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Energy efficient pumpable cement concrete with nanomaterials embedded PCM for passive cooling application in buildings
Materials Today: Proceedings xxx (xxxx) xxx
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Energy efficient pumpable cement concrete with nanomaterials embedded PCM for passive cooling application in buildings V. Vinayaka Ram a, Rhythm Singhal a, R. Parameshwaran b,⇑ a b
Department of Civil Engineering, Birla Institute of Technology and Science-Pilani, Hyderabad Campus, Hyderabad 500 078, India Department of Mechanical Engineering, Birla Institute of Technology and Science-Pilani, Hyderabad Campus, Hyderabad 500 078, India
a r t i c l e
i n f o
Article history: Received 1 October 2019 Accepted 26 December 2019 Available online xxxx Keywords: Energy efficiency Nanomaterials Phase-change material Pumpable cement concrete Thermal energy storage Thermo-structural properties
a b s t r a c t The growing energy demand and energy requirements in the construction sector have paved way to the development and incorporation of the energy efficient materials and technologies in building envelopes. This research work is aimed at investigating the suitability of a pumpable cement concrete with nanomaterials embedded phase change material (PCN-PCM) for achieving energy efficiency in buildings through passive cooling application. In this work, an attempt was made to mix the flyash and ground-granulated blast-furnace slag (GGBS) as replacement materials for the cement along with the super plasticisers. To this engineered pumpable concrete, different sequential processes of adding the organic PCM (lauryl alcohol) embedded with nanomaterials (ZnO and hybrid Cu-TiO2) have been carried out. The mixing process was then optimised based on the incorporation of the PCM (0% to 20% with incremental steps of 5%) and the nanomaterials (0.01%–0.05% with incremental steps of 0.01%) into the cement concrete. The asprepared PCN-PCM was characterized and tested from both thermal and structural aspects. The XRD results suggest that, the nanomaterials prepared were highly crystalline, and the adsorption of the Cu nanoparticles on the surface of the TiO2 nanoparticles were significant as observed from the FESEM images. The FTIR results confirm that the PCN-PCM composite were chemically stable for the mixdesign combinations. In addition, the as-prepared composite achieved a characteristic compressive strength of 20 MPa, which confirms its structural stability. Furthermore, the experimental results reveal that, the PCN-PCM composite exhibited good latent heat potential by storing thermal energy and thereby; regulated the indoor air temperature of the test room around 24 °C. Based on the aforementioned attributes, the as-prepared PCN-PCM composite is expected to serve as an energy efficient candidate for achieving good thermal storage capabilities and structural integrity through passive cooling in buildings. Ó 2020 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 2nd International Conference on Recent Advances in Materials & Manufacturing Technologies.
1. Introduction It is an undeniable fact that energy is the prime mover of human life. Fossil fuels are the main source of energy in the world at present. Since fossil fuels are limited and their formation takes a long time, conservation of fossil fuels, through efficient utilization, is of utmost importance for any country to sustain in the long run. Moreover, environmental pollution due to over exploitation of fossil fuels is also a matter of concern throughout the world. Hence, serious research efforts are made in the field of renewable energy ⇑ Corresponding author. E-mail address: [email protected] (R. Parameshwaran).
resources. Also, it is imperative to note that most economies have formulated their policies to promote usage of technologies based on renewable energy sources. Solar energy is the primary energy source, which, abundantly is available for the whole year and its energy received by the planet earth, as per one estimate, is 10,000 times the entire earth’s energy demand. This energy resource can be captured through a thermal storage medium like phase change material (PCM) thus cutting down, drastically, the active energy consumption through HVAC systems in buildings. This could be made possible through incorporation of PCMs in floors, walls and ceilings of building and satisfy all dimensions of sustainable development including the social, economic and
https://doi.org/10.1016/j.matpr.2019.12.356 2214-7853/Ó 2020 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 2nd International Conference on Recent Advances in Materials & Manufacturing Technologies.
Please cite this article as: V. Vinayaka Ram, R. Singhal and R. Parameshwaran, Energy efficient pumpable cement concrete with nanomaterials embedded PCM for passive cooling application in buildings, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.356
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environmental dimensions. PCM can absorb and release heat during phase changing process and when incorporated into concrete, will serve as passive thermal regulator of indoor temperature. As a principle, for PCM to function as a thermal regulator, its phase transition temperature should lie in the vicinity of expected ambient room temperature [1]. It has been reported that PCM possess high energy storage density and temperature variation attenuating capacity. Even though the construction material behaviour becomes complex with PCM inclusion, it has been found that the resulting composite can be used in light weight construction and non-load bearing applications with advantage. Also, PCM is a latent heat storage medium which occupies less volume when compared to sensible thermal storage media [2]. Though PCM appears to be a superior alternative among others, it leads to different complications when it is included in building elements. The problems pertain to corrosion, leakage and compatibility with the concrete. Performance of PCM based building material heavily depend on the incorporation method, sequence of mixing, curing methodology and the type of PCM being used. Many researchers have identified three methods of incorporating PCM with concretes namely the direct mixing method, capsule method and immersion method [3,4]. Phase change materials (PCMs) can be broadly classified as organic, inorganic and eutectic. Organic materials include Paraffin and non-paraffins. Paraffins have chain like structure, which releases energy. The length of chain is an indication of latent heat of fusion and melting points. Melting point temperature for paraffins usually falls in the range of 12 °C to 71 °C. Apart from high latent heat, paraffins are known for their non-corrosive nature and are free from sub-cooling phenomenon. Paraffins are cost effective, reliable and chemically stable. However, they suffer from limitations such as low thermal conductivity, incompatibility with plastics, tendency to slip away from the matrix and high volume changes [5–7]. Non-Paraffins, like esters, glycols, fatty acids, usually possess exclusive characteristics, which provide multiple options to the user. These are gaining popularity due to high latent heat, absence of phase separation tendency and low super cooling characteristics. However, non paraffins are expensive than the paraffins and flamable, limiting their application for low temperature ranges only [5–7]. Inorganic PCMs were also gaining popularity due to their affordability. These PCMs have strikingly different properties when compared with their organic counterparts with regard to their tendency to exhibit high latent heat per unit mass and high thermal conductivity. The main drawback of these PCMs is that they exhibit in-congruent phase change process and also these PCMs are quite expensive than the organic PCMs [5–7]. Phase change materials can be incorporated in construction materials in multiple ways namely through direct mixing, dipping into liquid PCM, adding in the form of encapsulated micro and macro capsules etc. Direct mixing involves mixing PCM and construction material in appropriate proportions. Dipping into PCM is another way where in the PCM is adsorbed into a porous substrate. Encapsulation involves covering PCM with polymeric shells to prevent their leakage during phase change process. PCMs can be micro-encapsulated or macro-encapsulated. Micro encapsulation involves covering PCM particles at micron level with polymers. Macro encapsulation involves confining the PCM in a container appropriate to the construction process and element being constructed. Shape stabilized PCMs and form stabilized PCMs are other viable alternatives for inclusion into construction materials when the thermal stability issues arise [8–9].
