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Record for a UF thesis. Title & abstract won't display until thesis is accessible after 2011-12-31.

Permanent Link: http://ufdc.ufl.edu/UFE0041266/00001

Material Information

Title: Record for a UF thesis. Title & abstract won't display until thesis is accessible after 2011-12-31.
Physical Description: Book
Language: english
Creator: Lopez, Ashley
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2009

Subjects

Subjects / Keywords: Building Construction -- Dissertations, Academic -- UF
Genre: Building Construction thesis, M.S.B.C.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Statement of Responsibility: by Ashley Lopez.
Thesis: Thesis (M.S.B.C.)--University of Florida, 2009.
Local: Adviser: Muszynski, Larry C.
Local: Co-adviser: Issa, R. Raymond.
Electronic Access: INACCESSIBLE UNTIL 2011-12-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2009
System ID: UFE0041266:00001

Permanent Link: http://ufdc.ufl.edu/UFE0041266/00001

Material Information

Title: Record for a UF thesis. Title & abstract won't display until thesis is accessible after 2011-12-31.
Physical Description: Book
Language: english
Creator: Lopez, Ashley
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2009

Subjects

Subjects / Keywords: Building Construction -- Dissertations, Academic -- UF
Genre: Building Construction thesis, M.S.B.C.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Statement of Responsibility: by Ashley Lopez.
Thesis: Thesis (M.S.B.C.)--University of Florida, 2009.
Local: Adviser: Muszynski, Larry C.
Local: Co-adviser: Issa, R. Raymond.
Electronic Access: INACCESSIBLE UNTIL 2011-12-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2009
System ID: UFE0041266:00001


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1 CARBON DIOXIDE ABSORPTION BY VARIOUS TYPES OF PAVEMENT BINDER MATERIALS By ASHLEY LAYNE LOPEZ A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGRE E OF MASTER OF SCIENCE IN BUILDING CONSTRUCTION UNIVERSITY OF FLORIDA 2009

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2 2009 Ashley Layne Lopez

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3 To my husband and my parents for your continued support and without whom this would not be possible

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4 ACKNOWLEDGMENTS I thank Dr. Muszy nski for your guidance and support during the process of this thesis. I also thank Dr. Issa for his assistance as graduate advisor throughout my graduate studies.

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS .................................................................................................. 4 LIST OF TABLES ............................................................................................................ 7 LIST OF FIGURES .......................................................................................................... 8 LIST OF ABBREVIATIONS ............................................................................................. 9 ABSTRACT ................................................................................................................... 10 CHAPTER 1 INTRODUCTION .................................................................................................... 12 Background ............................................................................................................. 12 Research Hypothesis .............................................................................................. 13 2 LITERATURE REVIEW .......................................................................................... 14 Introduction ............................................................................................................. 14 Eff ects of CO2 on Concrete ..................................................................................... 14 Cement Mortar Types ............................................................................................. 15 Portland Cement .............................................................................................. 15 Port land Cement plus Fly Ash .......................................................................... 15 Portland Cement plus Slag ............................................................................... 16 Portland Cement plus Fly Ash and Slag ........................................................... 16 SET 45 (Magnesium phosphate) ................................................................... 17 Asphalt ............................................................................................................. 17 Novacem .......................................................................................................... 18 Calera Cement ................................................................................................. 18 Eco Cement ..................................................................................................... 18 Standard ................................................................................................................. 20 3 RESEARCH METHODOLOGY ............................................................................... 21 Introduction ............................................................................................................. 21 Procedure ............................................................................................................... 21 Baselines .......................................................................................................... 21 Standard Mortar Cubes .................................................................................... 21 Filling the Molds ............................................................................................... 21 Curing ............................................................................................................... 22 Data Collection and Testing ............................................................................. 22 Group 1 ...................................................................................................... 22 Group 2 ...................................................................................................... 22

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6 4 DA TA ANALYSIS AND RESULTS .......................................................................... 24 Baseline Information ............................................................................................... 24 Mix Designs ............................................................................................................ 25 Data ........................................................................................................................ 25 Carbon dioxide Absorption and Compressive Strength .................................... 25 Constant Humidity ............................................................................................ 31 5 CONCLUSION ........................................................................................................ 34 Carbon dioxide Absorption ...................................................................................... 34 Compressive Strength ............................................................................................ 36 C onstant Humidity .................................................................................................. 36 6 RECOMMENDATIONS ........................................................................................... 37 Continuation of Research ....................................................................................... 37 Othe r Types of Binders ........................................................................................... 37 Effect on Reinforcing Steel ..................................................................................... 37 APPENDIX A BASELINE FIGURES ............................................................................................. 39 LIST OF REFERENCES ............................................................................................... 44 BIOGRAPHICAL SKETCH ............................................................................................ 46

