Presently, the concerns related to the buildings energy consumption are greater, emerging in this way the need to incorporate materials in the construction products which aim the improvement of the energetic efficiency of buildings. Therefore, the application of phase change materials appears as a possible solution in an attempt to solve, or at least minimize, the massive energetic consumption related with buildings. This analysis aims the understanding of the influence of microcapsules of phase change materials (PCM) on lime and gypsum mortars, which should present a compromise between workability, mechanical resistance and aesthetical appearance.Fundação para a Ciência e a Tecnologia (FCT

Aguiar, J. L. Barroso de

Alves, Vítor H.

Cunha, Sandra Raquel Leite

Ferreira, Victor S.

Universidade do Minho: RepositoriUM

1  Sandra Cunha1, Vítor Alves1,José B. Aguiar1, Victor M. Ferreira2  1) University of Minho, Guimarães, Portugal 2) University of Aveiro, Aveiro, Portugal   Use of phase change materials microcapsules in aerial lime and gypsum mortars    1. Introduction   Nowadays, the largest part of the energy consumption in residential sector is associated with heating and cooling. The incorporation of Phase Change Materials (PCM) in mortars for the internal coating, have the objective of keep temperatures constant. Contributing in that way, for a bigger level of comfort in internal buildings and for a biggest energetic efficiency. The benefits to the comfort inside buildings appear during the phase change of the PCM. There are transferences of energy that occur during the transitions solid-liquid through the heat storage and liquid-solid with the release of energy previously absorbed. In order that PCM will not disperse in material matrix should be microencapsulated. The exterior of the microcapsules is made with a polymer (1, 2).  Latent heat thermal energy storage, through the incorporation of PCM, presents the following advantages: narrow the gap between the peak and off-peak loads, levelling the electricity demand, decreasing the load on the network and eventual supply failure; reduce operation costs by shifting the electrical consumption from peak periods to off-peak periods; contribute to the interior thermal comfort in buildings, by using and storing solar energy (for space heating in winter) and storing natural cooling by ventilation at night during the summer, thus reducing electricity use for heating and cooling (1, 2).  Between all phase change materials possible applications in buildings, the most interesting is its incorporation in construction materials with the aim of altering these materials thermal properties. There are a series of possibilities: the PCM may be used as a mean for thermal storage for passive solar heating, by being integrated on the floor, walls or ceilings, as 2  well as being an integrating part of the most complex energetic system, such as heat pumps and solar panels (3).  The main objective of this work was the production of a lime and gypsum mortar with incorporation of polymeric microcapsules, which must have a compromise between workability, mechanical strength and shrinkage. The quantification of shrinkage was made since the fresh state until to the hardness state. These mortars can be applied not only in the construction of new buildings, but also in rehabilitation operations.  2. Phase change material  Phase change materials (PCM) possesses the capability to alter its own state as function of the environmental temperature (3). In other words, when the surrounding environmental temperature of PCM increases until the materials fusion point, the material suffers a change from a solid state to a liquid state, absorbing and storing the heat energy from the environment. While, when the temperature decreases until the PCM solidification point, the material alters its state from the liquid state to solid state, releasing the previously storage energy to the environment (Fig. 1). This application could be made in coating mortars of buildings, with advantage in the passive regulation of internal temperature with increase of thermal inertia (4).  