impact of sodium silicate pentahydrate as phase change material in concrete … · 2017-02-02 ·...

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International Journal of Civil Engineering and Technology (IJCIET) Volume 8, Issue 1, January 2017, pp. 999–1007 Article ID: IJCIET_08_01_119 Available online at http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=1 ISSN Print: 0976-6308 and ISSN Online: 0976-6316 © IAEME Publication Scopus Indexed

IMPACT OF SODIUM SILICATE PENTAHYDRATE

AS PHASE CHANGE MATERIAL IN CONCRETE

CUBES FOR ENHANCING THE THERMAL

COMFORT

K. Christopher Gunasingh

Department of Civil Engineering, Karunya University, Coimbatore, India

G. Hemalatha

Department of Civil Engineering, Karunya University, Coimbatore, India

ABSTRACT

In the present study, the impact of Phase Change Material (PCM) on M20 grade concrete

is studied experimentally. Concrete cubes were tested by the addition of different weight

percentage (0.5, 0.75, 1.0 and 1.25 wt. percentage of cement) of sodium silicate pentahydrate

as PCM. The concrete cubes were tested for X-ray diffraction pattern (XRD) analysis,

compressive strength and thermal energy storage measurement. XRD pattern of the concrete

revealed the presence of sodium silicate pentahydrate without any chemical reaction with

cement. Compressive strength test was performed for evaluating the strength of the M20 grade

concrete cubes with the addition of PCM. The experimental results reveal the optimum

percentage of PCM to be added for giving maximum thermal energy storage in concrete cubes

and it is evident from the results there is reduction in temperature to improve the thermal

comfort.

Key words: PCM, XRD, M20 & TEC

Cite this Article: K. Christopher Gunasingha and G. Hemalathaa, Impact of Sodium Silicate Pentahydrate as Phase Change Material in Concrete Cubes for Enhancing the Thermal Comfort. International Journal of Civil Engineering and Technology, 8(1), 2017, pp. 999–1007. http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=1

1. INTRODUCTION

In the recent decade, there is a need for increase of electricity demand in many developing countries and there increases a need for constructing energy efficiency building. Construction industries in developing countries is a major consumer of energy resources which records nearly 40% of usage in total production [1,2]. For conserving energy, a suitable solution is thermal energy storage systems (TES) which is capable of storing energy for later stage use with either sensible thermal energy storage materials or latent heat storage materials. The energy required to change the phase of a material is known as latent heat [3-5]. Present TES materials adopted in the construction industry, materials like steel, masonry and water, are sensible heat storage materials which stores thermal energy when the

Impact of Sodium Silicate Pentahydrate as Phase Change Material in Concrete Cubes for Enhancing the Thermal Comfort


temperature of the material is raised. Latent heat storage materials are referred to as phase change materials (PCM) preferably with solid liquid phase change [6, 7].

A phase change material (PCM) is a substance with a high heat of fusion which by melting and solidifying at a certain temperature, is capable of storing and releasing large amounts of energy. Heat is absorbed or released when the material changes from solid to liquid and vice-versa [8, 9]. Thus, PCMs are classified as latent heat storage (LHS) units. Integration of phase in to building system can increase the thermal storage capacity of the building envelope. PCMs are capable of storing energy at constant or nearly constant temperature which is referred as the phase transition temperature of the PCM [10]. Cementitious materials as the most widely used construction materials in buildings has a great potential in developing high performance thermal storage material. Stimulation of thermal of thermal energy storage in concrete characterizes the heat transfer behaviour and thermal properties of this composite material [11].

The Phase Change Materials (PCM) can be used in the built environment to reduce internal temperature change by storing latent heat in the solid-liquid or liquid-gas phase change of a material [12, 13]. PCMs are able to store 5 to 14 times more thermal energy per unit volume than conventional thermal storage materials [14]. Heat is absorbed and released almost isothermally and is used to reduce the energy consumed by conventional heating and cooling systems by reducing peak loads [15, 16]. Two types of PCMs, organic and inorganic PCMs have been used for building applications. Organic materials are further described as paraffin’s and non-paraffin’s[17,18]. These organic PCMs have desirable properties of cohesion, chemical stability, non-reactivity and recyclability as their advantages [19-26]. But these organic materials are comparatively low heat conductivity in the solid state. But inorganic compounds have a high latent heat absorbing capability and it is non-flammable. Inorganic PCMs have high thermal energy storage and are cheaper than organic PCMs [27-29].

