ct

AGH

bilitII/AlysepoesuII/

from coal combustion processextraction from electro-ltercollec

to ord[1]. Thlicatiodata inir nen

ical corrosion [1215]. The pozzolanic reaction proceeding in yash cement decreases amount of Ca(OH)2 released in OPC hydra-tion. Incorporation of y ashes in cement reduces calcium alumi-nate content in cement, resulting in lower amount of calciumaluminate hydrates in cement paste. Fly ashes limits alkali-silicareaction [16,17] and increases freeze resistance of concrete [18].

Addition of y ashes to concrete in amount of 60% can keep condi-tions necessary for passivation of steel in concrete [19].

Role of y ash fractions in modication of cement propertieswas investigated [2025]. The ner y ash fractions have high poz-

erable amount of y ashes. Incorporating y ashes below 16 lmfrom the 2nd section of electro-lter y ash Portland cement typeCEM II/A-V 42.5R or pozzolanic cement type CEM IV/A-V 42.5 Ncan be obtained, whereas application of y ash fraction below16 lm from the 3rd section gives y ash Portland cement typeCEM II/A-V 52.5 N or pozzolanic cement type CEM IV/A-V 42.5R.Fly ashes from the 2nd and the 3rd section of electro-lter possesshigher Blaine surface than conventional y ashes. Analysis ofchemical composition of these y ashes conrm the lowest SiO2content, whereas the content of Al2O3 is much higher. Moreover,

Corresponding author. Tel./fax: +48 12 617 24 82.

Construction and Building Materials 28 (2012) 633639

Contents lists available at

B

evE-mail address: tkaczews@agh.edu.pl (E. Tkaczewska).phase composition as well as glass structure [28]. According toauthors [9,10] co-burning bituminous coal and biomass decreasespozzolanic activity of y ashes.

The inuence of y ashes on cement properties was investi-gated. Fly ash cement show longer setting time [1,8]. The charac-teristic property of y ash cement is lower early compressivestrength, but with time its compressive is comparable or higherthan that of ordinary Portland cement (OPC) [1,11,12]. Analysisof literature data conrms high y ash cement resistance on chem-

Up to now, there are not many papers conrming possibility ofobtaining y ash Portland cement of 42.5 class according to stan-dard PN-EN 197-1:2002. Necessary condition is suitable grain-sizedistribution of y ashes. The most activity is fraction below 45 lm[20]. This y ash fraction is connected with increase of early ce-ment compressive strength, whereas coarse y ashes increase ce-ment compressive strength after long time [22]. According toauthor [25] y ash fraction below 32 lm especially below16 lm give cement of 52.5 class, even in the presence of consid-1. Introduction

Fly ash is a waste that is releasedin electric power stations [1]. Fly ashis made in three sections. Fly ashessection show different properties.

Fly ash has been used as additive(OPC) or as admixture for concreteashes, which decides about their appnic activity. The analysis of literatureactivity of y ashes is depend on the0950-0618/$ - see front matter 2011 Elsevier Ltd. Adoi:10.1016/j.conbuildmat.2011.10.022ted from the particular

inary Portland cemente main property of yn in cement, is pozzola-dicates that pozzolanicess, their chemical and

zolanic activity and give considerable growth amount of CSHfrom pozzolanic reaction in cement paste [6,7,9,22,23]. The micro-structure of cement paste containing ner y ashes is more tight incomparison to conventional y ashes [9,22,26,27]. This cementpaste reveals lower capillary porosity and higher content of gelpores and as a consequence of that higher compressive strengthand higher resistance to chemical attack [22,26,27].Compressive strengthCoalbiomass y ashes for cement produ

E. Tkaczewska , R. Mrz, G. jDepartment of Building Materials Technology, Faculty of Materials Science & Ceramics,

a r t i c l e i n f o

Article history:Received 8 April 2011Received in revised form 14 September2011Accepted 2 October 2011Available online 29 November 2011

Keywords:Coalbiomass y ashFly ash fractionBlended cementHydration heat

a b s t r a c t

This paper presents possicement production of CEMcipitator system were anachemical composition andcements were examined. Rto obtain cement type CEM

Construction and

journal homepage: www.elsll rights reserved.ion of CEM II/A-V 42.5R

University of Science and Technology, Mickiewicz Ave. 30, 30-059 Krakow, Poland

ies of use of y ashes from co-burning bituminous coal and biomass in-V 42.5R. Fly ashes from the 2nd and the 3rd section in electrostatic pre-d. The following properties of y ashes were tested: physical properties,zzolanic activity. Heat of hydration and compressive strength of y ashlts showed that y ashes from the second and the third section can be usedA-V 42.5.

