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

A review of microencapsulated and composite phase change materials: Alteration of strength and thermal properties of cement-based materials

Due to the population growth and the increased reliance on cooling and heating systems, buildings have become the largest energy consumer worldwide. The use of phase change material (PCM) has shown great potential to reduce the annual cooling and heating load by up to 50%. Nowadays, the direct incorporation of PCM in cement-based materials (CBM) is creating a considerable debate in the research community with regards to the proper selection and the beneficial utilization of PCM (microencapsulated or composite) in CBM. Therefore, this paper reviews the pros and cons of using microencapsulated and composite PCM in CBM by highlighting the mechanisms involved in the mechanical strength loss and thermal properties enhancement. Generally, a high thermal energy storage CBM was obtained. However, PCM exhibited a negative effect on the compressive strength of CBM. In view of the literature review, the compressive strength reduction varies considerably with no clear trend which is understandable in view of the differences in mix designs as well as the variety of materials used in each study. Finally, an up-to-date PCM case studies, gaps and future directions are also presented to provide a reliable basis and helpful reference for the future development of eco-friendly and energy-efficient building materials containing PCM

Mechanical and thermal properties of cement mortar composites incorporating micronized miscanthus fibers

This study examines the impact of incorporating micronized miscanthus fibers into a cement mortar, focusing on the mechanical and thermal effects. Initially, an experimental procedure was devised to create mortar mixtures with varying amounts of miscanthus fibers, with a maximum dosage of 7 wt%. This involved saturating the fibers with water beforehand to maintain the workability of the fresh mixes. The resulting hardened bio- based mortars were then evaluated after 28 days in terms of their microstructure, me- chanical strength (assessed through flexural and compression tests), and thermophysical properties (measured using the Hot-Disk technique to determine thermal conductivity/ diffusivity and volumetric heat capacity). The experimental findings revealed significant enhancements (up to 87%) in the thermal resistance of the mortars due to the addition of fibers. However, this improvement was accompanied by a considerable reduction in me- chanical strength. As a result, while these bio-based mortars are unsuitable for structural applications, they still possess adequate mechanical properties for handling and are appropriate for insulation purposes in constructionANR-11-LABX-022-0

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

Micromechanical contribution for the prediction of the viscoelastic properties of high rate recycled asphalt and influence of the level blending

This research deals with an experimental and micromechanical study of high rate recycled asphalt with 70% of RAP. Rheological measurements of shear complex modulus of virgin, RAP and blended binders were performed at different temperatures and frequencies. Then, a micromechanical model based on the generalized self-consistent scheme (GSCS) was suggested for the prediction of the effective mechanical properties of the recycled asphalt. The GSCS-based approach aims to homogenize the heterogeneous material taking into account the intergranular porosity, on the one hand, and the possible interactions between its phases on the other one. The suggested method was compared to a step-by-step (successive) homogenization approach and literature data in elastic case were used for this purpose. The results have shown that the GSCS-based approach presents a good agreement with the data especially for higher volume fractions of aggregates. Furthermore, the significant influence of the blend homogeneity level on the estimation of the effective mechanical properties of the recycled asphalt was highlighted

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

Prediction of the viscoelastic properties of an asphalt mixture: Micromechanical and experimental approaches(Article) [Prédiction des propriétés viscoélastiques des enrobés bitumineux Approches micromécaniques et expérimentales]

The asphalt mixtures are composed of aggregates and asphalt used in the construction of the majority of roads. In order to ensure the sustainability of the infrastructures, the evaluation of the quality and the performances of these materials are essential. In this context, several researches have been focused on the development of predictive models, often empirical ones, in order to deduce the viscoelastic properties of an asphalt mixture based on the properties of its constituents (binder and/or aggregate). In this context, we suggest a homogenization model based on the generalized self-consistent scheme (GSC) to predict the complex module of the asphalt concrete from the properties of its components. In the aim of the approach validation, different types of mixtures (hot and warm) made in the laboratory were tested. The results showed that one can predict the complex modulus of the different types of asphalt concretes for temperatures less than 20 °C. However, beyond this temperature, the precision of the model decreases. Besides, the comparison of the micromechanical model with the rheologic models in literature showed that the suggested model can be also relevant in terms of predictions as the considered models

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

Predictive coalescence modeling of particles from different polymers: application to PVDF and PMMA pair

This paper aims to study the coalescence phenomenon of two different polymers PVDF and PMMA. The paper is divided in two parts: the first part is devoted to the experimental work, and the second one focuses on the modeling of the coalescence phenomenon. The first step was a physicochemical and rheological characterization. Then, the coalescence tests have been performed on droplets derived from PVDF and PMMA polymers using a polarized light optical microscope combined with a hot stage. The effect of several significant parameters like temperature and particle size was investigated. The second part of this study is focused on the modeling of the coalescence phenomenon based on the well-known Bellehumeur model. The latter has been commonly used to describe the coalescence phenomenon between identical grains. The novelty of the present work consists in the extension of the coalescence model to wider describe the coalescence phenomenon between grains of different polymers. In addition, probabilistic analysis was performed in order to investigate the effect of the parameters governing the coalescence model, namely the viscosity, the surface tension and the relaxation time. The results have shown a good compromise between the experimental results and the predictive generalized Bellehumeur model