Direct incorporation technique involves incorporation of the PCM directly into the concrete mix. It is undoubtedly the most practical and least expensive method. However, its successful application depends on the way the PCM is integrated with the mix without interfering the hydration process and affecting the strength of the mortar-aggregate bonding in the concrete. Also, there shouldn’t be any significant reaction happening between the PCM and either the components of the mix or the products of hydration [10–12]. Immersion technique involved dipping the cement concrete blocks directly into PCM. The process is quite flexible and can range from an automated continuous production line to a simple and relatively inexpensive batch process. Studies have indicated that this process is more expensive than the direct incorporation method [10–12]. Encapsulation can be treated as a variation of the direct incorporation process in which the PCM is fed into the mix in encapsulated form. The choice of the shell material used to make the encapsulated PCM is crucial since it must not react with either the PCM or the concrete, must demonstrate reasonably good heat transfer properties and shall withstand the rigours of processes involved like manufacturing, transport, construction and use. Currently, this procedure looks to be too expensive. However, the development of a large market for PCM concrete would justify further research into improving the feasibility of this process which could possibly be the best route to direct incorporation [10–12]. In the present research work, taking the clues from the literature review being carried out, an attempt has been made with an objective of developing and testing the copper-titania (Cu-TiO2) hybrid nanoparticles impregnated non paraffin based organic PCM embedded concrete material for achieving indoor temperature regulation through passive cooling and thermal storage. The major reasons for preferring organic non-paraffin are high latent heat of fusion and relatively low inflammability. Also, the melting point of the chosen PCM (lauryl alcohol) is very close to the ambient room temperature. 2. Study Methodology: With a view to ensure the required strength, pumpability and thermal storage properties for the proposed pumpable cement concrete embedded with hybrid copper titania nanoparticlesbased Phase Change Material (PCM) for passive cooling of buildings, this research work is being carriedout in 7 different stages as depicted in Fig. 1. Each of the listed stages are detailed in the subsequent sections. All the stages are self explanatory in nature 3. Results and discussions Experimental investigations were carried out as outlined in the methodology flow chart presented in art 2.0. Details of all the investigations are presented in the following sections along with critical discussions. 3.1. Stage 1 This stage involved preparation of standard 15 cm 15 cm 15 cm Plain Cement Concrete (PCC) cube samples for a design characteristic compressive strength of 20 MPa (M20 mix design) with varying proportions of ingredients. A slump of 75 mm (within the range of 50–100 mm slump for pumpable concrete) was also targetted during the mix design. Concrete mix included the following ingredients:
Please cite this article as: V. Vinayaka Ram, R. Singhal and R. Parameshwaran, Energy efficient pumpable cement concrete with nanomaterials embedded PCM for passive cooling application in buildings, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.356
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Fig. 1. Research Methodology Stages.
Cementitious materials: 53 Grade Ordinary Portland Cement (OPC), Class F flyash obtained from Vijayawada thermal power station (India) and Ground Granulated Blast Furnace Slag (GGBS) Fine aggregates (Crusher fines confirming to Zone 1 gradation as per IS 10262: 2009) Coarse Aggregates with nominal maximum size of 10 mm Potable water for mixing and curing Lignosulphate based super plasticiser to achieve the adequate workability, viscosity and slump retention capability. Different combinations of cementitious materials (cement, flyash and GGBS) were being tried while keeping the total cementi-
tious components at 548 kg/m3. Also the total of fine and coarse aggregates is fixed at 1600 kg/m3 and different permutations of Coarse and fine aggregate ratios have also been tried to optimise the same. Water to Cement (W/C) was kept constant at 0.45, while the Super Plasticiser was fixed at 0.7% by weight of cement. The mixes with reference code numbers ranging from 101 to 118 have been tried and for each code, 6 samples have been prepared. Three samples were used for finding 7-day strengths while the other 3 samples were used for finding 28-day strengths. All the samples had slumps in the range of 50–100 mm and also had reatined the slumps for almost 1 h after mixing, thus satisfying the requirements of pumpable concrete. Saturated Surface Dry (SSD) aggregates were only used to prevent any loss of water from
Please cite this article as: V. Vinayaka Ram, R. Singhal and R. Parameshwaran, Energy efficient pumpable cement concrete with nanomaterials embedded PCM for passive cooling application in buildings, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.356
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the concrete. All the tried mix proportions have been summarised and presented in Table 1 for ready reference. Cube samples, demoulded after 24 h, were cured in water, with 50% of the samples being cured for 7 days and the rest 50% samples being cured for 28 days. Further, they were tested with a 200 kN strain controlled compression testing machine (CTM). To verify the repeatability and reproducibility of the experiments, 3 samples each for 7day and 28-day curing, were tested and the results are summarised and presented in Table 2.
3.2. Stage 2: This stage involved the synthesis and characterization of ZnO nanoparticles and Cu-TiO2 hybrid nanoparticles using sol–gel process. For the preparation of ZnO nanoparticles, the precursor solution used was Zinc acetate and NaOH aqueous solution was employed as the reducing agent on a hot plate magnetic stirrer, with 350 RPM and 55 °C until nanoparticles were formed in the aqueous medium. The synthesis of Cu-TiO2 hybrid nanoparticles involved more rigorous process. Titanium dioxide and cupric nitrate were used as precursors during this process. In addition, Polyvinyl Pyrolidone aqueous solution was used as stabilising agent. Sodium borohydride and ascorbic acids were employed as reducing agents during the reaction phase. The complete process is depicted through Fig. 2 for more clarity. Particle size analysis of ZnO particles, as presented in Fig. 3, revealed that the size was not in nanoscale range. Hence, investigations with ZnO particles was not carried out further and the work was continued with Cu-TiO2 hydrid nano particles. The as synthesised Cu-TiO2 hybrid particles were subjected to the following characterisation to establish the suitability of these particles for the intended use. Field Emission Scanning Electron Microscope (FESEM) and Energy-dispersive X-ray spectroscopy (EDX) studies Fourier Transform Infrared Investigations (FTIR) X ray Diffraction (XRD)
3.2.1. FESEM and EDX studies on Cu-TiO2 hybrid nanoparticles FESEM provides surface morphology and elemental information with the capability of providing the magnifications ranging from 10x to 300,000x. In addition, this instrument has the capability to
Table 2 7-day and 28-day characteristic compressive strengths (MPa) of reference samples. Mix code
Average compressive strengths of 7day cured samples (MPa)
Average compressive strengths of 28-day cured samples (MPa)
101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118
20 20.5 19 24.5 26 24 22.5 21.8 21.7 17.5 16.7 16.1 22.8 21.7 21.1 19.8 20.1 20.4
28.1 29.7 25.5 34.8 35.5 33.1 31.8 31.1 33.4 26.8 25.3 26.1 31.2 30.4 30.9 27.9 28.1 27.4
provide the elemental composition of the given sample through EDX analysis. During the current study, both FESEM and EDX investigations were carried out on the synthesised hybrid Cu-TiO2 nanoparticles. The FESEM micrograph is presented in Fig. 4. The size marked on the micrograph confirms the particles being formed in nano dimension. The EDX analysis, presented in Fig. 5 and Table 3 confirms the presence of both Cu and TiO2 particles.
