Special Topics CEE 8813
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This 0 page Class Notes was uploaded by Coty Von on Monday November 2, 2015. The Class Notes belongs to CEE 8813 at Georgia Institute of Technology - Main Campus taught by Kimberly Kurtis in Fall. Since its upload, it has received 18 views. For similar materials see /class/234174/cee-8813-georgia-institute-of-technology-main-campus in Civil and Environmental Engineering at Georgia Institute of Technology - Main Campus.
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Date Created: 11/02/15
Metakaolin Lauren McCormick CEE 8813 Material Science of Concrete Dr Kimberly Kurtis 04042007 Outline 0 Introduction 0 Production 0 Properties 0 Pozzolanic Reaction 0 Hydration Heat and Rate of Heat Evolution 0 Pore Size Distribution and Chemistry 0 Workability 0 Mechanical Properties 0 Durability Metakaolin MK 0 Highly reactive amorphous alumino silicate SCM b ASTM C618 Class Nnatural pozzolan pure form 0 Pure or Impure form depends on refinement 0 Structural Bridge decks piers durability issues HPC toxic material storage Sabir 2001 0 Architectural white color exposed concrete Jubilee Church Rome Italy MK with white cement Metakaolin Production o Produced from kaolin a white clay quot 39 Wh39tem d Reso ces Inc 2007 o Kaolin quarries in Wood Mountain Canada 39 u r 0 Deposits also in GA between Columbus and Augusta Metakaolin Production properties 1 WHITEMUD RESOURCES INC swam nun F i summiqu I 7 anquot 1Nl39ilTEl li39llrld Manulacturing Procze i39vlisLs lNEIUftlilb l v ETHNISOLIH FEDEUG I IDN 3 i m MM i39 vno nonucnun 339 I Whitemud Resources Inc 2007 02 amp 4 a quot Tquotquot 39 o MK iS a primary product SF and FA are secondary products Produced under controlled process to achieve desired Kaolin is mined and crushed Kaolin separated from sand refined to remove impurities and stored Kaolin is fed into rotary kiln to produce metakaolin MK is crushed to a fine powder and stored 5 Metakaolin Production o Overheating or overcalcined results in recrystallization and metakaolin begins converting to inert nonreactive materials it 3 0 Heat kaolin between 650 800 C to form MK 0 Process called dehydroxylation Metakaolin 55mm 2A12 03 o 25 i M2030 BSich Organi I B ulna at 200 Spinel pMu ite E39l39lj jfallljfl 32A1203 Ssiq I AdsnrbedWater Loss 2E3A1203 25th Ssiq H 20 1 Equot E39l39ljr d rm 11a l1 on Kaolith Metakaolin M2030 ZSiOZ 0 2H 0 A1203 25102 2 Of 14 DTA thelmogram of kaolin DTA and TGA of Bali Clay and Kaolin 1998 6 Justice 2005 Properties Composition 50 55 SiO2 amp J 4045 AIZO3 39 w r 39 Surface Area10000 25000 mZkg Iilvmlmnlin Avg Particle Size 80 olt2pm WhitemdRe5 urce5391 cquot2 7 Density 2600 kgm2 Specific Gravity 25 Particle Shape Angular COST 500t cement 100t Property lament Metakaolin Speci c gravity 315 25 Blaine rmness mirkg 330 13000 Average particle size um 12 1 Justice 2005 Color Gray W11 its Al Akhras 2006 Pozzolanic Reaction C4AH13 amp C3AH6 hydrated calcium metakaolin aluminates CZASH8 gehlenite hydrate or stratlingite can incorporate alkalis o Reacts with calcium hydroxide CH up to 16 times it mass 0 SiO2 consumed more rapidly while AIO4 incorporates into CSH structure forming long chains 0 Creates a foil like CSH structure opposed to primary CSH needle like structure Pozzolanic Reaction 0 Maximum of pozzolanic reaction occurs at 14 days After CH increases due to formation of inhibiting layer on surface of MK Wild 1996 0 Why not use MK to consume all CH E a g 39 39 Ambient g mquot c conditions 3 39 ig f require 3040 E 3 n3 5 quot replacement not 3 quot iuomei i realistic 3539 05 met a 2 A A10met D in 1 10 100 1000 Curing Time days Wild and Khatib 1996 9 Pozzolanic Reaction 0 Factors effecting degree of hydration Increased replacement levels 0 BUT can be higher with lower replacement levels more cementmore CH Frias and Cabrera 1996 Increased fineness of MK Increased temperature accelerating PC hydration 10 Heat of Hydration 0 Reaction with CH highly exothermic Wild et al 1996 Due to accelerating effect on PC hydration 0 Higher levels of replacement 10 15 increase in temperature between 30 C 35 C Several degrees higher than PC peak temperature 0 Negative effects on durability 35 Peak 1Empem1ure nsen L Control 5 143 15 1 3mm trial 11 lal PL MK pm Wild and Bai 2002 Rate of Heat Evolution aan C3A as 8 MK235B 35 15 MK235 oi 8 Mkaagioji 15 MK349 E 8 SF 9 m 9 4 Heat evolution Mg 6 L1 3 m 5 o 2005 12 Again 0 C3A peak higher than C3S peak opposite of control PC 0 MK accelerates cement hydration Reaction with CH results in earlier reaction with C3A Cause of increased heat evolved associated with C3A peak VVHd etaL 1996 12 O O Pore Size Distribution Pores gt 01pm decrease Pores lt 005pm increase Total porosity same or slightly higher Increase in number of fine capillary pores Frias 2006 Rate of pore refinement rapid up to 14 days Little change after 14 days Sabu2001 Reduction and refinement in pore size beneficial to durability Total pore volume has little effect on durability 0 1091 209 g5 Pmnraggs at we a Frias 2006 D W O U AD 0 0 0 A D DDD A O A A 640 O o leunl Pom Valuma radius 20nm 0 met El 5 met b A 10meii O 15mel 2 39 100 1 1D Khatib and Wild 1996 Amiga 100 Pore Chemistry o Metakaolin able to bind more hydroxide