The aim of this paper is to research new thermally-efficient concrete walls, analyzing the mechanical behavior of a self-compacting concrete to manufacture an uncoated solid structural panel, with the incorporation of a micro-encapsulated phase change material as additive. Different dosages are tested and mechanical properties of the product obtained from the molding of concrete specimens are evaluated, testing mechanical compressive strength, slump flow, and density.
The results reveal the optimum percentage of additive in the mixture that enables compliance with the technical specifications required by the product to be manufactured. A test is also performed for measuring the thermal conductivity for the optimal sample obtained and it evidences the reduction thereof.
For existing industries, the term sustainability is paramount when dealing with innovation. The design and development of sustainable products is a factor of increasing importance in industrial engineering. The construction industry, the main consumer of material resources and energy, has great potential in the development of new efficient materials to reduce energy consumption in buildings, so materials research aimed at sustainable construction and its applications appear as the engine of economic competitiveness.
The research project of which the results are presented this paper optimizes the design and construction of buildings by improving thermal insulation or storage. In order to achieve this, it is based on the following combination: This optimization implies integrating microencapsulated PCM into self-compacting concrete SCC"Self consolidating concrete disadvantages of solar" increasing the capacity of thermal storage of the building envelope.
SCC has been selected due to its several advantages: The thermal energy storage in buildings can be achieved mainly by sensible heat or by latent heat for example, including PCMs. The main advantage of the latent heat is the high storage density at small temperature intervals. PCMs have been classified into three major groups: Organic PCMs have been chosen from the beginning as the preferred means of research because of their important advantages and their manageable disadvantages [ 45
Self consolidating concrete disadvantages of solar.
To integrate PCMs in building, various techniques have been investigated, like immersion processes or macrocapsules; however, because of their limitations, these techniques have not been well received in the market [ 6 ]. Recent advances in Self consolidating concrete disadvantages of solar technology it suitable for introducing organic PCMs preferably paraffin wax in thermal energy storage systems [ 7 ].
Microcapsules are small PCM particles forming the core, coated with another material that forms a thin protective insulating film, with the great advantage that it is easier to manipulate the PCM, in addition to tolerating volume changes, reducing the reactivity of the paraffin wax with the outside and increasing the heat transfer area [ 8 ].
The use of PCMs in building materials for thermal storage has been extensively studied since the s [ 91011 ] and the number of articles relating to the integration of PCMs in walls of buildings has increased enormously in the last five years [ 12 ].
The most relevant to this investigation are contributed by authors such as Cabeza et al. The same microencapsulated PCM was used by Entrop et al. Finally, Meshgin et al.
These results are compared with the other samples containing different percentages and rubber particle size. The main objective of this paper is to contribute to existing knowledge in the use of PCMs in SCC, in particular, the new structural precast concrete panel must have the following characteristics: The chosen PCM is an aqueous dispersion of a mixture of formaldehyde-free microencapsulated paraffin.
The determination of the maximum percentage of PCM to be added to mass concrete is mainly limited by the mechanical strength of the structural panel to be obtained. Therefore, a study of mixes with the following PCM percentages by mass of cement is performed: The research cited above shows loss of mechanical strength in the concrete and breakage of the encapsulation of the PCM, followed by exudation and loss thereof, and segregation of the PCM to the upper surface of the SCC and poor dispersion in the mass.
To evaluate these aspects as well as the mechanical properties of fresh SCC, the following actions have been carried out:. As shown in the particle size Figure 1 and in the certificates, it is clean sand and gravel with continuous grain size and without slabs. If the interior temperature rises above the phase change temperature, the wax melts within the microcapsules and absorbs excess heat, Self consolidating concrete disadvantages of solar if the temperature drops, the wax solidifies and the capsules release heat.
A PCM whose transition temperature liquid-solid is in the temperature range in which people feel more comfortable should be chosen, and also depending on the characteristics of each region, so that the thermal inertia of concrete matches the day-night temperature cycle.
