Incorporation of Phase Change Materials into Cementitious Systems by Breeann Sharma A Thesis Presented in Partial Fulfillment of the Requirements for the Degree Master of Science Approved September 2013 by the Graduate Supervisory Committee: Narayanan Neithalath, Chair Subramaniam Rajan Barzin Mobasher ARIZONA STATE UNIVERSITY December 2013 ABSTRACT Manufacture of building materials requires significant energy, and as demand for these materials continues to increase, the energy requirement will as well. Offsetting this energy use will require increased focus on sustainable building materials. Further, the energy used in building, particularly in heating and air conditioning, accounts for 40 percent of a buildings energy use. Increasing the efficiency of building materials will reduce energy usage over the life time of the building. Current methods for maintaining the interior environment can be highly inefficient depending on the building materials selected. Materials such as concrete have low thermal efficiency and have a low heat capacity meaning it provides little insulation. Use of phase change materials (PCM) provides the opportunity to increase environmental efficiency of buildings by using the inherent latent heat storage as well as the increased heat capacity. Incorporating PCM into concrete via lightweight aggregates (LWA) by direct addition is seen as a viable option for increasing the thermal storage capabilities of concrete, thereby increasing building energy efficiency. As PCM change phase from solid to liquid, heat is absorbed from the surroundings, decreasing the demand on the air conditioning systems on a hot day or vice versa on a cold day. Further these materials provide an additional insulating capacity above the value of plain concrete. When the temperature drops outside the PCM turns back into a solid and releases the energy stored from the day. PCM is a hydrophobic material and causes reductions in compressive strength when incorporated directly into concrete, as shown in previous studies. A proposed method for mitigating this detrimental effect, while still incorporating PCM into concrete is to i encapsulate the PCM in aggregate. This technique would, in theory, allow for the use of phase change materials directly in concrete, increasing the thermal efficiency of buildings, while negating the negative effect on compressive strength of the material. ii ACKNOWLEDGMENTS I would like to express my deepest gratitude to my committee chair, Dr. Neithalath, for allowing me this opportunity to step out of my comfort zone, and guiding me through this experience. I would also like to extend my thanks to Dr. Rajan and Dr. Mobasher for being a part of my committee and teaching me structural engineering necessities. I would like to thank my fellow research students, Amie Stockwell, Ussala Chowdhury, Matt Aguayo, Sumanta Das, Vikram Dey, Robert Kachala and Ben Rehder, in the structures department for always listening and helping whenever I had questions, specifically to Kirk Vance who showed me how to use nearly every piece of equipment, and to Akash Dakhane for assisting with experiments when I was unavailable. This thesis is dedicated to my loving parents, George and Robyn Sharma, who have always supported me in any way they can while going through school all these years, and to my fiancé, Chris Draper, who took care of me and many of the house hold chores while I worked on this degree. iii TABLE OF CONTENTS Page LIST OF TABLES ............................................................................................................. vi LIST OF FIGURES .......................................................................................................... vii LIST OF SYMBOLS ......................................................................................................... ix CHAPTER INTRODUCTION .............................................................................................................. 1 1.1 Objective .................................................................................................................. 2 1.2 Organization of Thesis ............................................................................................. 3 LITERATURE REVIEW ................................................................................................... 4 1.3 Phase Change Materials ........................................................................................... 4 1.3.1 PCM Classification .............................................................................................. 6 1.4 PCM Incorporation into Building Materials ............................................................ 8 1.5 PCM Incorporation into Cementitious Systems .................................................... 10 1.5.1 Incorporation into LWA ..................................................................................... 12 1.5.2 Direct Incorporation ........................................................................................... 13 MATERIALS, MIXTURES AND METHODS ............................................................... 16 1.6 Materials ................................................................................................................ 16 iv 1.6.1 Cement ............................................................................................................... 16 1.6.2 Pure Temp .......................................................................................................... 