Abstract
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.
Highlights
The building sector has a huge impact on the environment
The increase/decrease in temperature of microencapsulated PCM (mPCM) mix was at a much slower rate before stabilization (Fig. 10 (b)). This reflects that mPCM could effectively improve the apparent thermal inertia of mortar and concrete which is in line with the results reported by Hunger et al [69]
It was highlighted that in some situations in particular when related to the compressive strength mPCM is more appropriate to be used than the other Composite phase change materials (cPCM) and vice versa
Summary
The building sector has a huge impact on the environment. This is mainly due to buildings’ life cycle (design, construction, operation, demolition and waste treatment) which contributes to a large share of CO2 emission [1]. Despite the economic benefits of this method, the direct contact of paraffin wax with highly alkaline cementitious environment often results in the poor stability of PCM which can affect its thermal properties [23,24,25] To overcome this issue, researchers are focusing on developing shape stabilizing PCM by using encapsulation (micro and macro) techniques [26,27]. The previous reviews provide generally repeating information related to PCM itself, the encapsulation techniques and heat transfer, the different methods to evaluate its thermophysical properties, the PCM's thermal conductivity enhancement as well as its application in CBM. Understanding the difference between the effect of mPCM and cPCM on the fresh and hardened properties of CBM is crucial for real concrete building applications. The recent case studies across different countries and climate regions, as well as research gaps are provided to possibly establish future directions in basic research and real application of PCM in CBM
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