The characteristics of the product according to the manufacturer's specifications are as follows:. The flow behavior of SCC is governed by the paste composition, paste volume, and particle size distribution of aggregates.
The factors governing the behavior of SCC are determined by the appropriate mix design method [ 22 ]. In this work the initial mix was estimated according to the method used by the Polytechnic University of Catalonia [ 23 ] developed for high-strength SCC, a methodology based on the use of locally available materials and testing techniques of common usage. The procedure is based on a separate optimization of the composition of the paste and the granular aggregate skeleton.
"Self consolidating concrete disadvantages of solar" paste consists of cement, filler, water and superplasticizer, while the granular skeleton is defined by the optimum ratio between sand and gravel that provides maximum compactness of the structure.
Table 1 shows the composition of
Self consolidating concrete disadvantages of solar reference mix obtained without incorporation of the PCM, the starting basic composition on which tests have been performed, characterized by: By adding the viscosity-modifying agent, the necessary proportions were modified to obtain the required self-compacting specifications.
The mixing procedure carried out in the laboratory has developed in the following steps: Then the filler and cement are added, and all solid components are shuffled for proper homogenization for another 1 min. Finally, for the reference mix, the remaining water and superplasticizer are to be rectified as needed to obtain the desired self-compacting characteristics.
However, for mixes in which the PCM "Self consolidating concrete disadvantages of solar" incorporated, it will be incorporated just before Self consolidating concrete disadvantages of solar mentioned final adjustments, to expose it to the shortest possible time to the mixing process and thus preventing the rupture of the microcapsules.
Control at this point is by visual inspection. Sampling of fresh concrete, with which standard specimens were developed, was carried out according to the UNE-EN It was observed that the concrete was behaving like a conventional concrete but with a lot of air entrainment and fermentation. Three testing methods have been researched in this study to determine the properties of SCC, both fresh and hardened: In order to evaluate self-compactability, slump flow test was performed according to the UNE-EN We performed a slump flow test for each mix.
We conducted a first test to the reference sample, containing no PCM, and once, selected the sample with the highest percentage of PCM that meets the required specifications, tests are performed to measure the thermal conductivity.
As a result of the slump flow analysis, all measures are in a narrow range but are classified in different groups, SF2 and SF1, because the range cut is mm.
The T 50 parameter alone cannot represent viscosity and can only score it when the value of the flow extension is constant in the evaluated mixes [ 25 ]. This is because the contribution of water is lower for similar PCM and superplasticizer increases.
It should be mentioned that the results of this study do not provide a direct measure of the assessment of the ready-mixed concrete to pass easily between the reinforcement
Self consolidating concrete disadvantages of solar the structural panel to be made. However, since there is slight reinforcement in this type of product, no risk of blockage is deemed, as such no further test has been considered necessary. In the remaining samples, we observed a uniform distribution of coarse aggregate and no segregation or exudation on the perimeter of the final spread "Self consolidating concrete disadvantages of solar" of the test.
Table 4 shows the values obtained for the density of each sample, m 1 being the container mass in kilograms, m 2 the container mass plus the mass of the mortar in the container in kilograms, m 24h is the difference between m 2 after 24 h and m 1 in kilograms, D is the fresh concrete density in kilograms per cubic meter, and D 24h is the density after 24 h in kilograms per cubic meter for the same volume.
Problems already occurred with that sample in the Self consolidating concrete disadvantages of solar flow test. This linear relation holds for the range of PCM contents considered. In order to further clarify the results obtained, Table 5 shows the average values of those densities in fresh and after 24 h, as well as the difference between them. The results shown reflect how both fresh and 24 h density is proportionately reduced as the percentage of PCM is increased in the sample.
What is also Self consolidating concrete disadvantages of solar from Table 5 is that incorporation of the PCM implies a worse homogeneity of the mix, resulting in pores with occluded air. Table 6 shows the values of the test. Strength decreases as the percentage of PCM added to the sample increases; this is corroborated by the results obtained in previous studies [ 141517 ].