16 1.6.3 Lightweight Aggregate ....................................................................................... 17 1.7 Mixture Proportions and Sample Preparation ........................................................ 18 1.7.1 Saturation of LWA ............................................................................................. 18 1.7.2 Coating of LWA ................................................................................................. 20 1.7.3 Mortar Mixes ...................................................................................................... 20 1.7.4 Cement Paste Mixes ........................................................................................... 22 1.7.5 Synthetic Pore Solution ...................................................................................... 23 1.8 Test Methods .......................................................................................................... 23 1.8.1 Differential Scanning Calorimetry ..................................................................... 23 1.8.2 Isothermal Calorimetry ...................................................................................... 25 1.8.3 Thermal Conductivity ........................................................................................ 25 1.8.4 Compressive Strength Testing ........................................................................... 27 1.8.5 Fourier Transform Infrared Spectroscopy .......................................................... 27 1.8.6 Mercury Intrusion Porosimetry .......................................................................... 29 1.8.7 Thermogravimetry Simultaneous Thermal Analysis ......................................... 30 INFLUENCE OF PCM ON MECHANICAL AND THERMAL PROPERTIES OF CEMENT PASTE ............................................................................................................. 31 1.9 Introduction ............................................................................................................ 31 1.10 Mixing Process....................................................................................................... 31 v 1.11 Compressive Strength Results ............................................................................... 32 1.12 MIP Results ............................................................................................................ 34 1.13 Isothermal Calorimetry Results ............................................................................. 38 1.14 DSC Results ........................................................................................................... 39 1.15 TGA-STA Results .................................................................................................. 45 1.16 Synthetic Pore Solution.......................................................................................... 48 1.16.1 FTIR................................................................................................................ 49 1.16.2 DSC ................................................................................................................ 52 1.17 Summary ................................................................................................................ 55 INFLUENCE OF IMPREGNATION OF PCM INTO LIGHTWEIGHT AGGREGATES ON THERMAL AND MECHANICAL PROPERTIES OF MORTARS ........................ 57 1.18 Introduction ............................................................................................................ 57 1.18.1 Saturation Method .......................................................................................... 57 1.19 Mechanical Effects of PCM in Mortar................................................................... 69 1.20 Investigation of Heat Evolution of Mortars ........................................................... 71 1.21 Thermal Efficiency of Cylindrical Mortar Samples .............................................. 73 1.22 FTIR Results .......................................................................................................... 76 vi 1.23 Summary ................................................................................................................ 80 CONCLUSIONS............................................................................................................... 82 1.24 Conclusions for PCM interaction with cement paste ............................................. 82 1.25 Conclusion on encapsulated PCM in LWA for mortar mixes ............................... 83 1.26 Recommendations for Further Work ..................................................................... 83 REFERENCES ................................................................................................................. 85 vii LIST OF TABLES TABLE PAGE 3-1: Typical chemical composition and physical properties of cement ............................ 16 3-2: Material thermal properties of Pure Temp chosen for this research ......................... 17 3-4: Specific gravity of materials used in mortar mixes ................................................... 21 3-5: mix proportions by volume in mL for 100 g samples size ........................................ 22 3-6: Specific gravity for materials used in cement paste mixes ........................................ 22 3-7: mix proportions by volume in mL for 100 g samples size ........................................ 