2011 Elsevier Ltd. All rights reserved.

SciVerse ScienceDirect

uilding Materials

ier .com/locate /conbui ldmat

the y ashes from the 3rd section reveal high amount of glass andsimultaneously the lowest content of crystalline quartz. The conse-quence of that is the best pozzolanic properties of these y ashes[25].

This paper evaluates possibilities of use of y ashes from co-combustion of bituminous coal and biomass for production of yash Portland cement type CEM II/A-V 42.5R. The basic researcheswere carried out to investigate cement hydration as well as itscompressive strength. Fly ashes came from the co-combustion ofbituminous coal and woody biomass, which contents in combus-

Al2O3 as well as Na2O and K2O. The increase in Al2O3 content in analysed y ashes in

and calcium aluminosilicate hydrates (hydrogehlenite C2ASH8 and hydrogarnetsC3AS3C3AH6). It can be seen that the separated y ashes show great variabilityin loss on ignition, probably caused by the presence of great residue of unburnedcarbon in them. According to PN-EN 450-1 standard the analysed y ashes are qual-

SiO2 22.1Al2O3 5.3Fe2O3 2.2CaO 63.7MgO 2.4SO3 3.1Na2O 0.12K2O 0.94Na2Oe 0.73CaOfree 1.6

Fig. 1. Micrograph of y ash FA3/II. The y ash grains are spherical and glassy andthe majority of them are below 10 lm. The individual grains are larger than20 lm. The large irregular fragments (of 100 lm) are unburned biomass and coal(A,B and C).

634 E. Tkaczewska et al. / Construction and Bucomparison to that in commercial y ash S, but with comparable SiO2 content, re-sults in forming during pozzolanic reaction the greater amount of CSH of lowerCaO/SiO2 molar ratio as well as calcium aluminate hydrates (C4AH13 and C2AH8)

Table 1The physical properties of Portland cement CEM I 42.5R.

Physical properties Portland cement CEM I 42.5R

Blaine value (m2/kg) 398Water requirement (%H2O) 27.6

Setting time (min)Initial setting time 145Initial setting time 195

Compressive strength (MPa)tion fuel was 10 wt%. The y ashes were precipitated in two sec-tions of electro-lter, this is the second and the third.

2. Experimental

2.1. Materials

Portland cement type CEM I 42.5R according to standard PN-EN 197-1 was usedin these investigations. The physical properties of Portland cement are presented inTable 1. The chemical analysis of Portland cement is shown in Table 2.

Fly ashes used in the experiment came from the 2nd and the 3rd section of elec-tro-lter from the same power station, in which the bituminous coal and biomasswere co-combustion. The y ashes FA1/II, FA2/II and FA3/II were collected fromthe 2nd section, whereas the FA1/III, FA2/III and FA3/III were y ashes from the3rd section. Commercial y ash sample is blend of the y ash fractions of all sectionof electro-lter was denoted as S.

The morphology of y ashes is presented in Figs. 1 and 2. The grains of y ashesare spherical and glassy. The large and irregular fragments (of several tens ofmicrometers) of unburned biomass and coal can be also observed. For y ashesfrom the 2nd section, the grains are below 10 lm and individual grains exceeds20 lm (Fig. 1). For ashes from the 3rd section, the grain size are majority smallerthan 5 lm (Fig. 2).

