Experimental and Numerical Thermal Properties Investigation of Cement-Based Materials Modified with PCM for Building Construction Use

Due to their latent heat storage capacity, phase-change materials (PCM) incorporated in wallboards are an effective solution to reduce energy consumption inside buildings. This is achieved by incorporating PCM in construction elements made of cement-based materials. The purpose of this research is to evaluate both the thermal conductivity and the heat storage capacity of mortars and concretes with different amounts of PCM in order to evaluate their thermal performance. Therefore, a laboratory-developed transient plane source experimental setup was used to measure these properties. First, several mortar and concrete specimens including different amounts of PCM (0%, 4.5%, 9%, and 13% by total mass of cement) were manufactured. Then, the experimental setup was used to measure the temperature development on PCM-concretes and PCM-mortars for a period of 1,000 s. The collected data were analyzed to back-calculate the thermal characteristics using a numerical optimization procedure. Numerical findings using the finite-element method show that the testing procedure efficiently provides accurate estimations of the thermal properties of the tested specimens. It was found that cement-based materials incorporating PCM have lower thermal conductivity and higher heat storage capacity, which indicates the improvement of their thermal behavior

Étude expérimentale et numérique pour la caractérisation thermique des bétons à changement de phase (BCP)

In order to satisfy the technological challenges required by the new building concepts in the aim of improved performances in terms of durability, thermal comfort and respect for the environment, many research ideas have been considered by researchers and building professionals. Among these ideas, the reinforcement of construction materials by innovative and eco-efficient materials known as phase change materials (PCM) has attractive and promising advantages. Known for their high latent heat storage capacities, PCMs combined with cementitious materials such as concrete, are presented in the construction market as potential and intelligent actors for “clean” and sustainable construction. However, when PCMs are incorporated into the concrete paste, the estimation of the thermal conductivity and the specific heat capacity of the latter is not trivial and thus requires solving the optimization problems known as “inverse heat transfer problems”. In this context, this work proposes an iterative parametric optimization procedure, using a numerical model developed in order to estimate the thermal conductivity and the specific heat of the material containing the PCMs, such as phase change concrete, for example. To achieve this, we will use thermograms obtained from experimental tests carried out with an experimental DEsProTherm, developed at the I2M laboratory of ENSAMBordeaux and based on the method of the hot plan. The tests were carried out on different types of concrete samples incorporating different amounts of PCM

Thermal analysis by DSC of Phase Change Materials, study of the damage effect

This paper deals with an experimental study of Phase Change Materials (PCMs) by DSC and focuses particularly on the influence of PCMs damage on their thermodynamic properties. First, different series of tests were performed on non-damaged PCMs (reference) using different masses and heating rates in order to optimize the choice of the experimental parameters used in DSC test. Accordingly, the specific heats at solid, liquid phases and the latent heats of PCMs were obtained. In addition, a fast approximate approach was suggested for the determination of the heat capacity of PCMs from a direct exploitation of the heat flux curves obtained by scanning PCMs at different heating rates. Finally, damaged PCMs were investigated and their thermal properties (specific heat and phase change enthalpy) were compared to the reference PCMs. It was shown from the obtained results that low heating rates are more suitable for PCMs scanning during DSC measurements in order to ensure a thermodynamic equilibrium within the sample. Furthermore, the results highlighted that damage of PCMs can lead to the loss of their specific heat capacity of about 28% compared to the non-damaged PCMs

Effect of the processing conditions on the viscoelastic properties of a high-RAP recycled asphalt mixture: micromechanical and experimental approaches

With the depletion of the virgin aggregates, many efforts have been oriented towards the recycling of the reclaimed asphalt pavement (RAP). However, quality control of the recycled product is required during the manufacture process. This research deals with the use of high-content RAP recycled asphalt mixture composed of 70% RAP based on experimental and micromechanical approaches. For the experimental part, a "Good" and a "Bad" blended mixture were manufactured in laboratory. Then, rheological measurements of the complex modulus of the different binders and mixtures were carried out. The micromechanical work is based on the generalised self-consistent scheme (GSCS) which was used to predict the mechanical properties of the recycled mixture. This approach aims to homogenize the heterogeneous material by taking into account both the intergranular porosity and the possible interactions between phases. The confrontation of the micromechanical model with the experimental results showed good agreements between measured data and predicted values of the complex modulus of the recycled asphalt. Moreover, it was highlighted from the experimental results that the blending process of the recycled mixture has a great influence on the viscoelastic properties of the recycled mixture. This result was also validated by the GSCS-based approach