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7 LIST OF TABLES Table page 2 1 Typ ical chemical oxides for various cementitious materials ............................... 17 4 1 Mix designs for concrete samples (for 6 cubes) ................................................. 25 4 2 Portland cement s pecimen data ......................................................................... 26 4 3 Portland cement plus fly ash specimen data ...................................................... 26 4 4 Magnesium phosphate specimen data ............................................................... 26 4 5 Portland cement plus slag data .......................................................................... 26 4 6 Portland cement plus fly ash and slag data ........................................................ 27 5 1 Absorpti on per specimen area and per volume of air ......................................... 35 5 2 Constant humidity data ....................................................................................... 36

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8 LIST OF FIGURES Figure page 2 1 Process of making Eco cement (TecEco 2009b). ............................................... 19 4 1 No specimen empty desiccators ..................................................................... 28 4 2 Portland cement mortar ...................................................................................... 29 4 3 PC plus fly ash mortar ........................................................................................ 29 4 4 Magnesium phosphate SET45 ......................................................................... 30 4 5 Po rtland cement plus slag mortar ....................................................................... 30 4 6 Portland cement plus fly ash and slag mortar ..................................................... 31 4 7 Asphalt concrete ................................................................................................. 32 4 8 Constant humidity Portland cement mortar ........................................................ 32 4 9 Constant humidity magnesium phosphate, SET 45 mortar ............................... 33 5 1 Carbon dioxide absorption by specimen type ..................................................... 34 A 1a Baseline figures taken from outside. ................................................................... 40 A 1b Baseline figures from o utside excluding stabilization. ......................................... 41 A 2 Baseline figures taken from office ....................................................................... 42 A 3 Baseline figures taken from house. .................................................................... 43

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9 LIST OF ABBREVIATION S ASTM American Society for Testing and Materials CO2 Carbon dioxide EPA Environmental Protection Agency PC Portland Cement PSI Pounds per Square Inch

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10 Abstract of Thesis Presented to the Graduate School of the Un iversity of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science in Building Construction CARBON DIOXIDE ABSORPTION BY VARIOUS TYPES OF PAVEMENT BINDER MATERIALS By Ashley Layne Lopez December 2009 Chair: Larry Muszynski Co chair: R. Raymond Issa Major: Building Construction The subject of this thesis is the absorption of carbon dioxide by various types of construction binders. The purpose of this research is to provide a baseline for further experimentation into carbon dioxide absorption by mortar and applied to concrete types. Various types of binders that were investigated are Portland cement, Portland cement with fly ash, Portland cement with slag, Portland cement with fly ash and slag, Set 45 (Magnesium phosphate), and asphalt. Standard mortar cubes were made of each binder material and placed in a controlled environment. The concentration of carbon dioxide was monitored over time as well as temperature and relative humidity. Baseline data was obtained for various environments. These environments were outside, inside a home, and inside an office building. Data collected from the mortar samples were compared to the baselines as well as the controls no specimen, regular Portland cement and as phalt. It was found that all types of mortars tested absorbed carbon dioxide. CO2 was absorbed over the first 30 minutes rapidly, but did not continue to be absorbed over time beyond the initial 30minute period. Portland cement mortar was just as effec tive at

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11 absorbing CO2 as other types tested. In fact, the absorption took place by Portland cement faster than was observed by any other type. Asphalt did not absorb CO2 to any degree.

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12 CHAPTER 1 INTRODUCTION Background A projects environmental impact has become an issue worth considering by designers and constructors alike. Growing popularity of Leadership in Energy and Environmental Design (LEED) has increased the knowledge base of the population while encouraging industry professionals to learn more about designing and constructing in a more environmentally friendly way. Concrete is a material specified in nearly all construction projects in some way shape or form. Concrete is usually based on Portland cement, which is produced on the order of 1.7 x 109 tons per year enough to produce over 6 km3 of concrete (Gartner 2004). Cement production yields carbon dioxide. Due to the large volume of concrete produced each year, the amount of carbon dioxide produced as a byproduct is immense. According to Gartner, for each cubic meter of concrete that is produced, 0.2 tons of CO2 are emitted as a byproduct (Gartner 2004). That comes to 1.36 x 108 tons of carbon dioxide annually. Carbon dioxide is a naturally occurring compound, in the gaseous form at room temperature. It is essential to the health of plants and is removed from the air by them. While plants need c arbon dioxide, if too much is prevalent in an atmosphere the plants and trees cannot absorb all. Excess carbon dioxide can cause smog as well as respiratory problems to humans and animals. According to a 2006 study of the U.S. Greenhouse Gas Emissions Inventory, concrete production is the fourth largest contributor of carbon dioxide emissions worldwide (EPA 2009). As one can imagine, a projects carbon footprint (or individual carbon dioxide contribution to the environment)

