1 2017 World of Coal Ash (WOCA) Conference in Lexingon, KY - May 9-11, 2017 hp://www.flyash.info/ Wha is a Pracical (ASTM C 618) SAI--Srengh Aciviy Index for Fly Ashes ha can be used o Proporion Concrees Conaining Fly Ash? Edwin R. Dunsan Jr. 1 1 ERD Consulans, LLC, Blume Sree, Brooksville, FL KEYWORDS: concree, fly ash, cemen, srengh, efficiency, index, K-facor ABSTRACT An early paper on he properies of Fly Ash in concree was wrien by Davis, Carlson e al (1937) and was probably he firs o sugges a specificaion for fly ash. Early use of fly ash was in mass concree in Hungry Horse Dam ; he Design Srengh was specified as he concree srengh a one years age. In mass concree dams fly ash was used as a one (1) par replacemen of one (1) par cemen. This is an efficiency (cemen/fly ash) of 1/1 = 1 (100%). In 1967, a he firs ash inernaional fly ash symposium (Pisburg); C.E. (Sam) Lovewell was honored for his work described in a 1958 paper suggesing ha for design srenghs a 28-days age cemen should be replaced wih a higher level of fly ash for example 1.2 pars fly ash o he one(1) par cemen or 1.4 o 1, or 1.6 o 1 ec. In his mehod assumed fly ash efficiency could be 1/1.20 = 0.83 (83%) or 1/1.6 =0.63 (63%) ec. There is a dis-connec beween fly ash use in concree and he curren fly ash specificaion (ASTM C618) which specifies a minimum SAI--Srengh Aciviy Index of 0.75 (75%). The SAI of ASTM C618 is no an efficiency comparing cemen o fly ash and canno be used o proporion concree. This paper will propose a new mehodology for ASTM C618 o produce a pracical Index (efficiency) ha can be used o proporion concrees, and for hisorical comparisons, mainain he long hisory of he curren SAI in ASTM C618.
2 INTRODUCTION An early paper on he properies of Fly Ash in concree was wrien by Davis, Carlson e al 1 (1937) and was probably one of he firs o sugges a specificaion for fly ash. This auhor had he privilege o mee Dr. Carlson a his home in Oakland, California in A primary focus of early specificaions was pozzolanic aciviy. The definiion of a pozzolan has been published hundreds of imes. ASTM C618 gives he following definiion: Siliceous or Siliceous and aluminous maerials which in hemselves possess lile or no cemeniious value, bu will in, in finely divided form and in he presence of moisure, chemically reac wih calcium hydroxide a ordinary emperaures o form compounds possessing cemeniious properies. Early specificaions included srengh ess for fly ash wih lime (calcium hydroxide) and wih porland cemen. The acceleraed lime-pozzolan es produced a 7-day srengh resul and he es wih porland cemen a 28-day es resul, basically he SAI (Srengh Aciviy Index) ha is in he curren ASTM C618 specificaion. In his auhor published his firs research repor on he use of fly ash in concree while working a he U.S. Bureau of Reclamaion Laboraory in Denver, Colorado. The fly ashes in he 1976 sudy were evaluaed based on Federal Specificaion SS-P-570B. The specificaion included a minimum srengh 900 lbs/in 2 (6.2 MPa) for he lime-pozzolan srengh a 7-days and a minimum of 75% of conrol for he es wih porland cemen. Previous o he 1960 s fly ash came from Easern USA coal sources from power plans burning anhracie and biuminous coal. In he 1960 s he mining indusry opened up lignie coal fields in he Dakoa s and a second specificaion for fly ashes was developed by Manz 3. A shor ime laer, sub-biuminous coals from Wyoming were uilized in power plans and hese fly ashes mee he new specificaion developed by Manz 3. The new specificaion addressed he properies of hese new ashes wih high free lime conens which were cemeniious in hemselves as well as being pozzolanic. The new fly ashes were classified as Class C o disinguish hem from Class F. In he 1980 s, his auhor paricipaed in ASTM wih he modificaion of es requiremens for ASTM C618. During ha period of ime he sub-commiee chairman for fly ash was Mr. Craig Cain of Chicago Fly Ash Company. Ohers on he sub-commiee included John Faber, he firs presiden of he Naional Ash Associaion and professor Oscar Manz who developed he original Class C specificaion for fly ash. The changes a ha ime included he removal of he lime-pozzolan 7-day srengh and i was replaced wih a 7-day srengh wih porland cemen. Many researchers including he auhor 2 found ha Class C ashes failed o mee he 900 psi (6.2 MPa) limi for he acceleraed lime-pozzolan es. None of
3 he five Class C ashes esed by he auhor 2 achieved 900 psi (6.2MPa) as specified by he lime-pozzolan es. SAI-STRENGTH ACTIVITY INDEX The curren es for SAI in ASTM C618 for 7-day and 28 day resuls is a 1(one) o 1(one) replacemen of cemen wih fly ash. The conrol morar includes 500 grams of cemen and he morar wih fly ash is a 20% replacemen of cemen. The fly ash es morar conains 400 grams of cemen and 100 grams of fly ash. The minimum srengh specified for he fly ash is ha he morar conaining fly ash is a minimum srengh of 75% of he conrol morar wih no fly ash. If he fly ash morar gives a srengh resul of 85% and passes, wha does ha mean? How much srengh does he fly ash produce compared o cemen? The fly ash does no produce 85% as much srengh as he cemen. In review, in he curren SAI es he cemen removed is replaced by an equal amoun of fly ash. The es resul hen deermines if fly ash produces 100% as much srengh as cemen. If he es resul is less han 100% he answer is no he fly ash does no produce as much srengh as cemen a 28 day s age. HISTORICAL USE OF FLY ASH IN CONCRETE (MASS CONCRETE) Early in he 20 h cenury he U.S. Bureau of Reclamaion and he Corps of Engineers were using naural pozzolans as parial replacemen of cemen in large mass dams. Based on he early work by Davis, Carlson, e al 1 and research a he U.S. Bureau of Reclamaion 4, fly