NaCl intensified the weight loss and strength reduction at 28-day age.
Article
A new type of environmentally-friendly Anti-Freeze Filler (AFF) was prepared in this work firstly. The main components of the AFF included in carrier, deicing chemicals and surface modifier. Additionally, a corrosion retardant was employed to mitigate the impact on the environment. Various characterization methods were used to optimize the proportion of each component in the AFF, including ice-melting test, penetration test, corrosion test, specific surface area test and scanning electron microscope test. The anti-freeze asphalt concrete (AFAC) was prepared with AFF, and its engineered performance was tested. The results of engineered performance test indicated that both high-temperature and low-temperature performances of AFAC decreased with the increase of the AFF content, but still met the specification requirements. The AFAC had better water stability, when the replacement rate of filler is less than 75%. The ice-adhesion pulling/shearing tests indicated that the pulling and shearing strength of the AFAC was about 50% lower than that of the controlled sample within the test temperature of 0~ −10 ℃. An environment-induced deterioration of AFAC’s anti-freezing ability was evaluated with an environment simulation platform based on the climate conditions in central China. With the environmental deterioration came to the fifth cycle, the pulling strength of the AFAC was still 25% lower than the controlled specimen at −3 ℃.
Article
The consumption of non-renewable resources has made the earth's resource crisis increasingly prominent. Renewable energy solar energy is more and more popular. Highways occupy a large proportion of the surface area and therefore become an excellent carrier for the development and utilization of solar energy. Solar pavement and asphalt pavement are the two most common ways to use solar energy. Phase change material (PCM) uses its own latent heat to enable asphalt to absorb or release a large amount of heat under constant conditions to regulate the road surface temperature. Based on these issues, this paper compares the development of solar pavement and asphalt pavement. It also introduces the principles of solar power generation and examples of heat utilization. The research methods of using phase-change materials to modify the temperature of solar pavement and asphalt pavement are reviewed. It summarizes the progress of materials in pavement application and prospects the future development trend of solar pavement.
Article
Phase change materials (PCMs) have been used for energy storage within a wide range of applications. However, they are scarcely used in the field of anti-icing of glass insulators in transmission lines under glaze ice (the icing temperature is 0∼-5°C). Herein, we prepared phase change microcapsules (MPCMs) and applied them to permanent room temperature vulcanized (PRTV) silicon rubber to prepare anti-icing coating on glass. The n-tetradecane and nucleating agent were used to obtain a requirable phase change temperature. The MPCMs in the coating released latent heat when the temperature dropped from 2.25°C to -4.73°C, which was consistent with the temperature of glaze icing. Furthermore, MPCMs roughened the coating surface and imparted superhydrophobic to the coating. Compared with PRTV coating, the prepared MPCM/PRTV coating extended the freezing time of water droplets from 1381 s to 3432 s. Additionally, the MPCMs in the coating could absorb and release energy repeatedly and maintain intactness without cracking during icing/melting cycles, and the anti-icing/deicing performance of the MPCM/PRTV coating demonstrated durability. The heat storage and release of the MPCM/PRTV coating is driven by the temperature difference, thus, we define this coating as having a “temperature switch” effect. The prepared coating shows potential anti-icing applications for glass insulators under glaze ice where the temperature fluctuates within the phase transition temperature range of this coating.
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The use of phase change materials (PCMs) in building elements has gained increasing popularity in recent years because of the potential energy savings that result from the heat stored during variable temperature–time histories. This paper describes the results of non-linear numerical analyses on sandwich panels characterized by different geometry and consisting of an innovative concrete, i.e., lightweight concrete with aggregates containing PCMs. The amount of embedded PCMs has no equal in the literature, and this calls for a detailed assessment of its thermal performance within a typical building element. The heat transfer process inside the panels is modelled via finite elements in order to evaluate the effectiveness of the addition of PCMs with regard to insulation. The results show that adding PCMs may significantly reduce (by up to 20%) the energy required for cooling in the hot season, while the reduction of the energy required for heating in the cold season is lower (up to 10%). Moreover, there is a significant reduction in the instantaneous power required, both for heating and cooling.