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13 has become an issue to be considered when designing and constructing a building. Because concrete is prevalent in almost all buildings and since concrete is responsible for p roducing carbon dioxide, the construction industry has begun to take steps in the direction of reduction of c arbon dioxide emissions. Methods of c arbon dioxide absorption do exist. One method is to use an additive in the concrete mixture that absorbs atmospheric carbon dioxide. This additive is also adaptable to paint products and can be applied to existing buildings to absorb atmospheric carbon dioxide. This would seem to be especially useful in densely populated areas where excess carbon dioxide in the atmosphere has already become a problem. Another method is to study different cement alternatives to the concrete mixture, such as fly ash, to evaluate carbon dioxide absorption over time. This thesis focus es on the evaluation of carbon dioxide absorpti on by various construction binder materials that are used in both road and building construction. Research Hypothesis Many types of concrete and many additives to the concrete mix design exist. Some concrete manufacturers claim that their product absorbs an unusually high amount carbon dioxide. It is expected that some types will absorb more carbon dioxide during the curing process than others. It is also expected that the compressive strength will be higher in those samples that have absorbed carbon dioxide and gone through the carbonation process on the outer surface than their counterparts that cured under water.

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14 CHAPTER 2 LITERATURE REVIEW Introduction This literature review is divided into three parts. The first describes the effects of carbon diox ide on concrete and reinforcing steel. The second part describes the various types of mortars tested in this paper. Lastly, the standards and specifications used will be discussed. Effects of CO2 on Concrete Carbon dioxide affects concrete both positively and negatively. Calcium hydroxide has a high pH, making it an alkaline compound. As CO2 comes in contact with a concrete surface, the calcium hydroxide in the concrete reacts with carbon dioxide in the air to form calcium carbonate. This process is c alled carbonation. (See Equation 21) Ca(OH)2 + CO2 = CaCO3 (carbonation) (2 1) The acidity in the CO2 decreases the pH, thus decreasing the alkalinity of the concrete. The highly basic nature of concrete protects the reinforcin g steel within. The rate of carbonation occurs on average at 0.04in. per year (ACI 2006). For example, if the concrete cover is about three inches, it would take about 75 years for the carbonated portion to reach reinforcing steel. Cracks in the concret e will decrease this number. Cracks in the surface allow CO2 to penetrate into the concrete. The rate of carbonation in a concrete crack 0.008 in. wide is about three orders of magnitude (1000 times) higher than in averagequality crack free concrete ( ACI 2006). Once the carbonation has reached the reinforcing steel, the steel is no longer protected and will

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15 begin corroding, ultimately weakening the structure. In addition, carbonation increases shrinkage of fully cured concrete, therefore causing addi tional cracking (ACI 2006). Carbonation has a positive effect physically on the concrete itself. The process causes the structure to be denser, increases the strength, and reduces the permeability of concrete (ACI 2006). These enhance concrete but would be more beneficial in concrete that does not contain reinforcing steel. Cement Mortar Types The following paragraphs describe the types of mortars considered in this research. Some types are proprietary names and were not available for the study. Portland Cement Portland cement concrete is the most widely used type of concrete. Portland cement itself requires 94% of the total energy consumed in making concrete (BuildingGreen.com 2003 ). Carbon dioxide emissions come from two sources in the production of concrete and mortar The first is from the burning of fossil fuels to operate the kiln used to make Portland cement. This source is the largest producer, at approximately tons of CO2 per ton of cement (BuildingGreen.com 200 3 ). The second is from the c hemical process of calcining limestone into lime in the cement kiln, producing approximately ton of CO2 for each ton of cement produced (BuildingGreen.com 2003 ). Worldwide cement production accounts for more than 1.6 billion tons of CO2 annually (Buildi ngGreen.com 200 3 ). Portland Cement plus Fly Ash The production of Portland cement takes a large amount of energy. To reduce the amount of Portland cement needed to make concrete or mortar would reduce the overall amount of energy needed. Fly ash, a wast e byproduct of the coal industry, can

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16 be substituted for 1535% of the cement in concrete or mortar mixes ( BuildingGreen.com 2003). Today, fly ash accounts for about 9% of the cement mix in concrete (BuildingGreen.com 2003). Fly ash increases concrete s trength, improves sulfate resistance, decreases permeability, reduces the water ratio required, and improves the pumpability and workability of the concrete (BuildingGreen.com 2003). The EPA requires that all buildings constructed using federal funding i nclude fly ash in the concrete mix ( BuildingGreen.com 2003 ). Portland Cement plus Slag Slag granules are a waste component of the iron industry. The molten slag ends up at the bottom of the blast furnace when iron is made. The molten slag is removed fro m the furnace and rapidly quenched with water (SCA 2002 a). Because it is cooled rapidly, crystals are unable to form and the product is glassy, nonmetallic silicates and aluminosilicates of calcium (SCA 2002a). The granules are ground and can be used as an additive to Portland cement in concrete or mortar mixes. The addition of slag to Portland cement results in many benefits, including better workability, higher compressive and flexural strengths, and improved resistance to aggressive chemicals (SCA 20 02a). Portland Cement plus Fly Ash and Slag Both fly ash and slag are products that can be recycled into concrete as a preconsumer material. This provides an added environmental benefit. The properties of fly ash plus slag cement vary which in turn res ults in varied concrete properties. The variation seen is a result of the processes that make these products. For example, slag is a by product of the iron industry, a tightly controlled process, which yields a similar result each time. Fly ash, on the other hand, is a by product of electrical power