The physical properties of y ashes are given in Table 3. The Blaine specic sur-face area of y ashes was determined according to PN-EN 196-6:1997 standard,grain size distribution using Malvern MasterSizer 2000, residue on 45-lm meshsize according to PN-EN 450-1:2009 standard and water requirement accordingto PN-EN 196-3:2002 standard. As shown in Table 3 the Blaine surface of y ashesfrom the 2nd section shows considerable variability, from 350 m2/kg (FA2/II) to va-lue of 880 m2/kg (FA3/II). The difference in Blaine surface can be probably attrib-uted to efciency of the electro-lter, resulting from too high or too low boileroperating load. The Blaine surface of y ashes collected in 3rd section is more sta-bility. One should be indicated that for y ashes FA1/II and FA3/II the Blaine surfaceis signicantly greater than their corresponding y ashes form the 3rd section,especially for ash FA3/II. These results are conrmed by grain size distributioncurves, presented in Fig. 3. The neness of y ashes, expressed as the mass propor-tion in percent of the ash retained when wet sieved on 45-lm mesh, are presentedin Table 3. These results are generally in correlation with Blaine surface values.According to PN-EN 450-1 standard y ashes FA2/III and FA3/II are classied as Cat-egory S (the neness not exceed 12 wt%). The other y ashes belong to Category N(the neness is lower than 40 wt%). All y ashes reveal water requirement lowerthan limit value for a given Category of y ashes.

The chemical analysis of y ashes was carried out using procedures described inPN-EN 196-2:2006 standard. The analysed y ashes represent typical compositionof class F y ashes according to standard ASTM C618 (Table 4). They satisfy require-ments of PN EN 450-1 standard in respect to content of main chemical compounds.The total content of SiO2, Al2O3 and Fe2O3 is more than 70% by mass. Independentlyof electro-lter section the all y ashes show slight changes in content of SiO2 andAfter 2 days 28.6Alter 28 days 53.0Table 2The chemical analysis of Portland cement CEM I 42.5R.

Chemical analysis (wt%) Portland cement CEM 1 42.5R

ilding Materials 28 (2012) 633639ied to Category C (loss on ignition between 4 and 9 wt%). The soluble phosphatecontent in analysed y ashes, calculated as phosphorus pentoxide, does not exceed100 mg/kg.

d BuE. Tkaczewska et al. / Construction anThe slight differences in content of main chemical compounds have not signif-icant inuence on phase composition of y ashes, especially on proportion betweenglassy and crystalline phases, as well as on glass structure. The results of X-ray dif-fraction of y ashes are presented in Figs. 46. The XRD patterns of all y ashesshow that it presents a halo typical of glassy phase at 2h angles between 15 and40. The signals corresponding to the crystalline phases, such as mullite and a-quartz, can also be found. The results illustrated in Fig. 6 shows that the all y ashesfrom the 2nd section give comparable intensity of main peak of quartz at 26.58 2h(d-spacing of 3.35 ), what conrms its similar content. In the case of y ashes fromthe 3rd section, the intensity of quartz line is more varied. Simultaneously withdecreasing intensity of quartz peak, the intensity of halo peak at 15 and 40 2hin XRD patterns of y ashes is increased. In the XRD pattern of commercial yash S the intensity of halo peak is closed to that of FA2/IIIII samples. The othery ashes independently on section of electro-lter give higher halo intensity, asa result of greater amount of glassy phase in these y ashes.

2.2. Experimental methods

The aim of this work was to examine the pozzolanic properties of y ashes fromthe co-burning bituminous coal and biomass as well as to determine properties ofcement with addition of coalbiomass y ashes.

The pozzolanic properties of y ashes was investigated by measurement of theamount of active components (SiO2 and Al2O3) in them according to ASTM C379-65T standard as well as by evaluation of the pozzolanic activity index accordingto PN-EN 450-1 standard.

Fig. 2. Micrograph of y ash FA3/III. The y ash grains are spherical and glassy. The mairregular fragments (of several tens micrometers) of unburned biomass and coal can be

Table 3The physical properties of y ashes.

Physicalproperties

FA1/II

FA1/III

FA2/II

FA2/III

FA3/II

FA3/III

Commercialy ash S

Blaine value(m2/kg)

710 580 350 680 880 690 340

Residue by wetsieving on 45-lm sieve(wt%) water

16 33 35 12 9 12 37

Waterrequirementas W/C + Pratio

0.24 0.22 0.34 0.45 0.45 0.28 0.25The y ash cement was investigated by determination of heat of hydration ofcement paste samples by calorimetric measurements and by assessing of compres-

jority of them are below 5 lm, but some of them are from 15 to 20 lm. The largeobserved (B,C and D).

ilding Materials 28 (2012) 633639 635sive strength of cement mortars. Calorimetric measurements were carried out usinga nonisothermal-nonadiabatic differential microcalorimeter BMR, Institute of Phys-ical Chemistry, Polish Academy of Science in Warsaw. The compressive strength ofcement mortars was measured according to procedure described in the PN-EN 196-1:1996 standard.

