Mössbauer, DTA and XRD study of Portland cement blended with fly ash and silica fume

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garia

Keywords:

onssbadransfodrat

2011 Elsevier Ltd. All rights reserved.

tracalche hydsum thsulfate

between these phases are negligible [2]. Mssbauer spectroscopyis a suitable method to study the iron distribution in cement, be-cause this approach allows to study directly the character of thebonding, the phase state and the electronic environments of theiron ions [3,4].

The iron in C4AF is bivalent (Fe2+) and trivalent (Fe3+) with thelatter being in tetrahedral (T) and octahedral (O) coordination

correlation has been found between the ratio of the iron quantityin tetrahedral andoctahedral state (Fe3+(T)/Fe3+(O)) and thestrengthof the cement paste.

The Mssbauer spectrum of sulfate-resistant Portland cement iswith two doublets the rst one of the ferrite phase and the sec-ond one, whose intensity increases during hydration, is of iron in-cluded in the monosulfate (AFm-phases). During hydration ofsulfate-resistant Portland cement and slag no Fe(OH)3 was formed[1517].

Hassaan et al. [20,21] has registered two doublets in theMssbauer spectrum of hydrating cement and has found that with

Corresponding author. Tel.: +359 2 9797055; fax: +359 2 9797056.

Construction and Building Materials 29 (2012) 3341

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evE-mail address: [email protected] (O. Petrov).monocarbonate and aluminates with different composition. Thehydration of C4AF proceeds slower but nally hydrate products areformedwith a composition similar to the products of the C3A hydra-tion. In the presence of lime and gypsum the AFt-phase is the mainproduct of reaction but the progress of hydration of C4AF is sloweddown due to the formation of AFt-layer at the surface of the C4AF-grains. In a subsequent step the AFt-phase converts to AFm, priorto complete consumption of calcium sulfate [1].

The distinction between iron-free and the iron-containing ana-logues is difcult to be found, because the structural differences

cement showed that the intensity of the doublets with which theMssbauer spectrum is described changes and after 10 years thedoublet of iron in non-hydrated cement disappeared completely[13].

Harchand et al. [1517] and Eissa et al. [18,19] have registeredthree doublets in the Mssbauer spectra of slag Portland cement two doublets characterizing iron in octahedral and tetrahedral stateand a third one of iron in the hardened monosufate. The authorshave proved that during hydration the relative content of iron inoctahedral state lowers, while that in tetrahedral state increases. AMssbauerCementFly ashSilica fumeHydration productsIron state

1. Introduction

Tricalciumaluminate (C3A) and teare main clinker phases in cement. Tquickly and during reaction with gypand at later stages additionallymono0950-0618/$ - see front matter 2011 Elsevier Ltd. Adoi:10.1016/j.conbuildmat.2011.10.030iumalumoferrite (C4AF)ration of C3A proceedsere is formed ettringiteoccurs accompanied by

and the iron atoms are weakly bonded in strongly deformed crystallattice [59]. Studies [10,11] have shown presence of ne magneticstructure in non-hydrated brownmillerite. During hydration thisphase disappears and the whole content of iron in the solid solu-tion is in octahedral coordination.

The studies of Pobell et al. [1214] on the hydration of PortlandAvailable online 24 November 2011hydration of plain cement portlandite and hydration products form below 450 C. Silica fume and yashes react with portlandite and form products decomposing above 620640 C.Mssbauer, DTA and XRD study of Portlaand silica fume

Vili Lilkov a, Ognyan Petrov b,, Yana Tzvetanova b, PaUniversity of Mining and Geology, Hristo Botev Str., Soa, Bulgariab Institute of Mineralogy and Crystallography, Bulgarian Academy of Sciences, Soa, Bul

a r t i c l e i n f o

Article history:Received 30 June 2011Received in revised form 15 September2011Accepted 2 October 2011

a b s t r a c t

Two octahedral Fe3+ positifor plain cement using Msand one Fe2+ doublets. Hyettringitemonosulfate trablet forms earlier. With hy

Construction and

journal homepage: www.elsll rights reserved.cement blended with y ash

en Savov a

with close isomeric displacements and quadrupole splittings were proveduer spectroscopy. In cements with silica fume iron is registered as two Fe3+

ting cement pastes display a third doublet of tetrahedral iron indicatingrmation. With silica fume and y ashes addition the tetrahedral iron dou-ion the tetrahedral iron increases at the expense of octahedral iron. During

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time the quantity of tetrahedral iron increases at the expense ofoctahedral iron. In the case of high-aluminate cement he has regis-tered three doublets of Fe3+(O), Fe3+(T1) and Fe3+(T2), respec-tively. The intensity of the last two changed with time and thiswas accepted as a measure for the degree of hydration of the ce-ment paste.

