外文翻译(英文)掺有粉煤灰、硅灰的硅酸盐水泥的热分析和微观结构

1、Thermal analysis and microstructure of Portland cement-y ash-silica fume pastesArnon Chaipanich ÆThanongsak NochaiyaReceived:31May 2009/Accepted:29July 2009/Published online:24September 2009ÓAkade´miai Kiado ´,Budapest,Hungary 2009Abstract Thermal analysis (thermogravimetry and d

2、if-ferential thermal analysiswas used with scanning electron microscopy technique to investigate the hydration mecha-nisms and the microstructure of Portland cement-Fly ash-silica fume mixes.Calcium silicate hydrate (CSH,ettringite,gehlenite hydrate (C 2ASH 8,calcium hydroxide (Ca(OH2and calcium car

3、bonate (CaCO 3phases were detected in all mixes.In the mixes with the use of silica fume addition,there is a decrease in Ca(OH2with increasing silica fume content at 5and 10%compared to that of the reference Portland-y ash cement paste and a corresponding increase in calcium silicate hydrate (CSH.Ke

4、ywords Thermal analysis ÁMicrostructure ÁFly ash ÁSilica fume ÁHydrationIntroductionFly ash,a by-product from coal power plants,has been recognized as an important construction material due to its environmental benets and engineering benets (produce less heat of hydration,increas

5、e workability and improve durability to chemical attacks such as chlorides and sul-phatesand has been used extensively world wide as a cement replacement material 1,2.However,it is com-monly known that y ash,which is a pozzolanic material i.e.will react to form a binding material similar to that of

6、Portland cement in the presence of water and calciumhydroxide,Ca(OH224.This pozzolanic reaction with Ca(OH2occurs slowly due to Ca(OH2has to be rst produced as a result of hydration product of Portland cement (PCand also that the particle size of normally usable y ash is somewhat coarser than that o

7、f PC.The particle size of typical y ash used is within the region of 66100%passing at 45l m or not more than 34%retaining at this sieve size according to ASTM C6185as compared to the average particle size of PC at &1015l m.Silica fume occurred as a by-product of the ferro-silicon alloys and sili

8、con metal industries,on the other hand,is very ne at the average particle size of &100nm 1.Its high reactivity is known to benet the strength of concrete where a signicant gain in strength of concrete has been reported 610when used on its own as a cement replacement material in its own right.The

9、 use of silica fume as an additional material in y ash blended cement such as Portland cement-Fly ash-silica fume mix has recently attracted interests in the research of its effects on properties of y-ash mixes,mainly in term of its strength and durability benets for use as a construction material 1

10、113.However,the hydration study of this mix in the paste system is limited 14,15.For the rst 24h the hydration of Portland cement-Fly ash silica fume paste has been reported to show that there is a reduction in Ca(OH2content 14.Little is known however,in terms of the effect thereafter and that no fu

11、ll investigation of the system have been found using both thermogravimetric and differential thermal analysis.In this work,y ash (FA,was blended with Portland cement (PCto produce Portland-Fly ash cement pastes and silica fume (SF,as a highly reactive material was then used to produce ternary cement

12、 paste mixes (Portland cement-Fly ash-silica fume.Thermal analysis in terms of thermogravimetric and differential thermal analysis were then used with scanning electronA.Chaipanich (&ÁT.NochaiyaCement and Concrete Research Laboratory,Department of Physics and Materials Science,Faculty of Sc

13、ience,Chiang Mai University,Chiang Mai 50200,Thailand e-mail:arnonchiangmai.ac.thJ Therm Anal Calorim (201099:487493DOI 10.1007/s10973-009-0403-ymicroscopy technique to investigate the hydration mecha-nisms and the microstructure of Portland cement-Fly ash-silica fume mixes.Silica fume was used as a

14、n additional material at 5and 10wt%to the Portland cement-y ash mixes.As part of this investigation compressive strength studies of the ternary blends were also carried out to cor-respond with the thermal analysis in order to determine hydration products of Portland cement-y ash-silica fume pastes w

15、ith further investigation on the microstructure of the samples were also carried out.Experimental techniquesPortland cement type I (PCwas used in the investigation.In this study,y ash (FAwas obtained from Mae Mao Power Plant,Lampang,Thailand and silica fume (SFwas obtained from Sikament Ltd.Chemical