Mixes containing y ashes from the 2nd section of electro-lter are marked asM-FA1/II, M-FA2/II, etc. The mixes containing y ashes from the 3rd section in elec-tro-lter are marked as M-FA1/III, M-FA2/III, etc. For cement replacement by com-mercial y ash, the mix is marked as M-S. The control mix was prepared fromPortland cement type CEM I 42.5R (OPC).

3. Results and discussion

3.1. Measurement of the amount of active components (SiO2 andAl2O3) in y ashes

The amount of active components was determined according toprocedure described in ASTM C379-65T standard. The results arepresented in Table 5.

The results indicate that pozzolanic activity of y ashes is chan-ged from the 1st section of electro-lter to the 3rd one (Table 5).The highest content of active SiO2 and Al2O3 is found for y ashesfrom the 3rd section. The factors affecting increase in pozzolanicreactivity of y ashes from the 3rd section are their more ner ne-ness, greater amount of glass and higher degree of depolimeriza-tion of [SiO4]4 anions in glass. In case of y ash OP3/III thepozzolanic activity is higher for the sample FA1/II, what is probablya consequence of low surface of ash FA1/II (Table 3). One should bepointed that the y ashes FA1-FA3/IIIII have much higher contentof active SiO2 and Al2O3 than commercial y ash S.

3.2. Pozzolanic activity index of y ashes

As it prescribed in PN-EN 450-1 standard pozzolanic activity in-dex of y ashes is dened as Strength Activity Index and is the ratio

636 E. Tkaczewska et al. / Construction and Building Materials 28 (2012) 633639Fig. 3. Grain size distribution curves of y ashes FA1, FA2 and FA3. (For colorinterpretation in this gure the reader is referred to see the web version of thisarticle.)(in %) of the compressive strength of mortar containing 75 wt% ofcement CEM I 42.5R and 25 wt% of y ashes and cement mortarwithout addition. According to PN-EN 450-1 standard the pozzola-nic activity index of y ashes is determined after 28 and 90 days ofhydration.

Thecompressivestrengthof cementwasmeasuredaccording toproce-duredescribed inPN-EN196-1standard,using40 40 160mmprismsofmortar.Thewater tosolid ratio inmortarswas0.5.Themixescontainingyashes fromthe2ndsection inelectro-lterweredenotedasM25-FA1/II,M25-FA2/II,etc.Themixescontainingyashesfromthe3rdsectioninelec-tro-lter weremarked asM25-FA1/III, M25-FA2/III, etc.

The values of pozzolanic activity index of y ashes are com-pared in Table 6. The compressive strength of mortars containing25 wt% of y ashes achieved after 28 and 90 days of hydrationrespectively minimum 75% and 85% of compressive strength ofcontrol cement mortar without addition. After 28 days all y ashcements; this is cement containing commercial y ash S and ce-ments with addition of classied y ashes from the 2nd and 3rdsection in electro-lter, have the comparable values of compressive

Table 4The chemical analysis of y ashes.

Chemical analysis (wt%) FA1/II FA1/III FA2/II

LOI 8.3 6.6 4.3SiO2 45.2 48.0 25.5Al2O3 23.0 23.3 7.4Fe2O3 8.2 7.5 1.6TiO2 1.6 1.4 45CaO 5.6 4.9 20MgO 2.2 3.2 0.7SO3 1.1 0.8 1.0Na2O 1.4 1.5 2.7K2O 3.0 2.7 2.6Na2Oe 3.4 3.3 2.7Fig. 4. XRD patterns of commercial y ash S: Qquartza, Mmullite.strength. However, the compressive strength of y ash cements islower than compressive strength of control cement mortar withoutaddition. With the time of hydration the differences in compressive

FA2/III FA3/II FA3/III Commercial y ash S

6.1 8.2 5.0 2.2469 44.8 46.4 50.7260 24.9 25.2 24.366 7.6 8.1 8.71.5 1.4 1.5 1.354 5.0 5.8 5.220 24 2.3 2.71.1 1.2 1.4 0.71.0 1.3 1.4 2.0226 2.9 2.8 2.202.7 3.2 3.2 3.43

Fig. 5. XRD patterns of y ashes FA1, FA2 and FA3: Qquartza, Mmullite. (Forcolor interpretation in this gure the reader is referred to see the web version of thisarticle.)