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This paper presents a one-dimensional finite difference model that is developed to describe the freeze-thaw behavior of an air-entrained mortar containing deicing salt solution. A phenomenological model is used to predict the temperature and the heat flow for mortar specimens during cooling and heating. Phase transformations associated with the freezing/melting of water/ice or transition of the eutectic solution from liquid to solid are included in this phenomenological model. The lever rule is used to calculate the quantity of solution that undergoes the phase transformation, thereby simulating the energy released/absorbed during phase transformation. Undercooling and pore size effects are considered in the numerical model. To investigate the effect of pore size distribution, this distribution is considered using the Gibbs-Thomson equation in a saturated mortar specimen. For an air-entrained mortar, the impact of considering pore size (and curvature) on freezing was relatively insignificant; however the impact of pore size is much more significant during melting. The fluid inside pores smaller than 5 nm (i.e., gel pores) has a relatively small contribution in the macroscopic freeze-thaw behavior of mortar specimens within the temperature range used in this study (i.e., +24 °C to -35 °C), and can therefore be neglected for the macroscopic freeze-thaw simulations. A heat sink term is utilized to simulate the heat dissipation during phase transformations. Data from experiments performed using a low-temperature longitudinal guarded comparative calorimeter (LGCC) on mortar specimens fully saturated with various concentration NaCl solutions or partially saturated with water is compared to the numerical results and a promising agreement is generally obtained.
Conference Paper
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Internally cured (IC) concrete is frequently produced in North America using pre-wetted lightweight aggregate (LWA). One important aspect associated with the production of quality IC concrete is the accurate determination of the moisture content, including absorbed moisture and surface moisture of the LWA. Knowledge of the moisture content enables aggregate moisture corrections to be made for the concrete mixture, thereby enabling an accurate water-to-cement ratio to be maintained. Two methods for determining the moisture content of LWA include the specified ASTM C1761-13b "paper towel method" and a method that uses a centrifuge (Miller, Barrett, Zander, & Weiss, 2014). There are limited data available on the variability associated with either of these approaches when the test is performed by multiple users. In this study, the absorption of four commercially available LWAs was tested by a single operator in a single laboratory using the centrifuge method. In addition, the absorption of three commercially available LWAs was tested by 25 users performing both experimental methods. This article provides an estimation of precision associated with both a single operator and multiple operators performing both the paper towel method and the centrifuge method to find the absorption of pre-wetted lightweight fine aggregate. © 2014 4th International Conference on the Durability of Concrete Structures.
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This paper investigates the potential use of phase change materials (PCM) in concrete pavements to store heat, which can be used to reduce ice formation and snow accumulation on the surface of the concrete pavement. The thermal properties of the PCMs are evaluated using a low-temperature differential scanning calorimeter (LT-DSC) while a longitudinal guarded comparative calorimeter (LGCC) is used to evaluate the thermal response of cementitious mortar containing the PCM. Paraffin oil (petroleum based) and methyl laurate (vegetable based) were selected as PCMs since they have high enthalpies of fusion (~130-170 J=g) and have desirable freezing temperatures (~2-3°C) during the liquid to solid phase transformation. Two approaches were used to place the PCM in the mortar specimens: (1) placing the PCM in lightweight aggregate (LWA) in mortar and (2) placing the PCM in an embedded tube that is placed in mortar. The durability and stability of the PCMs in the cementitious system were studied by monitoring the change in enthalpy of fusion, mass loss, pulse velocity, and compressive strength. When the PCM was placed in the mortar specimen using LWA, the paraffin oil can release a considerable amount of heat during phase transformation, which can be used to melt ice and snow. However, it was observed that the methyl laurate reacts with the cementitious matrix, causing damage to the mortar. Both paraffin oil and methyl laurate showed promising performance to melt ice and snow when the PCM was placed in an embedded tube in the mortar specimen.