16、 composition of these materials are given in Table 1.The mixes of Portland cement-Fly ash-silica fume pastes are given in Table 2.Fly ash was used as a Portland cement replacement at 10,20and 30wt%to produce Portland-y ash cement and silica fume was used as an additive material which was added at 5a

17、nd 10wt%to Portland-y ash cement.The water/binder ratio of these cement pastes used was 0.5.To increase the homogeneity,the binders (PC,FA and SFwere rst mixed together in the mixer for 3min,and then the water was added.The mixture was mixed for another 2min.After that,the mixes were poured into oil

18、ed molds (50950950mm 3and then compacted.The specimens were then surface-smoothed,and covered with plastic lm.All specimens were removed from the moulds 1day after casting.Thereafter,they were cured in water at room (&25°Ctemperature.For compressive strength tests of the pastes,y ash was us

19、ed as a cement replace-ment at 10,20and 30wt%with and without silica fume addition.Compressive strength tests were carried out using three specimens for each test and an average result was then obtained at the age of 7,28and 90days.Also at 28days,selective samples of mainly 20%y ash were used to rep

20、resent typical sample of the mixes with and without silica fume for microstructure and thermal analyses.The microstructure of the samples was investigated using scanning electron microscopy (SEM;JEOL-JSM-840Aandthen ground for thermal analysis (thermogravimetry and differential thermal analysisusing

21、 the Mettler Toledo TG/SDTA 851e .The samples were heated from room tem-perature to 1,000°C with a scanning rate of 10°C min -1under nitrogen atmosphere condition.In addition,thermogravi-metry and differential thermal analyses were also carried out for Portland cement-y ash (20%-silica fum

22、e (10%sample at 7,28and 90days in order to determine the effect of time on the hydration phases of the ternary mix.Results and discussionThe inuence of silica fume on the compressive strengths of the Portland-y ash cement pastes at 28days is shown in Fig.1a.The results show for all 10,20and 30wt%of

23、y ash content without silica fume content,the values of compressive strength of y ash mixes (3745MPaare all less than those of Portland cement paste (47MPaas can be seen from Fig.1a.However,when silica fume was added (Portland cement-y ash-silica fume pastes,the compressive strength was found to inc

24、rease signicantly with the use of silica fume in the mix.In some cases (10FA5SF and 10FA10SFthe compressive strengths (48.5and 50MPa,respectivelywere higher than Portland cement paste.For 20%y ash mix with silica fume withTable 1Chemical compositions of Portland cement,y ash and silica fume Material

25、sOxide content/%SiO 2Al 2O 3Fe 2O 3CaO MgO Na 2O K 2O P 2O 5TiO 2SO 3LOI Portland cement 20.85 4.98 3.5264.30 1.530.120.59 2.60 1.40Fly ash 39.8221.5213.6815.24 2.78 1.08 2.000.180.42 2.39 1.00Silica fume95.300.650.280.270.410.260.771.230.25Table 2Mix proportions and analysis of the investigated pas

26、tes Mixesw/bMix proportion (PC/wt%PCFA a SF b PC 0.510010FA 0.5901010FA5SF 0.59010510FA10SF 0.590101020FA 0.5802020FA5SF 0.58020520FA10SF 0.580201030FA 0.5703030FA5SF 0.57030530FA10SF0.5703010a Cement replacement bAdditional materials488 A.Chaipanich,T.Nochaiya10%addition of silica fume (20FA10SFthe

27、 compressive strengths were very close to that of Portland cement paste at 28days and become just slightly higher at 90days as shown in Fig.1b (57.0MPa compare to control PC of 56.5MPa.It also remained to be signicantly higher than the reference y ash mix without silica fume where the compressive st

28、rength was at 53.0MPa.The enhancement in the strength was expected to be due to the pozzolanic reaction of silica fume where thermal analysis is required in order to conrm this pozzolanic reaction has taken placed.This is described in the following section.From X-ray diffraction traces of the Portla

29、nd cement-y ash-silica fume pastes (Fig.2,dominant peaks detected by means of X-ray diffraction (XRDwas calcium hydroxide Ca(OH2noted as CH.The Ca(OH2peaks can be seen in all mixes,thus this give an idea of the hydration reaction of each mixes.As can be seen from XRD traces,it is clear that for the