3.2.2. Fourier Transform Infrared investigations (FTIR) With a view to understand the chemical compatibility of PCM with cement as well as hybrid Cu-TiO2 nanoparticles, Fourier Transform Infra-Red (FTIR) spectrums were obtained for pure cement, cement + PCM combination and PCM + Cu-TiO2 hybrid nanoparticle combination. These spectrums are presented through Figs. 6–8. A close observation of FTIR spectrum of Ordinary Portland Cement (OPC) with that of combined OPC and PCM reveals that there are no decipherable differences in peaks, except a few changes observed near the wave number 3000 cm 1. This confirms that the PCM is not causing any major changes to cement properties when they are together. However, spectrogram of OPC plus PCM revealed a major absence of peak at a wave num-
Table 1 Reference M30 pumpable concrete mix proportions. Mix code
Cement
Fly ash
GGBS
Fine aggregate
Coarse aggregate
W/C
SP
No. of samples
101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118
333 333 333 333 333 333 333 333 333 215 215 215 215 215 215 215 215 215
215 215 215 0 0 0 107.5 107.5 107.5 333 333 333 0 0 0 166.5 166.5 166.5
0 0 0 215 215 215 107.5 107.5 107.5 0 0 0 333 333 333 166.5 166.5 166.5
835 960 1120 835 960 1120 835 960 1120 835 960 1120 835 960 1120 835 960 1120
765 640 480 765 640 480 765 640 480 765 640 480 765 640 480 765 640 480
0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45
0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7%
6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6
Please cite this article as: V. Vinayaka Ram, R. Singhal and R. Parameshwaran, Energy efficient pumpable cement concrete with nanomaterials embedded PCM for passive cooling application in buildings, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.356
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Fig. 2. Synthesis of Cu-TiO2 hybrid nanoparticles.
Fig. 3. Particle Size Analysis for ZnO nanoparticles.
ber 2700 cm 1 which was available in the spectrum of pure PCM. This aspect, which needs further probe, is left for future investigation.
However, the FTIR spectrograms, obtained for pure PCM and PCM + hybrid nanoparticles, clearly indicate that there are no observable differences in peaks or signatures, thus proving that
Please cite this article as: V. Vinayaka Ram, R. Singhal and R. Parameshwaran, Energy efficient pumpable cement concrete with nanomaterials embedded PCM for passive cooling application in buildings, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.356
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sion was taken to take this combination forward for further investigations.
Fig. 4. FESEM image for Cu-TiO2 hybrid nanoparticles.
3.2.3. X-ray diffraction (XRD) studies on Cu-TiO2 hybrid nanoparticles XRD studies are usually carried out to check the presence or absence of crystalline phase in the material being investigated. This can also be extended to perform Quantitative phase analysis (QPA) to quantify the crystalline phase. Further, XRD studies can reveal the presence of amorphous phase in the material too. XRD studies were carried out for Cu-TiO2 hybrid nanoparticles durng the current study and the difraction patterns were presented in Fig. 9. The formation of coppertitania hybrid nanoparticles was confirmed through the sharp and intense XRD peaks obtained, which were ascribed to their lattice planes. The presence of copper nanoparticles on the surface of titania particles as justified from the FESEM analysis is in good agreement with the XRD results obtained. That is, the sharp peaks corresponding to copper and titania were obtained due to the scattering at interplanar spacing and signified the high crystalline nature of the Cu-TiO2 hybrid nanoparticles. The peak intensity obtained at planes (111), (200) and (220) were in good agreement with the JCPDS standards [13] and with the similar results in [14]. 3.3. Stage 3 - selection of PCM for the intended application and characterization: After a thourough study of many PCMs with regard to the following properties, Lauryl alcohol (C12H26O) was chosen for the current study as PCM.
Fig. 5. EDX analysis for Cu-TiO2 hybrid nanoparticles.
Table 3 Elemental composition for Cu-TiO2 hybrid nanoparticles from EDX. Element
Wt (%)
Atomic Wt (%)
O Ti Cu
40.91 38.65 20.44
69.38 21.89 8.73
there is no active chemical interaction happening between them. Overall, it was observed that the chemical interaction between the nanoparticles, cement and PCM is minimal and hence the deci-
Thermo physical properties like fusion temperature, latent heat of fusion, high specific heat, thermal conductivity, congruent phase transition and low volumetric capacity change; Chemical properties like non corrosiveness, chemical stability on long run, non toxic, non explosive, non flammable and good molecular bonding capability Economic point of view 3.4. Stage 4 - trials with PCM, hybrid nanomaterial with varying concrete mix sequencing and finalising the sequence for further experimentation: Mix proportion numbered 109 was chosen as the reference mix after ensuring the adequate compressive strength while fulfilling
Fig. 6. FTIR Spectrum for Ordinary Portland Cement.
Please cite this article as: V. Vinayaka Ram, R. Singhal and R. Parameshwaran, Energy efficient pumpable cement concrete with nanomaterials embedded PCM for passive cooling application in buildings, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.356
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Fig. 7. FTIR spectrum for the combination of ordinary portland cement and 1-dodecanol PCM.