ash was used in lieu of naural pozzolan in Hungry Horse Dam ( ). The fly ash was sold by an employee of Chicago Fly Ash Company, Waler Handy 3 (The owners of Chicago Fly Ash being Harry Cain and his son Craig Cain). The U.S. Bureau of Reclamaion specified he srengh for mass concree dams as he concree srengh a 1 year s age. There have been hundreds of papers over he years ha confirm ha wih a 1(one) o 1(one) replacemen of cemen wih class F fly ash he srengh a long ages (1 year) will be equal or greaer han he srengh of concree wih cemen only. Hisorically for mass concree a 1-years age a a 1 o 1 replacemen of cemen wih fly ash he concree srengh will be equal (100% or greaer), han a mixure wih an equal weigh of cemen. HISTORICAL USE OF FLY ASH IN CONCRETE (28-DAY S AGE STRUCTURAL CONCRETES) The concree design srengh for srucural concree is normally a 28-day s age. A his age, hisorical Class F fly ashes will no a a 1 o 1 replacemen produce equal srengh o ha of he cemen replaced. This is demonsraed in he curren ASTM SAI es procedure
4 for Class F ashes. The SAI index a boh 7 day s age and 28 day s age for Class F ashes are ypically less han 100%. In C.E. (Sam) Lovewell, e al, suggesed ha 1(one) par cemen should be replaced wih a larger porion of fly ash o obain equal srenghs a 28-days age o a concree wih cemen only. This auhor had he opporuniy o mee and discuss fly ash concrees a couple imes wih Mr. Lovewell during he lae 1970 s while his auhor was sill employed a he U.S. Bureau of Reclamaion Laboraories in Denver. The following is a quoe of he firs conclusion of Mr. Lovewell s paper: In order o obain approximaely equal compressive srenghs a early ages, beween 3 and 28 days, mixes made wih fly ash mus have a oal weigh of porland cemen and fly ash greaer han he weigh of he cemen used in he comparable sraigh porland cemen mixes. For example if a concree conains 500 lbs/yd 3 (296.6 Kg/m 3 ) of porland cemen only, an equal srengh concree mixure wih fly ash migh conain 440 lbs/yd 3 (261.0 Kg/m 3 of Porland cemen and 100 lbs/yd 3 ( 59.3 Kg/m 3 ) of fly ash. One (1) par cemen (60 lbs)(27.2 Kg) was replaced wih 1.66 pars fly ash (100 lbs)(45.4 Kg). The fly ash efficiency is 60/100(27.2/45.4) = 0.60 = 60% (1/1.66 = 0.60 = 60%). In 1967 Smih 6 developed a cemening efficiency facor (K-facor) which is he efficiency of fly ash compared o cemen. In he previous paragraph he efficiency of fly ash is described as 0.60 or 60% which is a cemening efficiency similar o he K-facor of Smih, bu i is no he same as he K-facor. The K-facor used by Smih is relaed o chemical reacion only. Fly ash efficiency is in wo pars, he srengh produced by reacing chemically and he srengh produced by reducing he waer conen of concree. A NEW PRACTICAL (ASTM C618) SAI STRENGTH ACTIVITY INDEX As discussed previously he curren fly ash morar for SAI in ASTM is based on an assumpion ha fly ash is 100% as efficien as cemen, a 1 o 1 replacemen. The following is he curren fly ash morar used o calculae SAI. Consider he following equaions? Ceq = cemen equivalen which equals 500 grams F = mass of fly ash in grams C = mass of cemen in grams Feff = Fly ash efficiency P% = percen fly ash = 0.20 decimal F = 0.25*C Ceq = (1-P%)*(C+F) + Feff K*P% (C+F) 500 = (1-0.2)*(C+0.25C) + Feff * 0.2* (C +0.25C)
5 500 = 0.8*C C + (Feff *0.2*C) + (Feff * 0.2* 0.25C)) C = 500/[1 + (Feff *.0.25)] Assuming a fly efficiency Feff = 1(100%) C = 500/1.25 = 400 grams F = 0.25 C = 100 grams The preceding calculaions as indicaed are for a morar assuming 100% efficiency, which is he curren morar referenced ASTM C618. Using he same relaionships as described above, wha is a morar assuming a fly ash has efficiency of 50%, Feff = The morar for 50% is as follows: C = 500/[(1 + (Feff *0.25)] C = 500/( ) = grams F = 0.25* C = Grams The new second fly ash morar is grams of cemen and grams of fly ash. The conrol morar remains he same wih 500 grams of cemen. es resuls. Le s now use he following Conrol Morar 28-Day Srengh 6350 psi (42.78 MPa) 7-Day Srengh 5080 psi (35.03 MPa) Curren Fly Ash Morar(100%) 28-Day Srengh 5400 psi (37.23 MPa) 7-Day Srengh 4300 psi (29.65 MPa) Waer % of Conrol 96.5% New Fly Ash Morar(50%) 28-Day Srengh 6480 psi (44.68 MPa) 7-Day Srengh 5180 psi (35.71 MPa) Waer % of Conrol 97.5%
6 Consider he following graph in English and a second in SI unis. S r e n g h y = -2160x y = -1760x % 50% 75% 100% 125% Assumed Fly Ash Cemening Efficiency 28-days 7-days Conrol-6140 psi Conrol-4900 Psi Linear (28-days) Linear (7-days) S r e n g h y = -14.9x y = x days 7-days Conrol-42.3 Mpa Conrol MPa Linear (28-days) Linear (7-days) % 50% 75% 100% 125% Assumed Fly Ash Cemening Efficiency The fly ash efficiency can be calculaed from he previous graphs. The 28-day line of fly ash morar srenghs crosses he 28-day compressive srengh line of he conrol (6350 psi)(43.78 MPa) a wha percenage? The slope of he line is ( )/(100%-