23 4-1: Cumulative volume and critical pore sizes for pastes at 3 days ................................ 35 4-2: Cumulative volume and critical pore sizes for pastes at 28 days .............................. 37 4-1: Enthalpy and efficiency percentages for cement pastes at 3 days (efficiency of the mixes was calculated by the enthalpy of the mix over the theoretical enthalpy for the percentage by mass of PT in the mix. Name for each mix is in percentage of volume of PT added) .......................................................................................................................... 40 4-4: Enthalpy and efficiency percentages for cement pastes at 28 days ........................... 42 5-1: Phase change temperature (onset temperature for pure PCM & peak temperature for PCM-LWA composites), enthalpy and PCM absorption for each saturation method and temperatures (32°C/40°C is 32°C saturation temperature with a 40°C oven drying temperature) ...................................................................................................................... 63 5-2: Enthalpy and PCM absorption for saturated sand and coated sand........................... 67 viii LIST OF FIGURES FIGURE PAGE 2-1: latent heat and sensible heat storage [18] , latent heat storage indicated by the horizontal line at isothermal conditions, while sensible heat storage is indicated by the sloped lines before and after the change of phase ............................................................... 5 2-2: Classification of Phase Change Materials “reprinted from Pasupathy et al” [19] ...... 6 3-1: DSC heating and cooling scans for PT 25, 27, & 29 ................................................. 24 3-2: Thermal conductivity apparatus ................................................................................ 26 3-4: FTIR Spectrum for PT and Micronal ........................................................................ 28 3-5: FTIR Spectra from Stalite LWA ............................................................................... 29 4-1: Compression strengths for a) w/c 0.3 mixes; b) w/c 0.5 and w/c 0.7 mixes ............. 32 4-2: 3 day OPC mixes; a) mercury intrusion volume; b) pore size distribution for w/c 0.3; c) pore size distribution for w/c 0.5 and w/c 0.7 ............................................................... 34 4-3: 28 day OPC mixes; a) mercury intrusion volume; b) pore size distribution for w/c 0.3; c) pore size distribution for w/c 0.5 and w/c 0.7........................................................ 37 4-4: Isothermal heat flow and cumulative heat flow for mixes noted. ............................. 38 4-5: Heating and cooling scans at 3 days for a) w/c 0.3 mixes and b) w/c 0.5 and w/c 0.7 mixes ................................................................................................................................. 40 4-6: Heating and cooling scans at 28 days for a) w/c 0.3 mixes and b) w/c 0.5 and w/c 0.7 mixes ................................................................................................................................. 41 4-7: Chemical structure of Paraffin [2] ............................................................................. 43 4-8: Thermal efficiency at varying curing ages ................................................................ 44 4-9: 3 day TGA a) weight loss (%) & b) mass loss rate for pure PT 25, pure Ca(OH) , and 2 30% PT 25 + Ca(OH) at 11 days. .................................................................................... 45 2 4-10: 3 day TGA mass loss rate for OPC mixes ............................................................... 47 4-11: 28 day TGA weight loss % for OPC mixes ............................................................. 48 4-12: FTIR Spectrum for a) pure PT; Pore Solution Mixes at b) 1 day, c) 5 days, d) 14 days, and e) 20 days .......................................................................................................... 51 4-13: DSC heating and cooling scan of pore solutions at 3 days...................................... 53 4-14: DSC heating and cooling scan of pore solutions at 14 days.................................... 53 4-15: DSC heating and cooling scan of pore solutions at 20 days.................................... 54 5-1: DSC heating and cooling scans for the 24 hr saturations methods using a) PT 25 & b) PT 29; vacuum saturation method for c) PT 25, & d) PT 29 ....................................... 58 5-2: Picture of A) PCM saturated LWA, B) plain LWA .................................................. 62 5-3: Heating and cooling scan for a) pure PT 25, Saturated LWA, Coated LWA; b) pure PT 29, Saturated LWA, Coated LWA .............................................................................. 66 5-4: Picture of coated LWA .............................................................................................. 68 5-5: Compression strengths a) PT 25 mixes, b) PT 29 mixes ........................................... 69 5-6: Isothermal Conductivity heat flow and cumulative heat flow for a) PT 25 mixes, and b) PT 29 mixes .................................................................................................................. 72 5-7: Thermal Conductivity ratio in relation to temperature for a) PT 25 mixes and b) PT 29 mixes ............................................................................................................................ 74 5-8: Thermal Conductivity results for all mortar mixes ................................................... 74 ix