Fig. 8. FTIR spectrums for Cu-TiO2 hybrid nanoparticles and 1-dodecanol PCM mix and PCM alone.
other target requirements, namely, pumpability and balanced use of flyash and GGBS as cementitious ingredients. After trying multiple mix sequences, a sequence was chosen based on the fact that it resulted in minimum PCM leakage when compared with other trials. A 6-stage sequence, depicted through Fig. 10, was followed throughout this phase of the work.
mixes were numbered with codes of 119 to 133 and cured. Details of these mixes is presented in Table 4 for ready reference.
3.5. Stage 5 - preparation and testing of modified cement concrete cube specimens with varying percentages of PCM and Cu-TiO2 hybrid nanoparticles as admixtures to the finalized reference PCC:
All the samples, cured for 7 days and 28 days in water, were tested under strain controlled 2000 kN capacity compression testing machine. The samples were then tested in the direction, orthogonal to the direction of casting the sample to ensure that the sample is tested along its weakest plane. The average 7-day and 28-day characteristic compressive strengths obtained from 3 tested samples are summarised and presented in Table 5. All the samples are grouped in to 3 batches with varying W/C ratios. The mix proportions numbered 119, 124 and 129, cast with 0% PCM in batches I, II and III respectively, were treated as refer-
Taking the mix proportion numbered 109 as the base proportion, 15 combinations of new proportions were worked out by trying the W/C ratios from 0.35 to 0.45 with increments of 0.5%. Also PCM (by percent weight of cement) was varied from 0% to 20% with 5% increments. 3 samples for 7 days and 3 samples for 28 day investigations were casted for each of the combinations. These
3.6. Stage 6 - establishing the optimum combinations of concrete ingredients, PCM and hybrid nanoparticles based on cube compressive strength:
Please cite this article as: V. Vinayaka Ram, R. Singhal and R. Parameshwaran, Energy efficient pumpable cement concrete with nanomaterials embedded PCM for passive cooling application in buildings, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.356
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Fig. 9. XRD diffraction patterns for Cu-TiO2 hybrid nanoparticles.
Fig. 10. Sequence followed for hybrid nanoparticles-based PCM embedded cement concrete sample preparation.
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V. Vinayaka Ram et al. / Materials Today: Proceedings xxx (xxxx) xxx Table 4 Trial mixes with changing W/C ratios and PCM. Mix number
Cement (kg/m3)
Fly ash (kg/m3)
GGBS (kg/m3)
Fine aggregate (kg/m3)
Coarse aggregate (kg/ m3)
W/ C
BASF SP (% by weight of cement)
Cu-TiO2 hybrid nanoparticles (% by weight of cement)
PCM (% by weight of cement)
No. of samples
119 120 121 122 123 124 125 126 127 128 129 130 131 132 133
333 333 333 333 333 333 333 333 333 215 215 215 215 215 215
107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5
107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5
1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120
480 480 480 480 480 480 480 480 480 480 480 480 480 480 480
0.35 0.35 0.35 0.35 0.35 0.40 0.40 0.40 0.40 0.40 0.45 0.45 0.45 0.45 0.45
0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7
0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05
0 5 10 15 20 0 5 10 15 20 0 5 10 15 20
6 6 6 6 6 6 6 6 6 6 6 6 6 6 6
Table 5 7-day and 28-day Characteristic Compressive Strengths of samples with nanoparticles and PCM. Batches
Sample number
7 day (Average)
28 day (Average)
Batch I with W/C = 0.35
119 120 121 122 123 124 125 126 127 128 129 130 131 132 133
27.8 24.7 21.6 18.5 13.2 24.5 22.6 18.4 15.1 9.1 21.9 17.9 14.1 9.8 6.8
40.2 38.1 31.5 28.0 22.2 38.9 35.4 26.7 24.8 17.8 34.1 27.2 23.8 16.5 12.1
Batch II with W/ C = 0.40
Batch III with W/ C = 0.45
ence samples representing each one of the batches. It can be observed from Table 5 that the increasing PCM has always resulted in considerable drop in characteristic compressive strength. However, since the target strength was 20 MPa (M20 concrete), there was a flexibility to increase the PCM percentage. Despite having more than required compressive strength, the samples with 10% and above percentage of PCM were observed to be profusely leaking, thus making them unacceptable for further consideration. Taking these points in consideration, mix number 120 with an average characteristic compressive strength of 38.1 MPa has been chosen as the ideal mix for the intended application. 3.7. Stage 7: Finalizing the specifications to develop pumpable cement concrete embedded with hybrid copper titania nanobased PCM for passive cooling of Buildings:
Class F Fly ash = 107.5 kg/m3 GGBS = 107.5 kg/m3 Fine Aggregates = 1120 kg/m3 Coarse Aggregates = 480 kg/m3 W/C ratio = 0.35 Super Plasticizer = 0.7% by weight of cement 1-dodecanol PCM by weight of cement = 5% Slump observed for the chosen composition = 76 mm
A small scale laboratory based pilot study was also conducted with the finalised modified concrete mix and the initial results were found to be quite encouraging. The PCM based modified concrete wall built in the laboratory model could reduce the heat flow substantially. However, more investigations are planned to confirm and validate these results and hence the details are not presented in this article 4. Conclusions and recommendations A novel sequence of integrating the Cu-TiO2 hybrid nanoparticles-based PCM in to cement was tried and the trials have proved that this sequence has resulted in minimum leakage of PCM. However, complete leakage prevention could not be realized during the current investigations, indicating the need of trying with encapsulated PCMs. A maximum of 5% Lauryl Alcohol PCM by weight of cement is recommended in the mix due to its tendency to reduce the strength with additional PCM content. The mix presented in section 3.7 is found to be satisfying both strength and thermal storage capacities. The small scale laboratory pilot study indicated a great promise towards achieving the end objectives of the study being carried out. 5. Scope for future work:
After a comprehensive characterisation of individual ingredients and the concrete, the specifications for the Pumpable Cement Concrete embedded with copper-titania hybrid nanoparticlesbased PCM were finalised during the present research activity. The mix specification is as follows: Mix Number: 120 Characteristic Compressive Strength = 38.1 MPa (after 28 days of curing) Leakage: Partial leakage was observed Cement (53 grade OPC) = 333 kg/m3
Encapsulated PCMs with enhanced heat storage capacity can be investigated in the similar manner. Large scale building model can be built with the proposed mix design and investigated.