7 50%) = or SI unis he slope is ( )/(100%-50%) = Pick a srengh value, such as he fly ash srengh for an assumed percenage of 100% which is 5400 psi (37.23 MPa). The inercep is hen (100%) =7560 psi and in SI unis ( (100%)) = MPa. The cemening efficiency of he fly ash a 28-days is hen ( )/-2160 = or Feff = 56.02% and in SI unis ( )/-14.9 = , 56.04% a 28-days age. The curren SAI a 28-days is 5400/6350 (37.23/43.78) = 85.0% compared o a pracical efficiency of 56.0%. The Cemen plus fly ash equivalen oal is 500/[0.8 + (0.2 *0.56)] = 500/0.912 = grams. The amoun of cemen is 0.8*548.2 = grams and he fly ash is = grams. The equivalen cemen is (0.56*109.6) = 500 grams. Tha is a morar wih grams of cemen and grams of ash should produce a morar ha has a srengh equivalen o he conrol of 6350 psi (43.78 MPa). Following he same procedure for 7-day as 28-day srenghs, Feff = , 55.68% a 7-days age. FLY ASH EFFICIENCY (TWO PARTS) As discussed previously, fly ash efficiency is boh chemical reacion and due o waer reducion. ASTM C618 requires a repor for waer as a percen of he conrol. In mos cases a fly ash reduces waer conen and herefore he percen of waer in he fly ash morar compared o he conrol morar is less han 100%. For he morars discussed above he average waer for he wo morars is 97.00%. In his case he fly ash morars require an average of 3.0% less waer han he conrol o have he same spread (flow) of morar (ASTM C1437). If he efficiency of he fly ash is 56.02% a 28-days wih waer being 97.00% of conrol how much of he srengh is due o chemical reacion and how much is due o waer reducion? The waer conen of he conrol morar is 242 grams or a waer o cemen raio of 242/500 = If he fly ash morar waer conen is 97.00% of conrol ha is % of 242 = grams. The conrol waer conen is 242 grams a waer o cemen raio of The equivalen cemen for grams of waer is /0.484 = grams. The equivalen cemen and fly ash calculaed earlier is grams of cemen and grams of fly ash. The chemical efficiency (K-facor of Smih) for his fly ash is ( )/ = 42.34%. The srengh produced due o waer reducion is 56.02% % = 13.68%. This ash has a cemening efficiency or K-facor of bu is oal efficiency is greaer due o waer reducion (42.34% % = 56.02%). As shown earlier, he SAI index is 85.0%. The equivalen cemen for he SAI fly ash morar in his example is (0.5602) = 456 grams of cemen which is 456/500 = 91.2% of he conrol cemen of 500 grams. Tha is 91.2% equivalen cemen produces an SAI of 85%. THE SPECIFICATION LIMIT FOR SAI (A MINIMUM OF 75%) Wha if SAI is 75% and, i is assumed here is no waer reducion? Wha is Feff (fly ash efficiency)? The auhor has no made hese morars bu assumes ha Feff will be a very low
8 number, probably greaer han zero, bu hese morars need o be made wih a non-chemically reacive maerial ha does no reduce waer. Consider he daa for he unknown maerial discussed near he conclusion of his paper. ILLUSTRATIONS --CONCRETE MIXES WITH AND WITHOUT FLY ASH Using he informaion developed a his poin we can proporion wo concree mixures, nonair enrained wih enrapped air of 2.0%.. The mixures are illusraed below. The firs is a sraigh cemen mixure, a a waer o cemen raio of which is he same as he conrol morar discussed earlier. The second is an equivalen srengh fly ash concree wih 20% fly ash. The auhor is currenly opimizing (reformulaing) concree mixures for a Mid-Eas USA Ready Mix Producer, locaed wihin 250 miles of Lexingon, KY he locaion for his WOCA meeing. The esimaed srenghs are prediced based on full loads of concree wih and wihou fly ash and esimaed based on in-house esing by he producer. The mixures are shown in Table 1A-English and Table 1B-SI unis in he following able. TABLE 1A Concrees a an Toal of Efficiency of 56.03% K- Facor = 42.34% Waer Cemen Fly Sand Rock Prediced Ash Srengh lbs/yd3 lbs/yd3 lbs/yd3 lbs/yd3 lbs/yd3 psi TABLE 1B Concrees a an Toal of Efficiency of 56.03% K- Facor = 42.34% Waer Cemen Fly Sand Rock Prediced Ash Srengh Kg/M3 Kg/M3 Kg/M3 Kg/M3 Kg/M3 MPa
9 The equivalen cemen for he fly ash mixure is (125.3*56.02%) = lbs/yd 3 or in SI unis (74.3*56.02%) = Kg/M 3. The w/c raio of he sraigh cemen mix is 276.6/571.4 (164.1/339) = Consider he following relaionship of Smih 6 where K is assumed o be he cemening efficiency of 42.34% as calculaed in his paper. The firs equaion is in English unis and second in SI unis. Equivalen W/C = W(c+f)) / (C + K*F) = 268.3/( *125.3) = Equivalen W/C = W(c+f)) / (C + K*F) = 159.2/( *74.3) = In review he w/c raio of he sraigh cemen mix is 276.6/571.4 = and he w/(c+f) raio of he fly ash mixure is 268.3/( ) = In SI unis w/c =164.1/339 = and w/(c+f) = 159.2/( ) = Are he oal efficiency of 56.02% and a cemening efficiency of 42.34% consans? The answer is no, bu hese numbers are sill pracical in proporioning concree mixures wih fly ash, which will be illusraed laer in his paper. ILLUSTRATIONS --CONCRETE MIXES WITH FLY ASH The mos imporan informaion needed o properly proporion concree is waer conen. Waer conen o achieve a arge slump is decreased wih he use of chemical admixures. Waer conen is decreased as he enrained air conen increases. Waer conen is reduced using fly ash and is reduced wih increased percenage of fly ash in concree. The waer conen changes wih sand o aggregae raio. To opimize concree mixures i necessary o fully undersand waer conen and he changes in waer conen for a paricular se of maerials and how waer conen affecs he efficiency of he cemeniious sysems (cemen and fly ash). Concree mixures wih and wihou fly ash are illusraed below. The mixures conain a normal dosage of a waer reducing agen based on he oal cemeniious. All of he following fly ash mixures conain 20% fly ash compared o he oal cemeniious conen and he concrees are non-air enrained (enrapped air 2.0%). The mixures ha follow were generaed by a model (equaion) for concree srengh developed by he auhor 7 over a 40 year period and he model was recenly used o reformulae he concree mixures for he Mid-Eas USA Ready Mix concree producer discussed earlier in his paper. The following mixes are based on he performance of he maerials used by he Ready Mix producer. The firs fly ash mixure following he sraigh cemen mixure illusraes he mixure ha has equal srengh o he sraigh cemen mix. These mixures indicae ha efficiency and K value decreases wih srengh level (decreases wih cemeniious conen, cemen and fly ash). The second fly ash mixure uses he oal efficiency 56.03% and K value of 42.34% developed from he es morars, a he beginning of his paper. The firs able ha follows is English unis and he second is SI unis.