3   Fig. 1. Encapsulated phase change material (5)  Passing the melting point, phase change material, alter its state from solid to liquid, and if the material is free to move in the matrix material that surrounds it, this disperses changing its shape and original position. For maintain the PCM without significant changes in time, this can be wrapped in other material with capacity to resist to physic and volumetric changes. The microencapsulation of phase change material consists in engage the material particles in solid or liquid state, that will be core of material, by a material in solid state, usually a polymer, commonly known capsule, with dimensions between 0.020 µm a 2000 µm (6). The polymer used could be polymethylmethacrylate, polyurea, polyurethane, polymethylmethacrylate or polivinilacetano and should respond at some demands of operation as high heat transfer.   In 1983 emerged the first classification of substances used for thermal storage. These are classified as organic, inorganic and eutectic mixtures. The eutectic mixtures result from the combination of two or more compounds of organic and/or inorganic nature. By this way it is possible better correspond to the need of more suitable transition temperatures for the demands (4).  Not all the existing PCM can be used for thermal storage. An ideal PCM must present certain thermophysics, kinetic, chemical and economic 4  properties. Relatively to thermophysical properties it is necessary that the selected PCM has a transition temperature in the operational temperature range desired with the intention of reassuring the storage and release of heat. Also, an elevated transition heat by volume unit, in order to storage the maximum energy possible, incorporating a minimal quantity of PCM; high sensitive heat, translated by its calorific capability in order to increase its energy storing capability; high thermal conductivity both in the solid and liquid state, so that it becomes easier to promote heat transfer with a reduced volume variation during the phase transition allowing the contention issues reduction (5).  From the kinetically point of view, the chosen PCM must have a high velocity for crystal growing, with the main purpose of avoiding the sub cooling of the liquid phase and respond to the surroundings demands (5). Concerning its chemical properties it should not present degradation after a high number of cycles; it must be non-corrosive to construction materials; non-flammable; non-toxic and non-explosive, for environmental and security concerns (5). Finally, from the economic point of view, it must be abundant, available and with a low acquisition cost, in order to become a competitive solution compared to other traditional constructive systems and thermal storing (5).  3. Materials, compositions and fabrication  3.1. Materials  This research used PCM microcapsules synthesized by polymerization process through emulsion and composed by a polymethylmethacrylate and a paraffin nucleus. The product is commercialized in powder (dry) or in emulsion, being that for this study it was decided to use a dry PCM in order to facilitate its incorporation into already prepared mortars. This PCM has a fusion temperature of about 23ºC and an enthalpy of 110kJ/kg. The superplasticizer used was a polyacrylate, with a density of 1.05g/cm3. The sand used has an average particle size of 439.9 µm. The lime used in the compositions was a hydrated lime, with a purity of 90% and density of 1100 kg/m3. The gypsum plaster used is a traditional, with high fineness and the fibres used are synthetic fibres of nylon.  3.2. Compositions and fabrication  5  We studied five compositions of aerial lime and gypsum mortars from the fresh state up to 28 days (Table 1). The L100G0 is the reference mortar without any addition. From L100G0 to L100G0PCM is added 20% of PCM microcapsules incorporated in polymer. In composition L100G0PCMF are added nylon fibres, and in the compositions L100G20PCMF and L100G40PCMF is added a gypsum content of 20% and 40%, respectively.  Table 1. Composition of mortars (PCM, superplasticizer, water and fibres as % of total mass of solid particles; gypsum and sand as % of binders mass) Compositions PCM Superplasticizer Fibers Gypsum Sand L100G0 0.0 0.0 0.0 0.0 561.4 L100G0PCM 20.0 1.0 0.0 0.0 561.4 L100G0PCMF 20.0 1.0 0.1 0.0 561.4 L80G20PCMF 20.0 1.0 0.1 20.0 561.4 L60G40PCMF 20.0 1.0 0.1 40.0 561.4  The mixture process and specimens manufacturing was performed in accordance with the standard EN 1015-11, with slight adaptations due to the PCM incorporation (6). To evaluate the behaviour and the mechanical properties (compression and flexural strength) of all the different compositions, it was moulded 3 prismatic specimens with 40x40x160 mm3. After its manufacturing, all the specimens were preserved during 7 days in polyethylene bags and subsequently placed into the laboratory at room temperature (about 22ºC) during 21 days.    4. Test procedures   The workability tests were performed with the main goal of verifying an adequate workability for handling the developed mortars.  