Acknowledgement Authors thankfully acknowledge central analytical laboratory and concrete laboratory, BITS Pilani, Hyderabad campus for their
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Please cite this article as: V. Vinayaka Ram, R. Singhal and R. Parameshwaran, Energy efficient pumpable cement concrete with nanomaterials embedded PCM for passive cooling application in buildings, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.356
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Energy efficient pumpable cement concrete with nanomaterials embedded PCM for passive cooling application in buildings V. Vinayaka Ram a, Rhythm Singhal a, R. Parameshwaran b,⇑ a b
Department of Civil Engineering, Birla Institute of Technology and Science-Pilani, Hyderabad Campus, Hyderabad 500 078, India Department of Mechanical Engineering, Birla Institute of Technology and Science-Pilani, Hyderabad Campus, Hyderabad 500 078, India
a r t i c l e
i n f o
Article history: Received 1 October 2019 Accepted 26 December 2019 Available online xxxx Keywords: Energy efficiency Nanomaterials Phase-change material Pumpable cement concrete Thermal energy storage Thermo-structural properties
a b s t r a c t The growing energy demand and energy requirements in the construction sector have paved way to the development and incorporation of the energy efficient materials and technologies in building envelopes. This research work is aimed at investigating the suitability of a pumpable cement concrete with nanomaterials embedded phase change material (PCN-PCM) for achieving energy efficiency in buildings through passive cooling application. In this work, an attempt was made to mix the flyash and ground-granulated blast-furnace slag (GGBS) as replacement materials for the cement along with the super plasticisers. To this engineered pumpable concrete, different sequential processes of adding the organic PCM (lauryl alcohol) embedded with nanomaterials (ZnO and hybrid Cu-TiO2) have been carried out. The mixing process was then optimised based on the incorporation of the PCM (0% to 20% with incremental steps of 5%) and the nanomaterials (0.01%–0.05% with incremental steps of 0.01%) into the cement concrete. The asprepared PCN-PCM was characterized and tested from both thermal and structural aspects. The XRD results suggest that, the nanomaterials prepared were highly crystalline, and the adsorption of the Cu nanoparticles on the surface of the TiO2 nanoparticles were significant as observed from the FESEM images. The FTIR results confirm that the PCN-PCM composite were chemically stable for the mixdesign combinations. In addition, the as-prepared composite achieved a characteristic compressive strength of 20 MPa, which confirms its structural stability. Furthermore, the experimental results reveal that, the PCN-PCM composite exhibited good latent heat potential by storing thermal energy and thereby; regulated the indoor air temperature of the test room around 24 °C. Based on the aforementioned attributes, the as-prepared PCN-PCM composite is expected to serve as an energy efficient candidate for achieving good thermal storage capabilities and structural integrity through passive cooling in buildings. Ó 2020 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 2nd International Conference on Recent Advances in Materials & Manufacturing Technologies.
1. Introduction It is an undeniable fact that energy is the prime mover of human life. Fossil fuels are the main source of energy in the world at present. Since fossil fuels are limited and their formation takes a long time, conservation of fossil fuels, through efficient utilization, is of utmost importance for any country to sustain in the long run. Moreover, environmental pollution due to over exploitation of fossil fuels is also a matter of concern throughout the world. Hence, serious research efforts are made in the field of renewable energy ⇑ Corresponding author. E-mail address: [email protected] (R. Parameshwaran).
resources. Also, it is imperative to note that most economies have formulated their policies to promote usage of technologies based on renewable energy sources. Solar energy is the primary energy source, which, abundantly is available for the whole year and its energy received by the planet earth, as per one estimate, is 10,000 times the entire earth’s energy demand. This energy resource can be captured through a thermal storage medium like phase change material (PCM) thus cutting down, drastically, the active energy consumption through HVAC systems in buildings. This could be made possible through incorporation of PCMs in floors, walls and ceilings of building and satisfy all dimensions of sustainable development including the social, economic and
https://doi.org/10.1016/j.matpr.2019.12.356 2214-7853/Ó 2020 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 2nd International Conference on Recent Advances in Materials & Manufacturing Technologies.
Please cite this article as: V. Vinayaka Ram, R. Singhal and R. Parameshwaran, Energy efficient pumpable cement concrete with nanomaterials embedded PCM for passive cooling application in buildings, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.356
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environmental dimensions. PCM can absorb and release heat during phase changing process and when incorporated into concrete, will serve as passive thermal regulator of indoor temperature. As a principle, for PCM to function as a thermal regulator, its phase transition temperature should lie in the vicinity of expected ambient room temperature [1]. It has been reported that PCM possess high energy storage density and temperature variation attenuating capacity. Even though the construction material behaviour becomes complex with PCM inclusion, it has been found that the resulting composite can be used in light weight construction and non-load bearing applications with advantage. Also, PCM is a latent heat storage medium which occupies less volume when compared to sensible thermal storage media [2]. Though PCM appears to be a superior alternative among others, it leads to different complications when it is included in building elements. The problems pertain to corrosion, leakage and compatibility with the concrete. Performance of PCM based building material heavily depend on the incorporation method, sequence of mixing, curing methodology and the type of PCM being used. Many researchers have identified three methods of incorporating PCM with concretes namely the direct mixing method, capsule method and immersion method [3,4]. Phase change materials (PCMs) can be broadly classified as organic, inorganic and eutectic. Organic materials include Paraffin and non-paraffins. Paraffins have chain like structure, which releases energy. The length of chain is an indication of latent heat of fusion and melting points. Melting point temperature for paraffins usually falls in the range of 12 °C to 71 °C. Apart from high latent heat, paraffins are known for their non-corrosive nature and are free from sub-cooling phenomenon. Paraffins are cost effective, reliable and chemically stable. However, they suffer from limitations such as low thermal conductivity, incompatibility with plastics, tendency to slip away from the matrix and high volume changes [5–7]. Non-Paraffins, like esters, glycols, fatty acids, usually possess exclusive characteristics, which provide multiple options to the user. These are gaining popularity due to high latent heat, absence of phase separation tendency and low super cooling characteristics. However, non paraffins are expensive than the paraffins and flamable, limiting their application for low temperature ranges only [5–7]. Inorganic PCMs were also gaining popularity due to their affordability. These PCMs have strikingly different properties when compared with their organic counterparts with regard to their tendency to exhibit high latent heat per unit mass and high thermal conductivity. The main drawback of these PCMs is that they exhibit in-congruent phase change process and also these PCMs are quite expensive than the organic PCMs [5–7]. Phase change materials can be incorporated in construction materials in multiple ways namely through direct mixing, dipping into liquid PCM, adding in the form of encapsulated micro and macro capsules etc. Direct mixing involves mixing PCM and construction material in appropriate proportions. Dipping into PCM is another way where in the PCM is adsorbed into a porous substrate. Encapsulation involves covering PCM with polymeric shells to prevent their leakage during phase change process. PCMs can be micro-encapsulated or macro-encapsulated. Micro encapsulation involves covering PCM particles at micron level with polymers. Macro encapsulation involves confining the PCM in a container appropriate to the construction process and element being constructed. Shape stabilized PCMs and form stabilized PCMs are other viable alternatives for inclusion into construction materials when the thermal stability issues arise [8–9].