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The conventional CaCl2-H2O phase diagram is often used to describe how calcium chloride behaves when it is used on a concrete pavement undergoing freeze-thaw damage. However, the chemistry of the concrete can alter the appropriateness of using the CaCl2-H2O phase diagram. This study shows that the Ca(OH)2 present in a hydrated portland cement can interact with CaCl2 solution creating a behavior that is similar to that observed in isoplethal sections of a ternary phase diagram for a Ca(OH)2-CaCl2-H2O system. As such, it is suggested that such isoplethal sections provide a reasonable model that can be used to describe the behavior of concrete exposed to CaCl2 solution as the temperature changes. Specifically, the Ca(OH)2 can react with CaCl2 and H2O resulting in the formation of calcium oxychloride. The formation of the calcium oxychloride is expansive and can produce damage in concrete at temperatures above freezing. Its formation can also cause a significant decrease in fluid ingress into concrete. For solutions with CaCl2 concentrations greater than about 11.3% (by mass), it is found that calcium oxychloride forms rapidly and is stable at room temperature (23°C).
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The behavior of two cementitious materials during thermal changes associated with freezing and thawing in presence of calcium chloride deicing salts was examined. The two systems consisted of a conventional portland cement-based material and an alternative economically friendly cement that formed a solid by carbonating a calcium silicate–based cement. Low-temperature differential scanning calorimetry was used to quantify the phase changes associated with ice formation, eutectic solution transformation, and calcium oxychloride formation. Longitudinal guarded comparative calorimetry was used to detect the damage that developed as a result of the expansive pressures created by these phases when they form. In both systems exposed to low salt concentration, the damage was primarily caused by hydraulic and osmotic pressure. This type of damage was moderate at low degrees of saturation (e.g., <90%); however, as the degree of saturation increased, so did the damage. In conventional cementitious systems at higher salt concentrations, the damage that developed was mainly caused by the formation of calcium oxychlorides. However, in the cementitious materials made by carbonating calcium silicate–based cement calcium, hydroxide was not present. Therefore, at higher salt concentrations, calcium oxychloride did not form, and as a result, no damage developed.
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It is well known that there is a need to develop technologies to achieve thermal comfort in buildings lowering the cooling and heating demand. Research has shown that thermal energy storage (TES) is a way to do so, but also other purposes can be pursued when using TES in buildings, such as peak shaving or increase of energy efficiency in HVAC systems. This paper reviews TES in buildings using sensible, latent heat and thermochemical energy storage. Sustainable heating and cooling with TES in buildings can be achieved through passive systems in building envelopes, Phase Change Materials (PCM) in active systems, sorption systems, and seasonal storage.
Conference Paper
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Different organic phase change materials (PCMs) are used in this study to evaluate their capability to use in concrete pavement. Thermal properties of some fatty acids and their methyl esters are evaluated by using a low temperature differential scanning calorimetry; and their potential in storing heat in concrete is investigated. A temperature range between +50 to -100 °C is applied and thermal response of PCMs is monitored. The temperatures at which different phase changes occur in PCMs are detected. In addition, latent heat absorbed or released by PCMs when the material changes from solid to liquid and vice versa are detected. The results are compared with Paraffin wax thermal response. Results show that the thermal properties of fatty acid methyl esters are less complex and more consistent. Also, their thermal properties can be changed by altering their compositions in order to stay in a desired temperature range. It is observed that the desired latent heat depends on the original type of fatty acid which is used to make the fatty acid methyl esters.
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Deicing salts are often applied to the surface of pavements and bridge decks in the winter to melt ice; thereby improving safety for the travelling public. In this paper, the influence of NaCl deicing salt on freezing and thawing temperatures of pore solution and corresponding damage of mortar specimens were investigated. A low-temperature longitudinal guarded comparative calorimeter (LGCC) was developed to cool down a mortar sample at a rate of 2 °C/h and to re-heat the mortar at a rate of 4 °C/h. Heat flux during freezing and thawing cycles was monitored, and the temperatures at which freezing and thawing events occurred were detected. During cooling and heating, acoustic emission activity was measured to quantify the damage (cracking) due to aggregate/paste thermal mismatch and/or phase changes. The results show that NaCl solution in a mortar sample freezes at a lower temperature than the value expected from its bulk phase diagram due to under-cooling. Conversely, the frozen solution in mortar melts at the same melting temperature as the bulk frozen NaCl solution. As the salt concentration increases, the freezing temperature is lowered. For samples containing more highly concentrated solutions, an additional exothermic event is observed whose corresponding temperature is greater than the aqueous NaCl liquidus line in the phase diagram. Damage also begins to occur at this temperature. For mortar samples saturated by solutions with 5 % and 15 % NaCl by mass, greater freeze/thaw damage is observed. The AE calorimeter developed herein is applicable for investigating damage behavior during freezing and thawing of different phases in pore solution (in mortars).
