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

Publicado en: (Cement and Concrete Research 132 (2020) 106039)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.We gratefully acknowledge funding from the Research Council of Norway, project number 238198. The authors gratefully acknowledge PhD. Luis Miguel Ordoñez at Kheme Chemical S.L. and Eng. Rino Nilsen at Østfold University College for technical assistance

Effect of Microencapsulated Phase Change Materials on the Flow Behavior of Cement Composites

Microencapsulated phase change materials (MPCMs) were incorporated into cement pastes of Portland cement (PC). Minislump tests and rheological properties of cement pastes containing three MPCMs with different surfaces (hydrophilic, amphiphilic and hydrophobic) were measured, and the water demand of MPCM in the cement matrix was evaluated. The hydrophilic MPCM was chosen for a more thorough rheological study, since it was found to be more compatible with the cement matrix. The dispersion of a high amounts (45 wt% with respect to the cement content, which corresponds to about 62 vol% of the total solids) of the hydrophilic MPCM in the cement pastes was achieved by optimization of the amount of superplasticizer through rheological measurements. For the viscometer tests, a Power Law model was found to give the best fit to the experimental data. While pastes (with 45 wt% of hydrophilic MPCM) prepared with low superplasticizer contents (<1.2 wt%) were found to be shear thinning, the paste exhibited a shear thickening behavior in the presence of higher amounts of superplasticizer. The shear thickening is probably caused by high water adsorption onto the microcapsules combined with deflocculation of the cement particles at high concentrations of superplasticizer. After the optimization of the superplasticizer content, homogeneous pastes were obtained, where the particles of the hydrophilic MPCM were well dispersed and unaltered after 28 days of hydration.MINECO -BIA2017-82391-R) y I3 (IEDI-2016-0079

Processing and characterisation of calcium sulphoaluminate ecocements containing Microencapsulated Phase Change Materials

Calcium SulphoAluminate (CSA) cements can be considered as ecocements, since their production releases up to 40% less CO2 than Ordinary Portland Cement (OPC) [1]. In addition, Microencapsulated Phase Change Materials (MPCM) are receiving a growing attention in the last years for their capability of storing and releasing high energy (latent heat storage) at a narrow temperature range. Thus, the use of CSA ecocements blended with MPCM would let control the inner temperature of buildings. This would allow a double reduction of CO2 emissions due to the use of CSA rather than OPC, and the better reconditioning of houses, with the consequent social, economic and environmental benefits. This work is focused on the dispersion of MPCM in a CSA ecocement matrix and the further characterisation of the corresponding materials. All the important parameters evolved in the preparation of homogeneous CSA pastes and CSA+MPCM pastes were optimised (e.g. percentage of superplasticiser) through rheological studies. MPCM particles were well dispersed in the paste and were kept unaltered in the matrix. The thermal analysis confirmed the phase change properties of the blended cement pastes. In addition, a CSA paste was successfully coated by CSA+MPCM paste, supporting the technical viability of this type of coatings in buildings. Finally, the optimal thickness of a coating of CSA+PCM mortar adhered in a typical building located in Malaga (south of Spain) was theoretically calculated to avoid/minimise the use of air conditioning/heating, resulting in an economically viable project with a considerable reduction of CO2 emissions. [1] M.A.G. Aranda, A.G. De la Torre, Sulfoaluminate cement, in: F. Pacheco-Torgal, S. Jalali, J. Labrincha, V.M. John (Eds.), Eco-efficient concrete. Woodhead Publishing Limited, Cambridge, 2013.Universidad de Málaga. Campus de Excelencia Internacional Angalucía Tech

Calcium sulfoaluminate composites incorporating microencapsulated phase change materials for thermal energy storage in buildings

This thesis focuses on investigating the development of new calcium sulfoaluminate cement composite incorporating microencapsulated phase change materials (MPCMs).Calcium sulfoaluminate cements are a type of more sustainable cements than traditional Portland cement. In addition to using a material that presents fewer emissions during its production, it has also been intended to obtain a final product that reduces energy consumption in buildings and homes, thus reducing CO2 emissions due to the consumption generated in buildings. In this sense, phase change materials (PCMs) can reduce the temperature peaks that occur in a building in a passive way if they are embedded in the materials used for the building construction. The first part of the thesis focus on investigating the interaction of cement with MPCMs. Especially in terms of properties in the fresh state in pastes. Once the dosage of the pastes had been decided by incorporating MPCM (45 wt.% referred to cement content), the study of the hydration reaction of the pastes was studied. The objective of this part has been to establish the influence of the addition of MPCM on the hydration mechanisms of cements. Once it was verified that the introduction of MPCM in cement pastes does not compromise the normal development of cement hydration, and that the mechanical resistance is good enough for a non-structural coating, the second part of the thesis studied the thermal properties of both paste and mortar composites in order to evaluate the main effect of MPCMs, which aims to improve thermal comfort within a living or building. The final part of this thesis has focused on the application of mortars in the intended use with MPCM. This is the reduction of energy consumption in buildings, as well as improving the thermal comfort of the occupants and of course, with lower CO2 emissions both due to the materials used to manufacture the product and during its useful life

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

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

Multiscale understanding of tricalcium silicate hydration reactions

<p>The understanding of microstructure and atomic arrangement in nanocrystalline phases with small particle sizes, below »50 Å, is intrinsically complicated. This challenge is exacerbated in samples with additional crystalline phase(s), like cement pastes. Here, we use synchrotron X-ray powder diffraction to quantitatively follow the tricalcium silicate hydration reactions. The dissolution of alite, an impure form of tricalcium silicate, as well portlandite crystallization and the calcium silicate hydrate (C-S-H) gel precipitation have been accurately measured by Rietveld methodology using an internal standard approach in unaltered pastes. Furthermore, synchrotron total scattering powder diffraction coupled to pair distribution function (PDF) methodology has been used to characterize the alite hydration products. We have used a multi r-range analysis approach, where the 40–70 Å r-interval allows determining the crystalline phase contents; the 10–25 Å r-range is used to get information about the atomic ordering in the nanocrystalline component; and the 2–10 Å region gives insights about the amorphous component. Specifically, a defective clinotobermorite, Ca₁₁Si₉O₂₈(OH)₂^.8.5H₂O with density »2.5 gcm^-3, gave the best PDF fit for a carefully-prepared hydrated alite sample. Furthermore, the PDF analysis also indicates that C-S-H gel is mainly composed of this defective tobermorite and monolayer calcium hydroxide which is stretched as recently predicted by first principles calculations. Chiefly, these outcomes together with nuclear magnetic resonance data, electron microscopy results and previous reports yielded a multiscale picture for C-S-H gel nanocomposite which help to explain the observed densities and Ca/Si atomic ratios at the nano- and meso- scales.</p