The tests were performed based on the flow table method stated by the European standard EN 1015-3 (7). The resulting value within the test was only considered when between 160-180 mm. For evaluate the shrinkage, was developed a device capable of performing the measurement of shrinkage from the time of placing the mortar in the mould until the demoulding (Figure 2), with the possibility of continuing to monitoring the evolution of the shrinkage in time with another device after demoulding. The device consists of a base for placing the triple mould with dimensions of 25x25x250 mm³ and six displacement transducers. Two displacement transducers were used for 6  each specimen in order to enable the measurement of shrinkage on both sides further away from the specimen. The transducers are connected to a data acquisition system, where point values are removed from the shrinkage of mortars in time. The amount of shrinkage is given by the following equation:   Where: ε – Shrinkage value; Li – First measurement value; Lt – Value of measurements made at time t.   Fig. 2. Measuring device for evaluation of shrinkage since the fresh state  The flexural and compressive behaviour was evaluated based in EN 1015-11. The specimens used for the flexural test were prismatic. The flexural tests were performed with force control at a speed of 10N/s. Compression tests was realized through the application of a load on the specimen with resource to a metallic piece, rigid enough to make the vertical charge uniform. The specimens used for the test were the flexural test resulting half parts. The tests were performed with a force control at a speed of 50N/s.  5. Results and discussion   5.1. Workability  Table 2 shows the obtained results for the workability tests from the experimental results. It is possible to verify a rise in the amount of water added to the mixture, with the incorporation of microcapsules PCM. To an ε = − 250 7  increase of 20% of PCM corresponds a rise in the amount of water of about 26%. This situation can be explained by the thinness of the used PCM and by the absorption of the polymeric wall of the microcapsule. The incorporation of fibers and gypsum causes a light increase in quantity of water. An increase of 20% of gypsum, resulted in a rise of about 3% of the water amount added to the mortar.  Table 2. Workability results  Compositions Water L100G0 23.0 L100G0PCM 29.0 L100G0PCMF 30.0 L80G20PCMF 31.0 L60G40PCMF 32.0     5.2. Shrinkage   With the device described above, it was possible to make an evaluation of shrinkage since the fresh state, due to changes caused by the introduction of polymer capsules. It was monitored the behaviour of different areal mortars from time zero to seven days. The results allowed us to verify that there is an increase in the measured value of the shrinkage with the incorporation of microcapsules. However, the addition of gypsum and nylon fibers, results in a decrease in shrinkage in the first 24 hours of monitoring (Figure 3).  8   Fig. 2. Shrinkage test since moulding until 24 hours   Fig. 3. Shrinkage test since moulding until 7 days  The analysis of the results up to 7 days of age (Figure 4) allows the identification of different behaviors in different aereal mortars. The introduction of 20% of microcapsules (L100G0PCM), causes an increase in shrinkage of about 4 times compared to the reference mortar (L100G0). The addition of nylon fibers (L100G0PCMF), causes a decrease in shrinkage to about half compared with the mortar L100G0PCM. With the addition of gypsum (L80G20PCMF and L60G40PCMF) is possible to observe a decrease in shrinkage. It was performed a practical application of mortar developed and subsequently made a comparison with the results obtained (Figure 5). For mortar L100G0 was obtained a value of 0.415 µm/m, showing no cracks in support. The introduction of 20% of microcapsules (L100G0PCM) the shrinkage value obtained was increased about 5 times, showing cracking in support. With the addition of nylon fibers (L100G0PCMF) the value obtained is about half comparatively to -0,50,00,51,01,52,02,53,00 2 4 6 