This linear relation is maintained for the considered parameter range. Such problems become more evident after the test Figure 6 Bwhere we can see an irregular breakage of the specimen and poor homogenization of the mixture, with many pores highlighting the lack of compaction. An additional problem shown in this specimen is segregation of the PCM particles to the upper surface of the concrete during curing, because its density is lower than that of ceramics and are also of very small size, so that the particles diffuse upwardly through the liquid, since the viscosity of this sample is unable to halt it; the aggregation of particles that huddle forming clusters can be clearly seen.
This occurs when dispersing solids and liquids of different polarity, as is the current case the liquid is water, polar, and the PCM is polymeric, non-polar. It is clearly Self consolidating concrete disadvantages of solar that the surface is uniform with good surface finish and good performance of cracking. The test conditions and the characteristics of the specimens are shown in Table 7.
A decrease in thermal conductivity can be clearly observed when PCM is added; such decrease is expected because of the reduction in the weight of the specimens, backed up by the results obtained in the determination of densities.
This reduction is brought about by the amount of air entrainment and the low thermal conductivity of the paraffin. This shows that thermal conductivity depends not only on the percentage of PCM, but also on the average size of the particles in the composition of the mix. The fact that an aqueous dispersion of PCM was used in Self consolidating concrete disadvantages of solar investigation makes it easier to integrate into the mixture and that the design of the mix is optimal.
The main objective of this research is to develop a structural panel, which allows energy savings, with the economic and environmental improvements that it entails, besides contributing to the comfort of the users of the buildings and facilities where they are used. Based on tests and subsequent analysis of the different mixes, we can conclude that as the percentage of PCM in the mixture increases:.
National Center for Biotechnology InformationU. Journal List Materials Basel v. Published online Aug Author information Article notes Copyright and License information Disclaimer. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license http: This article has been cited by other "Self consolidating concrete disadvantages of solar" in PMC.
Abstract The aim of this paper is to research new thermally-efficient concrete walls, analyzing the mechanical behavior of a self-compacting concrete to manufacture an uncoated solid structural panel, with the incorporation of a micro-encapsulated phase change material as additive. Introduction For existing industries, the term sustainability is paramount when dealing with innovation.
To evaluate these aspects as well as the mechanical properties of fresh SCC, the following actions have been carried out: It has a high initial mechanical strength, which facilitates handling and demolded at early stages.
Its primary mission is to increase the viscosity of the mixture, to stabilize the water within the concrete, and to increase the Self consolidating concrete disadvantages of solar tension and the cohesion thereof. Open in a separate window.
It is an aqueous dispersion comprised of microcapsules with a wax core serving as latent heat accumulator. Composition of the Reference Mix The flow behavior of SCC is governed by the paste composition, paste volume, and particle size distribution of aggregates. Table 1 Composition of the reference mix. The test program has been developed in the following steps: Table 2 Mix composition. Testing Methods Three testing methods have been researched in this study to determine the properties of SCC, both fresh and hardened: The appropriate behavior of SCC in the fresh state requires high fluidity with enough viscosity and cohesion among the components to ensure a continuous and uniform flow throughout the mass, not showing segregation, and without causing concrete blocking between reinforcements.
In order to determine density, a total of six samples were analyzed for each dosage, Self consolidating concrete disadvantages of solar to UNE-EN To make a more comprehensive assessment, strength was calculated at seven and 60 days. Results and Discussion 3. In this paper, Self consolidating concrete disadvantages of solar of self-consolidating concrete (SCC) and conventional concrete (CC) is investigated regarding the types of aggregates.
Self compacting concrete (SCC) is a special type of concrete that spreads through the congested . One of the limitations of SCC is that there is no . recommended; they reduce solar-heat gain, thus reducing the concrete temperature.
Keywords: self-compacting concrete, phase change materials, important advantages and their manageable disadvantages [4,5].  in concrete floors in order to help heat homes during the night by using solar radiation.
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