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

Mechanical and hygrothermal properties of cement mortars including miscanthus fibers

International audienceThis study investigates the improvement of thermal and hygric performances of cement mortars through the introduction of micronized miscanthus fibers. Micronized fibers were chosen because they are expected to promote fine and homogeneous fiber distribution within the cementitious matrix, hence opening possibilities for the design of 3D printable mortar mixes including vegetal fibers. An experimental protocol was first developed for preparing five mortar mixes with miscanthus fiber contents up to 7 wt.%. These bio-based mortars were then characterized at the age of 28 days, in terms of mechanical strength (under flexural and compression tests), thermophysical properties (determination of the thermal conductivity/diffusivity and the volumetric Heat Capacity by the Hot-Disk method), and in terms of hygric properties as well (evaluation of the Moisture Buffer Value MBV according to the Nordtest method). The results of this experimental campaign showed that increasing the miscanthus fiber content leads to large improvements in both thermal resistance (up to 87%) and moisture buffer capacity of mortars (with MBV values up to 2.05), suggesting that such bio-based mortar is a good insulating material and has an excellent ability to mitigate external moisture variations. On the other hand, the introduction of vegetal fibers was also found to decrease very significantly the mechanical strength of the modified mortars, making these latter incompatibles with structural applications. Nevertheless, the developed bio-based mortars retain sufficient mechanical properties for handling and are suitable for building insulation

Effect of Phase Change Materials (PCMs) on the hydration reaction and kinetic of PCM-mortars

International audienceThe Phase Change Materials (PCMs) are considered as an attractive way to reduce energy consumption thanks to their heat storage capacity. Their incorporation in the construction materials (gypsum, concrete) contribute to the reduction of the energy consumption of the building structures.Even though PCMs have shown their reliability from a thermal point of view, some drawbacks linked to their use were emphasized such as the loss of the compressive strength of the cementitious material with the addition of PCMs.This paper attempts to provide a possible explanation by the investigation of the hydration kinetic of PCM-mortars. The conventional semi-adiabatic Langavant test was adapted for this purpose. The results showed a lower heat released by the PCM-mortars compared to a control mortar as well as a delay in the hydration process with the addition of PCMs which may contribute to the loss of the compressive strength

Effect of Phase Change Materials on the hydration reaction and kinetic of PCM-mortars

International audienceThe Phase Change Materials are considered an attractive way to reduce energy consumption thanks to their heat storage capacity. Their incorporation in the construction materials allows the energy to be an integral part of the building structure. Even though PCMs have shown their reliability from a thermal point of view, some drawbacks linked to their use were emphasized such as the loss of the compressive strength of the PCM-material. This paper attempts to provide an explanation by the investigation of the hydration kinetic of PCM-mortars. The semi-adiabatic Langavant test was adapted to this case. The numerical Diffuse Element Method was used for the computation of the heat flux which is a compulsory step for the determination of the hydration degree. The results showed a lower heat released by the PCM mortars compared to a control mortar as well as a delay in the hydration progress with the addition of PCMs

Investigation expérimentale et modélisation multi-échelle des propriétés thermiques des bétons incorporant des Matériaux à Changement de Phase (MCPs)

National audienceRÉSUMÉ. L'utilisation des matériaux à changement de phase (MCP) dans le domaine des bâtiments est une solution attractive contribuant à la réduction de la consommation d'énergie ainsi qu'à l'amélioration du confort thermique. Ce travail est consacré à l'étude des propriétés thermiques des MCP et des bétons modifiés (chaleur spécifique, conductivité thermique). Des techniques expérimentales ont été mises en jeu telles que la calorimétrie différentielle à balayage (DSC), le Hot Disk et le laser flash. Une modélisation micro-macro est aussi présentée afin de prédire la conductivité thermique des bétons-MCP en se basant sur quelques schémas d'homogénéisation classiques. ABSTRACT. The use of Phase Change Materials (PCMs) in the building sector is an attractive solution contributing to the reduction of energy consumption as well as the improvement of the thermal comfort. This research is devoted to the study of thermal properties of PCMs and modified concrete (specific heat, thermal conductivity). Experimental techniques were used such as the Differential Scanning Calorimetry (DSC), the Hot Dish and the Laser Flash. Also, a micro-macro modelling is presented in order to predict the thermal conductivity of PCM-concrete using some classic homogenization schemes

Experimental and multi-scale analysis of the thermal properties of Portland cement concretes embedded vith microencapsulated Phase Change Materials (PCMs)

International audienceThe present research deals with the investigation of a Portland cement concrete modified with organic microencapsulated Phase Change Materials (PCMs) named Micronal DS 5001 X, using experimental and homogenization approaches. First, a laboratory characterization of the PCM smart materials was performed using different experimental techniques. Second, different PCM-concrete mixtures were manufactured with different amounts of PCM. The specific heat capacity of PCM-concrete was analyzed by differential scanning calorimetry technique whereas the thermal conductivity was measured by hot disk. In addition, PCM-concrete mixes were subjected to artificial ageing then their thermal properties were analyzed. Besides, a homogenization approach was carried in order to predict the thermal conductivity of the PCM-concrete mixes. The results highlighted an improvement of the heat storage capacity of the PCM-concrete with the addition of PCMs. Moreover, a good correlation was noticed between the experience and the homogenization method for the thermal conductivity prediction