8 10 12 14 16 18 20 22 24Retracção x10^3 (mm/m)Idade (horas)L100G0 (2,633µm/m)L100G0PCM (2,422µm/m)L100G0PCMF (2,451µm/m)L80G20PCMF (1,771µm/m)L60G20PCMF (1,547µm/m)-2,03,08,013,018,023,028,00 1 2 3 4 5 6 7Retracção x10^-3 (mm/m)Idade (dias)L100G0 (6,020µm/m)L100G0PCM (24,908µm/m)L100G0PCMF (12,580µm/m)L80G20PCMF (5,628µm/m)L60G20PCMF (10,237µm/m)9  the mortar L100G0PCM, with consequently lower cracking the mortar before. The subsequent incorporation of 20% gypsum results in a decrease in cracking presented in support. With the increase of gypsum content of 40%, the amount of shrinkage obtained is 0.304µm/m, which is lower than the value obtained for the shrinkage of mortar L80G20PCMF (0.475 µm/m) and also lower than the reference mortar (0.415 µm/m) with no cracking in the support.   5.3. Flexural and compressive behaviour  Concerning the mechanical strengths, in general terms and based in the obtained results, presented in Table 3, it is possible to find that the mechanical properties show an improvement with the addition of PCM microcapsules. The addition of 20% of PCM leads to an increase of the flexural strength about 450%. For the compression strength, the increase observed is about 788%. These values were obtained comparing to the composition without the incorporation of phase change materials.     Fig. 4. Comparison between the values of shrinkage and cracking  Table 3. Flexural and compressive results  Compositions Flexural strength, MPa Compression strength, MPa L100G0 0.17 [10.98] 0.25 [8.09] L100G0PCM 0.93 [11.22] 2.22 [6.09] L100G0PCMF 0.72 [10.57] 1.79 [5.99] L80G20PCMF 1.36 [4.52] 2.27 [10.6] L60G40PCM 1.01 [12.72] 2.00 [11.7] 0,4151,1900,569 0,4750,3040,00,40,81,21,6Shrinkage at 8 Hours (µm/m)10  F Note: In parentheses we present the coefficient of variation in percentage.   6. Conclusion  The experimental work led to the conclusion that it is possible use polymeric microcapsules in mortar, obtaining a balance between the aesthetic and functional performance. The results obtained from tests for shrinkage concluded that the combined use of fibre and gypsum is a good solution for solving problems related to cracking caused by the incorporation of polymeric microcapsules. The specific devices developed at the University of Minho, has proved effective in quantitative evaluation of the shrinkage. It was also possible to make a practical application and verification of the values obtained in the laboratory.  It was even possible to verify the existence of a clear rise of the water necessary to incorporate into the mortar within the increasing of PCM percentage, this with the aim of obtaining a suitable workability. The compression and flexural resistance measured in each performed test allows observing a tendency to its increase, with a greater incorporation of PCM microcapsules. The mortar with 60% of aerial lime and 40% of gypsum with incorporation of PCM microcapsules, is more interesting because it showed an excellent compromise between high mechanical strengths and low shrinkage.   ACKNOWLEDGEMENTS  The authors wish to express their thanks to the Portuguese Foundation for Science and Technology, for funding the project PTDC/ECM/102154/2008, Contribution of Thermal Active Mortars for Building Energy Efficiency.   References  11  1. M. Félix, J. Aguiar, Study of a Cement Mortar with Incorporation of PCM Microcapsules, 6th Asian Symposium on Polymers in Concrete, Shanghai, 2009. 2. N. Silva et al., Properties of Gypsum-PCM Based Mortars for Interior Plastering of Construction Systems, Materials Science Forum, Vol. 587-588, pp. 913-917 (2008). 3. Y. Zhang et al., Application of latent heat thermal energy storage in buildings: State-of-the-art and outlook, Building and Environment, 42, 2209 (2007).  4. B. Zalba et al., Review on thermal energy storage with phase change: materials, heat transfer analysis and applications, Applied Thermal Engineering, 23, 251 (2003). 5. L. Cabeza et al., Materials used as PCM in thermal energy storage in buildings: A review, Renewable and Sustainable Energy Reviews, 15, 1675 (2011). 6. European Committee for Standardization (CEN), EN 1015-11 (1999), Methods of test for mortar for masonry - Part 11: Determination of flexural and compressive strength of hardened mortar. 7. European Committee for Standardization (CEN), EN 1015-3(2004), Methods of test for mortar for masonry - Part 3: Determination of consistence of fresh mortar (by flow table). 

