Description:FORM 2
THE PATENT ACT, 1970
(39 of 1970)
COMPLETE SPECIFICATION
(See section 10, rule 13)

TITLE
PHASE CHANGE MATERIAL ENHANCED FOAM CONCRETE AS THERMAL INSULATION BUILDING MATERIAL

INVENTORS
MADHAVAN, Mini, K, Citizen of India
DORA Sushreeta, Citizen of India
Department of Civil Engineering
Amrita School of Engineering, Amrita Viswa Vidyapeetham
Coimbatore-641112
TamilNadu, India

APPLICANT
AMRITA VISHWA VIDYAPEETHAM
Amrita School of Engineering,
Coimbatore Campus,
Coimbatore-641112,
TamilNadu, India

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

PHASE CHANGE MATERIAL ENHANCED FOAM CONCRETE AS THERMAL INSULATION BUILDING MATERIAL
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] None.
FIELD OF THE INVENTION
[0002] The invention generally relates to construction and building materials and in particular to foam concrete mixture incorporated with phase change material for enhancing the thermal storage in buildings.
DESCRIPTION OF THE RELATED ART
[0003] The construction industry, which represents the primary sector for energy consumption, consumes over 40% of the total energy utilized globally. To improve thethermal comfort in buildings, the usage of air conditioners and othermechanical devices continues to increase in the domestic sector. Heating, ventilation and air conditioning (HVAC) systemsaccount for 38 % of buildings energy consumption, which plays a majorrole in climate change and contributes to one third of global energyconsumption and one quarter of CO2 emissions from the residential sector. Different energy saving solutions were investigated andimplemented in practical fields to lower building energy consumption and to maintain the thermal balance. These energy saving methods are mainly focused on building envelopes, central heating/cooling, and the development and use of new energy sources. Therefore, it is a major concern for researchers to enhance energy storage capabilities by adopting thermal insulation in buildings to meet building energy demand.
[0004] The usage of thermal storage materials in construction can meet the target of United Nations sustainable development goals 2030 (SDG 7) by addressing this global issue by providing reliable and affordable sources of energy to maintain the environmental sustainability. Researchers have addressed this issue by using highly porous building materials with lower thermal conductivity, thus minimizing the cost of HVAC systems.Phase change materials (PCMs) are a specific type of material with alow melting point and a high latent heat of fusion. During thephase transition, they release a significant amount of thermal energy. Identification of suitable PCMs for successful application inbuildings depends on thermal, chemical, and economic factors. It is reportedthat PCMs are particularly useful for thermal energy storageapplications because of economic feasibility, high latent heatstorage capacity, thermal stability, non-toxicity, low heat of vaporizationin the liquid state, and the ability to be integrated with cementitious materials. Cement based furnace slag/capric acid shapestabilized PCMs can be utilized as thermal energy storage for buildingapplications [14]. Apart from its advantages, these PCMs are prone toleakages when embedded in construction and therefore require specificpackaging methods, which can be carried out through adsorption, microencapsulation or impregnation.
[0005] Foam concrete is a mixture of cement sand slurry with protein based or synthetic foam and is highly porous with low density and provides effective thermal insulation. The strength of foam concrete can be enhanced by the addition of mineral admixtures and industrial waste. The sustainability approach in concrete is achieved by theaddition of glass powder, waste plastics and crumb rubber. Various strength and durability properties were assessed and reported that the addition of these waste materials can lead to an eco-friendly solution for the disposal of waste with a proper utilisation. It is also observed that a large quantity of nano silica content can lead to aggregation and deteriorate some characteristics of the concrete by decreasing the hydration rate and setting time. The thermal storage capacity of PCMs in foam concrete for building applications and the thermoregulation performances of solar energy has been investigated. US20130298991A1 discloses methods of producing phase change aggregates including particulate phase change material. US20190359871A1 describes thermal regulating building materials and other construction components containing phase change materials. However, there is still a need for improved foam concrete mixtures with better mechanical properties, durability, and thermal insulation in buildings.