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17 generation. This process is not as constant from source to source, yielding a product that varies from source to source (SCA 2002b). Because of this, slag cement yields a product with more uniform properties (SCA 2002b). Both cements lower permeability and increase resistance to sulfate attack (SCA 2002b). The differences between the two cements are based on the type of oxide contained in each. Table 21, summarizes the different oxides. Table 21. Typic al chemical o xides for v arious cementitious m aterials Portland cement Slag cement Fly a sh C Fly a sh F CaO 65 45 25 3 SiO 2 20 33 37 58 Al 2 O 3 4 10 16 20 Fe 2 O 3 3 1 7 10 MgO 3 6 7 1 This table was taken from Slag Cement and Fly Ash from the Slag Cement Association (SCA 2002b). SET 45 (Magnesium phosphate) SET 45 is a prepackaged concrete patching and repair mortar manufactured by BASF Construction Chemicals, LLC. This product is ready to drive on after 45 minutes, hence the name. This product is convenient because it comes as a just addwater mix. SET 45 contains magnesium phosphate and claims resistance to sulfate attack (BASF The Chemical Company 2008). While the company makes no claims of CO2 absorption, it is worth testing because of the claim from other companies that the utilization of magnesium aid s in the absorption of atmospheric CO2. Asphalt According to the Asphalt Industry website, asphalt concrete can be defined as a dark brown to black cementitious material in which the predominat ing constituents are bitumens, which occur in nature or are obtained in petroleum processing. Asphalt is a

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18 constituent in varying proportions of most crude petroleum and used for paving, roofing, industrial and other special purposes (Asphalt Institute 2003). Asphalt is widely used, especially in road paving, and the mix will not be manipulated in this test, which makes a good control for experimentation. Novacem Novacem is a company based in London making a product called Novacem. Novacem is made by c onverting magnesium silicate to magnesium oxide. After the addition of proprietary additives, the cement is complete (Evans 2008). This process replaces the traditional process of converting limestone to clinker and grinding to make Portland cement. Nov acem claims that by utilizing magnesium silicate, CO2 is not released as a byproduct (Evans 2008). Because of this and the absorption of CO2 as Novacem cures, the claim is a negative effect of CO2 (Novacem 2009). Calera C ement Calera Corporation, a Calif ornia based company, has an emerging product called Calera cement. Calera cement utilizes seawater and flue gas to create a cement which can be a replacement for Portland cement and will absorb carbon dioxide (Hampton 2009). Copying a process used by cor al to create reefs, Calera sends carbon dioxide emissions through seawater to create a carbonate byproduct (Block 2009). Calera claims that for every ton of cement produced 2/5 of a ton of carbon dioxide are stored within the cement (Block 2009). Eco Ceme nt Eco Cement is the trade name for a cement made by TecEco Pty. Ltd. This cement has a large amount of reactive magnesia, or magnesium oxide, allowing this cement to sequester large amounts of CO2 from the atmosphere in the production

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19 process ( TecEco 2009a). ( See Figure 21 ) TecEco also claims that Eco Cement provides a greater resistance to sulphate and chloride and reduced corrosion of steel and other reinforcing (TecEco 2009a). In addition to the sequestration of carbon dioxide during the product ion of the cement, Eco Cement absorbs CO2 from the atmosphere as it sets and hardens (TecEco 2009b). EcoCement is made by combining reactive magnesia with Portland cement (TecEco 2009b). Eco Cement is able to include a greater amount of waste (saw dust, slag, bottom ask, plastic, paper) than other cements, such as Portland cement, because it is much less alkaline, which reduces the incidence of delayed reactions that reduce the overall strength of the concrete ( TecEco 2009b). Figure 21. Process of m aking Ecocement (TecEco 2009b).

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20 Standard ASTM C109, Standard Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2 inch Cube Specimens) was used in this thesis for the procedure to make standard cement mortar cubes and also for finding the compressive strength of the standard cement mortar cubes. This standard was used in order to establish a universally accepted means of making and testing the specimens used in this thesis.