10 Table 2A Concrees wih Sraigh Cemen and 20% Ash Firs Concree a each Srengh Level--Sraigh Cemen Firs Fly Ash Mixure--Equal Srengh o Sraigh Cemen Mixure Second Fly Ash Mixure--Efficiency 56.03% K = 42.34% Third Fly Ash Mixure--w/(c+f) = 90.0% of w/c Design w/c w/(c+f) o Waer Cemen Fly Fly Sand Rock Prediced Toal K-Facor Srengh or w/c raio Ash Ash Srengh Efficiency Psi w/(c+f) % lbs/yd3 lbs/yd3 lbs/yd3 % lbs/yd3 lbs/yd3 Psi % % This auhor has augh Class F fly ash mix proporioning for years, using a 10% reducion from w/c o w/(c+f) which is shown as he las mixure in he able above and he able ha follows. Tha is w/(c+f) is 90% of w/c. In he fly ash mixures shown here is very lile difference in prediced srengh from a shif in w/(c+f) o w/c from a change of 87.2% o 90.0%. A shif in w/(c+f) raio of 10% can be used (for 20% Class F ash mixures),as well as using he oal efficiency and K-facor which will be discussed laer in his paper.
11 Table 2B Concrees wih Sraigh Cemen and 20% Ash Firs Concree a each Srengh Level--Sraigh Cemen Firs Fly Ash Mixure--Equal Srengh o Sraigh Cemen Mixure Second Fly Ash Mixure--Efficiency 56.03% K = 42.34% Third Fly Ash Mixure--w/(c+f) = 90.0% of w/c Design w/c w/(c+f) o Waer Cemen Fly Fly Sand Rock Prediced Toal K-Facor Srengh or w/c raio 0 0 Ash Ash 0 0 Srengh Efficiency 0.00 MPa w/(c+f) % Kg/m3 Kg/m3 Kg/m3 % Kg/m3 Kg/m3 MPa % % As discussed he facor ha is he closes o a consan is he change in w/c raio o w/(c+f) raio. For equal srenghs his raio varies from a high of 88.3% for 5000 psi (34.5 MPa) o a low of 87.2% for 2500 psi (17.2 MPa) concrees. For all pracical purposes a reducion of 85.5% could be used for all of hese concrees and is shown as he second fly ash mixure for all srengh levels. Noice ha K= 42.34% in he morars a he beginning of his paper. A K of 42.34% is a 57.66% ( ) reducion from he efficiency of cemen which is assumed o be
12 100%. This is a 57.66% reducion for 20% fly ash or * 20.0% = 11.5% reducion for w/c o w(c+f). Keep his in mind when reviewing he nex se of concree mixures illusraed below. As shown in hese mixes, even hough oal efficiency and K-facor are reduced wih an increase in w/c raio, he change is really no significan when proporioning concrees wih his class F ash, 56.03% oal efficiency and K= 42.34% produce similar resuls. A more difficul series of mixes o proporion, are concrees wih a consan fly ash conens. Many ready mix companies use a fixed amoun of fly ash per yard, for example 80 lbs/yd 3 (47.5 Kg/m 3 ), 100 lbs/yd 3 (59.3 Kg/m 3 ), 120 lbs/yd 3 (71.6 Kg/m 3 ) or 140 lbs/yd 3 (83.1 Kg/m 3 ). The Florida ready mix company he auhor firs worked for used 140 lbs/yd 3 (83.1 Kg/m 3 ) for heir mixes. The efficiency of fly ash is reduced as he fly ash percenage increases. The verificaion concrees by Lovewell 5 (able 6 of his repor) conain 138 lbs/yd 3 (81.9 Kg/m 3 ). The auhor has chosen 140 lbs/yd 3 (83.1 Kg/m 3 ) which is ha firs used by he auhor and very close o he verificaion concrees of Lovewell. In he following ables he firs fly ash mixure following he sraigh cemen mixures illusraes he mixure ha has equal srengh o he conrol mix. These mixures indicae ha efficiency and K value decreases wih srengh level and percenage of fly ash. The second fly ash mixure uses he K value of 42.34% developed from he es morars, a he beginning of his paper. The firs able ha follows is Table 3A English unis and he second is Table 3B SI unis. Table 3A Concrees wih Sraigh Cemen wih Fixed Fly Ash Conen Firs Concree a each Srengh Level--Sraigh Cemen Firs Fly Ash Mixure--Equal Srengh o Sraigh Cemen Mixure Second Fly Ash Mixure-- K = 42.34% w/(c+f) Design Waer w/c o Cemen Fly Sand Rock Toal Fly K-Facor Prediced Srengh or w/c raio Ash Ash Srengh Efficiency Psi w/(c+f) % lbs/yd3 lbs/yd3 lbs/yd3 % lbs/yd3 lbs/yd3 Psi % %
13 The 140 lbs/yd 3 (83.1 Kg/m 3 ) fly ash mixures illusraed above follow have 23.0% fly ash in he 5000 psi (34.5 MPa) concree o a high of 32.3% for he 2500 psi (17.2 MPa) concree. Using he K value of 42.34% produces good resuls compared o sraigh cemen mixes for all srengh levels. Of ineres is he las 2500 psi(17.2 MPa) fly ash concree mixure wih cemen of 293 lbs/yd 3 (173.8 Kg/m3)and fly ash 140 lbs/yd 3 (83.1 Kg/m 3. In 1988 his auhor began work wih a ready mix producer in Florida. A ha ime for residenial concree hey regularly produced 2500 psi (17.2 MPa) concree wih 285 lbs/yd 3 (169.0 Kg/m 3 ) of cemen and 140 lbs/yd 3 (83.1 Kg/m 3 ) of fly ash and i is referenced by he auhor in an earlier publicaion 7. Tha concree mixure wih an Easern USA Class F fly ash daes back o he lae 1970 s or early 1980 s and is sill in use o his day. This Florida mixure has been used successfully for 40 years. Table 3B Concrees wih Sraigh Cemen wih Fixed Fly Ash Conen Firs Concree a each Srengh Level--Sraigh Cemen Firs Fly Ash Mixure--Equal Srengh o Sraigh Cemen Mixure Second Fly Ash Mixure-- K = 42.34% Design w/c w/(c+f) o Waer Cemen Fly Fly Sand Rock Prediced Toal K-Facor Srengh or w/c raio 0 0 Ash Ash 0 0 Srengh Efficiency 0 MPa w/(c+f) % Kg/m3 Kg/m3 Kg/m3 % Kg/m3 Kg/m3 MPa % %