and chloride ions Therefore less present in pore solution 0 Reduces overall pH of pore solution 0 CZASH8 or stratlingite is able to incorporate ions into structure F r BO 0 1 00 4 a a Time days 12a Coleman and Page 1996 WMK 10 MK 20 MK 20 C 14 Influence on Interfacial Transition Zone Typically 25 100 pm thick MK reduces to approx 10 pm thick Very small particle size of MK 0 Increase packingdecrease wall effectquot 0 Less than a tenth the size of cement particles able to fill gap spaces formed between cement near surface of aggregate Increased CSH due to secondary CSH Less CH in paste therefore less to fill voids at interface 0 Increased bond strength between paste and aggregate Less ettringite formed in ITZ due to reduced size and less CH available as a hydration product 00 O 15 Workability 0 Significant reduction in workability 0 Extremely high surface area Increase in water demand to maintain consistency o Irregular particle shape difficult to mix 0 Usually requires superplastizer 24D 7 r a H 220kquot a 0 Los Angeles EHum smaplastbcia ll lfa 23 story building 200 a Hi h seismic zone H quot g Emo Video Link aquot P I 160 F 511mm 1mm MM 140 1 I I El 5 l 15 2390 Mzmkmlin ma a Qian and Lee 2001 Setting Time o Reduces setting time in Due to acceleration of PC hydration 0 Influences workability 3 50 31m i 253 2m minutes 150 Tim e 100 50 in Using Vicat needle test Mechanical Properties Compressive Strength High early strengths 0 3 contributions to increased strength Filler effect 0 immediate PC hydration 0 during first 24 hrs Pozzolanic reaction Wild et al 1996 0 Due to refinement of ITZ Compressive strength MPa o Effected by fineness of MK I l l l O 40 80 120 160 Curing time days FIG 2 Compressive strength V39s curing time CurCIo 1998 18 Mechanical Properties Tensile Strength o Increases with the increase in compressive strength clue to direct relation between them 0 Maximum strengths occur at approx 14 days and remains relatively stable after Sabir 2001 EContml IMK235 DMK34 9 T Strength MP3 Age days 19 Justice 2005 Mechanical Properties Flexural Strength 3 200 Justice 2005 Eli i iF 7 a DI D strength 3934 50 f I MK235 MIlt349 SF Increase over 1413r CONTROL I 3 I 28 I 9 Ageldays o Flexural strength increases but not as significant as compressive and tensile strength 0 Increases with increase in MK replacement level and fineness of MK 20 Mechanical Properties Elastic Modulus El Control I MK235 40 U MK349 I2 SF I SF Redo 040 050 060 wlcm Figure 429 Modulus of elasticity E at 28 days of age Justice 2005 Increases but not significantly Less microcracking clue to denser and reduced ITZ and refined pore structure Similar influences for flexure compressive and tensile strength 21 Durability Permeability o Refined pore structure extremely beneficial in reducing permeability 0 Secondary CSH helps refine pore structure Al Akhards 2006 0 Reduction in chloride ion concentration and diffusion o MK pozzolanic reaction hydration products able to bind free chloride ions introduced in mix water and from environment Chloride concentration 91 a 0 SD 100 1 50 Inn 250 300 350 Time days Fig 11 Chloride diffusion rates for mortars with CEM I 425 mciakaolin and kaolin 22 Courard et al 2003 Durability Alkali Silica Reaction Reduces ASR expansion Due to reduction of alkalis and lower pH in pore solution Reduced CH means less calcium and hydroxide ions in solution 0 Benefits at 1 O 1 500 Comrol 03 304 MK235 replacement 0 BMK349 8 la SF 39 I39 15 MK235 i 15 MK349 Wild et al 1996 9 U10quot 9lt39 15 SF Length change l 7 14 21 28 Age islast Justice 2005 Durability Sulfate Attack 0 Increased resistance to sulfate attack Decrease in available CH for sulfate ions to react with 0 Less formation of gypsum and ettringite which have a higher volume than the primary hydration products Discontinuous and refined pore structure Resistance decreases with increasing wc ratios Approx 1015 replacement required 016 D U Sulfate Expansion 34 D I 0 2 4 6 a 10 12 14 16 1B Sulfate Exposure Period month AI39Akh raS 2006 24 Durability Shrinkage and Creep 0 Increase in autogeneous shrinkage 0 Increase in chemical and drying shrinkage at low replacement levels 0 Some research has shown at higher levels of replacement 1015 drying and chemical shrinkage decrease Due to increase in lower density CZASH8 and decrease in higher density C4AH13 0 Results in overall volume increase Brooks and Johari 2001 I OF39C MK5 MK10 MK15 i 1 rl 39 v0 0 4 4gt A F oltgt 0 Total creep reduced at high replacement Creep microsl rain N D o Brooks and Johari 2001 2 5 Time days Advantages of Metakolin o Durability Change in pore size and structuredecreased permeability Reduction in available alkalis to cause ASR Reduction in CH to help prevent sulfate attack Very beneficial to use in aggressive environments 0 Strength Consumption of CH to create secondary CSH 0 Results in stronger concrete 0 Good for highstrength highperformance concrete 26 Future Research 0 Cause of inhibiting layer which forms on MK after approx 14 days of hydration resulting in increase in CH content 0 Effects of MK on deformation Define reasoning why low levels increases expansion and high levels reduces expansion 0 Ways to reduce overall cost 27
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