Table 6The pozzolanic activity index of y ashes according to PN-EN 450-1.

Sample Compressive strength(MPa)

Pozzolanic activity indexof y ashes (%)

At 28 day At 90 day At 28 day At 90 day

E. Tkaczewska et al. / Construction and Building Materials 28 (2012) 633639 637strength of cement are more visible for the benet of y ashes fromthe 3rd section. After 90 days, the compressive strength of mortarsM25-FA2/III and M25-FA3/III is as much higher than that of OPC.The difference in 90-day compressive strength of M25-FA2/III mor-tar is 21.6%. The increases in compressive strength of cement with

Fig. 6. Intensity of a -quartz peak 26.58 2h (d-spacing of 3.35 ) in the XRDpatterns of y ashes FA1, FA2 and FA3.y ashes FA2/III and FA3/III can be attributed to high surface ofthese ashes (Table 3) as well as to considerable amount of activeSiO2 and Al2O3 in them (Table 5).

The results presented in Table 6 show that the strength activityindex of separated y ashes exhibits minimum 75% and 85% after28 and 90 days, respectively. The average 90-day pozzolanic activ-ity index of y ashes from the 2nd section of electro-lter is onlyslightly lower than that of y ashes from the 3rd section. The high-est pozzolanic activity indices (above 100%) are found for y ashesFA2/III and FA3/III. The factors affecting the increase in pozzolanicactivity index of these y ashes include their ner neness andhigh pozzolanic reactivity.

3.3. Calorimetric measurements

The heat evolved values after 12, 24, 41 and 72 h of hydration are given in Table 7. The quantitative estimation of hydrationheat was determined on the basis of relationship of heat evolvedvalue and temperature measured in calorimeter. The researchwas carried on cement paste samples, containing 75 wt% of cementCEM I 42.5R and 25 wt% of analysed y ashes. The water to solidration was 0.5. The samples were hydrated in calorimeter at 20 C.

Table 5The pozzolanic activity of y ashes according to ASTM C379-65T.

Active component (wt%) FA1/II FA1/III FA2/II

SiO2 16.1 13.0 12.0Al2O3 7.0 5.5 4.3SiO2 + A12O2 23.1 18.5 16.3The mixes with y ashes FA1, FA2 and FA3 from the 2nd sectionin electro-lter are marked as M15-FA1/II, M15-FA2/II, etc. Themixes with these y ashes, but from the 3rd section in electro-lter, are marked as M15-FA1/III, M15-FA2/III, etc. For cementreplacement by commercial y ash, the mix is marked as M15-S.The control mix was prepared from Portland cement type CEM I

OPC 50.1 533 100 100M25-FA1/II 43.7 57.3 87 108M25-FA1/III 42.7 54.7 85 103M25-FA2/II 40.5 54.8 81 103M25-FA2/III 42.1 64.8 84 122M25-FA3/II 48.8 65.5 97 123M25-FA3/III 43.4 63.6 87 119M25-S (commercial y ash) 36.2 48.8 72 92

Table 7The heat evolved value of cement paste samples.

Sample Heat-evolved value (kJ/kg)

At 12 h At 24 h At 41 h At 72 h

OPC 106.7 191.8 244.6 290.7M25-FA1/II 53.0 131.8 185.5 221.3M25-FA1/III 68.3 139.9 183.5 217.4M25-FA2/II 63.7 130.7 175.5 209.0M25-FA2/III 57.3 137.8 191.5 227.7M25-FA3/II 47.6 124.6 181.6 219.2M25-FA3/III 55.3 135.1 188.4 225.7M25-S (commercial y ash) 54.6 109.1 187.4 219.942.5R (OPC).The results of calorimetric measurements indicate that after

12 h the hydration heat of cements with y ashes from the 2ndsection of electro-lter is 43.7% lower than that of OPC. After24 h the hydration heat increase up to 31.2%, but with time ofhydration this difference becomes smaller and is 26.2% and26.0%, respectively after 41 and 72 h. In the presence of y ashesfrom the 3rd section the increase in heat evolved values of cementsare higher. After 12, 24, 41 and 72 h the drop of hydration heat ofthese cements is 43.7%, 23.1% and 22.9%, respectively. It is easy tonotice that the hydration heat value of cements with addition ofclassied y ashes independently of electrostatic precipitatorsection in which y ashes are collected are signicantly higherthan that of cements containing commercial y ash. In comparisonto traditional siliceous y ashes collected from bituminous coalcombustion [27], the hydration heat of analysed cements withcoalbiomass y ashes is higher. One should be noted that, in pa-per [27] the content of y ashes in blended cement was 20% bymass of cement, whereas in analysed y ash cements the additionof y ashes is 25 wt%.