Evaluating the Impact of Drone Signaling in Crosswalk Scenario

International audienceThe characteristic pillars of a city are its economy, its mobility, its environment, its inhabitants, its way of life, and its organization. Since 1980, the concept of smart city generally consists of optimizing costs, organization, and the well-being of inhabitants. The idea is to develop means and solutions capable of meeting the needs of the population, while preserving resources and the environment. Owing to their little size, their flexibility, and their low cost, Unmanned Aerial Vehicles (UAV) are today used in a huge number of daily life applications. UAV use cases can be classified into three categories: data covering (like surveillance and event covering), data relaying (like delivery and emergency services), and data dissemination (like cartography and precise agriculture). In addition, the interest to Cooperative Intelligent Transportation Systems (C-ITS) has risen in these recent years, especially in the context of smart cities. In such systems, both drivers and traffic managers share the information and cooperate to coordinate their actions to ensure safety, traffic efficiency, and environment preservation. In this work, we aimed at introducing a UAV in a use case that is likely to happen in C-ITS. A conflict is considered involving a car and a pedestrian. A UAV observes from the top of the scene and will play the role of the situation controller, the information collector, and the assignment of the instructions to the car driver in case of a harmful situation to avoid car-pedestrian collision. To this end, we highlight interactions between the UAV and the car vehicle (U2V communication), as well as between the UAV and infrastructure (U2I communication). Hence, the benefit of using UAV is emphasized to reduce accident gravity rate, braking distance, energy consumption, and occasional visibility reduction

Experimental and numerical analysis of the energy efficiency of PCM concrete wallboards under different thermal scenarios

This paper aims to investigate the energy efficiency of PCM-concrete wallboards using experimental and numerical approaches. First, a laboratory experimental work was performed to manufacture PCM-concrete mixtures with different proportions of PCMs. Then, an innovative bench test based on the transient plane source theory was used for the thermal analysis of the mixtures. Besides, numerical simulation by finite element method was carried and the confrontation of the numerical results with the experience has showed an excellent agreement. Accordingly, the numerical approach was validated and generalized for the study of PCM-concrete at macro scale under different thermal scenarios and PCM distributions (homogeneous/Bilayer/Matrix-inclusions). The numerical simulations highlighted clearly the role of PCMs in decreasing the indoor temperature of the different PCM-wallboards as well as the thermal fluctuations. Moreover, the time delay in the temperature peaks emphasized the enhancement of the energy efficiency of PCM-wallboards in comparison with a traditional concrete, especially for the case of the bilayer wallboard

System of Unmanned Aerial Vehicles for road safety improvement

International audienceIn this paper we aim at introducing Unmanned Aerial Vehicles (UAVs) to prevent accidents, considering a use case that is likely to happen in cities where vehicles are circulating and when approaching an intersection like a pedestrian crossing, a railway crossing or a crossroad. A first UAV observes from the top of the scene and will, in certain cases, notify a second UAV which will exchange information either with the car driver if its behavior is far from a reference profile, or with the infrastructure in the ultimate case. We highlight interactions between the two UAVs (U2U communication) as well as between the UAV and the car vehicle (U2V communication) and between the UAV and infrastructure (U2I communication). Hence, we emphasize the benefit of using UAVs to enhance safety and reduce accident gravity rate

Nonlinear Analysis of Cable Structures with Geometric Constraints

International audienceThe purpose of this paper is the modelling in large displacement of systems composed of a rigid platform suspended by flexible cables, as can be observed in lifting systems of a construction crane or in cable-driven parallel robots (CDPRs). A recent approach has been proposed in the literature to model the nonlinear behavior of a cable element based on three dimensional catenary elastic modelling and the general displacement control method (GDCM) as solver. In this paper, two modifications of this method are proposed to take into account the geometric constraints coupling the large displacements of the cable extremities. The first approach is to consider these constraints using penalty functions thus modifying the tangent stiffness matrix and the second method by adding external explicit elastic forces. These two methods are tested and compared by using numerical examples. The first method is numerically safer because it is not dependent on the poor numerical conditioning of the cable’stiffness matrix encountered when internal cable’s tension cannot balance the external forces