Use of phase change materials microcapsules in aerial lime and gypsum mortars

1 
 
Sandra Cunha
1
, Vítor Alves
1
,José B. Aguiar
1
, Victor M. Ferreira
2 
 
1)
 University of Minho, Guimarães, Portugal 
2)
 University of Aveiro, Aveiro, Portugal 
 
 
Use of phase change materials microcapsules in aerial lime 
and gypsum mortars  
 
 
1. Introduction  
 
Nowadays, the largest part of the energy consumption in residential sector 
is associated with heating and cooling. The incorporation of Phase Change 
Materials (PCM) in mortars for the internal coating, have the objective of 
keep temperatures constant. Contributing in that way, for a bigger level of 
comfort in internal buildings and for a biggest energetic efficiency. The 
benefits to the comfort inside buildings appear during the phase change of 
the PCM. There are transferences of energy that occur during the 
transitions solid-liquid through the heat storage and liquid-solid with the 
release of energy previously absorbed. In order that PCM will not disperse 
in material matrix should be microencapsulated. The exterior of the 
microcapsules is made with a polymer (1, 2). 
 
Latent heat thermal energy storage, through the incorporation of PCM, 
presents the following advantages: narrow the gap between the peak and 
off-peak loads, levelling the electricity demand, decreasing the load on the 
network and eventual supply failure; reduce operation costs by shifting the 
electrical consumption from peak periods to off-peak periods; contribute to 
the interior thermal comfort in buildings, by using and storing solar energy 
(for space heating in winter) and storing natural cooling by ventilation at 
night during the summer, thus reducing electricity use for heating and 
cooling (1, 2). 
 
Between all phase change materials possible applications in buildings, the 
most interesting is its incorporation in construction materials with the aim 
of altering these materials thermal properties. There are a series of 
possibilities: the PCM may be used as a mean for thermal storage for 
passive solar heating, by being integrated on the floor, walls or ceilings, as 
2 
 
well as being an integrating part of the most complex energetic system, 
such as heat pumps and solar panels (3). 
 
The main objective of this work was the production of a lime and gypsum 
mortar with incorporation of polymeric microcapsules, which must have a 
compromise between workability, mechanical strength and shrinkage. The 
quantification of shrinkage was made since the fresh state until to the 
hardness state. These mortars can be applied not only in the construction of 
new buildings, but also in rehabilitation operations. 
 
2. Phase change material 
 
Phase change materials (PCM) possesses the capability to alter its own 
state as function of the environmental temperature (3). In other words, 
when the surrounding environmental temperature of PCM increases until 
the materials fusion point, the material suffers a change from a solid state 
to a liquid state, absorbing and storing the heat energy from the 
environment. While, when the temperature decreases until the PCM 
solidification point, the material alters its state from the liquid state to solid 
state, releasing the previously storage energy to the environment (Fig. 1). 
This application could be made in coating mortars of buildings, with 
advantage in the passive regulation of internal temperature with increase of 
thermal inertia (4). 
 
3 
 
 
Fig. 1. Encapsulated phase change material (5) 
 
Passing the melting point, phase change material, alter its state from solid 
to liquid, and if the material is free to move in the matrix material that 
surrounds it, this disperses changing its shape and original position. For 
maintain the PCM without significant changes in time, this can be wrapped 
in other material with capacity to resist to physic and volumetric changes. 
The microencapsulation of phase change material consists in engage the 
material particles in solid or liquid state, that will be core of material, by a 
material in solid state, usually a polymer, commonly known capsule, with 
dimensions between 0.020 µm a 2000 µm (6). The polymer used could be 
polymethylmethacrylate, polyurea, polyurethane, polymethylmethacrylate 
or polivinilacetano and should respond at some demands of operation as 
high heat transfer.  
 
In 1983 emerged the first classification of substances used for thermal 
storage. These are classified as organic, inorganic and eutectic mixtures. 
The eutectic mixtures result from the combination of two or more 
compounds of organic and/or inorganic nature. By this way it is possible 
better correspond to the need of more suitable transition temperatures for 
the demands (4). 
 
Not all the existing PCM can be used for thermal storage. An ideal PCM 
must present certain thermophysics, kinetic, chemical and economic 
4 
 
properties. Relatively to thermophysical properties it is necessary that the 
selected PCM has a transition temperature in the operational temperature 
range desired with the intention of reassuring the storage and release of 
heat. Also, an elevated transition heat by volume unit, in order to storage 
the maximum energy possible, incorporating a minimal quantity of PCM; 
high sensitive heat, translated by its calorific capability in order to increase 
its energy storing capability; high thermal conductivity both in the solid 
and liquid state, so that it becomes easier to promote heat transfer with a 
reduced volume variation during the phase transition allowing the 
contention issues reduction (5). 
 