The pozzolanic reaction is relatively slow and its effect on thecement hydration and its properties is visible after long hardeningperiod (90 days and longer). The calorimetric curves of cement

FA2/III FA3/II FA3/III Commercial y ash S

14.0 10.2 12.8 11.25.7 4.4 6.1 2.1

19.7 14.6 18.9 13.3

pastes are presented in Figs. 7 and 8. The prolongation of inductionperiod of cements containing these y ashes is connected with itslower pozzolanic activity. In the presence of y ashes FA1, FA2 andFA3, the cement hydration is delayed, so little amount of calciumions is released to the solution. Therefore, it prolongs the inductionperiod by increasing the time when the supersaturated state can bereached. However, the initiation of the pozzolanic reaction in thecase of y ashes from the 2nd section of electro-lter takes placesome time after the initiation of cement hydration, more time laterthan that found for y ashes the 3rd section. The increased heat ofhydration can be attributed to the increased number of nucleationsites by y ashes for deposition of cement hydrates.

3.4. Compressive strength test

The compressive strength of y ash cements was measuredaccording to PN-EN 196-1 standard, using 40 40 160 mmmor-tar prisms. The water to solid ratio was 0.5.

In studies the y ash Portland cements were obtained by inter-mixing Portland cement CEM I 42.5R (Blaine surface of 398 m2/kg)with analysed y ashes in amount of 25% by mass of binder ce-ment. The mixes containing y ashes from the 2nd section in elec-tro-lter are marked as M25-FA1/II, M25-FA2/II, etc. The mixescontaining y ashes from the 3rd section in electro-lter aremarked as M25-FA1/III, M25-FA2/III, etc. For cement replacementby commercial y ash, the mix is marked as M25-S.

The results of compressive strength measurements after 2, 28

of OPC. For mixes containing y ashes FA2 and FA3, the differencesin 90-day compressive strength is 12.2% and 21.1%, respectively.The mix M25-S reaches lower values of strength after 2, 28 and90 days. The incorporation of 25 wt% of commercial y ash S givesy ash Portland cement of 32.5R class according to PN-EN 197-1standard.

The y ash cement are composed in order to verify the possibil-ity of production of cement CEM II/A-V 42.5R according to standardPN-EN 197-1. As a control y ash Portland cement was used com-mercial cement CEM II/A-V 42.5R from cement plant in Poland(Blaine surface of 450 m2/kg). The laboratory mix, named as mixM15-FA1-FA3/IIIII was mix of y ashes of FA1/IIIII, FA2/IIIIIand FA3/IIIII. The binder cements were obtained by intermixingPortland cement CEM I 42.5R (Blaine surface of 398 m2/kg) withthese mixes of y ashes in amount of 15% by mass of cementCEM I 42.5R. The binder cement M15-S was the laboratory yash cement with commercial y ash S. As a control y ash cementwas used cement CEM II/A-V 42.5R (Blaine surface of 450 m2/kg).The results of compressive strength measurements are given in Ta-ble 9. It can be seen that incorporating of 15 wt% replacementrange of ner y ashes from the 2nd and 3rd section in electro- l-ter can produce y ash Portland cement CEM II/A-V of class42.5R. The faster development of compressive strengths of mix

M25-FA2/III 23.2 44.1 64.8M25-FA3/II 24.9 52.8 65.5M25-FA3/III 23.8 47.4 63.6M25-S (commercial y ash) 19.8 36.2 48.8

Table 9he compressive strength of cement mortars.

