Hydration development and thermal performance of calcium sulphoaluminate cements containing microencapsulated phase change materials

Susana G Sanfelix,Jesus D Zea-García,Diana Londono-Zuluaga,Isabel Santacruz,Angeles G De La Torre,Anna-Lena Kjøniksen

doi:10.1016/j.cemconres.2020.106039

Susana G Sanfelix, Jesus D Zea-García + Show 4 more

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https://doi.org/10.1016/j.cemconres.2020.106039

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Abstract

Microencapsulated phase change materials (MPCM) incorporated in buildings walls can reduce indoor temperature fluctuations, conserving energy and enhancing thermal comfort. MPCM were incorporated in calcium sulphoaluminate cement (CSA) at high concentrations to achieve a significant effect on the thermal properties. The cement hydration development was studied by isothermal calorimetry and laboratory X-ray powder diffraction (LXRPD). The hydration mechanism was not affected by the addition of MPCM. In order to obtain homogeneous mortars in the presence of MPCM, a superplasticizer (SP) was used. However, the SP causes a significant delay of the hydration. Although the mineralogical composition of the hydrated pastes did not change with the addition of MPCM, the mechanical strengths decrease dramatically. This decrease is well described by the Bolomey equation, assuming MPCMs act as air voids. This is a physical effect due to the high volume of MPCM, and not due to a change in the hydration chemistry.

Highlights

Calcium sulphoaluminate cements (CSA) are considered low CO2 emission materials [1]
This study has been focused in the development of CSA cement mixed with Microencapsulated phase change materials (MPCM) incorporating superplasticizer in the composites in order to improve workability
The mechanism of hydration of CSA is not affected by the addition of MPCM, since the phase assemblage is the same at all studied hydration ages

Summary

Introduction

Calcium sulphoaluminate cements (CSA) are considered low CO2 emission materials [1]. The main constituent of the clinker is ye'elimite (C4A3S ) in combination with other phases such as belite, gehlenite and calcium aluminates. In order to obtain an optimum setting time, strength development, and volume stability, the clinker is ground with 10–25 wt% calcium sulphate (usually anhydrite). CSA cements have been evaluated as seasonal thermal storage materials, since their main hydrated compound is ettringite, a mineralogical phase with a high number of water molecules in its structure [8,9,10]. Some of the drawbacks of using ettringite for thermal energy storage is a lack of stability, and crack formation. It is difficult to achieve an optimal charging and discharging of the reversible energy storage

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