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21 CHAPTER 3 RESEARCH METHODOLOGY Introduction The following procedure was performed on all test samples. A CO2 monitor was used to detect and record CO2 concentration in the air, temperature, and relative humidity. All samples were tested under similar conditions. The same CO2 monitor was used for all readings. Procedure The procedure used in this paper was adapted from ASTM C109. Baselines To gather a baseline for comparison, CO2 readings were gathered for a 24 hour period in three places: outside, inside a home, and inside an office building. See Appendix A f or the data. Standard Mortar Cubes Standard mortar samples were made using ASTM C109. Ingredients were weighed out according to the formulas listed in Table 41. The water was added first into the mixing bowl. Next, the cement was added and mixed for 3 0 seconds at slow speed. Standard sand was slowly added over a 30 second interval while the mixer was continuously mixing. The mortar was mixed at medium speed for another 30 seconds and then allowed to rest for 90 seconds. The mortar was mixed at mediu m speed another 60 seconds. Filling the Molds A thin coating of mold release was applied to the interior of each specimen mold. A 1 inch layer of mortar was added to each of the molds. Each cube was tamped 32

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22 times in four rounds, set at right angles to each other. Another layer of mortar was added to each cube and tamped, as was done in the first layer. The excess mortar was removed from the top of each cube by using a knife in a sawing motion across the top. When complete, each cube was 2 inches dee p. Six 2 inch cubes were made for each type o f concrete tested. Curing The cubes were allowed to cure under water for at least 24 hours. The molds were removed after 24 hours. Data Collection and Testing Three of the cubes were placed in an air tight desiccator along with the CO2 monitor. Measurements for CO2 concentration, temperature, and relative humidity were taken for 24 hours. The three remaining cubes were left to cure underwater. After the 24 hour period, all six cubes were tested for compr essive strength using ASTM C109. Group 1 Group 1 for each type of mortar consisted of the three sample cubes that were tested for compressive strength after curing in water. Each cube was placed below the center of the upper bearing block of the testing machine. The test was initiated and the load at failure was recorded. Compressive strength for the three samples were computed in psi and averaged. Group 2 Group 2 for each type of mortar consisted of the three sample cubes allowed to absorb CO2. The desiccator with silica gel in the bottom, and CO2 monitor consisted of the testing apparatus. Data was collected for 30 minutes before the samples were added in order to establish the atmosphere inside the desiccator. The three samples

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23 were added to the apparatus and the apparatus was sealed. Silica gel was placed in the bottom of the desiccator in order to lower the humidity since the cubes had been curing under water. After 24 hours, the apparatus was opened and the samples removed. The data, CO2 con centration, temperature, and relative humidity, were removed from the CO2 monitor. Each sample was tested for compressive strength. The load at failure was recorded. Compressive strength for the three samples were computed in psi and averaged. The findings for Groups 1 and 2 were compared.

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24 CHAPTER 4 DATA ANALYSIS AND RESULTS Baseline Information Baseline figures were obtained for CO2 concentration that would typically be found. The three baselines obtained were outside, in a home, and in a smal l office building. Each baseline was run over a 24hour period. The peak CO2 obtained outside was 824ppm, the low was 460ppm and the average was 530.7ppm. (See Appendix A, Figure A 1a.) The peak value was also the initial value taken. The CO2 concentr ation is initially high, but stabilizes after 14 minutes. (See Appendix A, Figure A 1b) Taking this into consideration, the average remains almost the same at 530.0ppm with a peak at 584ppm and a low at 460ppm. Overall, the CO2 concentration outside rem ained fairly steady with no real trend increases or decreases. The baseline in the office building showed trends that are explainable by the occupation of space by people over time. (See Appendix A, Figure A 2) The data starts midday and CO2 concentrations increase as the time gets closer to 5:00pm. The peak high reached was 1000ppm. A decline was seen throughout the evening and night resulting in a low of 516ppm. At 8:00am the CO2 concentration began to rise again. The typical workday in this office b uilding is 8:00am to 5:00pm, consistent with the data seen. The low concentration of 516ppm is consistent with the average outdoor concentration as seen in Figure A 1a. The baseline representing inside a home shows data that varies greatly. The CO2 conce ntration decreases over a period of about 10 hours, increases for the next 10 hours, and begins to decrease again. (See Appendix A, Figure A 3) The occupants of