Direct incorporation technique involves incorporation of the PCM directly into the concrete mix. It is undoubtedly the most practical and least expensive method. However, its successful application depends on the way the PCM is integrated with the mix without interfering the hydration process and affecting the strength of the mortar-aggregate bonding in the concrete. Also, there shouldn’t be any significant reaction happening between the PCM and either the components of the mix or the products of hydration [10–12]. Immersion technique involved dipping the cement concrete blocks directly into PCM. The process is quite flexible and can range from an automated continuous production line to a simple and relatively inexpensive batch process. Studies have indicated that this process is more expensive than the direct incorporation method [10–12]. Encapsulation can be treated as a variation of the direct incorporation process in which the PCM is fed into the mix in encapsulated form. The choice of the shell material used to make the encapsulated PCM is crucial since it must not react with either the PCM or the concrete, must demonstrate reasonably good heat transfer properties and shall withstand the rigours of processes involved like manufacturing, transport, construction and use. Currently, this procedure looks to be too expensive. However, the development of a large market for PCM concrete would justify further research into improving the feasibility of this process which could possibly be the best route to direct incorporation [10–12]. In the present research work, taking the clues from the literature review being carried out, an attempt has been made with an objective of developing and testing the copper-titania (Cu-TiO2) hybrid nanoparticles impregnated non paraffin based organic PCM embedded concrete material for achieving indoor temperature regulation through passive cooling and thermal storage. The major reasons for preferring organic non-paraffin are high latent heat of fusion and relatively low inflammability. Also, the melting point of the chosen PCM (lauryl alcohol) is very close to the ambient room temperature. 2. Study Methodology: With a view to ensure the required strength, pumpability and thermal storage properties for the proposed pumpable cement concrete embedded with hybrid copper titania nanoparticlesbased Phase Change Material (PCM) for passive cooling of buildings, this research work is being carriedout in 7 different stages as depicted in Fig. 1. Each of the listed stages are detailed in the subsequent sections. All the stages are self explanatory in nature 3. Results and discussions Experimental investigations were carried out as outlined in the methodology flow chart presented in art 2.0. Details of all the investigations are presented in the following sections along with critical discussions. 3.1. Stage 1 This stage involved preparation of standard 15 cm 15 cm 15 cm Plain Cement Concrete (PCC) cube samples for a design characteristic compressive strength of 20 MPa (M20 mix design) with varying proportions of ingredients. A slump of 75 mm (within the range of 50–100 mm slump for pumpable concrete) was also targetted during the mix design. Concrete mix included the following ingredients:
Please cite this article as: V. Vinayaka Ram, R. Singhal and R. Parameshwaran, Energy efficient pumpable cement concrete with nanomaterials embedded PCM for passive cooling application in buildings, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.356
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Fig. 1. Research Methodology Stages.
Cementitious materials: 53 Grade Ordinary Portland Cement (OPC), Class F flyash obtained from Vijayawada thermal power station (India) and Ground Granulated Blast Furnace Slag (GGBS) Fine aggregates (Crusher fines confirming to Zone 1 gradation as per IS 10262: 2009) Coarse Aggregates with nominal maximum size of 10 mm Potable water for mixing and curing Lignosulphate based super plasticiser to achieve the adequate workability, viscosity and slump retention capability. Different combinations of cementitious materials (cement, flyash and GGBS) were being tried while keeping the total cementi-
tious components at 548 kg/m3. Also the total of fine and coarse aggregates is fixed at 1600 kg/m3 and different permutations of Coarse and fine aggregate ratios have also been tried to optimise the same. Water to Cement (W/C) was kept constant at 0.45, while the Super Plasticiser was fixed at 0.7% by weight of cement. The mixes with reference code numbers ranging from 101 to 118 have been tried and for each code, 6 samples have been prepared. Three samples were used for finding 7-day strengths while the other 3 samples were used for finding 28-day strengths. All the samples had slumps in the range of 50–100 mm and also had reatined the slumps for almost 1 h after mixing, thus satisfying the requirements of pumpable concrete. Saturated Surface Dry (SSD) aggregates were only used to prevent any loss of water from
Please cite this article as: V. Vinayaka Ram, R. Singhal and R. Parameshwaran, Energy efficient pumpable cement concrete with nanomaterials embedded PCM for passive cooling application in buildings, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.356
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the concrete. All the tried mix proportions have been summarised and presented in Table 1 for ready reference. Cube samples, demoulded after 24 h, were cured in water, with 50% of the samples being cured for 7 days and the rest 50% samples being cured for 28 days. Further, they were tested with a 200 kN strain controlled compression testing machine (CTM). To verify the repeatability and reproducibility of the experiments, 3 samples each for 7day and 28-day curing, were tested and the results are summarised and presented in Table 2.
3.2. Stage 2: This stage involved the synthesis and characterization of ZnO nanoparticles and Cu-TiO2 hybrid nanoparticles using sol–gel process. For the preparation of ZnO nanoparticles, the precursor solution used was Zinc acetate and NaOH aqueous solution was employed as the reducing agent on a hot plate magnetic stirrer, with 350 RPM and 55 °C until nanoparticles were formed in the aqueous medium. The synthesis of Cu-TiO2 hybrid nanoparticles involved more rigorous process. Titanium dioxide and cupric nitrate were used as precursors during this process. In addition, Polyvinyl Pyrolidone aqueous solution was used as stabilising agent. Sodium borohydride and ascorbic acids were employed as reducing agents during the reaction phase. The complete process is depicted through Fig. 2 for more clarity. Particle size analysis of ZnO particles, as presented in Fig. 3, revealed that the size was not in nanoscale range. Hence, investigations with ZnO particles was not carried out further and the work was continued with Cu-TiO2 hydrid nano particles. The as synthesised Cu-TiO2 hybrid particles were subjected to the following characterisation to establish the suitability of these particles for the intended use. Field Emission Scanning Electron Microscope (FESEM) and Energy-dispersive X-ray spectroscopy (EDX) studies Fourier Transform Infrared Investigations (FTIR) X ray Diffraction (XRD)
3.2.1. FESEM and EDX studies on Cu-TiO2 hybrid nanoparticles FESEM provides surface morphology and elemental information with the capability of providing the magnifications ranging from 10x to 300,000x. In addition, this instrument has the capability to
Table 2 7-day and 28-day characteristic compressive strengths (MPa) of reference samples. Mix code
Average compressive strengths of 7day cured samples (MPa)
Average compressive strengths of 28-day cured samples (MPa)
101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118
20 20.5 19 24.5 26 24 22.5 21.8 21.7 17.5 16.7 16.1 22.8 21.7 21.1 19.8 20.1 20.4
28.1 29.7 25.5 34.8 35.5 33.1 31.8 31.1 33.4 26.8 25.3 26.1 31.2 30.4 30.9 27.9 28.1 27.4
provide the elemental composition of the given sample through EDX analysis. During the current study, both FESEM and EDX investigations were carried out on the synthesised hybrid Cu-TiO2 nanoparticles. The FESEM micrograph is presented in Fig. 4. The size marked on the micrograph confirms the particles being formed in nano dimension. The EDX analysis, presented in Fig. 5 and Table 3 confirms the presence of both Cu and TiO2 particles.