In this present work sodium silicate pentahydrate is selected as the phase changing material to improve the thermal comfort of the building, XRD analysis was carried out to reveal the presence of PCM in the concrete cubes with and without PCM. The compressive strength of the casted concrete cubes were tested. Sodium Silicate pentahydrate is available cheaply and using as PCM it reduces the cost of energy efficient buildings.

2. EXPERIMENTAL PROCEDURE

2.1. Mix Design for M20 Grade Concrete

The proportion of constituents of concrete was calculated for M20 grade concrete based on ISO: 10262:2009 method. The quantity of materials for a volume of 1 m3of concrete was taken as 382 Kg of cement, 644 Kg of fine aggregate, 1240 Kg of coarse aggregate and 181.6 litre of water. For improving the thermal comfort of the concrete block, sodium silicate pentahydrate (Na2SiO3.5H2O) is selected as PCM admixture. Addition of sodium silicate pentahydrate is selected in terms of various percentage (0.5, 0.75, 1.0 and 1.25 on quantity of cement) and then the mixture is added to the aggregates for the preparation of concrete cubes. For the homogenous mixing of sodium silicate pentahydrate with cement, both materials were ball milled for 6 hours under controlled atmosphere.

2.2. Position of Thermocouple in Concrete Cube

For measuring the temperature variation inside the concrete cubes ‘K-type’ thermocouple was fixed in the centre and side of the mould before the casting of concrete cubes as shown in Fig.1,The temperature was measured using an indigenously fabricated digital thermometer which has a digital LED display with 7 segments as shown in Fig.1. It was fabricated in such a way that it was able to measure the temperature inside the concrete cube.

K. Christopher Gunasingha and G. Hemalathaa


Figure 1 Manufactured Concrete cubes with K-Type Thermocouple inserted and Temperature Measurement Set-up

2.3. Preparation of Concrete Cubes

The measured quantity of cement, fine and coarse aggregate and different weight percentage of sodium silicate pentahydrate was mixed with water to fabricate the concrete. The prepared concrete was poured inside the mould, where the ‘K-type’ thermocouple was already fixed. The concrete cubes were casted as per the IS code standard. The number of concrete cubes casted for the testing purpose were9 numbers with thermocouple for temperature measurement and 12 numbers of concrete cubes for compressive strength test in varying weight percentage of sodium silicate pentahydrate as PCM and normal concrete without the addition of PCM.

2.4. Preparing the Specimen for XRD Test

From the casted concrete cubes for varying weight percentages of PCM added concrete and normal concrete specimen were taken for X-ray Diffraction analysis for identifying the presence of PCM in the concrete cubes casted. Powder from each concrete cubes were collected by crushing the concrete cubes using the compressive strength testing machine on 30th, 60th and 90thday after water curing.

2.5. Preparing the specimen for Compressive Strength

The casted concrete cubes were removed from the mould after 24 hours and water cured for 28days. Compressive strength test was carried out in a compressive testing machine as per IS: 516:1959 procedure on fabricated samples on 7th, 14th and 28thday for three specimens, for each batch of casted concrete cubes.

2.6. Temperature Measurement

After water curing the casted specimens for 28 days, specimens with ‘K-type’ thermocouples were tested visually for cracks or damages. After allowing the specimen for drying, from 30th day onwards the temperature was measured on the specimen using specially fabricated digital thermometer shown in Fig.1. specimens are kept in an open uncovered place under natural ambient condition and temperature readings are taken on each sets of specimens prepared for each batch of concrete and recorded.



3. RESULTS AND DISCUSSION

3.1. XRD Analysis of Concrete/Na2SiO3.5H20

The concrete cubes casted with M20 Grade concrete added with sodium silicate pentahydrate were tested for the presence of Sodium Silicate Pentahydrate (Na2SiO3.5H20). Concrete powders were collected from the concrete cubes from crushed concrete cubes using the compressive strength test machine on 30th, 60th and 90th day for XRD analysis. The XRD pattern of the casted concrete specimen with and without PCM is shown in Fig.2. The XRD peaks from the pattern clearly indicate the presence of Na2SiO3.5H20 in concrete and intensity of diffraction peak increases as Na2SiO3.5H20 content increased in the concrete. It is evident from the Fig.2. that diffraction peak of PCM incorporated concrete slightly shifted to lower value compared to the normal concrete. This observation leads to a conclusion that integrity of Na2SiO3.5H20 is preserved during the casting of concrete cubes and thermodynamically stable during the casting of concrete specimens. From XRD pattern it is evident that after 30, 60 and 90 days the integrity of the Na2SiO3.5H20 as PCM has been preserved.