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This paper describes a series of experiments that were performed to assess the freeze-thaw behavior of mortar specimens exposed to NaCl solutions. A low-temperature longitudinal guarded comparative calorimeter was used to perform cyclic freeze-thaw testing on mortar specimens saturated with NaCl solutions. Heat flow and acoustic emission activity were monitored during the freeze-thaw experiment to detect ice formation and cracking. Although the conventional water-NaCl phase diagram would suggest that no freezing or damage would occur in specimens saturated with 15 % and 23.3 % NaCl solution by mass within the applied freeze-thaw temperature range, damage was observed. For these specimens, an additional heat flow peak attributed to an unexpected phase change, accompanied by acoustic activity, was detected at a temperature higher than the expected freezing point. To better understand the source of this damage, a low temperature differential scanning calorimeter was used to investigate the influence of NaCl on freeze-thaw behavior of water, two pore solutions, hydrated cement powder, and calcium hydroxide powder. The results showed that the pore solution alters the freeze-thaw behavior slightly; however, it does not exhibit the unexpected phase change at higher concentrations. The specimens made with hydrated cement powder showed the unexpected phase change in high concentrations of NaCl solution in a temperature range between 0 °C and 8 °C. While the exact nature of this phase change is not definitively known, it appears that it results in premature damage during freeze-thaw when high concentration salt solutions are used, even if freezing of the solution is not occurring.
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The possible incorporation of phase change materials (PCMs) in building materials has attracted a lot of research interest worldwide due to the concern on global warming and the ability of PCMs to reduce energy consumption in building because of their thermal energy storage abilities. As a substance with a high heat of fusion, PCM is capable of storing and releasing large amounts of energy in the form of heat during its melting and solidifying processes at the specific transition temperature. For the past 20 years, significant research has been undertaken on the potential use of PCMs in concrete. The results showed that PCM-concrete has some useful characteristics such as better latent heat storage and thermal performance. On the other hand, PCMs have some negative impacts on the properties of concrete. However, the negative impacts can be minimized if an appropriate PCM and a suitable means of incorporation are employed during the production of the PCM-concrete. In this paper, a general review of different types of PCMs, means of their incorporation and the influence of PCMs on the properties of concrete at the fresh and hardened stages are reviewed. The stability of the PCMs, the problems in relation to using them in concrete, as well as their thermal performance in concrete are also presented.
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h i g h l i g h t s " A novel apparatus was used to measured absorption of PCM by LWA. " High viscosity PCMs were found to be impractical for use with LWA. " This technology is most effective across the south and Pacific Northwest. a b s t r a c t A new technique to extend the service life of bridge decks, by reducing freeze/thaw damage through the incorporation of phase change materials (PCMs), has been investigated. The impregnation of two light-weight aggregates (LWAs) with four different PCMs was quantified, and compressive strength, isothermal calorimetry, and thermal property analyses were used to determine the effects of PCM incorporation on the physical properties of mortars. Physical and thermal property data were used to refine a previously-developed model and determine locations in the United States where PCM incorporation to reduce freeze/thaw damage may be a viable technology.
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During a freezing event, pore solution in cementitious bodies expands and creates stresses that can cause damage; therefore, reducing the number of freeze/thaw cycles experienced by a structure will extend the structure's service life. The incorporation of phase-change materials (PCMs) to reduce the number of freeze/thaw cycles experienced by bridge decks has been investigated by modeling, mechanical testing, calorimetry, and X-ray microtomography. Models identified geographical regions in which freeze/thaw damage is not a significant concern and regions where this technology may be practical, increasing the service life of a bridge deck by at least 1 year. The incorporation of PCM reduces strength by varying amounts and for varying reasons, depending on which PCM is used and how it is in-troduced into the concrete. Because a variety of methods exist to address this loss in strength, PCM incorporation shows promise as a technique for addressing one aspect of worldwide infrastructure maintenance challenges.
