models for the structure of C-S-H- applicability to hardened pastes of tricalcium silicate

Tobermorite/jennite-and tobermorite/calcium hydroxide-based models for the structure of C-S-H:applicability to hardened pastes of tricalcium silicate,h -dicalcium silicate,Portland cement,and blends of Portland

cement with blast-furnace slag,metakaolin,or silica fume

I.G.Richardson *

Civil Engineering Materials Unit,School of Civil Engineering,University of Leeds,Leeds LS29JT,UK

Received 26May 2004;accepted 27May2004

Abstract

The purpose of this article is to discuss the applicability of the tobermorite–jennite (T/J)and tobermorite–‘solid-solution’calcium hydroxide (T/CH)viewpoints for the nanostructure of C-S-H present in real cement pastes.The discussion is facilitated by a consideration of the author’s 1992model,which includes formulations for both structural viewpoints;its relationship to other recent models is outlined.The structural details of the model are clearly illustrated with a number of schematic diagrams.Experimental observations on the nature of C-S-H present in a diverse range of cementitious systems are considered.In some systems,the data can only be accounted for on the T/CH structural viewpoint,whilst in others,both the T/CH and T/J viewpoints could apply.New data from transmission electron microscopy (TEM)are presented.The ‘inner product’(Ip)C-S-H in relatively large grains of C 3S or alite appears to consist of small globular particles,which are c 4–8nm in size in pastes hydrated at 20j C but smaller at elevated temperatures,c 3–4nm.Fibrils of ‘outer product’(Op)C-S-H in C 3S or h -C 2S pastes appear to consist of aggregations of long thin particles that are about 3nm in their smallest dimension and of variable length,ranging from a few nanometers to many tens of nanometers.The small size of these particles of C-S-H is likely to result in significant edge effects,which would seem to offer a reasonable explanation for the persistence of Q 0(H)species.This would also explain why there is more Q 0(H)at elevated temperatures,where the particles seem to be smaller,and apparently less in KOH-activated pastes,where the C-S-H has foil-like morphology.In blended cements,a reduction in the mean Ca/Si ratio of the C-S-H results in a change from fibrillar to a crumpled-foil morphology,which suggests strongly that as the Ca/Si ratio is reduced,a transition occurs from essentially one-dimensional growth of the C-S-H particles to two-dimensional;i.e.,long thin particles to foils.Foil-like morphology is associated with T-based structure.The C-S-H present in small fully hydrated alite grains,which has high Ca/Si ratio,contains a less dense product with substantial porosity;its morphology is quite similar to the fine foil-like Op C-S-H that forms in water-activated neat slag pastes,which has a low Ca/Si ratio.It is thus plausible that the C-S-H in small alite grains is essentially T-based (and largely dimeric).Since entirely T-based C-S-H is likely to have different properties to C-S-H consisting largely of J-based structure,it is possible that the C-S-H in small fully reacted grains will have different properties to the C-S-H formed elsewhere in a paste;this could have important implications.D 2004Elsevier Ltd.All rights reserved.

Keywords:Calcium-silicate-hydrate (C-S-H);Cement paste;Granulated blast-furnace slag;Metakaolin;Silica fume

1.Introduction

What is it that is produced during the hydration of Portland cement (PC)that results in the formation of a hardened mass?This rather fundamental question was first addressed experimentally by Henri Le Chatelier and Wil-helm Michae ¨lis in their classic works of the late 19th and

early 20th centuries.Their competing theories for the hardening of cement resulted in a long-continued and somewhat polarized debate:Michae ¨lis’‘colloids’theory (e.g.,Refs.[1,2])(and its derivatives, e.g.,Ref.[3]),against Le Chatelier’s ‘crystalloids’theory (e.g.,Refs.[4,5]).Le Chatelier believed that the principal binding phase was a calcium silicate hydrate of formula CaO áSiO 2á2.5H 2O;Newberry and Smith [6]also thought that it was a calcium silicate hydrate,but with the formula 1.5–2CaO áSiO 2á(aq),whilst Rankin [7]thought it a

0008-8846/$–see front matter D 2004Elsevier Ltd.All rights reserved.doi:10.1016/j.cemconres.2004.05.034

*Tel.:+44-113-343-2331;fax:+44-113-343-2265.

E-mail address:i.g.richardson@https://www.sodocs.net/doc/3215940210.html, (I.G.Richardson).Cement and Concrete Research 34(2004)

1733–1777

hydrous silica.Bogue concluded in his book in 1955that the probable composition was close to 1.5CaO áSiO 2á(aq)[8].Bernal et al.[9]found through X-ray studies on hydrated C 3S pastes that the calcium silicate hydrate (C-S-H)that was formed was nearly amorphous and thus difficult to characterize structurally;they did,however,consider that it was related to C-S-H phases formed in dilute suspensions,which they called calcium silicate hydrates (I)and (II)[10],which had low and high Ca/Si ratios,respectively.Calcium silicate hydrate (I)had a layer structure,with the layers elongated in one direction that resulted in a fibrous structure,and showed similarities to tobermorite,a rare crystalline calcium silicate hydrate that had been found in Northern Ireland,which has the approx-imate constitutional formula Ca 4(Si 6O 18H 2)áCa á4H 2O and a Ca/Si ratio of 0.83.Its structure—first described by Megaw and Kelsey in 1956[11]—contains linear silicate chains of the ‘dreierkette’form in which the silicate tetrahedra coordinate themselves to Ca 2+ions by linking in such a way as to repeat a kinked pattern after every three tetrahe-dra.Two of the three tetrahedra share O–O edges with the central Ca–O part of the layer;these are linked together and are often referred to as ‘paired’tetrahedra (P).The third tetrahedron,which shares an oxygen atom at the pyramidal apex of a Ca polyhedron,connects the two ‘paired’tetrahedra and so is termed ‘bridging’(B).The dreierkette-type chain present in tobermorite is illustrated in Fig.1.Taylor and Howison [13]suggested that the Ca/Si ratio could be raised above 0.83by the removal of some of these ‘bridging’tetrahedra and replaced by interlayer Ca 2+

ions.Various dreierkette-based models have subsequently been proposed,which broadly fall into two categories that have different ways of raising the Ca/Si ratio to the value observed experimentally in C 3S or neat PC pastes,i.e.,1.7–1.8.The first category envisages elements of tober-morite-like structure interstratified with layers of calcium hydroxide:the so-called tobermorite–‘solid-solution’calci-um hydroxide,or T/CH,viewpoint [14–16].The second category envisages elements of tobermorite-like structure intermixed with others of jennite-like structure [17]:the tobermorite–jennite,or T/J,viewpoint.Jennite is another crystalline calcium silicate hydrate that has dreierkette silicate chains,but it has a much higher Ca/Si ratio than tobermorite (formula Ca 9Si 6O 18(OH)6á8H 2O;Ca/Si ratio

of

Fig.1.Schematic diagrams showing dreierkette chains present in 14A

?tobermorite (which in theory are of infinite length)projected along [010](top)and [210](crystal structure data from Bonaccorsi et al.[12]and private communication).The chains have a kinked pattern where some silicate tetrahedra share O –O edges with the central Ca –O layer (called ‘paired’tetrahedra,P)and others that do not (called ‘bridging’tetrahedra,

B).

Fig.2.Schematic diagrams showing layers of Ca(OH)2(top)and dreierkette chains present in the structure of jennite (which in theory are of infinite length)projected along [010](middle;hydroxyl groups are indicated by ‘H’)and [100](bottom)(jennite data from Bonaccorsi et al.[20]).‘Paired’and ‘bridging’tetrahedra are labelled ‘P’and ‘B’,respectively.The oxygen atom labelled ‘H’on the ‘bridging’tetrahedron is only likely to be Si –OH in synthetic jennites,which are generally deficient in Ca (i.e.,the deficit in positive charge resulting from the absence of interlayer Ca 2+is balanced by OH àgroups).

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1.5),and the central Ca–O part of its structure is corru-gated,as illustrated in Fig.

2.The purpose of this article is to discuss the applicability of the T/J and T/CH viewpoints for the nanostructure of C-S-H present in real cement pastes.The discussion in this article is facilitated by a consideration of the author’s1992model[18,19],which includes formulations for both structural viewpoints;its relationship to other recent models is outlined.The struc-tural details of the model are clearly illustrated with a number of schematic diagrams,some of which have only been made possible by the recent determinations of the crystal structures of1.4nm tobermorite and jennite[12,20]. The model is shown to account for a number of experi-mental observations on the nature of C-S-H present in a diverse range of cementitious systems.The T/J and T/CH viewpoints and many other aspects of calcium silicate hydrates formed both naturally and in cements and also those synthesized in the laboratory,are discussed at length in a forthcoming RILEM report[21].

2.Experimental

The experimental details for all the systems discussed in this article are reported in other publications,which are referenced as appropriate,and should be consulted when necessary.The specimens for transmission electron micros-copy(TEM)were prepared as outlined in Ref.[22]. Excessive beam damage was avoided by restricting the maximum magnification to?25,000;the problems asso-ciated with attempting to view hardened cement specimens at higher magnifications in the TEM are discussed in detail in Ref.[22].