From the kinetically point of view, the chosen PCM must have a high 
velocity for crystal growing, with the main purpose of avoiding the sub 
cooling of the liquid phase and respond to the surroundings demands (5). 
Concerning its chemical properties it should not present degradation after a 
high number of cycles; it must be non-corrosive to construction materials; 
non-flammable; non-toxic and non-explosive, for environmental and 
security concerns (5). Finally, from the economic point of view, it must be 
abundant, available and with a low acquisition cost, in order to become a 
competitive solution compared to other traditional constructive systems 
and thermal storing (5). 
 
3. Materials, compositions and fabrication 
 
3.1. Materials 
 
This research used PCM microcapsules synthesized by polymerization 
process through emulsion and composed by a polymethylmethacrylate and 
a paraffin nucleus. The product is commercialized in powder (dry) or in 
emulsion, being that for this study it was decided to use a dry PCM in 
order to facilitate its incorporation into already prepared mortars. This 
PCM has a fusion temperature of about 23ºC and an enthalpy of 110kJ/kg. 
The superplasticizer used was a polyacrylate, with a density of 1.05g/cm
3
. 
The sand used has an average particle size of 439.9 µm. The lime used in 
the compositions was a hydrated lime, with a purity of 90% and density of 
1100 kg/m3. The gypsum plaster used is a traditional, with high fineness 
and the fibres used are synthetic fibres of nylon. 
 
3.2. Compositions and fabrication 
 
5 
 
We studied five compositions of aerial lime and gypsum mortars from the 
fresh state up to 28 days (Table 1). The L100G0 is the reference mortar 
without any addition. From L100G0 to L100G0PCM is added 20% of 
PCM microcapsules incorporated in polymer. In composition 
L100G0PCMF are added nylon fibres, and in the compositions 
L100G20PCMF and L100G40PCMF is added a gypsum content of 20% 
and 40%, respectively. 
 
Table 1. Composition of mortars (PCM, superplasticizer, water and fibres 
as % of total mass of solid particles; gypsum and sand as % of binders 
mass) 
Compositions PCM Superplasticizer Fibers Gypsum Sand 
L100G0 0.0 0.0 0.0 0.0 561.4 
L100G0PCM 20.0 1.0 0.0 0.0 561.4 
L100G0PCMF 20.0 1.0 0.1 0.0 561.4 
L80G20PCMF 20.0 1.0 0.1 20.0 561.4 
L60G40PCMF 20.0 1.0 0.1 40.0 561.4 
 
The mixture process and specimens manufacturing was performed in 
accordance with the standard EN 1015-11, with slight adaptations due to 
the PCM incorporation (6). To evaluate the behaviour and the mechanical 
properties (compression and flexural strength) of all the different 
compositions, it was moulded 3 prismatic specimens with 40x40x160 
mm
3
. After its manufacturing, all the specimens were preserved during 7 
days in polyethylene bags and subsequently placed into the laboratory at 
room temperature (about 22ºC) during 21 days.   
 
4. Test procedures  
 
The workability tests were performed with the main goal of verifying an 
adequate workability for handling the developed mortars.  The tests were 
performed based on the flow table method stated by the European standard 
EN 1015-3 (7). The resulting value within the test was only considered 
when between 160-180 mm. For evaluate the shrinkage, was developed a 
device capable of performing the measurement of shrinkage from the time 
of placing the mortar in the mould until the demoulding (Figure 2), with 
the possibility of continuing to monitoring the evolution of the shrinkage in 
time with another device after demoulding. The device consists of a base 
for placing the triple mould with dimensions of 25x25x250 mm³ and six 
displacement transducers. Two displacement transducers were used for 
6 
 
each specimen in order to enable the measurement of shrinkage on both 
sides further away from the specimen. The transducers are connected to a 
data acquisition system, where point values are removed from the 
shrinkage of mortars in time. The amount of shrinkage is given by the 
following equation: 
 
 
Where: 
ε – Shrinkage value; 
Li – First measurement value; 
Lt – Value of measurements made at time t. 
 
 
Fig. 2. Measuring device for evaluation of shrinkage since the fresh 
state 
 
The flexural and compressive behaviour was evaluated based in EN 1015-
11. The specimens used for the flexural test were prismatic. The flexural 
tests were performed with force control at a speed of 10N/s. Compression 
tests was realized through the application of a load on the specimen with 
resource to a metallic piece, rigid enough to make the vertical charge 
uniform. The specimens used for the test were the flexural test resulting 
half parts. The tests were performed with a force control at a speed of 
50N/s. 
 