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25 this house include two adults and three cats. The increase and decreases in the data represe nt when levels of activity were higher or lower. The average CO2 concentration observed was 1055ppm with a peak of 1290ppm and a low of 620ppm. One would not expect the concentration to reach that of the outdoor average since the house was continuously occupied. Mix Designs ASTM C109 was utilized to obtain typical proportions of the ingredients. For example, one part cement to 2.75 parts sand and a water cement ratio of 0.485 were applied. Table 41 shows the quantities used for each type of concrete t ested. Table 41. Mix designs for concrete samples (for 6 cubes) Type Cement (g) Sand (g) Water (g) Fly Ash (g) Slag (g) PC 500 1375 242 --PC + FA 400 1375 242 100 -PC + Slag 250 1375 242 -250 PC + FA + Slag 200 1375 242 100 200 SET 45 20 00* 160 SET 45 is a prepackaged blended cement with a proprietary amount of cement, fine aggregate and fillers. Data Carbon dioxide A bsorption and C ompressive S trength After curing for 24 hours, the mortar cubes were removed from the molds. For each type of specimen tested, the samples from Group 1 were left to cure under water while the samples from Group 2 were placed in the desiccator to be tested for carbon dioxide absorption for 24 hours. The data obtained during testing is summarized in Tabl es 4 2 through 47. After this period of time, all six samples were tested for compressive strength. Figures 41 through 47 show the CO2 concentration in parts per million, temperature in degrees Celsius, and the relative humidity in percent of the air

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26 inside the desiccators during the testing. Portland cement was used as a control. Additional controls, with no specimen (see Figure 41) or with asphalt ( see Figure 48) were utilized. Table 42. Portland cement specimen data Sample n umber W=Wet c ured D =Desiccated Load (lb) Strength (psi) Days cured Average strength (psi) 1 W 7410 1852 5 2 W 6900 1725 5 3 W 8510 2130 5 1902 4 D 6170 1542 5 5 D 9600 2400 5 6 D 8200 2050 5 1997 Table 43. Portland cement plus fly ash specimen data Sample n umber W=Wet c ured D=Desiccated Load (lb) Strength (psi) Days cured Average strength (psi) 1 W 9410 2350 7 2 W 8210 2050 7 3 W 8170 2040 7 2147 4 D 7390 1847 7 5 D 7220 1805 7 6 D 9840 2230 7 1961 Table 44. Magnesium phosphate specimen data Sample n umber W=Wet c ured D=Desiccated Load (lb) Strength (psi) Days cured Average strength (psi) 1 W 11040 2760 6 2 W 12860 3210 6 3 W 11010 2750 6 2907 4 D 11520 2880 6 5 D 9030 2260 6 6 D 11850 2960 6 2700 Table 45. Portland cement plus slag dat a Sample n umber W=Wet c ured D=Desiccated Load (lb) Strength (psi) Days cured Average strength (psi) 1 W 10230 2560 12 2 W 7300 1826 12 3 W 11610 2900 12 2429 4 D 11220 2810 12 5 D 8910 2230 12 6 D 11530 2880 12 2640

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27 Table 46. Portland cement plus fly ash and slag data Sample n umber W=Wet c ured D=Desiccated Load (lb) Strength (psi) Days cured Average strength (psi) 1 W 8660 2160 14 2 W 9570 2390 14 3 W 7180 1795 14 2115 4 D 5750 1437 14 5 D 3250 813 14 6 D 8070 2020 14 1423 The strength for the Group 1 and Group 2 samples for each specimen type were averaged and this average is displayed in the last column of Tables 42 through 46. A significant difference is not seen between Groups 1 and 2. It is to be noted that all of the samples for all of the specimen types were made on the same day, each type was tested one at a time and after each testing session those cubes tested were broken. Therefore, each specimen type was a different age when broken. Sample cubes were compared with other cubes of the same type, but compressive strength was not compared to other specimen types except to view a trend. The first 30 minutes of data in Figures 42 through 47 depict the starting atmosphere for this specimen test. It is apparent when the cubes were added by the drop in CO2 concentration. Data for each specimen group was analyzed to determine the rate of absorption and length of time to reach equilibrium. It is noted that the CO2 concentration in the test with no specimen present does fal l over the 24 hour period. The CO2 concentration reduces from approximately 1050ppm to approximately 1015ppm (See Figure 41). This reduction may be associated with a small amount of absorption from the silica gel. The reduction, however, is negligible when compared to the change in CO2 concentration seen in all specimens tested.

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28 Figure 42 shows the absorption form Portland cement mortar. Due to a complication with the CO2 monitor, data was collected for only four hours forty minutes. The data clearly depicts carbon dioxide absorption and that equilibrium was reached, however. Figure 41. No s pecimen empty desiccators Portland cement mortar reduced the CO2 concentration to below 200ppm (Figure 4 2). When fly ash was added to Portland cement, t he absorption was not as good, resulting in a final concentration right around 200ppm (Figure 43). Figure 44 shows the CO2 absorption by magnesium phosphate, which is comparable to Portland cement with fly ash. When slag was added to Portland cement, f or both specimen types of Portland cement plus slag and Portland cement plus fly ash and slag (Figures 45 and 4 6), the absorption resulted in a CO2 just above 200ppm.