3.Results and discussion

Significant advances in the characterization of C-S-H have been achieved in the past40years through the application of a variety of new techniques:the electron microprobe in the1960s;scanning electron microscopy (SEM)in the1970s;trimethylsilylation gel permeation chromatography(TMS-GPC),analytical TEM,and solid-state nuclear magnetic resonance(NMR)spectroscopy in the1980s and1990s.Whilst these studies confirmed that the principal binding phase in hardened cements is a C-S-H with linear(alumino)silicate chains of the dreierkette form, they also showed that its exact nature is affected by many factors—including the composition of the cement,the water-to-cement ratio(w/c),the curing temperature,the degree of hydration,and the presence of chemical and mineral admixtures—with the result that there is tremendous variation in its composition,nanostructure,and morphology. Any model for the structure of C-S-H must account for these observations.The most important of them are summarized in the following sections,with some additional new results.3.1.Chemical composition

Any model for the structure of C-S-H must account for the observed compositional variations and distributions of composition within any particular system;it must account for the following:

(i)The mean Ca/Si ratio of C-S-H phases present in

commercial cements varies considerably,from c2.3 to c0.7[23].

(ii)C-S-H displays very fine-scale compositional hetero-geneity;for example,in neat C3S or h-C2S pastes where the mean Ca/Si ratio is about1.75[24–29],different regions analysed in the TEM(at the scale of about100 nm)have values ranging between2.1and1.2[28,29]. (iii)C-S-H tends to become compositionally more homo-geneous with age;for example,the C-S-H present in neat ordinary PC(OPC)pastes has been observed to have a bimodal distribution at young age,which becomes unimodal as hydration progresses[28]. (iv)The mean Ca/Si ratio of C-S-H in neat C3S or OPC pastes does not vary with age(see,e.g.,the top part of Fig.2in Ref.[29]).

(v)The C-S-H present in many types of cement contains significant amounts of substituent ions,the most important being Al3+.For example,in granulated iron blast-furnace slag–PC blends the Al/Ca ratio increases linearly with increasing Si/Ca ratio[30];the compo-sitions of the C-S-H present in the‘outer product’(Op)1region and in the slag and alite‘inner product’(Ip)regions are all affected similarly.A number of examples that will be discussed in this article in terms of models for the nanostructure of C-S-H are shown in Figs.3,4,and5[31–33].These figures show Al/Ca against Si/Ca ratio scatter plots for TEM analyses of C-S-H present in water-and KOH-activated slag–white PC blends,in a KOH-activated20%metakaolin–80% white PC blend,and in a KOH-activated synthetic slag glass.Each point represents an analysis of Op C-S-H at the scale of about100nm,which had been checked by selected area electron diffraction(SAED)to be free of admixture with crystalline phases.The labels on the figures—which relate to the models for the structure of C-S-H—are discussed in Section4.

3.2.Morphology and structural order of C-S-H

Any model for the structure of C-S-H must account for the various morphologies of C-S-H and varying degrees of structural order;many of these are outlined in the following sections.

1C-S-H that forms within the original volume of reacting cement grains is termed Ip C-S-H and the C-S-H that forms in the originally water-filled spaces is termed Op C-S-H.There is not necessarily an exact correspondence between the positions of the outer boundaries of Ip and the original grains.

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3.2.1.C-S-H in hardened pastes of C3S,b-C2S or PC

hydrated at20j C and80j C

(i)Inner product.Ip C-S-H that forms from the reaction

of reasonably large grains of C3S or alite has a

compact,fine-scale,and homogeneous morphology (see,e.g.,SEM[34]and TEM[35]);the morphology of C-S-H present in small fully reacted grains is discussed in Section3.2.6.Groves[35]estimated from TEM that the pores in this type of Ip C-S-H are less than c10nm,which is consistent with results from small-angle neutron scattering experiments[36,37].

The fine morphology of this Ip C-S-H is illustrated on the left of Fig.6(a),which shows a TEM micrograph of

a region in a hardened C3S paste hydrated for8years

at20j C with w/c=0.4.Fig.6(b)shows an enlargement of an area of the Ip;the Ip C-S-H appears to consist of aggregates of small globular particles,the particles being4–6nm in diameter.The pores—if simplistically considered to be the regions of lighter contrast—are certainly less than10nm.If the boundary between the Ip and Op product regions is assumed to be along the area indicated by the white arrows,then it is evident that in some of the Ip the globules are aligned so as to give a fan-like texture.

Fig.7(a)shows an example of fine-textured C-S-H present in a PC paste(hydrated for12months at20j C;

w/c=0.4).Fig.7(b)shows an enlargement of part of the micrograph;again,the Ip C-S-H appears to consist of small globular particles,but in this case,they are more homogeneously distributed than in Fig.6and perhaps a bit larger,between6and8nm in diameter.

Whilst the fine-textured morphology is certainly the most common form in grains greater than a few micrometers in size,C-S-H with a more

pronounced Fig.5.Al/Ca against Si/Ca atom ratio plot of TEM analyses of Op C-S-H present in hydrated samples of a hardened white PC/20%metakaolin blend (.)[45]and a synthetic slag glass(?)[33]both activated with5M KOH

solution.

Fig.4.Al/Ca against Si/Ca atom ratio plot of TEM analyses of Op C-S-H

present in hydrated samples of5M KOH-activated white PC/GGBS blends

with0%(+),50%(5),and90%(w)slag.Experimental details are given in

Ref.[31]

.

Fig.3.Al/Ca against Si/Ca atom ratio plot of TEM analyses of Op C-S-H

present in hydrated samples of water-activated white PC/GGBS blends with

50%(o)and90%(D)slag.Experimental details are given in Ref.[31].

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texture is also sometimes observed in PC pastes,as well as in C 3S pastes (example in Fig.6);an example is shown in Fig.8.The globules of C-S-H are of similar dimensions to those in Fig.7,but they are packed together differently (compare Figs.7(b)and 8(b)).Fig.9(a)shows a micrograph illustrating C-S-H present in a C 3S paste hydrated at elevated temperature (at 80j C for 8days with w/c =0.51).The Ip C-S-H again has a fine homogeneous morphology,similar to that in Fig.6.However,the globules of C-S-H appear to be significantly smaller,between 3and 4nm:Comparison of Figs.6(b)and 9(b)shows that the particles of C-S-H in the higher temperature system are about half the size of those present at lower temperature.Careful examination of a number of regions in both systems led to the same conclusion.(ii)Outer product.The Op C-S-H present in hardened C 3S

or OPC pastes has a fibrillar,directional morphology (e.g.,SEM [34]and TEM [35,38]).This morphology is a function of space constraint:where it forms in large pore spaces,the fibrils form with a high length to width aspect ratio (which will be referred to as coarse fibrillar );in smaller spaces,it retains a directional aspect but forms in a more space-efficient manner (‘fine fibrillar’);C-S-H morphological terminology is discussed in Ref.[22].The spaces between the

fibrils

Fig.6.(a)A TEM micrograph showing Ip and Op C-S-H present in a hardened C 3S paste with w/c =0.4hydrated at 20j C for 8years.White arrows indicate the Ip –Op boundary;the Ip is in the upper left of the micrograph.(b)An enlargement of a region of Ip C-S-H.(c)An enlargement of a fibril of Op C-S-H.

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of Op C-S-H form a three-dimensional interconnected pore network:the capillary porosity.Op C-S-H present in a hardened C 3S paste (hydrated for 8years at 20j C;w/c =0.4)is shown on the right of Fig.6(a),and an enlargement of a section of a coarse fibril is shown in Fig.6(c).The fibril—which is about 100nm wide—appears to consist of a large number of long thin particles aligned along its length.The particles are—like those in the Ip—about 3nm in their smallest dimension,but they are of variable length from a few nanometers to many tens of nanometers.This is a common observation,both in hardened C 3S and h -C 2S pastes.Coarse fibrillar Op C-S-H present in a h -C 2S paste is shown in Fig.10(hydrated for 1month at 20j C;w/c =0.4).Op C-S-H formed by the hydration of C 3S at elevated temperatures also appears to consist of long thin particles:Fig.9(c)shows an enlargement of some of the fine fibrillar C-S-H present on Fig.9(a).The Op C-S-H present in neat PC pastes typically has a finer morphology than that present in C 3S or h -C 2S pastes.

(iii)Interlayer space and gel pores.If in the micrographs

discussed above the regions of lighter contrast in the C-S-H are taken to essentially correspond to pores,and if it is assumed that by drying the contrast has been enhanced,then these gel pores are clearly very small.

If

Fig.7.(a)A TEM micrograph showing fine Ip C-S-H present in a hardened OPC paste with w/c =0.4hydrated at 20j C for 1year.(b)An enlargement of a region of Ip C-S-H.Experimental details are given in Ref.[28]

.

Fig.8.(a)A TEM micrograph showing Ip C-S-H present in a hardened OPC paste with w/c =0.4hydrated at 20j C for 1year;the C-S-H has a more pronounced texture than that in Fig.7.(b)An enlargement of a region of Ip C-S-H.Experimental details are given in Ref.[28].

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it is assumed that the particles of C-S-H consist of elements of structure based on tobermorite and/or jennite,then their dimensions are such that they must consist of very few layers of these structures,in some cases as few as two.It is clear that the boundary between interlayer space and gel pore space is likely to be very indistinct.