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In internal curing, pre-wetted lightweight aggregates (LWA) serve as internal reservoirs to supply the extra water needed by the cementitious and pozzolanic components of the concrete during their hydration processes. Due to their porous nature and reasonably high absorption capacity, the LWA can also be filled with other materials, such as phase change materials (PCMs). In this paper, three potential applications of PCM-filled LWA in concrete technology are presented. In addition to the previously explored application of increasing the energy storage capacity of concrete in residential and commercial construction by using a PCM with a transition temperature near room temperature, applications for higher and lower temperature PCMs also exist. In the former case, a PCM can be used to reduce the temperature rise (and subsequent rate of temperature decrease) of a large concrete section during (semi)adiabatic curing, to minimize thermal cracking, etc. In the latter case, a PCM can perhaps reduce the number or intensity of freeze/thaw cycles experienced by a bridge deck or other concrete exposed to a winter environment. In this paper, these latter two applications are preliminarily explored from both experimental and modeling viewpoints.
Article
This paper employs a numerical simulation strategy to elucidate the influence of phase change materials (PCMs) on the thermal response of concrete pavements. Simulations of both the early- and late-age response of concrete pavements containing microencapsulated PCMs, with considerations of mixture proportions, PCM types, and structural and environmental boundary conditions, are carried out. The latent-heat response of PCMs is explicitly integrated into the model. The early-age simulations show significant reductions in peak hydration temperature and the heating/cooling rates when PCMs, either as a partial replacement of the cement paste or fine aggregates, are incorporated in concrete, resulting in reduced cracking probabilities. Simulations on mature pavements also indicate temperature and curling stress reductions when appropriate PCMs are used. PCM type(s) and dosage, depending on the imposed external temperature regimen, can be chosen based on the model to reduce the magnitude of critical stresses at both early- and late ages. The numerical model thus enables engineers and designers rationally design crack-resistant concrete pavements.
Article
Macro-encapsulated aggregates (ME-LWAs) consisting of expanded clay lightweight aggregates (LWAs) impregnated with a paraffin wax phase change material (PCM) was produced. To fully exploit the thermal energy retaining properties of PCM, it is fundamental to retain as much of the PCM as possible within the pores of the LWA. This paper investigates 3 different commercial materials to create a total of 14 different coating regimes to determine the most efficient coating method and material regarding its ability at retaining the PCM. The ME-LWAs are then further used as aggregates in geopolymer binders made from a combination of aluminosilicate rich mud and waste glass. Physical properties such as thermal conductivity and mechanical strength are determined for the geopolymer binder with and without the addition of the ME-LWA. A polyester resin was determined to be the most suitable choice of coating material for the ME-LWA, producing a practically leak-proof coating. The ME-LWA was also determined to be chemically neutral, showed a 42% higher thermal conductivity than the LWA in their raw state and maintained a latent heat of 57.93 J/g before and after being used in the geopolymer binder. Carbon fibres and graphite spray were used to improve the thermal conductivity of the resin coating, however no significant increase was detected. Finally, the compressive strength and thermal conductivity results achieved are acceptable for applications in buildings for enhancement of their energy efficiency.
Article
This paper assesses the feasibility of impregnation/encasement of phase change materials (PCMs) in lightweight aggregates (LWAs). An impregnation process was adopted to carry out the encasement study of two different PCMs in four different LWAs. The leakage of the impregnated/encased PCMs was studied when they were submitted to freeze/thawing and oven drying tests, separately. The results confirmed that, the impregnation/encasement method is effective with respect to the large thermal energy storage density, and can be suitable for applications were PCMs cannot be incorporated directly such as asphalt road pavements.