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29 Figure 42. Portland cement mortar Figure 43. PC plus f ly a sh mortar

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30 Figure 44 Magnesium phosphate SET45 Figure 45 Portland cement plus slag mortar

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31 Figure 46. Portland cement plus fly ash and slag mortar All of the mortar samples in Figures 41 through 46 were cured under water. The asphalt samples, however, were not cured under water. Figure 47 shows that no CO2 absorption occurred while in the desiccators. Asphalt was not expected to absorb CO2, but it must be noted that the curing process was not consistent with that of the other samples. Constant H umidity To determine whether the humidity level in the desiccator influenced CO2 absorption, testing using Drierite to maintain constant humidity was performed. Tests were run on plain Portland cement mortars and on magnesium phosphate mortars. See Figures 48 and 49 for the data.

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32 Figure 47. Asphalt concrete Figure 48. Constant humidity Portland cement mortar

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33 Constant humidity specimen testing consisted of placing three 2 x 2 x 2 mortar cubes in the desiccators and replacing the silica gel with D rieirite. The Drieirite held the relative humidity near 80% whereas the specimens tested without Drieirite saw the humidity rise over time, nearing 100% by the end of the 24hour period. Constant humidity tests were performed for Portland cement mortars and for magnesium phosphate, SET 45 specimens only. Figure 49. Constant humidity magnesium phosphate, SET 45 mortar

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3 4 CHAPTER 5 CONCLUSION Carbon d ioxide Absorption Carbon dioxide was absorbed by all samples. This absorption occurred over the first 30 minutes of exposure and was rapid. Approximately 800 ppm were absorbed over the 30minute interval. After this initial interval, no CO2 was observed to be absorbed. The level of CO2 within the apparatus remained constant with no significant differe nce over the next 23 hours. Figure 51. Carbon dioxide absorption by specimen type Figure 51 shows that the absorption by magnesium phosphate, SET 45 mortar occurred slower than by all other types of mortars tested. Also, Portland cement mortar was seen to have absorbed more CO2 than the other specimen types. It can be inferred

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35 that it may not be necessary to specify another type of mortar for the purpose of absorbing CO2 solely. All of the mortar samples were 2 x 2 x 2 cubes, yielding a total s urface area of 24 in2 per cube. Three cubes were placed in the desiccator during each test giving a total surface area of 72 in2 or 0.5 ft2. The asphalt samples were c ylindrical with a diameter of 515/16 and a height of 15/8 yielding a surface area o f 85.69 in2 or 0.60 ft2. The volume of the desiccator was found to be 6500 cc and can contain 0.23 ft3 of air. Table 51 compares the change in CO2 concentration during each test to the absorption area and to the volume of the container. Table 5 1 Abs orption per specimen area and per volume of air Sample type CO 2 a bsorption, (ppm) Total specimen surface area (ft2) CO 2 a bsorption per ft ,2 (ppm) Volume of a ir, (ft3) CO 2 a bsorption per ft3 of a ir,(ppm) Control a ir 0 0.23 PC 949 0.50 1898 0.23 4126.09 PC + FA 919 0.50 1838 0.23 3995.65 PC + slag 862 0.50 1724 0.23 3747.83 PC + FA + slag 991 0.50 1982 0.23 4308.70 Mag. phos. 985 0.50 1970 0.23 4282.61 Asphalt 263 0.60 438.33 0.23 1143.48 Absorption was calculated as the difference between peak CO2 concentration and the lowest CO2 concentration. The Portland cement, Portland cement plus fly ash, Portland cement plus slag, Portland cement plus fly ash and slag, and magnesium phosphate mortar specimens absorbed about the same amount of CO2 w ith Portland cement plus fly ash and slag mortars absorbing the highest amount both per area and per volume (See Table 51). Asphaltic concrete absorbed only a small amount of CO2

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36 as compared to all other samples. The test with just air did yield a very small amount of CO2 absorption can be attributed to absorption by the silica gel. Compressive Strength Compressive strength was obtained for all samples. The results are listed in Tables 42 through 46. It does not appear that a significant difference exists between samples that were wet cured as opposed to samples that underwent exposure to CO2. Constant Humidity Data from the constant humidity testing is tabulated in Table 5 2. Results for both Portland cement and magnesium phosphate mortars showed l ower absorption quantities than when humidity was not controlled. However, in both cases Portland cement mortars performed slightly better. Table 52. Constant humidity data Sample type CO 2 a bsorption, (ppm) Total specimen surface area (ft2) CO 2 a bsorption per ft2, (ppm) Volume of a ir, (ft3) CO 2 a bsorption per ft3 of a ir, (ppm) PC 758 0.50 1516 0.23 3295.65 Mag. phos. 671 0.50 1342 0.23 2917.39 From the data collected in this research, no one type of mortar performed significantly better than any other, with the exception of the asphalt concrete which did not absorb much CO2. The conclusion of this research is that no one type of cement mortar was significantly better at absorbing CO2 from the atmosphere than any other type tested. But the researc h does indicate that pavements constructed using Portland cement binders with or without mineral admixtures, and magnesium based binders may indeed reduce the carbon footprint of a particular area, eg. a subdivision, relative to pavements in a subdivision constructed using asphalt as a binder.