(iv)Structural order.Powder X-ray diffraction (XRD)of

water-activated cement pastes show only two weak,broad peaks for C-S-H,centred between 3.2–2.7and

1.86–1.79A

?[39,40].There is never any sign of layer spacing.SAED studies have produced results consistent with those from XRD (e.g.,Ref.[41]).As an example,Fig.11shows a SAED pattern for an area that contained both C-S-H and CH in a hardened paste of ordinary PC (hydrated for 12months at 20j C;w/c =0.4).The figure consists of a diffuse C-S-H ring superimposed on a [031]zone axis pattern for CH.The

diffuse ring ranges between about 3.2and 2.7A

?.A faint ring at about 1.83A

?is also commonly observed.Spacings in the region of 3and 1.8A

?correspond to important repeat distances in the Ca–O parts of the structures of tobermorite and jennite,as well as in the structure of CH,which is illustrated in Fig.12.

(v)Calcium hydroxide.CH is typically observed as large

crystals (several micrometers in size)in the Op

regions

Fig.9.(a)A TEM micrograph showing Ip and Op C-S-H present in a hardened C 3S paste with w/c =0.51hydrated at 80j C for 8days.(b)An enlargement of a region of Ip C-S-H.(c)An enlargement of a fibril of Op C-S-H.

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of hardened pastes of C 3S,h -C 2S,and PC hydrated at around 20j C.It is also commonly observed in the Ip of PC pastes.Whilst large crystals of CH also occur in pastes hydrated at elevated temperatures,microcrystal-line CH is also present.Fig.13(a)shows an example of CH microcrystals (which appear dark where they are oriented such that they Bragg-reflect electrons strongly and are blocked by the objective aperture in a bright field image)intermixed with C-S-H in a white PC hydrated at 80j C;Fig.13(b)shows an enlargement of part of the region and Fig.13(c)shows a typical SAED.3.2.2.C-S-H in water-activated hardened pastes of PC blended with different amounts of blast-furnace slag (i)Inner product.As the fraction of slag increases the chemical composition of Ip C-S-H that forms from the reaction of reasonably large grains of alite changes:the mean Ca/Si ratio decreases whilst the mean Al/Ca increases [30].However,it nevertheless retains the typical compact,fine-scale,and homogeneous mor-phology.The C-S-H present in small fully reacted grains has a different morphology,which is discussed in Section 3.2.6.An example for a 50%slag blend (hydrated at 25j C for 3weeks;w/s =0.4)is shown on the right of Fig.14(a),with an enlargement of part of the region shown in Fig.14(b);the globules of C-S-H appear to be around 4–8nm in diameter.C-S-H present in the Ip of reacted slag grains has a similar chemical composition,but it is intermixed on a range of scales with a hydrotalcite-type phase [30].

(ii)Outer product.The morphology of Op C-S-H is

dependent on its chemical composition,which is determined by the amount of slag in the blend.Whilst some micrographs demonstrating the change in mor-phology that occurs on increasing the slag fraction

have

Fig.10.A TEM micrograph showing coarse Op C-S-H present in a hardened h -C 2S paste with w/c =0.4hydrated at 20j C for 3

months.

Fig.11.SAED pattern for an area in a hardened paste of ordinary PC (hydrated for 12months at 20j C;w/c =0.4)showing a C-S-H ‘halo’superimposed on a [031]zone axis pattern for CH (calculated pattern shown on the right).

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been published [22,23,29,30],additional examples are

included here for the specific purpose of relating this change to possible changes in the nanostructure of C-S-H.These micrographs are at the same magnifications—including enlargements—as those discussed in Section 3.2.1to facilitate comparison between the different systems,and thus the different chemical compositions.Figs.14–17show Op C-S-H present in blends with 50%,75%,90%,and 100%slag,respectively.The compositional data in Fig.3correspond to Figs.14(o )and 16(D ).The Op C-S-H in neat C 3S pastes is,as discussed above,fibrillar;the fibrils are often quite coarse and appear to consist of agglomerations of long thin particles,approximately 3nm in their smallest dimension.Coarse fibrils are generally less evident in neat PC pastes,the C-S-H generally having a finer morphology,which nevertheless retains a linear directional aspect (described as ‘fine fibrillar’).This morphology is broadly maintained as the mean Ca/Si ratio of the C-S-H decreases from a mean value of about 1.75in neat PC pastes to about 1.5in pastes with 50%slag;the latter also contains a significant amount of Al (Al/Ca c 0.07to 0.10)(see Ref.[30]and Fig.3).An example for a 50%slag blend is shown on the left of Fig.14.Fig.14(c)shows an enlargement of an area of this Op C-S-H;it still appears to consist of agglomerations of long thin particles,but in this case,they are perhaps thicker (say 3–6nm)than in Fig.6(c).The morphology of Op C-S-H changes more noticeably with further increases in the proportion of slag in the paste.Fig.15shows an example for a paste containing 75%slag where the mean Ca/Si ratio is 1.34(and Al/Ca =0.13)[30].Much of the Op C-S-H in this micrograph retains a very linear,directional character,

but it now seems to have a likeness to fanned-out cre

?pe paper (a description first used by Copeland and Schulz in 1962[41]);other areas—for example on the left of

Fig.15(a),have lost the linear aspect.Examples of Op C-S-H present in a blend containing 90%slag (mean Ca/Si =1.26and Al/Ca =0.14)and in a neat water-activated slag paste (mean Ca/Si =1.18and Al/Ca =0.19)are shown in Figs.16and 17,respectively.The Op C-S-H in these two pastes has the appearance of crumpled sheet-like https://www.sodocs.net/doc/3215940210.html,parison of the Op C-S-H morphologies shown in Figs.6(c),14(c),15(b),16(b),and 17(b)suggests strongly that as the mean Ca/Si ratio decreases (and the Al/Ca ratio increases)a transition occurs from essentially one-to two-dimensional growth;i.e.,long thin particles to thin foils.

(iii)Structural order .SAED patterns of Op C-S-H in water-activated slag–PC blends show only a diffuse ring

ranging between about 3.2and 2.7A

?,and occasionally a faint ring at around 1.8A

?,regardless of chemical composition.3.2.3.C-S-H in alkali-activated blast-furnace slag pastes (i)Inner product.The Ip of hydrated slag grains in KOH-or NaOH-activated slag pastes is very similar to that formed in water-activated slag–PC blends.Again,it consists of a hydrotalcite-type phase mixed over a range of scales with C-S-H that has a similar composition to the Op C-S-H in the same paste [33,42].An example is shown in Fig.18(a)(left centre and upper right)with an enlargement of part of one of the regions shown in Fig.18(b)(slag activated with 5M KOH and hydrated for 8years at 20j C;s/s =0.4).The laths or platelets present in the Ip—which are quite small in this example—are the hydrotalcite-type phase.The fine scale intermixing of the hydrotalcite-type phase and the Al-substituted C-S-H might be due to a strong attraction between their oppositely charged main layers [43]

.

Fig.12.A single layer of CH structure (SG =P à3m 1;a =b =3.593A

?;c =4.909A ?)illustrating the 3.1(=b sin(60))and 1.8(=a /2)A ?repeat distances.I.G.Richardson /Cement and Concrete Research 34(2004)1733–17771741

(ii)Outer product.The morphology of the Op C-S-H

present in KOH-or NaOH-activated slag pastes is,like that in the neat water-activated slag paste,foil-like,but the foils tend to be less crumpled,which suggests a greater degree of structural order.An example is shown in the central region of Fig.18(a)with an enlargement of part of the region shown in Fig.18(c).The Op C-S-H in this paste had a mean Ca/Si =0.99and Al/Ca =0.20.

(iii)Structural order.As suggested by its morphology,the

C-S-H in an alkali hydroxide-activated slag is indeed structurally better ordered than in a water-activated slag paste.SAED patterns of Op C-S-H in KOH-or NaOH-activated slag pastes show ring patterns corresponding to C-S-H (I),which is structurally

related to 14A

?tobermorite;the peaks at 3.07,2.80,and 1.83A

?represent the three shortest repeat distances in the plane of a distorted CH layer [40].An example of a pattern is given in Ref.[33];the layer spacing in the example was smaller than detected by powder XRD due to drying during sample preparation and/or examination in the electron microscope.C-S-H (I)synthesized in the laboratory has been observed by TEM to have a foil-like morphology [44].Since the C-S-H in Fig.18has structural order intermediate between that in the water-activated neat slag

paste

Fig.13.(a)A TEM micrograph showing microcrystalline CH present in a hardened white PC paste with w/c =0.4hydrated at 80j C for 19days.(b)An enlargement of a region in (a).(c)SAED pattern for an area in (a)showing reflections characteristic of microcrystalline CH.

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(Fig.17)and crystalline tobermorite,crystals of the latter are shown at the same magnifications in Fig.19for comparison with the other micrographs.

3.2.