30、y ash mix with the use of silica fume addition,the intensity of Ca(OH2is less than that of the reference y ash mix without silica fume.This shows that the pozzolanic reaction (SiO 2and/or Al 2O 3reaction with Ca(OH224has taken placed,whereby Ca(OH2was being clearly consumed by silica fume.Thermograv

31、imetric analysis (TGwas then used to further analyse the phases which do not appear by the useof XRD technique which only shows the crystalline phases.The results obtained from TG,as shown in Fig.3,for Portland cement and Portland-Fly ash cement pastes with and without the addition of SF (using FA a

32、t 20%to rep-resent typical effect of SFshows three mass loss transition with the rst being from room temperature &30420°C,the second from &420500°C and the third &5001,000°C.TG can be used to determine quantitatively from the mass loss of the liquid (H 2Oor gas (CO 2of the

33、 hydrated phases.The phases detected by means of TG at the rst transition which consist of several hydrated phases at this range which are ettringite,CSH and C 2ASH 8.The second transition which occurred from the (dehydroxila-tionof water from Ca(OH2,and the third transition of mass loss occurred fr

34、om the decarbonation of calcium carbonate.The mass loss of the pastes of each phases can be cal-culated from each transition occurring in the TG curves and also can be further calculated to give the relative mass loss if taken overall mass loss as 100%.The calculated values for Portland cement,y ash

35、 mixes with and without silica fume are given in Table 3,where the relative mass lossFig.1Comparison of compressive strengths ofPortland-y ash cement pastes with silica fume after curing at a 28days and b at different agesFig.3TG curve results and mass loss of phase 1(ettringite ?CSH ?C 2ASH 8and ph

36、ase 2(calcium hydroxideof Portland cement paste and y ash cement pastes with and without silica fume at 28daysPortland cement-y ash-silica fume pastes 489from all transitions can be seen as both the mass loss of the sample and also as mass loss to overall mass loss.For these calculations,a selective

37、 mixes of y ash with silica fume were selected i.e.using 10%y ash with 5%SF and 20%y ash with both 5and 10%SF as representatives.For the case without SF,the rst transition which covers the mass loss of the hydrated phases (ettringite,CSH and C 2ASH 8between room temperature to 420°C was found t

38、o be highest in Portland cement paste (21.10%.For the reference Portland cement-y ash mix without silica fume,this mass loss was found to be less (at 20.35%for 10%FA mix and 19.90%for 20%FA mixdue to less amount of the CSH phase which would result in lower strength as found.On the other hand this ma

39、ss loss was found to increase slightly with the addition of silica fume at 5%(21.63and 19.97%for 10%FA mix and 20%FA mix respectively.Moreover,it is clear from the second phase that calcium hydroxide can be seen to reduce when FA is used (3.44%for 20%FA with no SFand is further reduced when SF is ad

40、ded (3.02%for 5%SF and 2.56%for 10%SFwhen compared to the control PC paste at 4.80%.Further analysis is then carried out in term of overall mass loss,the mass loss in each transition to overall mass loss (i.e.overall mass loss is taken as 100%for Portland cement-y ash-silica fume mixes using y ash a

41、t 20%with and without SF to represent a typical effect of SF,is shown (insetin Fig.3.An increase in the mass loss in the rst transition attributed to ettringite,CSH and C 2ASH 8with respect to SF content can be seen and as a consequent there is a decrease in the second transition attributed to Ca(OH

42、2due to the pozzolanic reaction (consumption of Ca(OH2with SF.Nonetheless,the mass loss in the rst transition cannot be used to single out an individual phase such as CSH since the range of mass loss in each transition is rather broad and therefore using TG alone can not established this.Derivative

43、thermogravimetric (DTGand differential thermal analysis (DTAtherefore,were used to further determine each phases.The DTG results of Portland cement pastes and of Portland cement-Fly ash-silica fume pastes are plotted as shown in Fig.4a.After 28days curing in water the DTG curves for all pastes show

44、detected phases which are calcium silicate hydrate (CSH,6CaO ÁAl 2O 3Á3SO 3Á32H 2O (ettringite,2CaO ÁAl 2O 3ÁSiO 2Á8H 2O or gehlenite hydrate (noted as C 2ASH 8,calcium hydroxide (notes as CH for convenienceand calcium carbonate (CaCO 3,noted as CCdetected at &7684&

45、#176;C,&104114°C,&157163°C,&458464°C and &667688°C,respectively.The comparison of DTG graphs of Portland-y ash cement pastes with and without silica fume (curing in water at 28dayswhen replaced Portland cement with y ash at 20wt%and added silica fume up toTable 3C