SUMMARY OF THE INVENTION
[0006] The present subject matter discloses a foam concrete composition for use as construction material providing thermal insulation in buildings.
[0007] According to one embodiment of the present subject matter, the foam concrete mixture comprises a mixture of phase change material (PCM), cement and M-sand. The mix ratio of cement and M-sand is 1:2. The PCM comprises of capric acid-ethyl alcohol and expanded vermiculite (CA-EA/EV) having capric acid to expanded vermiculite proportion of 55% by weight. PCM is mixed with the cement and M-sand and the PCM 5% by weight of M sand is added as replacement to M-sand. Nano silica at 5% and coir fiber at 2% by weight of cement are added to obtain the foam concrete mixture.
[0008] According to some embodiments, the capric acid-ethyl alcohol is impregnated into the porous and multi layered structure of expanded vermiculite. The nano silica has a particle size of 50-200nm. The coir fiber improves tensile strength and reduces shrinkage due to inclusion of EV. The particle size of M-sand is in the range of 0.09 mm to 0.30mm. The foam concrete mixture shows latent heat capacities of 69.16 J/g and 43.90 J/g for heating and cooling, respectively.
[0009] According to some embodiments, the coir fiber acts as a crack filler in the concrete mix and fills the voids and enhances the flexural strength of the mix. The compressive strength of the foam concrete mixture is more than 5.5 MPa.The nano silica in the foam concrete mix fills the void and reduces the capillary water absorption of the mix.The concrete mix has large number of pores and leads to lower heat transfer and lower thermal conductivity. The foam concrete mix has a thermal conductivity in the range of 0.122W/m-K to 0.129W/m-K.
[0010] According to another embodiment, a process for preparation of foam concrete mixture for use as construction material and for thermal insulation in buildings is disclosed. The process includes blending capric acid (CA) and ethyl alcohol (EA) for approximately an hour using stirring to form a CA/EA liquid mixture. The method includes heating expanded vermiculite (EV) at 800°C for 2hours in an oven. The method next includes releasing CA/EA mixture into a conical flask containing oven dried expanded vermiculite gradually, using a vacuum pump for 1 hour. The method further includes allowing dissipation of CA/EA mixture into layers of vermiculite by vacuum impregnation method for 1 hour to obtain a CA/EV composite, wherein the proportion to CA to expanded vermiculite is 55%. The method further comprises drying the CA/EV composite for 3 hours at 20°C to obtain a CA-EA/EV phase change material (PCM).
[0011] In some embodiments, the method includes mixing the PCM, cement and M-sand with water and foaming agent. The ratio of cement to sand is 1:2 and PCM taken is 5% by weight of M-sandas replacement to M-sand. The method includes adding5% nano silica and 2% coir fiber by weight of cement to obtain the PSC 5% foam concrete mix. The method further includes demolding and curing in water for 28 days to obtain the required foam concrete mixture specimen. The EV acts as a PCM carrier due to its highly porous nature and multi-layered structure. The coir fiber improves tensile strength and reduces the shrinkage that occurs due to the inclusion of EV. The coir fibre is dried after soaking in NaOH solution for three hours followed by 5 hours of oven drying at 90°C and cooling to room temperature to reduce the bio-degradable nature of coir fiber. The nano silica is added to improve strength of the foam concrete.
[0012] This and other aspects are described herein.

BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The invention has other advantages and features, which will be more readily apparent from the following detailed description of the invention and the appended claims, when taken in conjunction with the accompanying drawings, in which:
[0014] FIG. 1 illustrates the steps involved in the preparation of foam concrete mixture.
[0015] FIG. 2 shows a schematic representation of the preparation procedure for the foam concrete mixture.
[0016] FIG. 3shows the DSC analysis of CA-EA/EV composite PCM.
[0017] FIG. 4illustrates the comparison of compressive strength of PSC foam concrete mix and the other mixtures.
[0018] FIG. 5 shows the flexural performance of various composite mixes.
[0019] FIG. 6 shows the rate of water absorption of different mixtures by immersion test.
[0020] FIG. 7illustrates the rate of water absorption of different mixtures by capillary test.
[0021] FIG. 8 shows the comparison of thermal conductivity (k) for 5 % and 10 % of EV, PCM, and PSC foam concrete panels.
[0022] FIG. 9 illustratesthe TGA for the control, PCM-5 %, and PSC-5 % foam concrete mixtures.
[0023] FIG. 10 shows the microstructural composition of the developed PCM sample obtained by scanning electron microscopy.
[0024] FIG. 11 illustrates the microstructural analysis of the control mix, EV-5 %, PCM-5 %, and PSC-5 % foam concrete samples obtained by scanning electron microscopy
[0025] FIG. 12 shows the elemental composition of PSC-5 % foam concrete sample obtained by energy dispersive X-ray spectroscopy.
[0026] FIG. 13 shows the Ca/Si ratio variation between the different composite mixtures
[0027] FIG. 14 showsDSC analysis for the control, PCM-5 %, and PSC-5 % foam concrete mixtures.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0028] While the invention has been disclosed with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from its scope.
[0029] Throughout the specification and claims, the following terms take the meanings explicitly associated herein unless the context clearly dictates otherwise. The meaning of "a", "an", and "the" include plural references. The meaning of "in" includes "in" and "on." Referring to the drawings, like numbers indicate like parts throughout the views. Additionally, a reference to the singular includes a reference to the plural unless otherwise stated or inconsistent with the disclosure herein.
[0030] The following are the abbreviations and nomenclature of materials and concepts which are mentioned in the examples and the embodiments. PCM- Phase Change Material, CA-Capric Acid, EA-Ethyl Alcohol, PPC-Portland Pozzolana Cement, M sand-Manufactured sand, EV-Expanded Vermiculite, C-Control foam concrete sample. EV-5%, EV-10%, EV-15%, EV-20%-Replacement of M sand with 5%,10%,15%, and 20% by wt. of EV in foam concrete mix. PCM-5%, PCM-10%-Replacement of M sand with 5% and 10% by wt. of PCM in foam concrete mix. PSC-5%-Foam concrete mix with addition of 5% nano silica and 2% coir fiber by wt. of cement added with PCM5% as replacement to M sand. PSC-10% Foam concrete mix with addition of 5% nano silica and 2% coir fiber by wt. of cement added with PCM10% as replacement to M sand. RCPT-Rapid Chloride Penetration Test. UPV-Ultrasonic Pulse Velocity. C-S-H Calcium silicate hydrate. C - H Calcium hydroxide.
[0031] The present subject matter describes a foam concrete composition for use as construction material and for providing thermal insulation in buildings.
[0032] The invention in various embodiments discloses a foam concrete composition for use as construction material providing thermal insulation in buildings. The foam concrete mixturecomprises a mixture of phase change material (PCM), cement and M-sand. The PCM comprises capric acid (CA)-ethyl alcohol (EA) and expanded vermiculite (CA-EA/EV). The proportion of capric acid (CA) to expanded vermiculite (EV) is 55% by weight. PCM is mixed with the cement and the M-sand and, the PCM added is 5% by weight of the M sand as replacement to M-sand. The foam concrete mixture comprises nano silica by 5% and coir fiber by 2% by weight of cement. The CA-EA/EV based PCM with added nano silica and coir fiber is denoted as PSC. The foam concrete mix with PCM replacing 5% by weight of M sand is denoted as PCM-5%. The foam concrete mix with addition of 5% nano silica and 2% coir fiber by weight of cement may be denoted as PSC-5%. According to one embodiment, the capric acid and ethyl alcohol may be impregnated into the porous and multi-layered structure of expanded vermiculite.
[0033] According to various embodiments, the particle size of nano silica added to the foam concrete mix is 50-200 nm. The particle size of M sand may be in the range of 0.09 mm to 0.30mm.The addition of coir fibre in the foam concrete mix is configured to improve tensile strength and reduces shrinkage due to the inclusion of EV. The coir fiber acts as acrack filler in the concrete mix and fills the voids and enhances the flexural strength of the mix. The nano silica in the foam concrete mix fills the void and reduces the capillary water absorption of the mix.