Dwivedi et al. [22], Rai et al. [23], and Singh et al. [24] haveproved using the Mssbauer effect the delaying effect on the ce-ment hydration of black gram pulse and superplasticizer, whileBarathan et al. [25] have studied the hydration of Portland cementwith addition of silica fume and have registered the transformationAFt? AFm.

The purpose of the present study is to investigate using the ef-fect of Mssbauer, DTA and XRD the hydration of cement with and

dissolution with diluted nitric acid. The content of FeO was determined by titratingwith KMnO4 after dissolution with H2SO4 in the presence of Na2CO3, which is a re-agent suppressing the oxidation of Fe2+. The content of Fe2O3 was determined as adifference from the total amount Fe2O3(t) and the content of FeO multiplied bythe coefcient for stoichiometric transformation (k = 1.11).

The Mssbauer spectroscopic investigation was performed with a spectrometeroperating in a symmetric triangle, constant acceleration mode. The acceleration cal-ibration is in relation to natural Fe-foil and the Mssbauer source is 57Co/Rh (57Co isintruded in rhodium foil) at room temperature. The obtained data are processed bythe least-squares method with the MOSFINT program. The approximation modelis a sum of doublets (tested for variants 2, 3, or 4 doublets). The program allowsapproximation of the experimental data with the so-called thin approximation

Fig. 1. Pozzolanic activity of the mineral additives.

Fig. 2. XRD patterns of the initial materials.

34 V. Lilkov et al. / Construction and Builwithout addition of silica fume and y ash with low content of Ca.

2. Used materials

The cement sample (PC) is from Zlatna Panega with mineral composition C3S 57.5%; C2S 23.4%; C3A 5.5%; C4AF 11.7%; and gypsum 1.8% and density 3 g/cm3.

Two types of y ashes were used from TEPS Republika (Bulgaria) (FA1) andTEPS Bobov Dol(Bulgaria) (FA2), classied 100% under 63 lm, as well as silicafume (SF) classied 90% under 10 lm and 60% under 1 lm. The specic surface ofthe particles of the mineral additions was determined by BET analysis as follows:SF (18.6 m2/g); FA1 (1.76 m2/g) and FA2 (2.67 m2/g). The chemical composition ofthe initial materials is given in Table 1. The results refer to analytically dry(105 C) sample.

3. Samples and methods

The prepared samples are of plain cement and cement with addition of 10 wt.%of FA and SF from the total quantity of the initial mixture (W/S = 0.5). The sampleswere hermetically closed in polymer containers up to the 24th hour of hydration,after that being removed and kept in water at temperature of 20 C up to a partic-ular age for investigation. For the samples studied in the rst 24 h there was appliedan interruption of the hydration process by drying and subsequent soaking in ace-tone and ether. Then, these samples were dried and ground in the form of dust be-fore analysis.

The specic surface of the ash particles was determined following low temper-ature adsorption (T = 77.4 K) a variant of the BET method.

The pozzolanic activity of the mineral additions was determined according toBulgarian standard BDS 16720-87/1988 by measuring the quantity of calcium diox-ide, which is bound by each additive from a solution of calcium hydroxide after con-tact for 30 days. Mineral addition of 0.5 g is added to 20% solution of calciumhydroxide with concentration of 1.15 mg/cm3. The content of CaO in the ltrate ob-tained after titrating of the solution was determined by titrating with complexon IIIin the presence of uorexon indicator (mixture of timolphtalein and potassiumchloride). The difference between the initial concentration in the solution and thesample obtained after titrating allows calculating the quantity of the bound CaOby the additive expressed in mg CaO per 1 g additive.

The starting materials and the hydrating cement pastes were analyzed fordetermination of the quantity of bi- and trivalent iron. The total content of iron,Fe2O3(t), was determined by the method optical-emission spectroscopy with asource of inductively coupled plasma (ICPOES) after alkaline melting with LiBO2

Table 1Chemical composition of the initial materials.