3.2.2. Fourier Transform Infrared investigations (FTIR) With a view to understand the chemical compatibility of PCM with cement as well as hybrid Cu-TiO2 nanoparticles, Fourier Transform Infra-Red (FTIR) spectrums were obtained for pure cement, cement + PCM combination and PCM + Cu-TiO2 hybrid nanoparticle combination. These spectrums are presented through Figs. 6–8. A close observation of FTIR spectrum of Ordinary Portland Cement (OPC) with that of combined OPC and PCM reveals that there are no decipherable differences in peaks, except a few changes observed near the wave number 3000 cm 1. This confirms that the PCM is not causing any major changes to cement properties when they are together. However, spectrogram of OPC plus PCM revealed a major absence of peak at a wave num-
Table 1 Reference M30 pumpable concrete mix proportions. Mix code
Cement
Fly ash
GGBS
Fine aggregate
Coarse aggregate
W/C
SP
No. of samples
101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118
333 333 333 333 333 333 333 333 333 215 215 215 215 215 215 215 215 215
215 215 215 0 0 0 107.5 107.5 107.5 333 333 333 0 0 0 166.5 166.5 166.5
0 0 0 215 215 215 107.5 107.5 107.5 0 0 0 333 333 333 166.5 166.5 166.5
835 960 1120 835 960 1120 835 960 1120 835 960 1120 835 960 1120 835 960 1120
765 640 480 765 640 480 765 640 480 765 640 480 765 640 480 765 640 480
0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45 0.45
0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7% 0.7%
6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6
Please cite this article as: V. Vinayaka Ram, R. Singhal and R. Parameshwaran, Energy efficient pumpable cement concrete with nanomaterials embedded PCM for passive cooling application in buildings, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.356
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Fig. 2. Synthesis of Cu-TiO2 hybrid nanoparticles.
Fig. 3. Particle Size Analysis for ZnO nanoparticles.
ber 2700 cm 1 which was available in the spectrum of pure PCM. This aspect, which needs further probe, is left for future investigation.
However, the FTIR spectrograms, obtained for pure PCM and PCM + hybrid nanoparticles, clearly indicate that there are no observable differences in peaks or signatures, thus proving that
Please cite this article as: V. Vinayaka Ram, R. Singhal and R. Parameshwaran, Energy efficient pumpable cement concrete with nanomaterials embedded PCM for passive cooling application in buildings, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.356
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sion was taken to take this combination forward for further investigations.
Fig. 4. FESEM image for Cu-TiO2 hybrid nanoparticles.
3.2.3. X-ray diffraction (XRD) studies on Cu-TiO2 hybrid nanoparticles XRD studies are usually carried out to check the presence or absence of crystalline phase in the material being investigated. This can also be extended to perform Quantitative phase analysis (QPA) to quantify the crystalline phase. Further, XRD studies can reveal the presence of amorphous phase in the material too. XRD studies were carried out for Cu-TiO2 hybrid nanoparticles durng the current study and the difraction patterns were presented in Fig. 9. The formation of coppertitania hybrid nanoparticles was confirmed through the sharp and intense XRD peaks obtained, which were ascribed to their lattice planes. The presence of copper nanoparticles on the surface of titania particles as justified from the FESEM analysis is in good agreement with the XRD results obtained. That is, the sharp peaks corresponding to copper and titania were obtained due to the scattering at interplanar spacing and signified the high crystalline nature of the Cu-TiO2 hybrid nanoparticles. The peak intensity obtained at planes (111), (200) and (220) were in good agreement with the JCPDS standards [13] and with the similar results in [14]. 3.3. Stage 3 - selection of PCM for the intended application and characterization: After a thourough study of many PCMs with regard to the following properties, Lauryl alcohol (C12H26O) was chosen for the current study as PCM.
Fig. 5. EDX analysis for Cu-TiO2 hybrid nanoparticles.
Table 3 Elemental composition for Cu-TiO2 hybrid nanoparticles from EDX. Element
Wt (%)
Atomic Wt (%)
O Ti Cu
40.91 38.65 20.44
69.38 21.89 8.73
there is no active chemical interaction happening between them. Overall, it was observed that the chemical interaction between the nanoparticles, cement and PCM is minimal and hence the deci-
Thermo physical properties like fusion temperature, latent heat of fusion, high specific heat, thermal conductivity, congruent phase transition and low volumetric capacity change; Chemical properties like non corrosiveness, chemical stability on long run, non toxic, non explosive, non flammable and good molecular bonding capability Economic point of view 3.4. Stage 4 - trials with PCM, hybrid nanomaterial with varying concrete mix sequencing and finalising the sequence for further experimentation: Mix proportion numbered 109 was chosen as the reference mix after ensuring the adequate compressive strength while fulfilling
Fig. 6. FTIR Spectrum for Ordinary Portland Cement.
Please cite this article as: V. Vinayaka Ram, R. Singhal and R. Parameshwaran, Energy efficient pumpable cement concrete with nanomaterials embedded PCM for passive cooling application in buildings, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.356
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Fig. 7. FTIR spectrum for the combination of ordinary portland cement and 1-dodecanol PCM.
Fig. 8. FTIR spectrums for Cu-TiO2 hybrid nanoparticles and 1-dodecanol PCM mix and PCM alone.
other target requirements, namely, pumpability and balanced use of flyash and GGBS as cementitious ingredients. After trying multiple mix sequences, a sequence was chosen based on the fact that it resulted in minimum PCM leakage when compared with other trials. A 6-stage sequence, depicted through Fig. 10, was followed throughout this phase of the work.
mixes were numbered with codes of 119 to 133 and cured. Details of these mixes is presented in Table 4 for ready reference.