[0034] According to one embodiment of the invention, the foam concrete mixture shows latent heat capacities of 69.16 J/g and 43.90 J/g for heating and cooling, respectively.The foam concrete PSC mix has a compressive strength of more than 5.5 MPa, according to one embodiment of the invention. The foam concrete mix has large number of pores and leads to lower heat transfer and lower thermal conductivity.The foam concrete possesses a large number of pores due to the inclusion of foam. Further, the addition of EV, PCM and PSC into foam concrete develops a large number of pores. As a result, the panel becomes less compact, which leads to lower heat transfer through the panel and lower thermal conductivity. The thermal conductivity is reduced to 52.73% compared to that of normal concrete and acts as a thermal storage material in foam concrete wall panels, according to one embodiment of the invention. The foam concrete mix has a thermal conductivity of 0.129W/m-K, according to one embodiment of the invention.
[0035] According to one embodiment of the invention, a process 100for preparation of foam concrete mixture for use as construction material and for thermal insulation in buildings is disclosed. FIG. 1 shows the steps involved in the preparation of the foam concrete mixture. The process 100includes blending capric acid (CA) and ethyl alcohol (EA) for approximately an hour using a magnetic stirrer to form a CA/EA liquid mixture at 102. The process next includes heating expanded vermiculite (EV) at 800°C for 2 hours in an oven at 104. Heating is done to remove the moisture content developed during the storage of the material. The method includes releasing CA/EA mixture into a conical flask containing oven dried expanded vermiculite gradually using a vacuum pump for 1 hour at 106. A separating funnel containing the blended CA/EA is placed on the top of conical flask carrying oven-dried vermiculite. The conical flask is attached to a vacuum pump, and the valve is gradually opened to release the CA/EA mixture into the conical flask for 1 h. The method next includes allowing 108 penetration of CA/EA mixture in to layers of vermiculite by vacuum impregnation method for 1 hour to obtain a CA/EV composite, wherein the proportion to CA to expanded vermiculite is 55%. Due to the environmental temperature changes, CA cannot stay a longer period in the liquid stage, even though it starts melting at 32?C. But, when ethanol is added to the CA followed by a magnetic stirrer method, the liquid phase of the CA is retained. This allows the easy impregnation of CA into the vermiculite layers through the vacuum impregnation method. 100 % EA is dissipated after one hour of vacuum impregnation to obtain CA/EV composite, which is then collected in a flask.
[0036] The method next includes drying 110 the CA/EV composite for 3 hours at 20°C to obtain a CA-EA/EV phase change material (PCM). The PCM, cement and M-sand are mixed with water and foaming agent at 112. The cement to sand ratio is 1:2 and PCM taken is 5% by weight of M sand and is added as replacement to M-sand. 5% nano silica and 2% coir fiber by weight of cement is added to obtain the PSC 5% foam concrete mix at 114. The coir fiber is surface dried after soaking in NaOH solution for three hours to reduce the biodegradable nature of the coir fiber and to enhance its bonding with concrete. The coir fiber is then oven dried at90°C before the fiber is cooled to room temperature. The developed PSC foam concrete mix is demolded and placed in water for 28 days of curing and taken out to obtain the foam concrete at 116. The EV acts as a PCM carrier due to its highly porous nature and multi-layered structure. The coir fiber improves tensile strength and reduces the shrinkage that occurs due to the inclusion of EV. The nano silica is added to the foam concrete mix to improve strength of the foam concrete mixture.
[0037] Foam concrete mix with CA-EA/EV based PCM with added nano silica and coir fiber combination (PSC) is prepared by the replacement of fine aggregate (M sand).PCM enhanced foam concrete mixture showed improved mechanical, hydration, durability, and thermal characteristics. In comparison to the control foam concrete and PCM foam concrete mixes, the addition of nano silica and coir fiber to foam concrete mixtures (PSC-5%) shows improved strength and shrinkage properties. These improved properties are attributed to the pozzolanic activity of nano silica and the bridging effects resulting from the fiber to micro cracks. The PSC-5% foam concrete mixture has high thermal resistance and possesses improved heat storage capacity, which ensures better and energy efficient solutions to providing thermal comfort in buildings. This results in a reduction of HVAC system loads and energy consumption in buildings and thus, a promising, sustainable and economic long-term thermal solution in building sector.
[0038] EXAMPLES
[0039] Example 1: Materials and methods for preparation of phase change material and foam concrete:
[0040] Phase change material (PCM): PCM was developed using capric acid (CA) also called decanoic acid with a molar mass of 172.268 g/mol and a concentration of greater than 98%, and ethyl alcohol.