46、alculated mass loss of the phases of Portland-y ash cement pastes MixesMass loss from TG curves/%Mass loss to overall mass loss/%CSH ?ettringite ?C 2ASH 8CH CC CSH ?ettringite ?C 2ASH 8CH CC PC 21.10 4.80 2.9473.1716.6410.1810FA 20.35 4.23 2.0576.4115.887.7110FA5SF 21.63 3.61 1.9179.6813.307.0220FA

47、19.90 3.45 2.2977.6413.458.9220FA5SF 19.97 3.02 2.3278.8811.939.1820FA10SF19.072.562.3579.5310.68 9.81490A.Chaipanich,T.Nochaiya10wt%are presented.Although,the phases detected were found to be similar to those in Portland cement paste,it is noticed from the DTG curves(Fig.4athat there is a decrease

48、in Ca(OH2with increasing silica fume content at 5and10%compared to that of the reference Portland-y ash cement paste.This was due to the increase in pozzo-lanic reaction when silica fume was also added thus con-suming more of calcium hydroxide.Consequently,it is evidently clear that more of calcium

49、silicate hydrate(CSH can be detected in both mixes with silica fume and this is seen increasing with silica fume content.This increase in CSH would therefore agree with the compressive strength results where the compressive strength also increases with SF content.DTA curves of hydrated Portland ceme

50、nt-y ash-silica fume samples usingy ash at20%samples with and without SF is shown plotted in Fig.4b.Three main endo-thermic peaks were detected as can be seen from theseDTA curves.Therst endothermic peak in the temperature range of82163°C is related to the dehydration of calcium silicates and c

51、alcium alumino silicate hydrates.Further-more,this peak can be noticed to be stronger in intensity for mixes with SF.The second endothermic peak can be seen at the temperature range of455466°C which is attributed to the Ca(OH2decomposition.The third endo-thermic peak can be seen at697724°C

52、 as a result of CaCO3decomposition.These temperature ranges for the three main peaks detected are in similar to the ones detected in DTA curves by Giergiczny16and Amer17.In addition,TG was used to study the effect of time on the mass loss of the Portland cement-y ash(20%-silica fume(10%sample at7,28

53、and90days and these results are shown in Fig.5.The mass loss can be seen to be greater with time and that the over mass loss is also greater with increasing period of curing.Again,the mass loss can be calculated as to the overall mass of the cement paste samples and also as relative percentages to t

54、he overall mass loss of100%,and the calculations of these mass loss at three main transitions are given in Table4.It can be seen that mass the loss in therst transition increased when the curing period was increased thus producing more hydration products with time.As a consequent,silica fume would c

55、onsumed more Ca(OH2and thus this reduction is seen.These trends are also clearly seen when plotted against time as relative percentages to overall mass loss percent-ages of three transitions as shown in the inset of Fig.5.The effect of curing time can also be further analysed with the use of DTG,whe

56、re the DTG plots for this ternary mix(20%FA with10%SFat90days are compared to the results of7and28days as shown in Fig.6a.Calculated mass loss of the phases in relation to these derivatives can also be seen in Table4.The hydration products such as calcium silicate hydrate(CSHcan clearly be noticed t

57、o increase with time and that a reduction of Ca(OH2is seen as a direct consequent of pozzolanic reaction with time to produce the resulting CSH.This therefore explained the increase in the compressive strength of this ternary mix when the curing time was increased.An increase in the endothermic peak

58、 for the hydration products is also evident in Fig.6b.In a sense the endo-thermic peak of CaOH2represented as CH,is weaker in sample of90days compared to the one at28days. Although,the endothermic peak of CaOH2at7days is not the strongest,it is however by far the broadest when compared to the peaks

59、at longer period.Therefore,DTA curves can be seen to show an increase in CSH but not clear for calcium hydroxide and calcium carbonate,this is not understood why.However,when also carefullyTable4Calculated mass loss of the phases of20FA10SF mix at different timeMixes Mass loss from TG curves/%Mass loss to overall mass loss/%CSH?ettringite? C2ASH8CH CC CSH?ettringite?C2ASH8CH CC20FA10SF7days17.32 2.77 2.7475.8712.1412.01 20FA10SF28days19.07 2.56 2.3579.5310.689