3.5. Stage 5 - preparation and testing of modified cement concrete cube specimens with varying percentages of PCM and Cu-TiO2 hybrid nanoparticles as admixtures to the finalized reference PCC:
All the samples, cured for 7 days and 28 days in water, were tested under strain controlled 2000 kN capacity compression testing machine. The samples were then tested in the direction, orthogonal to the direction of casting the sample to ensure that the sample is tested along its weakest plane. The average 7-day and 28-day characteristic compressive strengths obtained from 3 tested samples are summarised and presented in Table 5. All the samples are grouped in to 3 batches with varying W/C ratios. The mix proportions numbered 119, 124 and 129, cast with 0% PCM in batches I, II and III respectively, were treated as refer-
Taking the mix proportion numbered 109 as the base proportion, 15 combinations of new proportions were worked out by trying the W/C ratios from 0.35 to 0.45 with increments of 0.5%. Also PCM (by percent weight of cement) was varied from 0% to 20% with 5% increments. 3 samples for 7 days and 3 samples for 28 day investigations were casted for each of the combinations. These
3.6. Stage 6 - establishing the optimum combinations of concrete ingredients, PCM and hybrid nanoparticles based on cube compressive strength:
Please cite this article as: V. Vinayaka Ram, R. Singhal and R. Parameshwaran, Energy efficient pumpable cement concrete with nanomaterials embedded PCM for passive cooling application in buildings, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.356
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Fig. 9. XRD diffraction patterns for Cu-TiO2 hybrid nanoparticles.
Fig. 10. Sequence followed for hybrid nanoparticles-based PCM embedded cement concrete sample preparation.
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V. Vinayaka Ram et al. / Materials Today: Proceedings xxx (xxxx) xxx Table 4 Trial mixes with changing W/C ratios and PCM. Mix number
Cement (kg/m3)
Fly ash (kg/m3)
GGBS (kg/m3)
Fine aggregate (kg/m3)
Coarse aggregate (kg/ m3)
W/ C
BASF SP (% by weight of cement)
Cu-TiO2 hybrid nanoparticles (% by weight of cement)
PCM (% by weight of cement)
No. of samples
119 120 121 122 123 124 125 126 127 128 129 130 131 132 133
333 333 333 333 333 333 333 333 333 215 215 215 215 215 215
107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5
107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5 107.5
1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120 1120
480 480 480 480 480 480 480 480 480 480 480 480 480 480 480
0.35 0.35 0.35 0.35 0.35 0.40 0.40 0.40 0.40 0.40 0.45 0.45 0.45 0.45 0.45
0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7
0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05
0 5 10 15 20 0 5 10 15 20 0 5 10 15 20
6 6 6 6 6 6 6 6 6 6 6 6 6 6 6
Table 5 7-day and 28-day Characteristic Compressive Strengths of samples with nanoparticles and PCM. Batches
Sample number
7 day (Average)
28 day (Average)
Batch I with W/C = 0.35
119 120 121 122 123 124 125 126 127 128 129 130 131 132 133
27.8 24.7 21.6 18.5 13.2 24.5 22.6 18.4 15.1 9.1 21.9 17.9 14.1 9.8 6.8
40.2 38.1 31.5 28.0 22.2 38.9 35.4 26.7 24.8 17.8 34.1 27.2 23.8 16.5 12.1
Batch II with W/ C = 0.40
Batch III with W/ C = 0.45
ence samples representing each one of the batches. It can be observed from Table 5 that the increasing PCM has always resulted in considerable drop in characteristic compressive strength. However, since the target strength was 20 MPa (M20 concrete), there was a flexibility to increase the PCM percentage. Despite having more than required compressive strength, the samples with 10% and above percentage of PCM were observed to be profusely leaking, thus making them unacceptable for further consideration. Taking these points in consideration, mix number 120 with an average characteristic compressive strength of 38.1 MPa has been chosen as the ideal mix for the intended application. 3.7. Stage 7: Finalizing the specifications to develop pumpable cement concrete embedded with hybrid copper titania nanobased PCM for passive cooling of Buildings:
Class F Fly ash = 107.5 kg/m3 GGBS = 107.5 kg/m3 Fine Aggregates = 1120 kg/m3 Coarse Aggregates = 480 kg/m3 W/C ratio = 0.35 Super Plasticizer = 0.7% by weight of cement 1-dodecanol PCM by weight of cement = 5% Slump observed for the chosen composition = 76 mm
A small scale laboratory based pilot study was also conducted with the finalised modified concrete mix and the initial results were found to be quite encouraging. The PCM based modified concrete wall built in the laboratory model could reduce the heat flow substantially. However, more investigations are planned to confirm and validate these results and hence the details are not presented in this article 4. Conclusions and recommendations A novel sequence of integrating the Cu-TiO2 hybrid nanoparticles-based PCM in to cement was tried and the trials have proved that this sequence has resulted in minimum leakage of PCM. However, complete leakage prevention could not be realized during the current investigations, indicating the need of trying with encapsulated PCMs. A maximum of 5% Lauryl Alcohol PCM by weight of cement is recommended in the mix due to its tendency to reduce the strength with additional PCM content. The mix presented in section 3.7 is found to be satisfying both strength and thermal storage capacities. The small scale laboratory pilot study indicated a great promise towards achieving the end objectives of the study being carried out. 5. Scope for future work:
After a comprehensive characterisation of individual ingredients and the concrete, the specifications for the Pumpable Cement Concrete embedded with copper-titania hybrid nanoparticlesbased PCM were finalised during the present research activity. The mix specification is as follows: Mix Number: 120 Characteristic Compressive Strength = 38.1 MPa (after 28 days of curing) Leakage: Partial leakage was observed Cement (53 grade OPC) = 333 kg/m3
Encapsulated PCMs with enhanced heat storage capacity can be investigated in the similar manner. Large scale building model can be built with the proposed mix design and investigated.
Acknowledgement Authors thankfully acknowledge central analytical laboratory and concrete laboratory, BITS Pilani, Hyderabad campus for their
Please cite this article as: V. Vinayaka Ram, R. Singhal and R. Parameshwaran, Energy efficient pumpable cement concrete with nanomaterials embedded PCM for passive cooling application in buildings, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.356
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Please cite this article as: V. Vinayaka Ram, R. Singhal and R. Parameshwaran, Energy efficient pumpable cement concrete with nanomaterials embedded PCM for passive cooling application in buildings, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.12.356