14 Comparisons can be made o he concrees of Lovewell 5 referenced earlier, in his rial baches he fly ash concrees had larger waer reducions han hose illusraed in he mixures wih 140 lbs/yd 3 (83.1 Kg/m 3 ). The Lovewell 5 concrees had efficiencies from 70.5% o a low of 53.7%. The following is a quoe of Mr. Lovewell s second conclusion: The maximum amoun of fly ash should be used wih lean concrees. Wih he maerials used in hese ess, 175 lbs (79.4 Kg) of fly ash was used o replace 1 sack(94 lbs-42.6 Kg) of cemen per cubic yard of concree in a nominal 4-sack mix, while 100 lb (45.4 Kg) of fly ash was used o replace 3/4:' sack of cemen per cubic yard of concree in a nominal 6-sack mix. The acual amouns will vary wih he ype of fly ash and aggregaes used as well as wih he richness of he mix. The following Tables illusrae he second conclusion by Lovewell shown above. Table 4A in English unis and Table 4B in SI unis. TABLE 4A Illusraions--Concree Mixures by Lovewell Waer Cemen Sand Rock Efficiency w/c Fly Prediced K-Facor or Ash Srengh % % w/(c+f) lbs/yd3 lbs/yd3 lbs/yd3 lbs/yd3 lbs/yd3 psi TABLE 4B Illusraions--Concree Mixures by Lovewell Waer Cemen Fly Sand Rock Prediced Efficiency K-Facor
15 Ash Srengh % % Kg/m3 Kg/m3 Kg/m3 Kg/m3 Kg/m3 MPa In he preceding Tables 4A and 4B, he illusraions of mixures by Lovewell indicaes a 5000 psi (34.5 MPa) he K-facor is 41.21% and for 3000 psi (17.2 MPa) 34.63%. The K-facors for he concree mixes in Table 2 a 5000 psi (34.5 MPa) are 41.20% and in Table3, 41.0%. The K- facors for he concree mixes in Table 2 a 3000 psi (17.2 MPa) are and in Table 3, 36.85%. This indicaes ha he auhor s mixures in Table 2 and Table 3 for concree maerials for he Mid-Eas concree producer have similar K-facors o he mixures of Lovewell (Chicago area maerials). The fly ash in boh cases is an Easern USA class F. DISCUSSION (ILLUSTRATED MIXTURES AND MORE) The following conclusions are aken from Michele Valen 8 eal in heir sudy of Ialian fly ashes: (1) Increasing he cemen conen a a given age and fly ash conen, he efficiency facor K increases. (2) Increasing he fly ash conen a a given cemen conen, he efficiency facor K increases o a peak, hen decreases. The model used by he auhor demonsraes ha as he cemen conen increases he efficiency K-facor increases as in (1) quoed. This is shown in he mixures illusraed in his paper. The auhor has used his model o es (2) above. The daa is no shown in his paper. Yes, wih a given cemen conen, he K-facor increases unil he opimum fly ash conen is reached and hen i begins o decrease. The opimum fly ash conen was discussed by he auhor in an earlier publicaion 7. None of he fly ash conens in his paper have reached he opimum percenage. The opimum for he ash used in his paper is a a fly ash percenage around 35% a long ages, bu wha is he opimum a 28-days? FLY ASH EFFICIENCY ( IS NOT A CONSTANT OR IS IT A CONSTANT?)
16 C.E. (Sam) Lovewell was honored a he firs Inernaional Fly Ash Symposium in 1967 for his research on concree mixures conaining fly ash. 3 As a ribue o Mr. Lovewell, I quoe his firs conclusion 5 again. In order o obain approximaely equal compressive srenghs a early ages, beween 3 and 28 days, mixes made wih fly ash mus have a oal weigh of porland cemen and fly ash greaer han he weigh of he cemen used in he comparable sraigh porland cemen mixes. In he richer mixes, 6 sacks (equivalen cemen 564 lbs(25.8 Kg)), ¾ sacks (70.5 lbs(32 Kg)) was replaced wih 100 lbs(45.4 Kg) of cemen. This is an efficiency of 70.5/100 (32/45.4) = 70.5%. In he leaner mixes, 4 sacks (equivalen cemen 376 lbs(170.6 Kg) of cemen), 1 sack is replaced wih 175 lbs(79.4 Kg) of cemen. This is an efficiency of 94/175 (42.6/79.4)= 53.7%. The efficiency of he leaner mix is a lower cemen conens and a a greaer percenage of fly ash. The efficiency is reduced due o less cemen and more fly ash. Does fly ash efficiency really change wih changes in cemen conen w/c raio? If fly ash chemical reacion does no change wih waer o cemen raio is here a possible explanaion? Maybe, fly ash efficiency in his paper is efficiency compared o cemen. Wha happens o cemen efficiency as waer o cemen raio increases? The hydraion daa of Mills 9 shows ha cemen will no fully hydrae and ha he amoun of hydraion a long ages is prediced by he following relaionship: Ulimae Hydraion = [1.031* (W/C)] / [ (W/C)] Using he above relaionship consider he following concree mixure illusraions wih 20% fly ash earlier in his paper. The 5000 psi (34.5 MPa) fly ash concree had a waer conen of lbs/yd 3 (159.2 Kg/m 3 ), a cemen conen of 478 lbs/yd 3 (283.6 Kg/m 3 and a fly ash conen of 120 lbs/yd 3 (71.2 Kg/m 3. The waer o cemen (only) raio of his fly ash mixure is 268.3(159.2) / 478(283.6) = The ulimae hydraion according o Mills 9 would be (1.031* 0.561) / ( ) = 0.766, 76.6%. The same calculaion can be made for he 3000 psi (20.7 MPa) fly ash mixure. The 3000 psi (20.7 MPa)fly ash concree had a waer conen of lbs/yd 3 (159.2 Kg/m 3 ), a cemen conen of 361 lbs/yd 3 (214.2 Kg/m 3,and a fly ash conen of 90 lbs.yd 3 (53.4 Kg/m 3 ). The waer o cemen (only) raio of his fly ash mixure is 268.3/361 (159.2/214.2) = The ulimae hydraion according o Mills 9 would be (1.031 * 0.743) / ( ) = 0.817, 81.7%. The difference in hydraion is 81.7% % = 5.1%. The K- Facor changes from 41.2% o 37.13% = 4.07%. Cemen hydraion differences explain mos of he changes in K-facor or maybe all of he changes. The increased efficiency of he cemen in leaner mixes compared o fly ash makes he fly ash appear o have lower efficiency, lower K- facor. Does fly ash reacion change wih changes in w/c, maybe bu i is overshadowed by he changes in cemen reacion.