[0041] Materials used for Foam concrete: Portland Pozzolana Cement (PPC) Grade 53 of Dalmia Cement (Bharat) Limited with standard consistency of 33 % and specific gravity of 3.08 is used for sample preparation. The fly ash-based cement with a 300 m2/kg fineness conforms with IS 1489 (Part 1 ) : 1991. Manufactured sand (M-sand), with a size of 300 µm or less and a specific gravity of 2.65 according to IS : 2386 ( Part III ) – 1963was utilized as fine aggregate for the preparation of the foam concrete specimen. The crushed M-sand was sieved through a 300 µm sieve and then dried for 12 h in the sun to remove the moisture content. The foaming agent is protein based and supplied by Altra Core chemical company. It is an ethoxylate vegetable protein extract. Expanded Vermiculite (EV) was used as the PCM carrier. The mineral vermiculite used is a hydrous phyllosilicate with excellent thermal conductivity, low bulk density, a relatively high melting point, excellent insulation properties and it is also chemically inert. A sieve shaker with an aperture of 300 µm was used to sieve vermiculite and was heated for 1 h at 800 ?C to achieve an exfoliated form with increased volume. The obtained EV was considered as a PCM carrier due to its highly porous nature and multilayered structure. Fine aggregate in the foam concrete was replaced with EV in varied percentages.
[0042] Coir fiber is used in foam concrete to improve tensile strength and reduce the shrinkage that occurs due to the inclusion of EV. To reduce the biodegradable nature of the coir fiber and to enhance its bonding with concrete, the fiber was surface dried after soaking in NaOH solution for three hours. This was followed by five hours of oven drying at 90 ?C before the fiber was cooled to room temperature. As foam concrete possesses low compressive strength due to voids, which can further be reduced due to the addition of the EV, nano silica is added to improve the strength. Nano silica with a particle size of 50–200 nm and 5% by weight of cement was incorporated as the filler to enhance the foam concrete mix characteristics.
[0043] Preparation of PCM (CA-EA/EV) composite:
[0044] The CA/EV composite PCM mixes are prepared using vacuum impregnation. Initially, specific percentages of capric acid (CA) and ethyl alcohol (EA) were blended for an hour using a magnetic stirrer. The expanded vermiculite (EV) was heated at 800 ?C for 2 h in the oven to remove the moisture content developed during the storage of the material. A separating funnel containing the blended CA/EA was placed on the top of a conical flask carrying oven-dried vermiculite. The conical flask was attached to a vacuum pump, and the valve was gradually opened to release the CA/EA mixture into the conical flask for 1 h. Due to the environmental temperature changes, CA cannot stay a longer period in the liquid stage, even though it starts melting at 32?C. But, when ethanol is added to the CA followed by a magnetic stirrer method, the liquid phase of the CA can be retained. This allows the easy impregnation of CA into the vermiculite layers through the vacuum impregnation method. 100 % EA was dissipated after one hour of vacuum impregnation, which was then collected in a flask. The developed CA/EV composite PCM was dried for 3 h at 20 ?C after beingvacuum impregnated for 1 h to produce the required PCM.
[0045] Preparation of foam concrete sample preparation and proportion of the foam concrete mix:
[0046] Foam concrete with a density of 1580 kg/m3 was prepared to cast the specimensrequired for testing. Wall panels of size45 cm × 30 cm × 1.8 cm, 5 cm cubes, and 10 cm diameter cylinders with 20 cm height were cast for various tests. A ratio of foaming agent to water of 1:30 was used to produce a foam density of 40 kg/m3. The cement and sand with a ratio of 1:2 and water to cement ratio of 0.5 were mixed for 2 to 5 min. Then, the foam was added slowly and mixed thoroughly for the preparation of foam concrete sample. The produced specimens were molded and then stored under ambient temperature for 24 h. Afterwards, the foam concrete samples were removed from molds and kept in water for a 28 day curing period.After curing, the samples were taken out of the curing tank and tested for various strength, durability and functional properties. FIG. 2 shows a schematic representation of the preparation procedure of the foam concrete mixture.
[0047] For the first phase sample preparation, M-sand was replaced with EV with a weight ratio of 0 %, 5 %, 10 %,15% and 20 % in the foam concrete mix, and a decrease in compressive strength was noted. Based on these test results, 5 % and 10 % PCM was substituted in place of M-sand in thefoam concrete mix in the second phase. Though the samples providedbetter thermal conductivity, a reduction in compressive strength was observed. Furthermore, to enhance the compressive strength of samples, which is reduced due to the addition of PCM as a replacement of M sand, in the third phase, 5 % nano silica and 2 % coconut fiber by cement weight were added to the second phase mixture. It was observed from the test results that along with strength, its durability and thermal properties were also enhanced.
[0048] Table 1 shows the percentage composition of different foam concrete mixtures used in the study.