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37 CHAPTER 6 RECOMMENDATIONS This paper focused on establishing baseline data regarding the absorption of carbon dioxide by various types of mortars. It does not compare all types of mortar or concrete that may absorb CO2. Further evaluation is recommended to expand upon the findings noted herein. Continuation of Research To further support the conclusions reached in this paper and extrapolate further, research to continue this thesis may be performed. The desiccator used in this research held 0.23 ft3 of air. Studies may be done using different sizes of container or even in controlled rooms to see the effect that the initial amount of CO2 available in the environment has on the absorption. This may be further inves tigated by controlling and manipulating the concentration of the initial CO2 in the environment. Other Types of Binders There are companies that explicitly claim that their product or type of concrete is superior because of its ability to absorb atmospheri c CO2. Three of these types, Novacem, Calera cement, and Eco cement, were unable to be tested for the purpose of this thesis, but would be beneficial for further study. Effect on Reinforcing Steel Concrete and mortar, because of the calcium hydroxide in it, has a pH around 10. The alkalinity of the substrate protects reinforcing steel contained within it from sulfate attack which weakens steel. When carbon dioxide is absorbed by concrete or mortar, a chemical reaction occurs which converts calcium hydroxide (or lime) into calcium carbonate and in turn lowers the pH. This more neutral pH does not protect

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38 reinforcing steel which would result in a weaker concrete or mortar unit if sulfate attack occurs. Further study would be prudent to determine the dept h of CO2 absorption with regard to the depth of reinforcing steel.

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39 APPENDIX A BASELINE FIGURES

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40 Figure A 1a. Baseline figures taken from outside.

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41 Figure A 1b. Baseline figures from outside excluding stabilization.

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42 Figure A 2. Baseline figures taken from office

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43 Figure A 3. Baseline figures taken from house.

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44 LIST OF REFERENCES American Concrete Institute (ACI) (2006). Technical Questions ACI Concrete Knowledge: Durability Carbonation, 26 June 2006, < http://www.concrete.org/FAQ/afmviewfaq.asp?faqid=50> 20 October 2009. Asphalt Institute (2003). Asphalt Industry Glossary of Terms, Asphalt Institute, 1 November 2009. BASF The Chemical Company (2008). SET45 and SET45 HW, Chemical action repair mortar, Product Data, 1 November 2009. Block, B. (2009). Capturing Carbon Emissionsin Cement? Worldwatch Institute, Vision for a Sustainable World, 26 January 2009, 31 October 2009. BuildingGreen.com (2003). Cement and Concrete: Environmental Considerations, Environmental Building News 1 March 2003, 18 June 2009. BuildingGreen.com (2005). Concrete as a CO2 Sink? Environmental Building News 1 September 2005, 18 June 2009. Environmental Protection Agency (EPA) (2009). Human Related Sources and Sinks of Carbon Dioxide, Climate Change Greenhouse Gas Emissions, 12 April 2009. Evans, S (2008). Novacem carbon negative cement to transform the construction industry, Innovation and Investment Opportunities in Carbon Capture and Storage, Energy Futures Lab, Imperial College, London, England. Gartner E. (2004). Industrially interest ing approaches to low CO2 cements. Cement and Concrete Research 34 (9) 14891498, < http://www.sciencedirect.com/science/article/B6TWG4BT11PD 1 /2/aacadad705aac612af361748013c1ec7> 22 March 2009. Hampton, T.V. (2009). New GreenConcrete Process Combines Seawater, Flue Gas, Engineering News Record, 18 February 2009, 31 October 2009. Novacem (2009). What we do 14 May 2009. SCA (2002a). Slag Cement, Slag Cement Association, 20 October 2009.

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45 SCA (2002b). Slag Cement and Fly Ash, Slag Cement Association, 2 0 October 2009. TecEco (2009a). EcoCement, TecEco Pty. Ltd. Sustainable Technologies 15 May 2009. TecEco (2009b). EcoCement, Introduction, TecEco Pty. Ltd. Sustainable Technologies 28 April 2009.

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46 BIOGRAPHICAL SKETCH Ashley Layne Lopez was born in January 1982 to Edward and Patricia Yankowich in Roanoke, Virginia. In the summer of 1983, the Yankowich family moved to Longwood, Florida (a suburb of Orlando) where she spent the next 17 years. Ashley graduated from Lake Brantley High School in Altamonte Springs in May 2000. In May 2005, she earned a Bachelor of Science in biology from the University of Central Florida. A year later, in 2006, she married J.A. Lopez, a tax accountant. Current ly, she is completing a Master in Building Construction at the M.E. Rinker, Sr. School of Building Construction at the University of Florida.