4.C-S-H in alkali hydroxide-activated hardened pastes of PC blended with different amounts of blast-furnace slag (i)Inner product.The Ip C-S-H that forms from the reaction of reasonably large grains of alite in KOH-activated slag–PC blends has the typical compact,fine-scale,and homogeneous morphology,regardless of the amount of slag in the paste.The Ip in hydrated slag grains is very similar to that formed in water-activated slag–PC blends.Again,it consists of a hydrotalcite-type phase mixed over a range of scales with C-S-H that has a similar composition to the Op C-S-H in the same paste.An example is shown on the right of Fig.20(a)for a blend with 90%slag (activated with 5M KOH solution and hydrated at 25j C for 3days;s/s =0.4);Fig.20(b)shows an enlargement of part of the region.Again,the laths or platelets present in the Ip are the hydrotalcite-type phase.

(ii)Outer product.The morphology of the Op C-S-H

present in KOH-activated slag–PC blends is

gener-

Fig.14.(a)A TEM micrograph showing Ip and Op C-S-H present in a hardened white PC-50%GGBS paste with w/s =0.4hydrated at 25j C for 3weeks;the Ip is on the right of the micrograph.A black arrow indicates the location of a relict of AFt;there are number of others in the micrograph.(b)An enlargement of a region of Ip C-S-H.(c)An enlargement of a region of Op C-S-H.Experimental details are given in Ref.[31].

I.G.Richardson /Cement and Concrete Research 34(2004)1733–17771743

ally foil-like,regardless of the amount of slag in the paste;it is foil-like at low and high Ca/Si ratio.An example for a high-slag blend is shown on the left of Fig.20(a)with an enlargement of part of the region shown in Fig.20(c).The Op C-S-H in this paste had a mean Ca/Si =1.14and Al/Ca =0.17[31].An example for a neat PC paste is shown on the lower right of Fig.21(a),which is a modification of Fig.5of Ref.[31];an enlargement of part of the region is shown in Fig.21(b).The Op C-S-H in this paste had a mean Ca/Si =1.69and Al/Ca =0.04,which is essentially the same as in water-activated pastes where the C-S-H has a fibrillar morphology.Op C-S-H also occurs as lath-like features,which often have lines of contrast running along them that readily coarsen in the electron beam (due to the formation of gaseous products),suggestive of a basal plane perpendicular to the plane of the page.An example for a low Ca system is indicated on Fig.20(a)by a white arrow.

(iii)Structural order.Again,as suggested by its morphol-ogy,the C-S-H in alkali hydroxide-activated slag–PC blends is structurally better ordered than in water-activated pastes.XRD and SAED data are consistent with C-S-H (I).This is true at both low and high Ca/Si

ratio.

Fig.15.(a)A TEM micrograph showing Op C-S-H present in a hardened ordinary PC-75%GGBS paste with w/s =0.4hydrated at 20j C for 14months.(b)An enlargement of a region of Op C-S-H.Experimental details are given in Ref.[30]

.

Fig.16.(a)A TEM micrograph showing Op C-S-H present in a hardened white PC-90%GGBS paste with w/s =0.4hydrated at 25j C for 3weeks.(b)An enlargement of a region of Op C-S-H.Experimental details are given in Ref.[31].

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(iv)Calcium hydroxide.CH is generally microcrystalline

and occurs interstratified with C-S-H at the nanometer scale;the regions can extend over many micrometers.An example is shown in the top/left/centre of Fig.21(a),with an enlargement of part of the region in Fig.21(c).A typical SAED pattern is given in Ref.[31],which is obviously similar to that shown in Fig.13(c),and CH peaks on powder XRD patterns are broader than with water activation,consistent with the smaller crystal size.3.2.5.C-S-H in alkali hydroxide-activated hardened pastes of PC blended with 20%metakaolin

The morphology of the Op C-S-H present in a KOH-activated 20%metakaolin–PC blend is foil-like;micro-graphs are reported elsewhere [45].TEM analyses for the blend are shown on Fig.5.

3.2.6.C-S-H in small fully hydrated particles

TEM of ion-thinned sections has shown that the hydrat-ed remains of relatively small particles—whether of PC,slag,or fly ash—contain a less dense product with sub-stantial porosity,surrounded by a zone of relatively dense C-S-H [23,28,30,46].An example from a PC paste,which is a modified version of Fig.3in Richardson and Groves [28],is shown in Fig.22(a).The boundary between Ip and Op is well defined (indicated by the white arrows).The Ip C-S-H is clearly less dense than that present in larger grains,as is readily noted on comparison with Fig.7.Indeed its morphology is quite similar to the fine foil-like Op C-S-H present in neat water-activated slag pastes,which has low Ca/Si ratio;an example for comparison is shown in Fig.22(b).

3.2.7.C-S-H in carbonated PC pastes

When C 3S or neat PC pastes undergo relatively gentle carbonation,the C-S-H is progressively decalcified and the spaces between the fibrils of Op C-S-H are filled with microcrystals of calcium carbonate [47,48].The fibrillar morphology of the Op C-S-H is strikingly well preserved,as illustrated in Fig.23(a),which is a modification of Fig.2of Ref.[48].The C-S-H in this particular paste was only partially decalcified—the Ip C-S-H had a mean Ca/Si of 1.41—and the Op C-S-H still appears to consist of agglom-erations of long thin particles;compare for example Fig.23(b)with Fig.14(c),which has a similar Ca/Si ratio.As carbonation proceeds and the C-S-H is decalcified further,the long thin particles are broken up,ultimately resulting in microporous https://www.sodocs.net/doc/3215940210.html,pare,for example,Fig.23(a)with Fig.3in Ref.[49].This striking preservation of Op C-S-H morphology upon carbonation strongly supports the view—as does TEM of replicas (see discussion in Ref.[22])—that it is a genuine feature and not an artefact introduced by specimen preparation.

3.3.(Alumino)silicate anion structure

Any model for the structure of C-S-H must be able to account for experimental observations on the nature of its (alumino)silicate anions;it must account for the following:(i)Sequence of (alumino)silicate chain lengths.Evidence from solid-state NMR spectroscopy [50–52]and TMS-GPC [24,53–55]have shown that the C-S-H that is formed during the first day of hydration of C 3S or neat PC contains mostly dimeric silicate units (the end of the induction period is associated with

the

Fig.17.(a)A TEM micrograph showing Op C-S-H present in a hardened neat GGBS paste with w/s =0.4hydrated at 40j C for 3.5years.(b)An enlargement of a region of Op C-S-H.Experimental details are given in Ref.[30].

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onset of the formation of dimer)and the TMS has shown that the C-S-H formed subsequently consists of both dimeric and higher polymeric species.The polymeric species are mainly linear pentamer and octamer,thus suggesting a 2,5,8...(3n à1)chain length sequence,where n is integer for individual structural units;n would of course be noninteger for mixtures of units of different lengths.At greater ages,polymeric units form at the expense of existing dimer (dimer peaking at about 6months),but dimer remains at c 40%when reaction is essentially complete [24,54,56],and even after ageing for 20–30years [54].The polymer fraction in very mature samples still contains pentamer and octamer in substantial amounts but larger anions,containing tens of tetrahedra,are also present [54].NMR and TMS-GPC have shown that in systems where there is significant substitution of Al for Si the 2,5,8...(3n à1)chain length sequence is maintained and the Al 3+substitutes for Si 4+in the bridging tetrahedra of dreierkette chains [23,57,58].This point is confirmed by the observation that dimer is still the main species detected by TMS-GPC:since TMS only probes the silicate portion of aluminosilicate

anions

Fig.18.(a)A TEM micrograph showing Ip and Op C-S-H present in a 5-M KOH-activated GGBS paste with s/s =0.4hydrated at 20j C for 8years.(b)An enlargement of a region of Ip C-S-H showing laths of a Mg,Al-rich phase intermixed with C-S-H.(c)An enlargement of a region of Op C-S-H.Experimental details are given in Ref.[33].

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1746

substitution of Al into paired tetrahedra would result in enhanced amounts of trimer and tetramer,which is not observed.

(ii)Mean (alumino)silicate chain lengths.In C 3S,h -C 2S,

and neat PC pastes,there is only a gradual increase in the mean silicate chain length (MCL)with hydration time:for example,Rodger [59]and Rodger et al.[60]reported increases over 12months from 2to 2.7for a h -C 2S paste,2to 3.3for a C 3S paste,and 2to 3.1for a neat PC paste.Even after 26years,the MCL for C-S-H in a C 3S paste is less than 5[50].Maximum MCL and Q 1/Q 2ratios 2in hydrating C 3S pastes have indicated that polymerization most probably occurs through the linking of dimers with monomers,in support of the (3n à1)sequence of chain lengths observed by TMS [52].Activation of C 3S with KOH solution results in shorter chains than with water activation [61].The MCL of C-S-H is longer in composite cements where the PC has been partially replaced by slag or a pozzolan.The following examples are discussed later in terms of models for the structure of C-S-H.Richardson and Groves [31]reported the MCL and Al/Si ratios calculated from 29Si NMR for C-S-H present in water-activated slag–PC blends [50%(o )and 90%(w )slag]and KOH-activated slag–PC blends [50%(5)and 90%(w )slag],and Love et al.[45]for C-S-H in a KOH-activated metakaolin–PC blend [20%(.)metakaolin].The MCLs are 4.1(o ),6.5(D ),3.6

(5),4.2(w ),and about 18(.),respectively.Analytical TEM data for the same pastes are reported in Figs.3,4,and 5(only mean values were reported previously for the slag blends [31]).Note that the MCL are again less with alkali activation than with water.Long chains also develop in blends with high levels of amorphous silica;for example,the C-S-H formed in a C 3S–silica system with overall Ca/Si of 1.0hydrated for 3months at 40j C (w/s =0.7)had an MCL of 8[62],and the C-S-H that formed in a PC–silica fume paste with >50%silica hydrated for 3months at 40j C (w/s =0.7)had a mean Ca/Si c 0.7!0.8and MCL of 8.5[63].As noted in Section 3.2.7,relatively gentle carbonation of C-S-H results in decalcification;this reduction in Ca content is accompanied by an increase in MCL [48,64].For example,Groves et al.[64]reported that a hardened C 3S paste that had been carbonated for 2months in air (at 72.6%relative humidity)contained a relatively homogeneous C-S-H with a mean Ca/Si ratio of 1.02;the MCL was 4.5—silica gel had not yet formed—which is longer than before it was carbonated.The MCL of the C-S-H in the sample represented by the micrograph in Fig.23(a)was about 3.4,which is again longer than would be expected for an uncarbo-nated PC of similar age [25].