Samples PC (%) FA1 (%) FA2 (%) SF (%)

SiO2 21.59 58.50 50.40 89.50Fe2O3 (t) 3.78 8.32 7.79 2.88Fe2O3 3.65 5.05 5.81 2.31FeO 0.12 2.95 1.78 0.51TiO2 0.15 0.73 0.71

BuilV. Lilkov et al. / Construction andThe powder XRD analysis was performed on a DRON UM1 diffractometer(Ni-ltered Cu radiation, 34 kV/20 mA). The registration of the diffraction lineswas performed by a scintillation counter.

The complex thermal analysis of the samples was done with apparatus type3427 MOM by heating from 20 C to 1000 C with 10 C/min steps in air andAl2O3 as inert material the mass of the samples was 800 mg each.

Fig. 3. DTA-effects of the samples of cement pastes 48th day of hydration.

Fig. 4. DTG-effects of the samples of cement pastes 48th day of hydration.

Table 2Weight loss during heating of the cement pastes at the 48th day of hydration.

Sample Weight loss during heating, mg/g solid substance (mg/g cement),due to hydrate products in groups

PI Pt PII Total

PC 318.1 75.2 54.1 447.4PCSF 295.2 49.6 93.2 438

(328) (55.1) (103.6) (486.7)PCFA1 266.8 54.2 80 401

(296.4) (60.2) (88.9) (445.5)PCFA2 271 52.7 100 423.7

(301.1) (58.6) (111.1) (470.8)ding Materials 29 (2012) 3341 354. Experimental results and discussion

4.1. Pozzolanic activity of the mineral additions

Fig. 1 represents the curves registered during determination ofthe pozzolanic activity of the minerals additives. The sample SFdisplays greatest pozzolanic activity up to the 15th day. On the

Fig. 5. XRD patterns of the hydrating cement paste PC.

Fig. 6. XRD patterns of the hydrating cement paste PCSF.

Buil36 V. Lilkov et al. / Construction and30th day the pozzolanic activity of the y ash from TEPS BobovDol is almost equal with this of the silica fume and twice as muchas that of the y ash from TEPS Republika.

The higher pozzolanic activity of silica fume in the initial hydra-tion is due to the higher content of amorphous silicon dioxide(about 90%, Table 1) as well as to the ner particles with severaltimes higher specic surface than that of y ash. The differencesin the pozzolanic activity of y ashes is due to the fact that the spe-cic surface of the particles of y ash from TEPS Bobov Dol is 1.5times higher than that of the y ash from TEPS Republika (Fig. 2).

4.2. DTA and DTG analysis

The thermal effects, registered at the 48th day of hydration,during heating of the samples of cement pastes (Figs. 3 and 4)are connected with decomposition of the hydration products andliberation of the hydrate water [30,31] and indicate presence of:calcium hydrosilicates, calcium hydroaluminates and ettringite

Fig. 7. XRD patterns of the hydrating cement paste PCFA1.

Fig. 8. XRD patterns of the hydrating cement paste PCFA2.ding Materials 29 (2012) 3341with temperature of dehydration up to about 435455 C, furtherdenoted as PI products; portlandite, Pt, with temperature of theendothermal peak at about 505510 C, and products denoted PIIincluding calcite and calcium hydrosilicates with temperature ofdehydration higher than 620640 C (Table 2). An effect at 180200 C was also registered for the cement pastes with y ash addi-tion, which probably is due to the thermal decomposition of Camonosulfoaluminate or less probably to hydrocarboaluminate.

For the compositions with mineral additions the peaks of theendothermal effects and their temperature boundaries are movedtowards higher temperature compared with these of the pure ce-ment paste. This is most expressed for the composition with addi-tion of y ash FA2.