Table1: Composition of Foam Concrete Mixtures Used

[0049] Example 2: Characterisation of PCM:
[0050] DSC analysis to examine the heat releasing and absorbing capacity of capric acid and the developed PCM was done. The DSC analysis of CA-EA/EV-PCM (Capric acid-Ethyl alcohol/Exapanded vermiculite) is shown in FIG. 3. The results revealed that the obtained PCM has a freezing point of 22.29 ?C and melting point of 32.47 ?C, with latent heat capacities of 115.82 J/g and 89.53 J/g for heating and cooling, respectively. These test outcomes confirm the efficiency of the developed PCM as a thermal energy storage material.
[0051] Example 3: Stability check of the developed PCM:
[0052] A set of CA-EA/EV PCM with mass fractions of 35 %, 40 %, 45 %, 50 %, and 55 wt% of CA to EV combinations were prepared and evaluated. The stability of these combinations was assessed by using a leakage test, where the combinations were placed in filter papers and kept in an oven for 2 h at 40 ?C. It was found that CA to EV of 55 wt% has the maximum absorption capacity, as no CA leakage was observed.
[0053] Example 4: Compressive strength of the foam concrete mix:
[0054] Based on the trial tests conducted with 5 % to 20 % EV in foam concrete, a significant reduction of 61.81 % and 67.18 % in strength compared to the control sample was observed with the addition of 15 % and 20 % of EV. This reduction in strength is attributed to the porous nature of EV particles. Accordingly, further studies were confined to 5 % and 10 % of EV and PCM foam concrete mixes. The EV and PCM incorporated foam concrete mixes showed a significant decrease in compressive strength compared to the control mix after 28 days of the curing period as shown in FIG. 4. This is due to the porous nature of EV and the waxy nature of PCM (CA/EA-EV), which provides a layer on the surface of an unhydrated concrete mix and creates a barrier for the cement hydration reaction. To compensate for the strengthreduction due to the addition of EV and PCM, 5 % of nano silica byweight of cement was added. The foam concrete is made up of foamincorporated cement slurry and is prone to shrinkage cracks. To avoidthese cracks and improve the tensile strength, 2 % of coconut fiber bycement weight is added to this mix (PSC).From FIG. 4 it is observed that the compressive strength of PSC mix is higher than that of PCM and EV foam concrete composite specimens. The increase in strength is due to the presence of nano silica, which reacts quickly in the presence of C-H over a long period to form C-S-H. After 28 days of curing PSC-5 %, PSC-10 % and PCM-5 % foam concrete specimens achieved compressive strengths of more than 5.5 MPa.
[0055] Example 5:Flexural strength of foam concrete mix:
[0056] The flexural performance of the various foam composite mixes, PSC-5 %, PCM-5 %, and PSC-10 % mixtures did not show significant variations in flexural strength from the control mixture as shown in FIG. 5. From the test results, it was observed that the addition of coconut fiber and nano silica in the PSC mixes contributes to the bridging of the micro cracks, fills the voids and thus improves the flexural strength compared to PCM mixtures.
[0057] Example 6: Rate of water absorption of PSC and PCM foam concrete mix:
[0058] The PSC and PCM foam concrete mix samples showed a reduction in water absorption by the immersion method shown in FIG. 6. Additionally, the EV foam concrete mixture exhibits higher water absorption relative to the control mix due to the porous nature of EV. The foam concrete mixtures with PCM had lower water absorption values due to the waxy texture of the PCM. The water absorption capacity of PCM-5 % and PSC-5 % was found to be reduced by 48.70 % and 25.36%, respectively, compared to the sample mix.FIG. 7 illustrates that the incorporation of PSC-5 % and PCM-5 % into the foam concrete mixture reduces the capillary absorption coefficient to 25.39 % and 43.62 %, respectively, compared to control mix at 1440 min. The inclusion of nano silica in the foam concrete mixture samples fills the voids and makes the sample more compact, which results in a reduction in capillary water absorption in the PSC foam concrete mix. Consequently, less water was absorbed by the PCM-5 % and PCM-10 % foam concrete mixes due to the waxy nature of PCM. EV-5 % and EV-10 % foam concrete mix shows maximum water absorption capacity due to the porous texture in comparison to other different mixtures. It was observed that PSC-5 %, PCM-5 %, PSC-10 %, and PCM-10 % foam concrete mixtures showed decreased water absorption capacity.
[0059] Example 7: Thermal conductivity test
[0060] The thermal conductivity (k) for 5 % and 10 % of EV, PCM, and PSC foam concrete panels has been evaluated at two specific temperature ranges, i.e. at 20 ?C and 50 ?C, after 28 days of water curing as shown in FIG. 8. As expected, the thermal conductivity of EV, PCM, and PSC foam concrete mixture panels decreased significantly due to the large number of voids present in the EV, PCM and PSC foam concrete panels. The presence of these voids increases the water absorption values as evident from Fig. 8. The measured thermal conductivity values are approximately the same in both temperatures tested, which shows the efficacy of the developed panel as a thermal insulation material in tropical climatic conditions. The foam concrete prepared with expanded vermiculite possesses a reducedthermal conductivity due to its layered structure. A further reduction in thermal conductivity may be achieved by the impregnation of developed PCM into the layered structure of EV. Apart from this, the porous structure of foam concrete reduces its thermal conductivity, but at the cost of compressive strength. Due to the presence of voids, foam concrete possesses low compressive strength which may be further reduced by the addition of EV. To counteract this strength reduction and hence to improve durability, coir fiber and nano silica may be added in the PCM foam concrete sample (PSC). Accordingly, the thermal conductivity of the EV foam concrete, is reduced to 49.60% compared to the normal concrete and is further reduced to 52.73% in the case ofPSC foam concrete sample. The thermal conductivity obtained for the foam concrete mix is 0.129W/m-K.