(iii)Hydrated monomer.Solid-state 29Si NMR techniques

have shown that the product formed during the induction period of hydrating C 3S contains exclusively hydrated monomeric silicate units (Q 0(H))[60].Hy-drated monomer persists to high degrees of reaction at a level of c 2%for curing at 20j C and between 8%and 3%at 75j C,depending on the degree of hydration [52,60].The exact nature of this persistent Q 0(H)has yet to be established.Either it must be accounted for within the C-S-H or in some other way.Interestingly,

there

Fig.19.(a)A TEM micrograph showing crystals of tobermorite.(b)An enlargement of overlapping crystals of tobermorite.

2

Q n (0V n V 4).Q is a silicate tetrahedron and n is the number of oxygen ions that bridge to adjacent tetrahedra;thus,Q 0are isolated tetrahedra,Q 1are chain-end groups,Q 2middle groups,etc.Increased polymerization of the Q n building units causes characteristic up-field chemical shifts on 29Si NMR spectra.In aluminosilicates,the shifts are further influenced by the replacement of Si by Al;there are 15possible Q n (mAl)structural units where n =0–4and m =0–n .

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does not appear to be very much,if any,Q 0(H)in KOH-activated C 3S pastes (see Figs.5and 6in Ref.[61])or in water-activated slag–PC blends containing 90%slag (see Fig.12of Ref.[31],both of which have Op C-S-H with foil-like rather than fibrillar morphology.

4.Richardson and Groves’generalized model for the nanostructure of C-S-H

The following sections attempt to explain Richardson and Groves’model more clearly than previously [18,19]

by the use of schematic diagrams;the model’s applicabil-ity to the experimental data outlined in Section 3is discussed.

4.1.C-S-H in hardened C 3S or b -C 2S pastes

Richardson and Groves [18]proposed a generalized model that included formulations that could be interpreted from both the T/CH and T/J structural viewpoints.They started their discussion by giving the general form for a calcium silicate hydrate composed of isolated silicate chains of varying length and with a variable number of

–OH

Fig.20.(a)A TEM micrograph showing Ip and Op C-S-H present in a hardened 5-M KOH-activated white PC-90%GGBS paste with s/s =0.4hydrated at 25j C for 3days;the Ip is on the right of the micrograph.(b)An enlargement of a region of Ip showing laths of a Mg,Al-rich phase intermixed with C-S-H.(c)An enlargement of a region of Op C-S-H.Experimental details are given in Ref.[31].

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groups attached to Si atoms,in ‘solid solution’with a variable amount of Ca(OH)2:

Ca X H 2N t1àX eTSi N O 3N t1eTáz Ca OH eT2ám H 2O

e1T

In this formula,N is the mean length of the silicate chains,X is the number of Ca 2+ions necessary to charge-balance the silicate chains,2(N +1àX )is the number of hydroxyl units attached to the chains,z is the number of Ca(OH)2units in ‘solid solution’,and m is the number of water molecules bound but not present as hydroxyl groups.They

noted that the special case of this formula for dimer (the predominant form in young C 3S or OPC pastes,as noted in Section 3.3),N =2,was the same as that given by Glasser et al.[65].The model was then extended to account for the experimentally observed sequence of chain lengths,i.e.,3n à1:

Ca X H e6n à2X TSi e3n à1TO e9n à2Táz Ca eOH T2ám H 2O

e2T

Formula (2)—the T/CH viewpoint—is essentially the pol-ysilicate version of Glasser’s compositional model

for

Fig.21.(a)A TEM micrograph showing Op C-S-H and microcrystalline CH present in a hardened 5-M KOH-activated neat white PC paste with s/s =0.5hydrated at 25j C for 5months.(b)An enlargement of a region of crumpled-foil Op C-S-H.(c)An enlargement of a region of Op C-S-H interstratified with microcrystalline CH.Experimental details are given in Ref.[31].

I.G.Richardson /Cement and Concrete Research 34(2004)1733–17771749

dimeric C-S-H.Richardson and Groves [18]gave an alternative formulation for their model:

f Ca 2n H w Si e3n à1TO e9n à2T

g áeOH Tw tn ey à2TáCa n áy 2ám H 2O

e3T

The number of silanol groups is given by w ,and the degree of protonation of the silicate chains by w /n .The limiting values of the variables in these formulations,

which are dictated by the requirement to maintain the layer structure and neutrality,are the following:for 0V y V 2;n e2ày TV w V 2n 2V y V 4;0V w V 2n

4V y V 6;

0V w V n e6ày Tand X ?1

2e6n àw T

z ?1

2

ew tn ey à2

TT

Fig.22.(a)A TEM micrograph showing Ip C-S-H in a hardened PC paste (w/c =0.4hydrated at 20j C for 1week),which is typical of the product formed in relatively small grains;the Ip is less dense than that formed in larger grains (e.g.,in Fig.7)and is surrounded by a zone of relatively dense Op C-S-H (this figure is a modified version of Fig.3in Ref.[28]).(b)A TEM micrograph showing fine foil-like Op C-S-H present in a neat water-activated GGBS paste (w/s =0.4hydrated at 20j C for 14months),which has a morphology similar to the Ip in (a)but has a low Ca/Si ratio (c 1.1)rather than high (c 1.7–1.8).Experimental details are given in Ref.[30].

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1750

The limits are illustrated graphically on Fig.24.The Ca/Si ratio is given by Ca =Si ?

n e4ty Te4T

On the T/CH viewpoint,the part of formula (3)contained within the braces is the tobermorite-like core.It consists of a highly disordered layer structure comprising finite sili-cate chains of mean length 3n à1.Dimeric species (n =1)are linked during polymerization by bridging tetrahedra to form pentamer (n =2)and higher polymers,thus account-ing for the experimentally observed sequence of silicate chain lengths (Section 3.3(i)).The 2n Ca 2+ions within the braces are main layer Ca 2+ions,and n à(w /2)of the

(n áy )/2Ca 2+ions outside the braces are interlayer Ca 2+ions required for charge-balance.The position of the remainder of the (n áy )/2Ca 2+ions depends on the structural viewpoint adopted.On the T/CH viewpoint they occur in layers of CH sandwiched between silicate layers of tobermorite-like structure whilst on the T/J viewpoint they form part of the main layer of jennite-based structural units (as Si–O–Ca–OH).The structural units—and thus the parameters in the formulations—may vary from one region of the C-S-H to another thus accounting for the local variations in composition observed by TEM (Section 3.1).To aid this discussion,the structural units derived from either jennite or 1.4-nm tobermorite will be identified by the use of ‘J’or ‘T’as labels [18].Hence,J2and T2correspond to dimeric structural units that result from omission of all bridging tetrahedra from jennite

and

Fig.23.(a)A TEM micrograph showing partially decalcified Op C-S-H and microcrystals of calcite in a carbonated white PC paste (this figure is a modified version of Fig.2in Ref.[48]).(b)An enlargement of a region of partially decalcified Op

C-S-H.

Fig.24.The combinations of the degree of protonation,w /n ,and y that are possible in formula (3)whilst maintaining the layer structure and neutrality [18].Taylor’s [17]tobermorite-based structural units occur at T,and his jennite-based units at J.

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tobermorite,respectively,and J l and T l represent infi-nite chain lengths and so correspond to the crystalline phases themselves.

The degree of protonation of the silicate chains,w /n ,is clearly flexible in the model:the line on Fig.24between T w /n =2and T w /n =0(o —o )represents tobermorite-based units,and,on the T/J viewpoint,the line between J w /n =2and J w /n =0(o ----o )represents jennite-based units.The effects of this flexibility in possible degree of protonation on the composition of the structural units is illustrated in Fig.25,which shows the variation in Ca/Si ratio with the reciprocal of the MCL for structural units derived from both jennite (J)and 1.4nm tobermorite (T),with the maximum,intermediate,and minimum levels of w /n [18].The compositional and structural details of a number of the units are outlined in greater detail in Figs.26–33;the positions of these units are indicated in Fig.25

.

Fig.25.Variation of Ca/Si ratio with mean chain length for structural units present in Richardson and Groves’model [18]with three different levels of protonation of the silicate chains:the minimum level (w /n =0),an intermediate level (w /n =1),which is equivalent to the units in Taylor’s model [17],and the maximum level (w /n =2).The structures of the eight units that are labelled are illustrated in Figs.26–33

.