Sample Compressive strength (MPa)

At 2 day At 28 day At 90 day

OPC 27.7 50.1 533M15-FA1-FA3/IIIII 24.6 54.5 54.2M15-S (commercial y ash) 20.1 43.5 54.1CEM II/A-V 42.5R 26.9 53.8

638 E. Tkaczewska et al. / Construction and Buand 90 days are presented in Table 8. The results show that ana-lysed y ashes can be used in the manufacture of y ash Portland ce-ment CEM II/A-V of 42.5R class according to PN-EN 197-1 standard.The 2-day compressive strength of all laboratory y ash cements islower than that of OPC, but exceed strength requirement of20.0 MPa. The 28-day compressive strength of cements M25-FA1/IIIII andM25-FA2/IIIII is lower in comparison to OPC, but the differ-ence is respectively 13.8% and 7.9%. After 90 days, the all laboratoryy ash cements reveal compressive strength much higher than thatFig. 7. Calorimetric curves of cement paste samples containing y ashes FA1, FA2and FA3. (For color interpretation in this gure the reader is referred to see the webversion of this article.)Fig. 8. Calorimetric curves of cement paste sample containing commercial y ash S.

Table 8The compressive strength of cement mortars.

Sample Compressive strength (MPa)

At 2 day At 28 day At 90 day

OPC 27.7 50.1 53.3M25-FA1/II 22.0 43.7 57.3M25-FA1/III 21.7 42.7 54.7M25-FA2/II 21.3 46.5 54.8

ilding Materials 28 (2012) 633639M15-FA1-FA3/IIIII in comparison to mix M15-S is attributed tothe higher Blaine surface of separated y ashes from the 2nd and3rd section in electro-lter.

4. Conclusions

1. The co-combustion of coal and biomass causes the deteriorationof y ash properties in comparison to conventional y ashesfrom the coal combustion.

2. The y ashes from the co-combustion of bituminous coal and bio-mass retard cement hydration and decrease cement strengthmorethan traditional siliceous y ashes from the coal combustions.

3. The separation of coalbiomass y ashes from the 2nd and 3rdsection in electro-lter causes increase in their pozzolanicactivity.

4. The cement with addition classied coalbiomass y ashesreveals higher degree of hydration and higher compressivestrengths in comparison to the commercial y ash generatedfrom the y ash fractions of all electro-lter sections.

5. The addition up to 15 wt% of intermixed y ash fraction from

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[11] Ogawa K, Uchikawa H, Takemoto K. The mechanism of the hydration in thesystem C3S pozzolan. Cem Concr Res 1980;10:68396.

[12] Takemoto K, Uchikawa H. Hydration of pozzolanic cement. In: SeventhInternational congress on the chemistry of cement, vol. 1. Paris; 1980. p. IV-2/1IV-2/29.

[13] Abdul-Maula S, Odler I. Hydration reactions in y-ash-Portland cements. In:Malhotra VM, editor. Proceedings of symposium N on effects of y ashincorporation in cement and concrete. Boston: Materials Research Society;1981. p. 10211.

[14] He JY, Scheetz BE, Roy DM. Hydration of y ash Portland cement. Cem ConcrRes 1984;14:58592.

[15] Hwang CL, Shen DH. The effect of blast-furnace slag and y ash on the hydrationof Portland cement. Cem Concr Res 1991;21:41025.

[16] Rayment PL. The effect of pulverized-fuel ash and the C/S molar ratio and alkalicontent of calcium silicate hydrates in cement. CemConcr Res 1982;12:13340.

[17] Uchikawa H. Effect of blending components on hydration and structureformation. In: Eighth international congress on the chemistry of cement, vol. 1.Rio de Janeiro; 1986. p. 25080.

[18] Ju-Yuan H, Scheetz BE, Roy DM. Hydration of y ash Portland cements. Cem

E. Tkaczewska et al. / Construction and Building Materials 28 (2012) 633639 639the 2nd and 3rd electro-lter section allow to obtain y ashPortland cement of strength class 42.5R. The 2-day compressivestrength of this cement reaches 24.6 MPa, whereas the 28-daycompressive strength of this cement is higher with differenceof 1.3%.

Acknowledgement

The paper is the result of Project No. 5.5.160.763, realizing inDepartment of Building Materials Technology, Faculty of MaterialsScience & Ceramics, AGH University of Science and Technology.

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Coalbiomass fly ashes for cement production of CEM II/A-V 42.5R1 Introduction2 Experimental2.1 Materials2.2 Experimental methods

3 Results and discussion3.1 Measurement of the amount of active components (SiO2 and Al2O3) in fly ashes3.2 Pozzolanic activity index of fly ashes3.3 Calorimetric measurements3.4 Compressive strength test

4 ConclusionsAcknowledgementReferences