5. Results and discussion  
 
5.1. Workability 
 
Table 2 shows the obtained results for the workability tests from the 
experimental results. It is possible to verify a rise in the amount of water 
added to the mixture, with the incorporation of microcapsules PCM. To an 
ε =
 − 
250
 
7 
 
increase of 20% of PCM corresponds a rise in the amount of water of about 
26%. This situation can be explained by the thinness of the used PCM and 
by the absorption of the polymeric wall of the microcapsule. The 
incorporation of fibers and gypsum causes a light increase in quantity of 
water. An increase of 20% of gypsum, resulted in a rise of about 3% of the 
water amount added to the mortar. 
 
Table 2. Workability results  
Compositions Water 
L100G0 23.0 
L100G0PCM 29.0 
L100G0PCMF 30.0 
L80G20PCMF 31.0 
L60G40PCMF 32.0 
 
 
 
 
5.2. Shrinkage  
 
With the device described above, it was possible to make an evaluation of 
shrinkage since the fresh state, due to changes caused by the introduction 
of polymer capsules. It was monitored the behaviour of different areal 
mortars from time zero to seven days. The results allowed us to verify that 
there is an increase in the measured value of the shrinkage with the 
incorporation of microcapsules. However, the addition of gypsum and 
nylon fibers, results in a decrease in shrinkage in the first 24 hours of 
monitoring (Figure 3). 
 
8 
 
 
Fig. 2. Shrinkage test since moulding until 24 hours 
 
 
Fig. 3. Shrinkage test since moulding until 7 days 
 
The analysis of the results up to 7 days of age (Figure 4) allows the 
identification of different behaviors in different aereal mortars. The 
introduction of 20% of microcapsules (L100G0PCM), causes an increase 
in shrinkage of about 4 times compared to the reference mortar (L100G0). 
The addition of nylon fibers (L100G0PCMF), causes a decrease in 
shrinkage to about half compared with the mortar L100G0PCM. With the 
addition of gypsum (L80G20PCMF and L60G40PCMF) is possible to 
observe a decrease in shrinkage. It was performed a practical application of 
mortar developed and subsequently made a comparison with the results 
obtained (Figure 5). For mortar L100G0 was obtained a value of 0.415 
µm/m, showing no cracks in support. The introduction of 20% of 
microcapsules (L100G0PCM) the shrinkage value obtained was increased 
about 5 times, showing cracking in support. With the addition of nylon 
fibers (L100G0PCMF) the value obtained is about half comparatively to 
-0,5
0,0
0,5
1,0
1,5
2,0
2,5
3,0
0 2 4 6 8 10 12 14 16 18 20 22 24
R
et
ra
cç
ã
o
 x
1
0
^
3
 (
m
m
/m
)
Idade (horas)
L100G0 (2,633µm/m)
L100G0PCM (2,422µm/m)
L100G0PCMF (2,451µm/m)
L80G20PCMF (1,771µm/m)
L60G20PCMF (1,547µm/m)
-2,0
3,0
8,0
13,0
18,0
23,0
28,0
0 1 2 3 4 5 6 7
R
et
ra
cç
ã
o
 x
1
0
^
-3
 (
m
m
/m
)
Idade (dias)
L100G0 (6,020µm/m)
L100G0PCM (24,908µm/m)
L100G0PCMF (12,580µm/m)
L80G20PCMF (5,628µm/m)
L60G20PCMF (10,237µm/m)
9 
 
the mortar L100G0PCM, with consequently lower cracking the mortar 
before. The subsequent incorporation of 20% gypsum results in a decrease 
in cracking presented in support. With the increase of gypsum content of 
40%, the amount of shrinkage obtained is 0.304µm/m, which is lower than 
the value obtained for the shrinkage of mortar L80G20PCMF (0.475 
µm/m) and also lower than the reference mortar (0.415 µm/m) with no 
cracking in the support.  
 