Fig.26.Diagrams illustrating tobermorite-based dimer (n =1)that has the maximum degree of protonation of the silicate chains (w /n =2).(a)A highly schematic diagram demonstrating chemical accounting;the values of the variables in Richardson and Groves’model [18]are indicated.(b)and (c)show more realistic structural representations derived using crystal structure data for tobermorite [66–68]with the silicate chains either aligned along the plane of the page or perpendicular to the page (i.e.,edge on).

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of与for的用法以及区别

of与for的用法以及区别 for 表原因、目的 of 表从属关系 介词of的用法 （1）所有关系 this is a picture of a classroom （2）部分关系 a piece of paper a cup of tea a glass of water a bottle of milk what kind of football，American of soccer？ （3）描写关系 a man of thirty 三十岁的人 a man of shanghai 上海人 （4）承受动作 the exploitation of man by man．人对人的剥削。 （5）同位关系 It was a cold spring morning in the city of London in England． （6）关于，对于 What do you think of Chinese food？ 你觉得中国食品怎么样？ 介词 for 的用法小结 1. 表示“当作、作为”。如: I like some bread and milk for breakfast. 我喜欢把面包和牛奶作为早餐。What will we have for supper? 我们晚餐吃什么?

2. 表示理由或原因,意为“因为、由于”。如: Thank you for helping me with my English. 谢谢你帮我学习英语。 Thank you for your last letter. 谢谢你上次的来信。 Thank you for teaching us so well. 感谢你如此尽心地教我们。 3. 表示动作的对象或接受者,意为“给……”、“对…… (而言)”。如: Let me pick it up for you. 让我为你捡起来。 Watching TV too much is bad for your health. 看电视太多有害于你的健康。 4. 表示时间、距离,意为“计、达”。如: I usually do the running for an hour in the morning. 我早晨通常跑步一小时。We will stay there for two days. 我们将在那里逗留两天。 5. 表示去向、目的,意为“向、往、取、买”等。如: let’s go for a walk. 我们出去散步吧。 I came here for my schoolbag.我来这儿取书包。 I paid twenty yuan for the dictionary. 我花了20元买这本词典。 6. 表示所属关系或用途,意为“为、适于……的”。如: It’s time for school. 到上学的时间了。 Here is a letter for you. 这儿有你的一封信。 7. 表示“支持、赞成”。如: Are you for this plan or against it? 你是支持还是反对这个计划? 8. 用于一些固定搭配中。如: Who are you waiting for? 你在等谁? For example, Mr Green is a kind teacher. 比如,格林先生是一位心地善良的老师。

to与for的用法和区别

to与for的用法和区别 一般情况下, to后面常接对象; for后面表示原因与目的为多。 Thank you for helping me. Thanks to all of you. to sb.表示对某人有直接影响比如，食物对某人好或者不好就用to; for表示从意义、价值等间接角度来说，例如对某人而言是重要的，就用for. for和to这两个介词，意义丰富，用法复杂。这里仅就它们主要用法进行比较。 1. 表示各种“目的” 1. What do you study English for? 你为什么要学英语？ 2. She went to france for holiday. 她到法国度假去了。 3. These books are written for pupils. 这些书是为学生些的。 4. hope for the best, prepare for the worst. 作最好的打算，作最坏的准备。 2．对于 1．She has a liking for painting. 她爱好绘画。 2．She had a natural gift for teaching. 她对教学有天赋/ 3．表示赞成同情，用for不用to. 1. Are you for the idea or against it? 你是支持还是反对这个想法？ 2. He expresses sympathy for the common people.. 他表现了对普通老百姓的同情。 3. I felt deeply sorry for my friend who was very ill. 4 for表示因为，由于（常有较活译法） 1 Thank you for coming. 谢谢你来。 2. France is famous for its wines. 法国因酒而出名。 5．当事人对某事的主观看法，对于（某人），对…来说（多和形容词连用）用介词to，不用for.. He said that money was not important to him. 他说钱对他并不重要。 To her it was rather unusual. 对她来说这是相当不寻常的。 They are cruel to animals. 他们对动物很残忍。 6．for和fit, good, bad, useful, suitable 等形容词连用，表示适宜，适合。 Some training will make them fit for the job. 经过一段训练，他们会胜任这项工作的。 Exercises are good for health. 锻炼有益于健康。 Smoking and drinking are bad for health. 抽烟喝酒对健康有害。 You are not suited for the kind of work you are doing. 7. for表示不定式逻辑上的主语，可以用在主语、表语、状语、定语中。 1．It would be best for you to write to him. 2．The simple thing is for him to resign at once. 3．There was nowhere else for me to go. 4．He opened a door and stood aside for her to pass.

常用介词用法(for to with of)

For的用法 1. 表示“当作、作为”。如: I like some bread and milk for breakfast. 我喜欢把面包和牛奶作为早餐。 What will we have for supper? 我们晚餐吃什么? 2. 表示理由或原因,意为“因为、由于”。如: Thank you for helping me with my English. 谢谢你帮我学习英语。 3. 表示动作的对象或接受者,意为“给……”、“对…… (而言)”。如: Let me pick it up for you. 让我为你捡起来。 Watching TV too much is bad for your health. 看电视太多有害于你的健康。 4. 表示时间、距离,意为“计、达”。如: I usually do the running for an hour in the morning. 我早晨通常跑步一小时。 We will stay there for two days. 我们将在那里逗留两天。 5. 表示去向、目的,意为“向、往、取、买”等。如: Let’s go for a walk. 我们出去散步吧。 I came here for my schoolbag.我来这儿取书包。 I paid twenty yuan for the dictionary. 我花了20元买这本词典。 6. 表示所属关系或用途,意为“为、适于……的”。如: It’s time for school. 到上学的时间了。 Here is a letter for you. 这儿有你的一封信。 7. 表示“支持、赞成”。如: Are you for this plan or against it? 你是支持还是反对这个计划? 8. 用于一些固定搭配中。如: Who are you waiting for? 你在等谁? For example, Mr Green is a kind teacher. 比如,格林先生是一位心地善良的老师。 尽管for 的用法较多，但记住常用的几个就可以了。 to的用法: 一：表示相对，针对 be strange (common, new, familiar, peculiar) to This injection will make you immune to infection. 二：表示对比，比较 1：以-ior结尾的形容词，后接介词to表示比较，如：superior ,inferior,prior,senior,junior 2: 一些本身就含有比较或比拟意思的形容词，如equal，similar，equivalent，analogous A is similar to B in many ways.

(完整版)介词for用法归纳

介词for用法归纳 用法1：(表目的)为了。如： They went out for a walk. 他们出去散步了。 What did you do that for? 你干吗这样做？ That’s what we’re here for. 这正是我们来的目的。 What’s she gone for this time? 她这次去干什么去了？ He was waiting for the bus. 他在等公共汽车。 【用法说明】在通常情况下，英语不用for doing sth 来表示目的。如： 他去那儿看他叔叔。 误：He went there for seeing his uncle. 正：He went there to see his uncle. 但是，若一个动名词已名词化，则可与for 连用表目的。如： He went there for swimming. 他去那儿游泳。(swimming 已名词化) 注意：若不是表目的，而是表原因、用途等，则其后可接动名词。(见下面的有关用法) 用法2：(表利益)为，为了。如： What can I do for you? 你想要我什么？ We study hard for our motherland. 我们为祖国努力学习。 Would you please carry this for me? 请你替我提这个东西好吗？ Do more exercise for the good of your health. 为了健康你要多运动。 【用法说明】(1) 有些后接双宾语的动词(如buy, choose, cook, fetch, find, get, order, prepare, sing, spare 等)，当双宾语易位时，通常用for 来引出间接宾语，表示间接宾语为受益者。如： She made her daughter a dress. / She made a dress for her daughter. 她为她女儿做了件连衣裙。 He cooked us some potatoes. / He cooked some potatoes for us. 他为我们煮了些土豆。 注意，类似下面这样的句子必须用for： He bought a new chair for the office. 他为办公室买了张新办公椅。 (2) 注意不要按汉语字面意思，在一些及物动词后误加介词for： 他们决定在电视上为他们的新产品打广告。 误：They decided to advertise for their new product on TV. 正：They decided to advertise their new product on TV. 注：advertise 可用作及物或不及物动词，但含义不同：advertise sth＝为卖出某物而打广告；advertise for sth＝为寻找某物而打广告。如：advertise for a job=登广告求职。由于受汉语“为”的影响，而此处误加了介词for。类似地，汉语中的“为人民服务”，说成英语是serve the people，而不是serve for the people，“为某人的死报仇”，说成英语是avenge sb’s death，而不是avenge for sb’s death，等等。用法3：(表用途)用于，用来。如： Knives are used for cutting things. 小刀是用来切东西的。 This knife is for cutting bread. 这把小刀是用于切面包的。 It’s a machine for slicing bread. 这是切面包的机器。 The doctor gave her some medicine for her cold. 医生给了她一些感冒药。 用法4：为得到，为拿到，为取得。如： He went home for his book. 他回家拿书。 He went to his friend for advice. 他去向朋友请教。 She often asked her parents for money. 她经常向父母要钱。

of和for的用法

of 1....的,属于 One of the legs of the table is broken. 桌子的一条腿坏了。 Mr.Brown is a friend of mine. 布朗先生是我的朋友。 2.用...做成的;由...制成 The house is of stone. 这房子是石建的。 3.含有...的;装有...的 4....之中的;...的成员 Of all the students in this class,Tom is the best. 在这个班级中,汤姆是最优秀的。 5.(表示同位) He came to New York at the age of ten. 他在十岁时来到纽约。 6.(表示宾格关系) He gave a lecture on the use of solar energy. 他就太阳能的利用作了一场讲演。 7.(表示主格关系) We waited for the arrival of the next bus. 我们等待下一班汽车的到来。