17 The auhors model (equaion) includes modificaions for cemen hydraion based on w/c raio and adjusmens for aggregae effecs such as pase o solids raios and hus correcly models changes in fly ash efficiency and K-facor. The quesion is, is he change in fly ash efficiency correc in his model? I is known ha efficiency and K-facor changes wih cemen conen 8. The K-facor is also reduced wih increases in fly ash conen, which is also shown by he auhors model. Has he auhor properly modeled fly ash reacions? The K-facors change in he auhors model is in he same direcion as published research, and a almos he same magniude. In he auhors opinion very close: bu maybe here is work ye o be done. Does a change in w/(c+f) raio have some small effec on he acual pozzolanic reacion? The quesion can be asked again, is fly ash pozzolanic reacion a consan, yes in he auhors opinion a his poin in ime. As illusraed in his paper, K-facor and oal efficiency are no consans, bu can hey sill be used o proporion concrees. They are no consans in ha hey change relaive o he hydraion of cemen, he volume of cemen and he volume of fly ash. Even wih hese changes, hese efficiencies can sill be used o proporion concree as illusraed earlier in his paper. CONCRETE STRENGTH MODEL (EQUATION) The auhor has modeled lime-pozzolan reacions and hey have been included in a concree compressive srengh model 7 (equaion). The curren model used by he auhor has a few minor changes from ha referenced. As shown by he Lovewell daa, he model calculaes a reduced fly ash efficiency as he waer o cemen raio increases and he model was calibraed o predic he efficiency of he Lovewell 5 daa of 70.5% for rich concrees and 53.7% for he leaner concrees wih higher percenages of fly ash. In he auhors model he fly ash reacion is a consan a 28-days, bu changes wih age. The fly ash reacion increases wih age. A one years age he fly ash reacion is equivalen o cemen (1 o 1 replacemen) and in mass concrees wih design srenghs a one year he fly ash concrees will have equal srengh o a sraigh cemen concree mixure. The K-facor will increase from a 28 days o 1.00 or more a around one years age. The auhor plans o publish an updae his compressive srengh model in a fuure paper. Addiional work on he model will include efficiency sudies which include silica fume, selfcemening fly ashes and slag. EARLY STRENGTHS (7-DAYS) In he above mixes, he overdesign required srengh is very conservaive. For all sudens of ACI 214 (Evaluaion of Srengh Tes Resuls of Concree), he Cov (coefficien of variaion is assumed o be 12%) and he overdesign facor Z = 2. For 4000 psi (27.6 MPa) as an example consider he following:
18 F cr = required srengh F c = design srengh Cov = Coefficien of Variaion Z = 2 F cr = 4000 psi / [1 (Cov * Z)] = 5260 psi F cr = 27.6 MPa / [1 (Cov * Z)] = 36.3 MPa The auhor ofen arges he 7-day srengh o be he design srengh. The over-design srengh is he increase in srengh from 7-days o 28-days. Review he graph of he morars which is copied from above. S r e n g h y = -2160x y = -1760x % 50% 75% 100% 125% Assumed Fly Ash Cemening Efficiency 28-days 7-days Conrol-6140 psi Conrol-4900 Psi Linear (28-days) Linear (7-days)
19 50.00 S r e n g h y = -14.9x y = x days 7-days Conrol-42.3 Mpa Conrol MPa Linear (28-days) Linear (7-days) % 50% 75% 100% 125% Assumed Fly Ash Cemening Efficiency From he graph he fly ash efficiency a 28 days is 56.03% as calculaed earlier. The formula for he 7-day srengh is y (7-day srengh) = -1760(x) +6060, where x is fly ash efficiency of 56.03% and in SI unis (7-day srengh) = (x) The prediced 7-day srengh is hen ( * ) = 5073 psi.(-12.12* ) = 35.0 MPa.) The 7-day srengh divided by he 28-day srengh is 5073/6350 (35/43.8) = (79.9%). The esimaed srengh a 28-days for 4000 psi (27.6 MPa) is 5260 psi (36.3 MPa) as calculaed above. The esimaed 7-day srengh is hen 5260 psi (36.3 MPa) * = 4202 psi (29.0 MPa). Similar numbers are calculaed for 3000 psi (20.7 MPa) wih has an esimaed 28-day srengh of 3950 psi (27.2 MPa). The esimaed 7-day srengh is 0.799* 3950 (27.2 MPa) = 3156 psi (21.8 MPa) and for 2500 psi (17.2 MPa) design srengh wih an esimaed srengh of 3300 psi (22.8 MPa) he esimaed 7-day srengh is 2636 psi (18.2 MPa). The 7-day srenghs are basically he design srenghs. However, he cemen used wih he morars may no be he same cemen ha is used by he ready mix producer. Therefore he relaionships beween 7-days and 28-days will vary wih he cemen source and hus may vary from hose calculaed. The same saemen can be made abou he fly ash efficiencies found in he wo morar ess. They will vary wih he cemen used. The relaionship beween he 7-day srengh and 28-day srengh will change wih fly ash percenage. The esimaed 7-day o 28-day raio calculaed is for 20% fly ash. A lower percenages of class F fly ash he 7-day o 28-day srengh will be greaer and a higher percenage lower. In his paper, for he cemen used in he conrol morar, he 7-day/28-day relaionship is 5080/6350 (35/43.8) = 80.0%.