Article
A group of promising phase change heat-storage materials was selected through study of the literature, laboratory tests of freeze—melt behaviour and determination of thermophysical properties. Means were developed of encapsulating these materials in metal or plastic containers. Four of these phase-change materials, suitably encapsulated, were tested in a sub-kale thermal storage unit of about 20MJ capacity, using air as the heat-transfer fluid. In most cases, measured thermal-storage capacity exceeded 90% of the theoretical value. After considering a number of heating and cooling schemes employing phase-change heat storage, we selected a forced hot air, central storage design, using CaCl2.6H2O encapsulated in plastic pipes. A home was designed, using a two-storey conservatory for solar collection with vertical glazing and movable insulation.
Article
The fatty acids are generally used as phase change materials (PCMs) in thermal energy storage (TES) applications, but the high cost of these PCMs is a big drawback which limits their applications. So, there is a need for low cost PCMs development with thermal stability, by using these PCMs the system cost may also reduce. Therefore, this paper deals with the development of binary mixtures based on commercial grade fatty acids such as lauric acid (LA), myristic acid (MA), stearic acid (SA) and palmitic acid (PA). In this regard, a series of binary mixtures i.e., LA–MA, LA–SA, LA–PA, MA–SA, MA–PA and PA–SA with varying weight percentages were developed and tested through the Differential Scanning Calorimetry (DSC). The DSC results showed that melting temperatures of LA–MA (30–80 wt.%), LA–SA (60–90 wt.%), LA–PA (40–90 wt.%), MA–SA and MA–PA (30–80 wt.%), and PA–SA (20–70 wt.%) are in the preferred temperature range 36–39, 34–38, 37–42, 45–50 and 56–58 °C respectively with high latent heat of fusion and these PCMs can be recommended for the buildings, solar water heating/drying/foot warmers applications.
Article
We re-examine experiments by Helmuth (1962) from which he concluded that ice grows in the pores of cement paste under heat-flow control, and that the internal temperature rises to the melting point given by the Gibbs–Thomson equation. We find that his conclusions are correct, but the growth rates he reports are misleading. Using experimental and computational methods, we show that the ice grows in the form of dendrites, which allows a constant growth rate under heat-flow control. A modification of the experimental procedure permits accurate measurement of the growth rate of ice in the pores.
Article
Recently, substantial interest has developed in using fine lightweight aggregate for internal curing in concrete. Mixture proportion development for these mixtures requires the specific gravity, water absorption, and water desorption characteristics of the aggregate. This paper presents results from a recent study in which the properties of commercially available expanded shale, clay and slate lightweight aggregates (LWA’s) were measured. This research measured the time-dependent water absorption response for the lightweight aggregate. The results indicate that a wide range of 24h water absorption values exist for commonly used fine lightweight aggregates (e.g., absorption between 6% and 31%). Desorption was measured and it was found that between 85% and 98% of the 24h absorbed water is released at humidities greater than 93%. These properties can be normalized so that they can be efficiently used in proportioning concrete for internal curing. Normalized plots of absorption and desorption demonstrate benefits for a single function that describes a large class of expanded shale, clay, and slate aggregate for use in internal curing.
Article
The pore structure of mortar (w/c=0.55) was examined using thermoporometry (TPM), nitrogen adsorption/desorption (NAD), and mercury intrusion porosimetry (MIP). The TPM measurements were calibrated by comparison to NAD and MIP measurements on porous glass; similar comparisons were made on dried and resaturated mortars. For undried mortars, TPM provides the size of pore entries (from the freezing cycle) and interiors (from the melting cycle). In keeping with previous studies, we find that there is an unfrozen layer of water between the ice and the pore wall in porous glass that is about 0.8nm thick; when lime-saturated water is used, the thickness of that layer increases by about 10%. In mortar, the unfrozen layer is about 1.0–1.2nm thick, so no freezing occurs in pores with diameters ≤4.5nm, at least down to −40°C (where the radius of the crystal/liquid interface is ∼1.5nm). Based on the hysteresis in the freezing and melting curves, the larger mesopores in mortar were found to be rather spheroidal, while the smaller ones were more cylindrical.