I have the complete works of Shakespeare. 我有莎士比亚全集。 8.来自...的;出自 He was a graduate of the University of Hawaii. 他是夏威夷大学的毕业生。 9.因为 Her son died of hepatitis. 她儿子因患肝炎而死。 10.在...方面 My aunt is hard of hearing. 我姑妈耳朵有点聋。 11.【美】(时间)在...之前 12.(表示具有某种性质) It is a matter of importance. 这是一件重要的事。 For 1.为,为了 They fought for national independence. 他们为民族独立而战。 This letter is for you. 这是你的信。

双宾语 to for的用法

1.两者都可以引出间接宾语，但要根据不同的动词分别选用介词to 或for：(1) 在give, pass, hand, lend, send, tell, bring, show, pay, read, return, write, offer, teach, throw 等之后接介词to。 如： 请把那本字典递给我。 正：Please hand me that dictionary. 正：Please hand that dictionary to me. 她去年教我们的音乐。 正：She taught us music last year. 正：She taught music to us last year. (2) 在buy, make, get, order, cook, sing, fetch, play, find, paint, choose,prepare, spare 等之后用介词for 。如： 他为我们唱了首英语歌。 正：He sang us an English song. 正：He sang an English song for us. 请帮我把钥匙找到。 正：Please find me the keys. 正：Please find the keys for me. 能耽搁你几分钟吗(即你能为我抽出几分钟吗)? 正：Can you spare me a few minutes? 正：Can you spare a few minutes for me? 注：有的动词由于搭配和含义的不同，用介词to 或for 都是可能的。如：do sb a favour＝do a favour for sb 帮某人的忙 do sb harm＝do harm to sb 对某人有害

for和of的用法

for的用法： 1. 表示“当作、作为”。如: I like some bread and milk for breakfast. 我喜欢把面包和牛奶作为早餐。 What will we have for supper? 我们晚餐吃什么? 2. 表示理由或原因,意为“因为、由于”。如: Thank you for helping me with my English. 谢谢你帮我学习英语。 Thank you for your last letter. 谢谢你上次的来信。 Thank you for teaching us so well. 感谢你如此尽心地教我们。 3. 表示动作的对象或接受者,意为“给……”、“对…… (而言)”。如: Let me pick it up for you. 让我为你捡起来。 Watching TV too much is bad for your health. 看电视太多有害于你的健康。 4. 表示时间、距离,意为“计、达”。如:

I usually do the running for an hour in the morning. 我早晨通常跑步一小时。 We will stay there for two days. 我们将在那里逗留两天。 5. 表示去向、目的,意为“向、往、取、买”等。如: Let’s go for a walk. 我们出去散步吧。 I came here for my schoolbag.我来这儿取书包。 I paid twenty yuan for the dictionary. 我花了20元买这本词典。 6. 表示所属关系或用途,意为“为、适于……的”。如: It’s time for school. 到上学的时间了。 Here is a letter for you. 这儿有你的一封信。 7. 表示“支持、赞成”。如: Are you for this plan or against it? 你是支持还是反对这个计划? 8. 用于一些固定搭配中。如:

for和to区别

1.表示各种“目的”，用for （1）What do you study English for 你为什么要学英语？ （2）went to france for holiday. 她到法国度假去了。 （3）These books are written for pupils. 这些书是为学生些的。 （4）hope for the best, prepare for the worst. 作最好的打算，作最坏的准备。 2．“对于”用for （1）She has a liking for painting. 她爱好绘画。 （2）She had a natural gift for teaching. 她对教学有天赋/ 3．表示“赞成、同情”，用for （1）Are you for the idea or against it 你是支持还是反对这个想法？ （2）He expresses sympathy for the common people.. 他表现了对普通老百姓的同情。 （3）I felt deeply sorry for my friend who was very ill. 4. 表示“因为，由于”（常有较活译法），用for （1）Thank you for coming. 谢谢你来。

（2）France is famous for its wines. 法国因酒而出名。 5．当事人对某事的主观看法，“对于（某人），对…来说”，（多和形容词连用），用介词to，不用for. （1）He said that money was not important to him. 他说钱对他并不重要。 （2）To her it was rather unusual. 对她来说这是相当不寻常的。 （3）They are cruel to animals. 他们对动物很残忍。 6．和fit, good, bad, useful, suitable 等形容词连用，表示“适宜，适合”，用for。（1）Some training will make them fit for the job. 经过一段训练，他们会胜任这项工作的。 （2）Exercises are good for health. 锻炼有益于健康。 （3）Smoking and drinking are bad for health. 抽烟喝酒对健康有害。 （4）You are not suited for the kind of work you are doing. 7. 表示不定式逻辑上的主语，可以用在主语、表语、状语、定语中。 （1）It would be best for you to write to him. （2） The simple thing is for him to resign at once.

常用介词用法(for-to-with-of)

常用介词用法(for-to-with-of)

For的用法 1. 表示“当作、作为”。如: I like some bread and milk for breakfast. 我喜欢把面包和牛奶作为早餐。 What will we have for supper? 我们晚餐吃什么? 2. 表示理由或原因,意为“因为、由于”。如: Thank you for helping me with my English. 谢谢你帮我学习英语。 3. 表示动作的对象或接受者,意为“给……”、“对…… (而言)”。如: Let me pick it up for you. 让我为你捡起来。Watching TV too much is bad for your health. 看电视太多有害于你的健康。 4. 表示时间、距离,意为“计、达”。如: I usually do the running for an hour in the morning. 我早晨通常跑步一小时。 We will stay there for two days. 我们将在那里逗留两天。

5. 表示去向、目的,意为“向、往、取、买”等。如: Let’s go for a walk. 我们出去散步吧。 I came here for my schoolbag.我来这儿取书包。 I paid twenty yuan for the dictionary. 我花了20元买这本词典。 6. 表示所属关系或用途,意为“为、适于……的”。如: It’s time for school. 到上学的时间了。 Here is a letter for you. 这儿有你的一封信。 7. 表示“支持、赞成”。如: Are you for this plan or against it? 你是支持还是反对这个计划? 8. 用于一些固定搭配中。如: Who are you waiting for? 你在等谁? For example, Mr Green is a kind teacher. 比如,格林先生是一位心地善良的老师。

英语形容词和of for 的用法

加入收藏夹 主题： 介词试题It’s + 形容词 + of sb. to do sth.和It’s + 形容词 + for sb. to do sth.的用法区别。 内容： It's very nice___pictures for me. A.of you to draw B.for you to draw C.for you drawing C.of you drawing 提交人：杨天若时间：1/23/2008 20:5:54 主题：for 与of 的辨别 内容：It's very nice___pictures for me. A.of you to draw B.for you to draw C.for you drawing C.of you drawing 答：选A 解析：该题考查的句型It’s + 形容词+ of sb. to do sth.和It’s +形容词+ for sb. to do sth.的用法区别。 “It’s + 形容词+ to do sth.”中常用of或for引出不定式的行为者，究竟用of sb.还是用for sb.，取决于前面的形容词。 1) 若形容词是描述不定式行为者的性格、品质的，如kind，good，nice，right，wrong，clever，careless，polite，foolish等，用of sb. 例： It’s very kind of you to help me. 你能帮我，真好。 It’s clever of you to work out the maths problem. 你真聪明，解出了这道数学题。 2) 若形容词仅仅是描述事物，不是对不定式行为者的品格进行评价，用for sb.，这类形容词有difficult，easy，hard，important，dangerous，（im）possible等。例： It’s very dangerous for children to cross the busy street. 对孩子们来说，穿过繁忙的街道很危险。 It’s difficult for u s to finish the work. 对我们来说，完成这项工作很困难。 for 与of 的辨别方法： 用介词后面的代词作主语，用介词前边的形容词作表语，造个句子。如果道理上通顺用of，不通则用for. 如： You are nice.(通顺，所以应用of)。 He is hard.(人是困难的，不通，因此应用for.) 由此可知，该题的正确答案应该为A项。 提交人：f7_liyf 时间：1/24/2008 11:18:42