[0061] Example 8: Thermo-gravimetric analysis (TGA)
[0062] The total thermal weight loss of PCM-5% and PSC-5% foam concrete mixtures in comparison to the control mix was assessed using Thermo-Gravimetric Analysis (TGA) and DTG tests. The TGA analysis is shown in FIG. 9. It was observed that the mass loss of up to 400°C occurs due to the evacuation of capillary water filled in pores and inner water layer in the concrete samples, dehydration of surface water, desorption of water associated with ettringite and calcium silicate hydrate (C-S-H). The second stage of mass loss is due to the thermal degradation of calcium hydroxide (C-H) and is classified by the decomposition of chemically bonded water from C-H at a temperature range of 400°C-500°C. The decrease of C-H content shows the usage of C-H during the cement hydration reaction.According to FIG. 10, the C-H weight percentage for the control specimen is 1.40 %, and PCM-5 % and PSC-5 % foam concrete specimens show values of 2.24 % and 1.74 %, respectively. It can be noticed that there is a small increase in the mass loss of C-H for the PCM foam concrete mixture compared to thecontrol sample. In contrast, the addition of nano silica led to a reduction in mass loss due to the degradation of C-H content in the case of PSC-5 %. This decrease in mass loss due to C-H content in addition to nano silica is due to the increased pozzolanic reaction, which made it feasible to consume C-H generated during the cement hydration process. Therefore, it is inferred that the addition of nano silica possesses an important role by reducing the adverse impacts of PCM during the hydration process, which is due to the nanoscale pozzolanic reactive properties of silica particles.
[0063] Example 9: Scanning Electron Microscopy (SEM)
[0064] FIG. 10 shows the microstructural analysis of the developed PCM sample, which shows the proper impregnation of CA/EA into the pores of EV. The microstructural analysis of the control mix, EV-5 %, PCM-5 %, and PSC-5 % foam concrete samples after 28 days of the curing period is shown in FIG. 11. FIG. 11(a) represents the uneven distribution of needle shaped ettringite, C-S-H, C-H, and unreacted tuffs found in the pores of foam concrete samples, along with a large number of voids due to the foam incorporation. The micro porous structure of EV can be seen in concrete samples observed in FIG. 11(b). The PCM-5% foam concrete mixture showed a smooth and compacted structure due to effective inclusion of PCM in the foam concrete mixture, as seen in FIG. 11(c). The micro structure of PSC-5% foam concrete possesses highly compacted surfaces which produces more C-S-H by absorbing C-H in the presence of nano silica. The nano silica present in this mixture reacts with the C-H present to produce C-S-H, as shown in FIG. 11(d).
[0065] Example 10: Energy Dispersive X-ray spectroscopy (EDS)
[0066] The elemental composition of PSC-5 % foam concrete sample is shown in Fig. 12. The peak of silica observed on the EDS image confirms the presence of nano silica in PSC-5% as shown in Fig. 13. Additionally, the PSC-5 % foam concrete mixture sample possesses better compacted structure than the PCM-5 % foam concrete mixture, which indicates the presence of nano silica, which can then fill the voids and improves the C-H content by enhancing the mass of C-S-H.
[0067] Example 11: Evaluation of Ca/Si ratio of the PSC-5% composite:
[0068] The Ca/Si ratio is used to evaluate the compatibility of the developed foam concrete specimens. A stable microstructure possesses a lower Ca/Si ratio which denotes more C-S-H formation by absorbing C-H content. Fig. 13 shows that the Ca/Si ratio for PSC-5 % is 2.87, which is significantly lower than that of 2.95 seen in PCM-5 % of the foam concrete sample mixture. This is observed due to the rapid formation of C-S-H in the presence of nano silica. An increased Ca/Si proportion of PCM-5 % signifies that the interference of PCM disturbed the hydrating mechanism. Fig. 13 illustrates that the Ca/Si ratio of cementitious mixtures including nano silica decreases by approximately 2.71 % compared to PCM mix. It is proved that the presence of nano silica filled the gaps present in the foam concrete mix occurred by the addition of PCM.
[0069] Example 12: Differential scanning calorimetry (DSC)
[0070] The DSC test results displayed in Fig. 14 shows the melting temperature, freezing temperature and latent heat flow of PCM-5 % and PSC-5 % foam concrete mix samples, along with the control. The obtained measurements reveal that the PCM-5 % and PSC-5 % foam concrete mix samples melt at 32.36 ?C and 31.51 ?C, respectively, and freeze at 21.31 ?C and 21.77 ?C, demonstrating the super cooling influence of the obtained PCMs.PCM-5 % mixture showed increased latent heat values by 1.99 % and 0.43 % compared to the PSC-5 % mixture corresponding to melting and freezing, respectively. The wide peak obtained for PSC-5 % foam concrete in the range of 50–70 ?C is due to the moisture or water evaporation from the coir fiber in the sample. Therefore, the PSC-5 % foam mixture can be highly recommended as thermal heat storage samples for construction applications as it has been proven to be able to hold large amounts of heat for a longer duration.
[0071] While the invention has been disclosed with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material the teachings of the invention without departing from its scope, which should be as defined by the claims appended herewith.

