Effect of Paraffin and Silica Matrix Phase Change Materials on Properties of Portland Cement Mortars.

Vicente Zetola,Fco Javier Neila González,Luis J Claros-Marfil,Alfonso García Santos

doi:10.3390/ma14040921

Vicente Zetola, Fco Javier Neila González + Show 2 more

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https://doi.org/10.3390/ma14040921

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Abstract

In the search for methods to incorporate Phase Change Materials (PCM) into Portland cement mortar mixtures, PCM based on paraffins adhered to a silica-based matrix appear as a suitable option. However, paraffin particles have been observed to escape from the silica matrix when water is added. There are only limited data on how the use of such PCM affects the behaviour of mortars. To evaluate the effect of this PCM addition, Portland mortar mixtures were elaborated with 5%, 10% and 15% of PCM content, and using CEM 42.5 I R and CEM I 52.5 R cement types. Physical properties such as density, open porosity, air content and water absorption were analysed for fresh and dry samples. The results obtained show that the PCM-added mixtures require greater water and cement amounts than the standard mortar mixtures to achieve similar compressive strengths. Compared to non-PCM mixtures the PCM-added mortars present a density lowering of 37% for fresh mixtures and near 45% for dry state forms. A maximum compressive strength of 15.9 MPa was reached for 15% PCM mixtures, while values beyond 40 MPa were achieved for 5% PCM mixtures. Thus, the proposed study contributes to broad the available knowledge of PCM cement mortar mixtures behaviour and their mix design.

Highlights

The energy storage in walls, ceilings and floors can be improved by adding phase change materials (PCM) to construction materials
The results shown as the compressive strength of both Geopolymer concrete (GPC) and Portland cement concretes (PCC) decreased when the quantity of microencapsulated phase change materials (MPCM) increased
Based on the mixing process observations, three different states are possible from the workability point of view: (1) when the mixing process is done at temperatures below the Phase Change Materials (PCM) phase change temperature, no paraffin is observed on the mixture surface during the mixing process; (2) if this mixing process is done at temperatures near the PCM melting point, where a part of the paraffin is changing its state, no paraffin is observed on the mixing surface, but an improvement on the workability is noticed, which suggests that paraffin may act as a plasticiser; (3) at a temperature higher than the paraffin melting point, the mixing process is fully developed, and liquid paraffin appeared on the mixture surface (Figure 5)

Summary

Introduction

The energy storage in walls, ceilings and floors can be improved by adding phase change materials (PCM) to construction materials. There is a vast range of available PCM that are classified as organic, inorganic and eutectic materials, depending on its composition and characteristics [4,5,6]. They can be added to construction materials by different methods [7] as direct application, immersion, microcapsules [8,9]. PCM addition to mortar and concrete mixtures has been widely studied They can be applied through immersion, impregnation in porous aggregates and direct mixing [12]

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