双宾语tofor的用法

1. 两者都可以引出间接宾语，但要根据不同的动词分别选用介词to 或for： (1) 在give, pass, hand, lend, send, tell, bring, show, pay, read, return, write, offer, teach, throw 等之后接介词to。 如： 请把那本字典递给我。 正：Please hand me that dictionary. 正：Please hand that dictionary to me. 她去年教我们的音乐。 正：She taught us music last year. 正：She taught music to us last year. (2) 在buy, make, get, order, cook, sing, fetch, play, find, paint, choose,prepare, spare 等之后用介词for 。如： 他为我们唱了首英语歌。 正：He sang us an English song. 正：He sang an English song for us. 请帮我把钥匙找到。 正：Please find me the keys. 正：Please find the keys for me. 能耽搁你几分钟吗(即你能为我抽出几分钟吗)? 正：Can you spare me a few minutes? 正：Can you spare a few minutes for me? 注：有的动词由于搭配和含义的不同，用介词to 或for 都是可能的。如： do sb a favou r do a favour for sb 帮某人的忙 do sb harnn= do harm to sb 对某人有害

to和for的用法有什么不同(一)

to和for的用法有什么不同（一） 一、引出间接宾语时的区别 两者都可以引出间接宾语，但要根据不同的动词分别选用介词to 或for，具体应注意以下三种情况： 1. 在give, pass, hand, lend, send, tell, bring, show, pay, read, return, write, offer, teach, throw 等之后接介词to。如： 请把那本字典递给我。 正：Please hand me that dictionary. 正：Please hand that dictionary to me. 她去年教我们的音乐。 正：She taught us music last year. 正：She taught music to us last year. 2. 在buy, make, get, order, cook, sing, fetch, play, find, paint, choose, prepare, spare 等之后用介词for 。如： 他为我们唱了首英语歌。 正：He sang us an English song. 正：He sang an English song for us. 请帮我把钥匙找到。 正：Please find me the keys. 正：Please find the keys for me. 能耽搁你几分钟吗(即你能为我抽出几分钟吗)? 正：Can you spare me a few minutes?

正：Can you spare a few minutes for me? 3. 有的动词由于用法和含义不同，用介词to 或for 都是可能的。如： do sb a favor＝do a favor for sb 帮某人的忙 do sb harm＝do harm to sb 对某人有害 在有的情况下，可能既不用for 也不用to，而用其他的介词。如： play sb a trick＝play a trick on sb 作弄某人 请比较： play sb some folk songs＝play some folk songs for sb 给某人演奏民歌 有时同一个动词，由于用法不同，所搭配的介词也可能不同，如leave sbsth 这一结构，若表示一般意义的为某人留下某物，则用介词for 引出间接宾语，即说leave sth for sb；若表示某人死后遗留下某物，则用介词to 引出间接宾语，即说leave sth to sb。如： Would you like to leave him a message? / Would you like to leave a message for him? 你要不要给他留个话？ Her father left her a large fortune. / Her father left a large fortune to her. 她父亲死后给她留下了一大笔财产。 二、表示目标或方向的区别 两者均可表示目标、目的地、方向等，此时也要根据不同动词分别对待。如： 1. 在come, go, walk, move, fly, ride, drive, march, return 等动词之后通常用介词to 表示目标或目的地。如： He has gone to Shanghai. 他到上海去了。 They walked to a river. 他们走到一条河边。

keep的用法及of 、for sb.句型区别

keep的用法 1. 用作及物动词 ①意为"保存；保留；保持；保守"。如： Could you keep these letters for me, please? 你能替我保存这些信吗？ ②意为"遵守；维护"。如： Everyone must keep the rules. 人人必须遵守规章制度。 The teacher is keeping order in class.老师正在课堂上维持秩序。 ③意为"使……保持某种(状态、位置或动作等)"。这时要在keep的宾语后接补足语，构 成复合宾语。其中宾语补足语通常由形容词、副词、介词短语、现在分词和过去分词等充当。如： 例：We should keep our classroom clean and tidy.(形容词) 我们应保持教室整洁干净。 You'd better keep the child away from the fire.(副词)你最好让孩子离火远一点。 The bad weather keeps us inside the house.(介词短语)坏天气使我们不能出门。 Don't keep me waiting for long.(现在分词)别让我等太久。 The other students in the class keep their eyes closed.(过去分词) 班上其他同学都闭着眼睛。 2. 用作连系动词 构成系表结构：keep＋表语，意为"保持，继续(处于某种状态)"。其中表语可用形容词、副词、介词短语等充当。如： 例：You must look after yourself and keep healthy.(形容词) 你必须照顾好自己，保持身体健康。 Keep off the grass.(副词)请勿践踏草地。 Traffic in Britain keeps to the left.(介词短语)英国的交通是靠左边行驶的。 注意：一般情况下，keep后接形容词较为多见。再如： She knew she must keep calm.她知道她必须保持镇静。 Please keep silent in class.课堂上请保持安静。 3. ①keep doing sth. 意为"继续干某事"，表示不间断地持续干某事，keep后不 能接不定式或表示静止状态的v-ing形式，而必须接延续性的动词。 例：He kept working all day, because he wanted to finish the work on time. 他整天都在不停地工作，因为他想准时完成工作。 Keep passing the ball to each other, and you'll be OK.坚持互相传球，你们就

202X中考英语：to和for的区别与用法.doc

202X中考英语：to和for的区别与用法中考栏目我为考生们整理了“202X中考英语：to和for的区别与用法”，希望能帮到大家，想了解更多考试资讯，本网站的及时更新哦。 202X中考英语：to和for的区别与用法 to和for的区别与用法是什么 一般情况下, to后面常接对象; for后面表示原因与目的为多。 Thank you for helping me. Thanks to all of you. to sb. 表示对某人有直接影响比如，食物对某人好或者不好就用to; for 表示从意义、价值等间接角度来说，例如对某人而言是重要的，就用for. for和to这两个介词，意义丰富，用法复杂。这里仅就它们主要用法进行比较。 1. 表示各种“目的” 1. What do you study English for? 你为什么要学英语? 2. She went to france for holiday. 她到法国度假去了。 3. These books are written for pupils. 这些书是为学生些的。 4. hope for the best, prepare for the worst. 作最好的打算，作最坏的准备。

2.对于 1.She has a liking for painting. 她爱好绘画。 2.She had a natural gift for teaching. 她对教学有天赋。 3.表示赞成同情，用for不用to. 1. Are you for the idea or against it? 你是支持还是反对这个想法? 2. He expresses sympathy for the common people.. 他表现了对普通老百姓的同情。 3. I felt deeply sorry for my friend who was very ill. 4 for表示因为，由于(常有较活译法) 1.Thank you for coming. 谢谢你来。 2. France is famous for its wines. 法国因酒而出名。 5.当事人对某事的主观看法，对于(某人)，对?来说(多和形容词连用)用介词to，不用for.. He said that money was not important to him. 他说钱对他并不重要。 To her it was rather unusual. 对她来说这是相当不寻常的。 They are cruel to animals. 他们对动物很残忍。

to of和for的区别

to , of 和for的区别 1.to有到的意思，常常和go，come，get连用引出地点。Go to school , go to the shop , go to the cinema. 常见的短语：the way to 去---的路 On one’s way to 在某人去---的路上 以上的用法中，当地点是副词home，here，there等是to 要去掉。如：get home，the way here To后跟动词原形，是不定式的标志 It is +形容词+(for/of +人+)to do sth.(括号内部分可以省略) It is easy for me to learn English. It is very kind of you to lend me your money. 当形容词表示人的行为特征时用of表示to do的性质时用for Want, hope ,decide, plan , try , fail等词后跟to do I want to join the swimming club. Would like to do I’d like to play basketball with them. It is time to have a break. Next to , close to , from ---to--- 2.for 为，表示目的。 Thank you for Buy sth for sb =buy sb sth It is time for bed. Here is a letter for you.

I will study for our country. 3.of表示所属关系意思是：---的 a map of the world a friend of mine

for和of引导的不定式结构的区别

for和of引导的不定式结构的区别 不定式是一种非谓语动词，不能单独作谓语，因此没有语法上的主语。但由于不定式表示的是动作，在意义上可以有它的主体。我们称之为逻辑主语。 提起不定式逻辑主语，人们首先想到的会是“for+名词（宾格代词）+不定式”的复合结构。如：It is important for us to study English well．然而，有时不定式的逻辑主语须要用“of+名词（代词宾格）”才行。例如：It is kind of you to help me．而不能说：It is kind for you to help me．在选择介词“for”还是“of”时，人们往往总是凭感觉而定。有时受习惯影响，多选介词“for”。于是常出现这样的错误：It was careless for him to lose his way．It is cruel for you to do so．由于众多语法书对这种结构中使用“for”与“of”的区别介绍甚少，一些人对其概念认识尚不完全清楚，笔者认为有必要就这一问题作些探讨与介绍。 一、在句中的语法作用不同 a．不定式for结构在句中可以作主、宾、表、定、状、同位语： 1．It is easy for Tom to do this work．（主语）汤姆做此工作是容易的。 2．I'd like for him to come here．（宾语）我喜欢他来这里。 3．His idea is for us to travel in two different groups．（表语）他的想法是：我们分成两组旅行。 4．Have you heard about the plan for you to go abroad．（定语）你听到让你出国的计划吗？ 5．The word is too difficult for him to pronounce well．（状语）这单词太难，他念不准。 6．In the most schools，it is the custom for the headmaster to declare the newterm start．在大部分学校，校长宣布新学期开始是一个习惯。 b．不定式of结构只能在句中作主语。 1．It was careless of him to leave his umbrella in the train．他把伞丢在火车上真是太粗心了。 2．It is awfully good of you to come to see me off at the station．谢谢你来车站送我。 二、逻辑主语的名词有所不同