20 A NEW PRACTICAL STRENGTH ACTIVITY INDEX (TO PROPORTION CONCRETE) As saed in he absrac he proposed mehodology mainains he conrol morar and he hisorical fly ash morar and hus he hisorical SAI can be calculaed. Adding he second morar gives informaion ha can now be used o proporion concrees wih fly ash. The fly ash efficiency mehod discussed in his paper gives an esimae of he oal efficiency and K-facor for 20% fly ash mixures ha compare o a sraigh cemen morar a a w/c raio of In he morars illusraed he equivalen srengh fly ash morar was a a w/(c+f) raio of The fly ash mixure has equal srengh a a w/(c+f) raio of o a w/c = morar wih cemen. Many years before his auhor began using a model for predicing concree srenghs, he auhor had assumed for 20% Easern class F fly ashes concrees he w/(c+f) raio should be 10% less han he w/c raio of a sraigh cemen mixes o have equal srenghs (20% Easern Class F fly ash mixures). For more reacive ashes Wesern Class F ashes and Class C fly ashes he reducion from w/c o w/(c+f) is less. For secondary maerials wih a higher efficiency han cemen (slag), he w/(c+s) raio will be greaer han he w/c o have equal srenghs. A Wesern Class F ash is discussed laer in his paper and i has efficiency slighly greaer han he Easern Class F discussed up o his poin. There are no surprises in proporioning concree mixures. The srengh is relaed o w/c or w/(c+f) raio. To proporion fly ash concrees you need o know wha w/(c+f) o use. How do judge he change from w/c o w/(c+f) o proporion concrees wih fly ash? Consider again he following relaionship: K = he K-facor calculaed wih he new proposed mehod (wo fly ash morars) P% = he percen of fly ash compared o oal cemeniious maerials. Change from w/c o w/(c+f) = (K -1) P% In he morar daa used in he concree illusraions earlier he relaionship is w/(c+f) divided by w/c or 0.428/0.484 = (88.43%) approximaely a 11.57% reducion from w/c o w/(c+f). K was calculaed from he morars a he sar of he paper o be and he fly ash percenage is 20%. Therefore, he change from w/c o w/(c+f) = (K -1) P% = ( ) (0.20) = or a reducion of 11.53%. (The small differences shown in his discussion are rounding errors). W/(c+f) is 88.4% of w/c. As discussed earlier he auhor for years has assumed a 10% reducion which gives very similar mixes and prediced srenghs. Noice ha he formula also works for he fixed fly ash conen mixes wih 140 lbs/yd 3 (82.9 Kg/m 3 ). If oal efficiency (56.03%) is assumed o be a consan i can be used o proporion he concrees. Consider he 4000 psi (27.6 MPa) concrees wih 140 lbs/yd 3 (82.9 Kg/m 3 ) of fly ash per cubic yard. The equivalen cemen for he fly ash is * 140 = 78.4 lbs ( * 82.9 Kg = 46.4 Kg). The sraigh cemen mix conains 477 lbs (283.0 Kg/m 3 ) of cemen,
21 herefore he esimaed cemen for he fly ash mixure is = lbs ( = Kg/m 3 ). The fly ash mixure hen conains lbs (283.0 Kg/m 3 ) of cemen and 140 lbs.yd 3 (82.9 Kg/m 3 ) of fly ash which is 26.0% fly ash. The shif in w/c o w/(c+f) will agree wih hese quaniies of cemen and fly ash. The shif in w/c o w/c+f) = (K-1) imes 26.0% raio is ( ) * 26.0 = 15.0% or w/c o w/(c+f) = 85.0% which is basically he hird fly ash mixure for 4000 psi (27.6 MPa) which conains 140 lbs/yd 3 (82.9 Kg/m 3 ) of fly ash. Wha if he fly ash percenage is 15%, 25% or 30% raher han 20%? The same procedure is used o calculae he reducion in w/c o w/(c+f). Consider he following calculaions. Change from w/c o w/(c+f) = (K -1) P% For 15% w/c o w/(c+f) = ( ) * 0.15 = , - 8.6% For 20% w/c o w/(c+f) = ( ) * 0.20 = , -11.5% For 25% w/c o w/(c+f) = ( ) * 0.25 = , % For 30% w/c o w/(c+f) = ( ) * 0.30 = , -17.3% The reducions shown are rue as long as he fly ash percenage does no exceed he opimum; see he auhors paper in ASTM 7. The following ables illusrae mixures for 15%, 20%. 25% and 30% fly ash for 4000 psi (27.6 MPa) concrees. The firs able ha follows is in English unis and he second SI unis. Table 5A Concrees wih increasing fly ash percenages Percenages 15%, 20%, 25%, and 30% Design w/c w/(c+f) o Waer Cemen Fly Fly Sand Rock Prediced Toal K-Facor Srengh or w/c raio Ash Ash Srengh Efficiency Psi w/(c+f) % lbs/yd3 lbs/yd3 lbs/yd3 % lbs/yd3 lbs/yd3 Psi % % % % % % % % % % % Table 5B Concrees wih increasing fly ash percenages Percenages 15%, 20%, 25%, and 30% Design w/c w/(c+f) o Waer Cemen Fly Fly Sand Rock Prediced Toal K-Facor Srengh or w/c raio 0 0 Ash Ash 0 0 Srengh Efficiency 0 MPa w/(c+f) % Kg/m3 Kg/m3 Kg/m3 % Kg/m3 Kg/m3 MPa % %
22 % % % % % % % % % Wha if he procedure is used for maerials oher han an Easern Class F ash? Consider he following resuls. ASTM C618/C311 TEST RESULTS Par of he ASTM C618/C311 morar daa discussed earlier in his paper is real, he SAI daa for he conrol and he firs fly ash morar are for an Easern USA coal source class F ash.. The srenghs for a second morar values were esimaed by his auhor o produce K-facors ha are similar o K-facors calculaed by he auhor for he Lovewell 5 concree daa and also he fly ash efficiencies found for he Mid-Eas Ready Mix Producer referenced in his paper. The K- facor, in his paper, which is very close o K-facors used in Europe (0.40) 8. The following wo ses of daa were produced (Feb-March 2017) by CTL-Thompson Maerials Engineers, Denver, Colorado. The firs is a Wesern coal USA Class F ash and he second is an unknown maerial. The firs is he Wesern USA Class F shown below: S r e n g h y = x y = -2300x % 50% 75% 100% 125% Assumed Fly Ash Cemening Efficiency 28-days 7-days Conrol-28-Day Conrol-7 Day Linear (28-days) Linear (7-days) This fly ash shown above has a 28-day SAI of 86.5% and is oal efficiency is 58.9% and is K- Facor is 43.73% which is slighly greaer han he Easern Class F of 42.34% used in his paper. This fly ash has an average waer of 97.6% of conrol. The 28-day conrol srengh is 6520 psi