Article
The present study experimentally investigates the effect of different diluted deicers on concrete deterioration. Laboratory simulations of environmental freeze/thaw cycling were first conducted on Portland cement concrete specimens in the presence of various deicers (NaCl, K-formate, NaCl-based deicer, K-acetate-based deicer, Na-acetate/Na-formate blend deicer, CMA deicer, or MgCl2 liquid deicer); and SEM/EDX measurements were then conducted for the concrete samples. Under the experimental conditions in this study, the CMA solid deicer and the MgCl2 liquid deicer were benign to the concrete durability, whereas K-formate and the Na-acetate/Na-formate blend deicer showed moderate amount of weight loss and noticeable deterioration of the concrete. NaCl, the NaCl-based deicer, and the K-acetate-based deicer were the most deleterious to the concrete. In addition to exacerbating physical distresses, each investigated chemical or diluted deicer chemically reacted with some of the cement hydrates and formed new products in the pores and cracks. Such physiochemical changes of the cement paste induced by the deicers pose various levels of risks for the concrete durability. KeywordsDeicer-Portland cement concrete-SEM-EDX-Freeze–thaw
Article
Thermal energy storage has recently attracted increasing interest related to thermal applications such as space and water heating, waste heat utilization, cooling and air-conditioning. Energy storage is essential whenever there is a mismatch between the supply and consumption of energy. Use of phase change material (PCM) capsules assembled as a packed bed is one of the important methods that has been proposed to achieve the objective of high storage density with higher efficiency. A proper designing of the thermal energy storage systems using PCMs requires quantitative information about heat transfer and phase change processes in PCM. This paper reviews the development of available latent heat thermal energy storage technologies. The different aspects of storage such as material, encapsulation, heat transfer, applications and new PCM technology innovation have been carried out.
Article
By combining calorimetric measurements with dilatometry, it has been possible to calculate the contributions of thermal expansion, pore pressure, and crystallization pressure of ice to the strain observed in a mortar during freezing/thawing cycles. Air-entrained mortars contract upon freezing, while non-air-entrained mortars expand. The expansion of the latter is attributed primarily to hydraulic pressure, owing to the rapid growth of ice, which nucleates at low temperatures in laboratory samples. Poromechanical calculations account quantitatively for the contraction of samples with air entrainment, assuming that ice crystals form in the air voids. As originally proposed by Powers and Helmuth, those crystals create suction in the pore liquid that offsets the crystallization pressure of ice in the mesopores of the paste, resulting in a net contraction. Ice in the matrix also contributes significantly to the increase in the thermal expansion coefficient of the mortar.
The Influence of 461 Calcium Chloride Deicing Salt on Phase Changes and Damage Development in 462 Acoustic Emission and Low 465
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Y. Farnam, S. Dick, A. Wiese, J. Davis, D. Bentz, J. Weiss, The Influence of 461 Calcium Chloride Deicing Salt on Phase Changes and Damage Development in 462 Cementitious Materials, Cem. Concr. Compos. 64 (2015) 1–15. 463 doi:10.1016/j.cemconcomp.2015.09.006. 464 [2] Y. Farnam, D. Bentz, A. Hampton, J. Weiss, Acoustic Emission and Low 465
The 476 deleterious chemical effects of concentrated deicing solutions on Portland cement 477 concrete, Final Report for the South Dakota Department of Transportation
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L. Sutter, K. Peterson, G. Julio-Betancourt, D. Hooton, T.V. Dam, K. Smith, The 476 deleterious chemical effects of concentrated deicing solutions on Portland cement 477 concrete, Final Report for the South Dakota Department of Transportation, 2008.
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Measurement and simulation of dendritic growth of ice in 567 cement paste
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F. Stoll, M.L. Drake, I.O. Salyer, Use of Phase Change Materials to Prevent 486 Overnight Freezing of Bridge Decks (NCHRP-94-ID022), 1996.
Evaluation of Phase 493 Change Materials to Store Energy in Concrete Pavements
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Y. Farnam, L. Liston, M. Krafcik, B. Tao, K. Erk, J. Weiss, Evaluation of Phase 493 Change Materials to Store Energy in Concrete Pavements, 2015.
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