The total quantity of the hydration products and of the productswith low temperature of dehydration (PI) and of portlandite in theplain cement paste is higher that the respective quantities in thecement pastes with mineral additions. As a result of the pozzolanicreactions of the silica fume and y ashes in the samples with min-eral additions the hydration products with high temperature ofdehydration get increased. The quantity of portlandite in the plaincement paste is 16.8% from the total quantity of the hydrationproducts, while in the compositions with minerals additions thisquantity is in the range 11.313.5%. The quantitative ratio between

Fig. 9. Mssbauer spectra of the initial materials (upper patterns experimental;lower patterns theoretical).

le sp

e3+

BuilTable 3Mssbauer parameters of the initial materials (d isomer displacement, D quadrup

Sample d1 (mm/s) Fe3+ d2 (mm/s) Fe3+ d3 (mm/s) Fe2+ D1 (mm/s) F

PC 0.22(O1) 0.27(O2) 1.24(O1)SF 0.31(T1) 0.66 0.86(T1)FA1 0.38(T1) 0.64(T2) 0.86 0.64(T1)FA2 0.20(T1) 0.45(T2) 0.58 0.92(T1)

V. Lilkov et al. / Construction andthe hydration products PI/PII for the compositions with mineraladditives is in the interval 2.73.3 and in the plain cement pasteit is 5.9.

If the quantity of hydration products is calculated per 1 g ce-ment in the cement pastes it is seen that for the pastes with addi-tion of silica fume and y ash FA2 this amount is 486.7 mg/gcement and 470.8 mg/g cement. In the plain cement paste and inthe paste with y ash FA1 it is respectively 447.4 and 445.5 mg/gcement. These results show that the silica fume and the y ashfrom TEPS Bobov Dol display high pozzolanic activity and stimu-late the hydration of cement.

4.3. XRD analysis

Fig. 2 presents the powder XRD patterns of the initial materialsand Figs. 58 the patterns of samples from the studied cementpastes. After 1 day of hydration the main peaks characterizing

Fig. 10. Mssbauer spectra of the plain cement paste at different ages of

Table 4Mssbauer parameters of the cement PC at different ages of hydration (d isomer displac

Time of hydration d1 (mm/s) (O1) d2 (mm/s) (O2) d3 (mm/s) (T) D1 (mm/s)

0 h 0.22 0.27 1.245 day 0.23 0.29 1.4614 day 0.24 0.29 0.24 1.4228 day 0.26 0.30 0.26 1.3548 day 0.28 0.30 0.28 1.36litting, I intensities).

D2 (mm/s) Fe3+ D3 (mm/s) Fe2+ I1 (%) Fe3+ I2 (%) Fe3+ I3 (%) Fe2+

1.65(O2) 46(O1) 54(O2) 2.36 82(T1) 181.11(T2) 2.25 31(T1) 23(T2) 460.95(T2) 2.31 39(T1) 36(T2) 25

ding Materials 29 (2012) 3341 37portlandite have higher intensities in the cement pastes with addi-tion of y ash and lower intensity for the paste with silica fume incomparisons with the same peaks for the cement paste withoutaddition. It follows that y ashes stimulate the process of hydra-tion up to the 24th hour and display lower pozzolanic activity com-pared to silica fume. On later ages of hardening the intensity of thepeaks of portlandite with minerals additions lowers, thus, indicat-ing that as a result of the pozzolanic reactions the quantity of port-landite lowers and up to the 48th day it is lower than therespective one of the plain cement paste.

4.4. Mssbauer spectroscopy

The Mssbauer spectra of the initial materials are presented onFig. 9. The spectra of the initial cement (PC) and silica fume (SF)(Fig. 9) were processed with a model of two doublets. The obtainedMssbauer parameters (Table 3) show that the iron atoms in the

hydration (left patterns experimental; right patterns theoretical).

ement, D quadruple splitting, I intensities).

(O1) D2 (mm/s) (O2) D3 (mm/s) (T) I1 (%) (O1) I2 (%) (O2) I3 (%) (T)

1.65 46 54 1.84 39 61 1.81 0.38 40 32 281.81 0.37 27 37 361.84 0.44 30 33 37

Fig. 11. Mssbauer spectra of the cement paste with addition of silica fume (PCSF) at different ages of hydration (left patterns experimental; right patterns theoretical).

Fig. 12. Mssbauer spectra of the cement paste with addition of y ash 1 (PCFA1) at different ages of hydration (left patterns experimental; right patterns theoretical).

38 V. Lilkov et al. / Construction and Building Materials 29 (2012) 3341

BuilV. Lilkov et al. / Construction andinitial cement are in trivalent state (Fe3+), distributed in two octa-hedral positions (O1) and (O2) with intensities I1 = 46% andI2 = 54%, respectively. A doublet that characterizes iron in bivalentstate (Fe2+) was not registered, probably due to its low content. Theiron atoms in the silica fume is distributed in trivalent state withtetrahedral coordination (T1) and in bivalent state with intensitiesI1 = 82% and I3 = 18%, respectively. The spectra of the y ashes (FA1and FA2, Fig. 9) were processed with a model with three doubletsthe rst two of which corresponding to trivalent iron in tetrahedralcoordination (T1) and (T2), while the third one being due to biva-lent iron (Table 3).