5.3. Flexural and compressive behaviour 
 
Concerning the mechanical strengths, in general terms and based in the 
obtained results, presented in Table 3, it is possible to find that the 
mechanical properties show an improvement with the addition of PCM 
microcapsules. The addition of 20% of PCM leads to an increase of the 
flexural strength about 450%. For the compression strength, the increase 
observed is about 788%. These values were obtained comparing to the 
composition without the incorporation of phase change materials.  
 
 
 
Fig. 4. Comparison between the values of shrinkage and cracking 
 
Table 3. Flexural and compressive results  
Compositions Flexural strength, MPa 
Compression strength, 
MPa 
L100G0 0.17 [10.98] 0.25 [8.09] 
L100G0PCM 0.93 [11.22] 2.22 [6.09] 
L100G0PCM
F 
0.72 [10.57] 1.79 [5.99] 
L80G20PCM
F 
1.36 [4.52] 2.27 [10.6] 
L60G40PCM 1.01 [12.72] 2.00 [11.7] 
0,415
1,190
0,569 0,475
0,304
0,0
0,4
0,8
1,2
1,6
Shrinkage at 8 Hours (µm/m)
10 
 
F 
Note: In parentheses we present the coefficient of variation in 
percentage. 
 
 
6. Conclusion 
 
The experimental work led to the conclusion that it is possible use 
polymeric microcapsules in mortar, obtaining a balance between the 
aesthetic and functional performance. The results obtained from tests for 
shrinkage concluded that the combined use of fibre and gypsum is a good 
solution for solving problems related to cracking caused by the 
incorporation of polymeric microcapsules. The specific devices developed 
at the University of Minho, has proved effective in quantitative evaluation 
of the shrinkage. It was also possible to make a practical application and 
verification of the values obtained in the laboratory. 
 
It was even possible to verify the existence of a clear rise of the water 
necessary to incorporate into the mortar within the increasing of PCM 
percentage, this with the aim of obtaining a suitable workability. The 
compression and flexural resistance measured in each performed test 
allows observing a tendency to its increase, with a greater incorporation of 
PCM microcapsules. The mortar with 60% of aerial lime and 40% of 
gypsum with incorporation of PCM microcapsules, is more interesting 
because it showed an excellent compromise between high mechanical 
strengths and low shrinkage. 
 
 
ACKNOWLEDGEMENTS 
 
The authors wish to express their thanks to the Portuguese Foundation for 
Science and Technology, for funding the project 
PTDC/ECM/102154/2008, Contribution of Thermal Active Mortars for 
Building Energy Efficiency. 
 
 
References 
 
11 
 
1. M. Félix, J. Aguiar, Study of a Cement Mortar with Incorporation of 
PCM Microcapsules, 6th Asian Symposium on Polymers in Concrete, 
Shanghai, 2009. 
2. N. Silva et al., Properties of Gypsum-PCM Based Mortars for Interior 
Plastering of Construction Systems, Materials Science Forum, Vol. 
587-588, pp. 913-917 (2008). 
3. Y. Zhang et al., Application of latent heat thermal energy storage in 
buildings: State-of-the-art and outlook, Building and Environment, 42, 
2209 (2007).  
4. B. Zalba et al., Review on thermal energy storage with phase change: 
materials, heat transfer analysis and applications, Applied Thermal 
Engineering, 23, 251 (2003). 
5. L. Cabeza et al., Materials used as PCM in thermal energy storage in 
buildings: A review, Renewable and Sustainable Energy Reviews, 15, 
1675 (2011). 
6. European Committee for Standardization (CEN), EN 1015-11 (1999), 
Methods of test for mortar for masonry - Part 11: Determination of 
flexural and compressive strength of hardened mortar. 
7. European Committee for Standardization (CEN), EN 1015-3(2004), 
Methods of test for mortar for masonry - Part 3: Determination of 
consistence of fresh mortar (by flow table). 


English

http://repositorium.sdum.uminho.pt/bitstream/1822/22234/1/Use%20of%20phase%20change%20materials%20microcapsules%20in%20aerial%20lime%20and%20gypsum%20mortars.pdf

Use of phase change materials microcapsules in aerial lime and gypsum mortars

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Universidade do Minho: RepositoriUM