23 (45.0 MPa) and he morar srenghs (100%) is 5640 psi (38.9 MPa) and (50%) is 6710 psi. (46.3 MPa). The Wesern Class F is shown below in SI meric S r e n g h y = x y = x days 7-days Conrol-42.3 Mpa Conrol MPa Linear (28-days) Linear (7-days) % 50% 75% 100% 125% Assumed Fly Ash Cemening Efficiency The second maerial is unknown and used in he same wo morar es procedure. The unknown maerial is shown below: The 28-day SAI is 5190/6520 (35.8/45.0) = 79.6 percen indicaing ha i passes as a pozzolan. Bu, he oal efficiency of his maerial is -0.76% and he K-facor is -3.95%. Noice ha if he unknown maerial lines (7-days and 28-days) were exended hey would no cross he conrol line a a posiive percenage. This maerial has no cemeniious value. The waer percen of conrol was 99.2% which may be he reason ha i barely passed he SAI limi of 75%. S r e n g h y = -1320x y = -920x % 50% 75% 100% 125% Assumed Fly Ash Cemening Efficiency 28-days 7-days Conrol-7-Day Conrol-28 Day Linear (28-days) Linear (7-days)
24 S r e n g h y = x y = x days 7-days Conrol-42.3 Mpa Conrol MPa Linear (28-days) Linear (7-days) The wo morar mehod would eliminae marginal maerials, like his unknown maerial, ha does no have cemeniious properies. CONCLUSIONS % 50% 75% 100% 125% Assumed Fly Ash Cemening Efficiency (1) Is he model daa in his paper rusworhy? The auhor has used he model in recen years o re-formulae (opimize) concree mixures for 6 differen ready mix companies locaed in 5 differen saes. The concree mixures are air-enrained and non-air. Fly ash conens have been a a consan percenage, 15% and 20%, or fly ash quaniies per cubic yard of 80 lbs (47.5 Kg/m 3 ), 100 lbs (59.3 Kg/m 3 ) and 140 lbs (83.1 Kg/m 3 ). The aggregaes include limesones and granies. Mos of he re-formulaed concree mixures are in service and used for design srenghs from 2500 psi (17.2 MPa) o 5000 psi (34.5 MPa). The over-designs were specifically designed a a safey facor ha was appropriae for each producer. (2) For Easern Class F ashes he auhor has hisorically used a 10% reducion from w/c o w/(c+f) o proporion fly ash concrees wih equal srengh o a sraigh cemen mix. The model used by he auhor predics basically he same reducion. (3) A new procedure for ASTM C618/C311 is proposed. The new procedure idenifies a pracical fly ash efficiency ha can be used o proporion concrees relaive o sraigh cemen concree mixures. The relaionships developed includes he oal efficiency of he fly ash, is cemening efficiency (K-facor), and he relaionship beween w/c and w/(c+f). (4) Fly ash efficiency increases wih cemen conen and a a consan cemen conen wih increasing fly ash conen. Fly ash efficiency increases wih a reducion in w/(c+f) raio. (5) K-facor and he percenage of fly ash can be used o calculae he required reducion in w/c o w/(c+f) o proporion fly ash concrees. (6) The auhor has advanced a heory ha fly ash chemical reacion may be consan. Fly ash efficiency appears o change because cemen hydraion changes wih changes in
25 w/c raio and due o pase o solids raios. Therefore fly ash efficiency appears o change; however, he real change is changes in cemen efficiency relaive o fly ash reacion. (7) The conceps discussed in his paper will be invesigaed for Class C fly ashes, silica fume and slag. The auhor expecs o find similar relaionships, and suggess ha a conrol and wo morars be used o evaluae oher secondary cemeniious maerials and in similar manner proporion concrees wih oher secondary cemeniious maerials. (8) The wo morar mehod can idenify maerials ha are ruly no cemeniious and herefore have very limied value in concree. REFERENCES: 1. Davis, R.E., Carlson, R.W., Kelly, J.W. and Davis, H.E., Properies of Cemens and Concrees Conaining Fly Ash, Journal of he American Concree Insiue, Vol. 33, 1937, pages Dunsan, E.R. Jr., Performance of Lignie and Subbiuminous Fly Ash in Concree- A Progress Repor, U.S Deparmen of he Inerior- Bureau of Reclamaion, January 1976, 23 pages. 3. Manz, Oscar, Pflughh0e-Hasse, Debra, Hisorical Perspecive of Coal Ash Markeing Ash Promoion in he USA, 2005 World of Coal Ash, April 11-15, Lexingon, KY, USA 4. Eilfer, R. J. Jr., Bureau of Reclamaion Experiences wih Fly Ash and Oher Pozzolans in Concree, Paper presened a he Third Inernaional Ash Uilizaion Symposium, Pisburg, PA, March 13-14, Lovewell, C. E. and Washa, G. W., Proporioning Concree Mixes Using Fly Ash, Journal of The American Concree Insiue, V.54. No. 12, June Iain A Smih, The Design of fly ash concree, paper 6982, Proceedings Insiuion of Civil Engineers, London, Vol 36, April 1967, pp Dunsan, E.R. Jr., and Zayed, A. Ph.D., A Logical Pozzolanic Index and Is Use in Concree Proporioning, Journal of ASTM Inernaional, Vol 3, No. 4, April 2006, 12 pages 8. Michele V, Vigneri M, Bressan M, Pasqualini A, Bianchini S and Liberaore, F.M. Use of Fly Ash in Concree: Efficiency Facors of he Supplemenary Cemening Maerial, Covenry Universiy and The Universiy of Wisconsin, Milwaukee Cenre for By-Producs Uilizaion, Second Inernaional Conference on Susainable Consrucion Maerials and Technologies, June 28-30, Mills, R. H., Facors Influencing Cessaion of Hydraion in Waer Cured Cemen Pases, Special Repor 90, Symposium on Srucure of Porland Cemen Pases and Concree, Highway Research Board, Naional Academy of Sciences, Washingon D.C., (1966) p