Figure 2 XRD Pattern of (A) Concrete/ Na2SiO3.5H20 After 30 Days (B) Concrete/ Na2SiO3.5H20 After 60 Days (C) Concrete/ Na2SiO3.5H20 After 90 Days

3.2. Effect of PCM in Concrete

The Fig. (3-6) shows the results of the effect of PCM added in M20 grade concrete cubes. From the Fig. (3-6) it is evident that the concrete added with varying weight percentage of Na2SiO3.5H20 (PCM) (0, 0.5, 0.75, 1 & 1.25 Wt. percentage of PCM) and latent heat storage capability of the PCM is recorded using the indigenous fabricated thermocouple which is shown in the Fig. (3-6). From the fig. (3-6) it is evident that due to the addition of Na2SiO3.5H20, atmospheric temperature absorbed by the concrete cube, stored as a latent heat in the core (centre) and reduces the temperature on the lateral side of the concrete cubes [30].The concrete cube added with 1 percentage by weight of Na2SiO3.5H20stored maximum latent heat and reduces the temperature on the lateral sides up to 3 to 6 degree centigrade which is shown in the Fig.5. which was measured for 30th, 60th and 90th day.



Figure 3 Temperature Reading on 0.5 Wt.% of (A) Concrete/ Na2SiO3.5H20 After 30 Days (B) Concrete/ Na2SiO3.5H20 After 60 Days (C) Concrete/ Na2SiO3.5H20 After 90 Days






Due to the addition of sodium silicate pentahydrate to concrete cubes the strength of the concrete is not affected and it is evident from compressive strength of the concrete cube which is shown in Fig.8. The XRD analysis of specimen with concrete/sodium silicate pentahydrate also clearly reveals the presence of sodium silicate pentahydrate and integrity was preserved after 30, 60 & 90 days which is shown in Fig.2.It was revealed that the effect of cooling has enhanced by the addition of sodium



silicate pentahydrate as PCM in the concrete cubes. The sodium silicate pentahydrate absorbs the heat and converts it to latent heat, the converted latent heat is stored in the core or centre of the concrete cube and it is evident from the shown Fig.(3-6).In fig.7. it clearly reveals that 1.0 weight percentage addition of PCM enhances the cooling effect on side walls has shown for the 30th day.

Figure 7 Comparing the Temperature Reading on PCM Effect on Side of Concrete Cubes on varying Wt.% of Concrete/Na2SiO3.5H20 After 30 Days

3.3. Compressive Strength

The values of the compressive strength test are shown in fig.8. A comparative analysis of compressive strength in terms of the percentage of added PCM is shown in Fig.8. It is evident from fig.8. the compressive strength of the concrete is not affected by the addition of sodium silicate pentahydrate as PCM in different weight percentages when compared with the normal concrete. The compressive strength of the casted concrete cubes was tested on 7th, 14thand 28th day. The compressive strength of the PCM added concrete cubes gradually increases on 28th day over the normal concrete.

Figure 8 Effect of Addition on Na2SiO3.5H20 content to concrete on compressive strength

4. CONCLUSION

The addition of sodium silicate pentahydrate as PCM with normal M20 concrete proves to be effective latent heat storage material in developing efficient thermal storage system in concrete. The addition of sodium silicate pentahydrate was added to normal concrete by varying weight percentage (0.5, 0.75, 1.0 & 1.25 on quantity of cement), from the experimental result was found that 1 wt. percentage of



sodium silicate pentahydrate added to normal concrete is effective in storage of maximum latent heat and provide good thermal comfort in the outer walls. The presence of sodium silicate pentahydrate in concrete cubes is also confirmed by the XRD pattern and when the sodium silicate pentahydrate weight percentage increases the peak of PCM is also slightly varied. The compressive test results on concrete cubes also evidenced that the addition of sodium silicate pentahydrate to concrete does not affect the compressive strength. 1.0 weight percentage of sodium silicate pentahydrate is effective enough to reduce the outer wall temperature upto 3-6 degree centigrade in the manufactured concrete cubes.

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impact of sodium silicate pentahydrate as phase change material in concrete … · 2017-02-02 ·...

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