Fig. 10 presents the Mssbauer spectra of the initial cement atdifferent ages of hydration and Table 4 contains the respectiveparameters obtained during processing of the spectra with a model

Fig. 13. Mssbauer spectra of the cement paste with addition of y ash 2 (PCFA2) at dif

Table 5Mssbauer parameters of the cement paste with addition of silica fume (PCSF) at different

Time of hydration d1 (mm/s) (O1) d2 (mm/s) (O2) d3 (mm/s) (T) D1 (mm/s)

10 h 0.23 0.30 1.391 day 0.26 0.29 0.30 1.386 day 0.25 0.29 0.30 1.4112 day 0.24 0.29 0.33 1.3724 day 0.25 0.29 0.34 1.3348 day 0.23 0.29 0.33 1.36

Table 6Mssbauer parameters of the cement paste with addition of y ash F1 (PCFA1) at differen

Time of hydration d1 (mm/s) (O1) d2 (mm/s) (O2) d3 (mm/s) (T) D1 (mm/s)

3 h 0.25 0.30 1.321 day 0.25 0.30 1.304 day 0.26 0.30 0.30 1.4212 day 0.25 0.30 0.30 1.4128 day 0.25 0.30 0.32 1.39ding Materials 29 (2012) 3341 39of two and three doublets for the different ages. Up to the 5th daywe observe redistribution of the ions of the trivalent iron (Fe3+) be-tween the two octahedral positions and its quantity increases inposition O2, which is connected with the hydration of the tetracal-cium alumoferrite.

Between the 5th and 14th day a new doublet is formed of thetrivalent iron in tetrahedral coordination (T) with intensityI3 = 28% as a result of lowering of its quantity in the octahedral po-sition O2. This doublet is connected with the formation of monos-ulfoaluminate in the cement pastes, which forms at the later stagesof hydration [2,32,33] and its intensity increases up to the 28thday. The Mssbauer parameters of the third doublet differ fromthose of Fe(OH)3 (d = 0.25 mm/s, D = 0.72 mm/s) and its gel(d = 0.45 mm/s, D = 0.72 mm/s) [17], which means that the during

ferent ages of hydration (left patterns experimental; right patterns theoretical).

ages of hydration (d isomer displacement, D quadruple splitting, I intensities).

(O1) D2 (mm/s) (O2) D3 (mm/s) (T) I1 (%) (O1) I2 (%) (O2) I3 (%) (T)

1.77 54 46 1.74 0.67 65 23 121.88 0.51 33 37 301.81 0.43 30 36 341.79 0.45 29 34 371.81 0.47 26 28 46

t ages of hydration (d isomer displacement, D quadruple splitting, I intensities).

(O1) D2 (mm/s) (O2) D3 (mm/s) (T) I1 (%) (O1) I2 (%) (O2) I3 (%) (T)

1.79 42 58 1.74 39 61 1.84 0.59 35 43 221.82 0.43 30 31 391.83 0.50 29 35 36

[9] Ekimov SP, Boikova AI, Grishchenko LV. Distribution of Fe in the structure of

ren

(mm

Builhydration of tetra-calcium alumoferrite there is no formation ofFe(OH)3 or its quantity is very low.

Figs. 1113 represent respectively the Mssbauer spectra of thecement pastes with silica fume and y ashes FA1 and FA2 recordedat different ages of hydration, while Tables 57 contain the respec-tive Mssbauer parameters.

Between the 10th and 24th hour of hydration in the spectrum ofthe cement paste with silica fume a third doublet is formed withintensity I3 = 12% indicating iron atoms in tetrahedral coordination.Up to the 48th day the quantity of tetrahedral iron increases up to46%, while the iron atoms in the two octahedral positions O1 andO2 is distributed almost equally (Table 5).

From Tables 6 and 7 it is seen that in the Mssbauer spectra ofthe cement pastes with y ash the doublet of trivalent iron in tet-rahedral coordination is formed earlier, compared with the plaincement pastes and its intensity increases with the time of hydra-tion. The reason for this is that in the presence of y ash smallerquantity of ettringite is formed and after the rst day smallerquantity of portlandite is formed as well thus resulting in slowingof the hydration of C4AF [34]. The nal result is formation of great-er quantity of monosulfate because of the lowering of the SO4/Al2O3 ratio in the system thus favoring AFm formation [35,36].