, Claims:We claim:
1. A foam concrete composition for use as construction material providing thermal insulation in buildings, comprising:
a mixture having phase change material (PCM), cement and M-sand, with cement and M-sand having a mix ratio of 1:2;
the PCM comprising capric acid-ethyl alcohol and expanded vermiculite (CA-EA/EV) having capric acid to expanded vermiculite proportion of 55% by weight wherein the PCM is mixed with the cement and the M-sand and, the PCM is 5% by weight of M-sand and added as replacement to M-sand; and
nano silica at 5% and coir fiber at 2% added by weight of cement.

2. The foam concrete composition as claimed in claim 1, wherein the capric acid-ethyl alcohol is impregnated into the porous and multi layered structure of expanded vermiculite.

3. The foam concrete composition as claimed in claim 1, wherein the nano silica has a particle size of 50-200 nm.

4. The foam concrete composition as claimed in claim 1, wherein the coir fibre is configured to improve tensile strength and reduce shrinkage due to inclusion of EV.

5. The foam concrete composition as claimed in claim 1, wherein the particle size of M-sand is in the range of 0.09 mm to 0.30mm.

6. The foam concrete composition as claimed in claim 1, wherein the foam concrete mixture showslatent heat capacities of 69.16 J/g and 43.90 J/g for heating and cooling, respectively, thereby acting as thermal storage.

7. The foam concrete composition as claimed in claim 1, wherein the coir fiber acts as a crack filler in the concrete mix and fills the voids and enhances the flexural strength of the mix.

8. The foam concrete composition as claimed in claim 1, wherein the compressive strength of the mixture is more than 5.5 MPa.

9. The foam concrete composition as claimed in claim 1, wherein the nano silica in the foam concrete mix fills the void and reduces the capillary water absorption of the mix.

10. The foam concrete composition as claimed in claim 1, wherein the concrete mix has large number of pores and leads to lower heat transfer and lower thermal conductivity.

11. The foam concrete composition as claimed in claim 1, wherein the thermal conductivity is in the range 0.122Wm-K to 0.129W/m-K.

12. A process (100) for preparation of foam concrete mixture for use as construction material and for thermal insulation in buildings, comprising:
blending (102) capric acid (CA) and ethyl alcohol (EA) for approximately an hour using a magnetic stirrer to form a CA/EA liquid mixture;
heating (104) expanded vermiculite (EV) at 800°C for 2hours in an oven;
releasing (106) CA/EA mixture into a conical flask containing oven dried expanded vermiculite gradually using a vacuum pump for 1 hour;
allowing (108) dissipation of CA/EA mixture in to layers of vermiculite by vacuum impregnation method for 1 hour to obtain a CA/EV composite, wherein the proportion to CA to expanded vermiculite is 55%;
drying (110) the CA/EV composite for 3 hours at 20°C to obtain a CA-EA/EV phase change material (PCM);
mixing (112) the PCM, cement and M-sand with water and foaming agent, wherein the cement to sand ratio is 1:2 and PCM taken is 5% by weight of M-sand;
adding (114) 5% nano silica and 2% coir fiber by weight of cement as replacement to M-sand to obtain the PSC 5% foam concrete mix;
demolding and curing (116) in water for 28 days to obtain the required foam concrete.

13. The process as claimed in claim 12, wherein the EV acts as a PCM carrier due to its highly porous nature and multi-layered structure.

14. The process as claimed in claim 12, wherein the coir fiber improves tensile strength and reduce the shrinkage that occurs due to the inclusion of EV.

15. The process as claimed in claim 12, wherein the coir fibre is dried after soaking in NaOH solution for three hours followed by 5 hours of oven drying at 90°C and cooling to room temperature.

16. The process as claimed in claim 12, wherein the nano silica is added to improve strength of the foam concrete.


Dr V. SHANKAR
IN/PA-1733
For and on behalf of the Applicants