The earlier appearance of the doublet of trivalent iron and high-er intensity for the cement pastes with silica fume compared withcements with y ash is due not only to accelerated hydration in ce-ments with silica fume in the rst 24 h [37,38], but at the sametime is also due to slowing of the hydration of tetracalcium alumo-ferrite in the presence of y ash.

5. Conclusions

In the initial cements iron is present in the form of Fe2O3 andFeO phases. The bivalent iron in the cement pastes is registeredonly chemically due to its low concentration. The trivalent ironin the initial cements is distributed in two octahedral positionswith close isomeric displacements and quadruple splittings.

(1) In the case of cements with silica fume the iron atoms arepresent in bi- and trivalent form, which on the Mssbauerspectra is registered with three doublets two for the triva-lent iron in tetrahedral coordination and one for iron atoms

Table 7Mssbauer parameters of the cement paste with addition of y ash F2 (PCFA2) at diffe

Time of hydration (day) d1 (mm/s) (O1) d2 (mm/s) (O2) d3 (mm/s) (T) D1

1 0.24 0.30 1.325 0.25 0.31 0.31 1.43

14 0.25 0.31 0.31 1.3928 0.25 0.29 0.32 1.3548 0.25 0.29 0.33 1.35

40 V. Lilkov et al. / Construction andin bivalent form.(2) The Mssbauer spectra of hydrating cement pastes display a

third doublet revealing iron in tetrahedral coordination indi-cating the transformation of ettringite intomonosulfate form.

(3) In the cement pastes with addition of silica fume and yashes the doublet of the tetrahedral iron is formed earliercompared to the plain cement pastes because the quantityof ettringite and portlandite is lower than those in the plaincement pastes and at the same time greater quantity ofmonosulfate is formed as well. With the time of hydrationthe relative content of iron in tetrahedral state increases atthe expense of iron in octahedral coordination.

(4) During hydration of tetracalcium alumoferrite no Fe(OH)3 isformed.calcium aluminoferrites. Sov Phys Crystallogr 1979;24(1):4854.[10] Vertes A, Ranagajic-Konor M, Tamas F. Brownmillerite hydration by

Mssbauer spectroscopy. Hung J Ind Chem 1975;3:33948.[11] Ferenc D, Tams F, Vrtes A. A Mssbauer study on the hydration of

brownmillerite (4CaO.A12O3.Fe2O3). Cem Concr Res 1973;3(5):57581.[12] Pobell F, Wittmann F. Mssbauer effect of 14.4 KeV for Fe in the

superparamagnetic ferrite in Portland cement. Z Angew Phys 1966;20:48892.[13] Pobell F, Wittmann F. Replacement of Fe3+ by Al3+ in calcium aluminate ferrite.

Phys Lett 1965;19:1756.[14] Wittmann F, Pobell F, Wiedemann W. Study of the hydration of iron contained

in clinker products by Mssbauer effect. Z Angew Phys 1965;19:2814.[15] Harchand KS, Kumar R, Vischwamittar, Chandra K. A hydration study of

calcium aluminoferrite phase in two special cements. In: Proceedingsinternational conference on the applications of Mssbauer effect, Srinagar,India; 1981. p. 296303.(5) During hydration of the plain cement there are formed pre-dominantly portlandite and hydration products with tem-perature of dehydration up to 450 C.

(6) Silica fume and y ashes react with portlandite, which isformed during the hydration of cement and take part inthe process of formation of products, which thermallydecompose at temperatures above 620640 C. The y ashfrom TEPS Republika is with lower activity that the yash from TEPS Bobov Dol. The highest initial pozzolanicactivity is displayed by the silica fume.

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V. Lilkov et al. / Construction and Building Materials 29 (2012) 3341 41

Mssbauer, DTA and XRD study of Portland cement blended with fly ash and silica fume1 Introduction2 Used materials3 Samples and methods4 Experimental results and discussion4.1 Pozzolanic activity of the mineral additions4.2 DTA and DTG analysis4.3 XRD analysis4.4 Mssbauer spectroscopy

5 ConclusionsReferences