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Durability and Microstructure of Ultra-High Performance Concrete

Having High Volume of Steel Slag Powder and Ultra-Fine Fly sh

Yanzhou Peng1,a

, Kai Chen2, 3, b

, Shuguang Hu3,b

1

College of Civil Engineering & Architecture,China Three orge! "niver!it#,Yichang $$3%%2,China2 China ail'a# (a)or *ri+ge econnai!!ance & e!ign -n!titute Co., /t+., 0uhan $3%%%,China

3 Ke# /aborator# for Silicate (aterial! Science an+ Engineering of (ini!tr# of E+ucation, 0uhan

"niver!it# of Technolog#, 0uhan $3%%%, China

an#zh4#ahoo.co5.cn,

b3%36771488.co5

!ey words" Steel !lag o'+er9 ultrafine fl# a!h9 ultrahigh erfor5ance concrete9 +urabilit#9 oro!it#.

Abstract. The durability, such as chloride ion permeability, freeze-thaw and sulfate attack resistance

of ultra-high performance concrete (UHPC ha!ing a large amount, ranged from "#$ to "%$ byweight of binder, of mineral admi&tures including steel slag powder ('', ultrafine fly ash (U)

and silica fume (' was studied and the microstructure of selected UHPC compositions was

in!estigated by *ercury porosimetry in this paper+ *oreo!er, the relationship between durability and

microstructure of UHPC was analyzed+ The mercury porosimetry studies demonstrated the !ery low

 porosity and a high proportion of the innocuous pores as well as the !ery small pore size in UHPCs,

whose most probable pore diameter did not e&ceed nm+ This porous structure of UHPCs would

definitely enable the material ha!e e&cellent durability+

Introduction

.eacti!e powder concrete (.PC, otherwise known as ultra-high performance concrete, has broad practical application prospects /,#0+ Con!entional .PC is composed of cement and ultra-fine

 powders such as crushed 1uartz and silica fume ('+ The pre!ious studies show that the utilization of

steel slag powder ('' and ultra-fine fly ash (U) is feasible for preparation of this new type UHPC

and the strength of UHPCs containing '', U) and ', cured in water with the temperature of 23C,

could achie!e more than %*Pa and 4*Pa respecti!ely /40+

5n this paper, the chloride ion permeability, freeze-thaw and sulfate attack resistance of UHPCs

ha!ing high !olume of '' and U) were studied+ *oreo!er, the porous structure of selected UHPC

compositions were in!estigated by *ercury Porosimetry (*P in order to gain a better understanding

of the influence of temperature and duration on hydration and microstructure as well as the

relationship between the durability and microstructrue of UHPCs containing '' and U)+

Experimental Program

Materials. The UHPCs considered here is prepared by the following ingredients6 7rdinary Portland

Cement (7PC from 8ezhouba Cement Co+, 9td (Hubei Pro!ince, China: steel slag powder (''

 pro!ided by ;uhan 8reen *etallurgical 'lag Technology <e!elopment Co+, 9td: ultra-fine fly ash

(U) from Power Plant of Hanchuan, ;uhan: undensified silica fume (appro&imately +-+# =m

and a polycarbo&ylate based superplasticizer ('P both from ;uhan Haoyuan Chemical >uilding

*aterials Co+, 9td+ ?atural fine sand with size of +@-+@4 mm is used as a fine aggregate and its

specific gra!ity is #+@A+ urthermore, brass coated steel fibers 4 mm long with the diameter of +#

mm is used to impro!e the ductility of concrete+ The tensile strength of and aspect ratio

(length-to-diameter ratio of steel fibers are #% *Pa and @A, respecti!ely+ The pertinent physical

and chemical properties of the cement, ', '' and U) used in this research are gi!en in Table +

Specimens preparation.  or each mi&ture whose mi& proportion is shown in Table #, all

components (cement, '', U), ' and sand are mi&ed, cast, and !ibrated in a similar se1uence as

 Advanced Materials Research Vols. 255-260 (2011) pp 452-456 Online available since 2011/May/31 at www.scientific.net © (2011) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.255-260.452

 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,www.ttp.net. (ID: 130.113.111.210, McMaster University, Hamilton, Canada-03/04/14,02:46:19)

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con!entional concrete+ 5nitially, dry powders (cement, ', '' and U) and sand are mi&ed at low

speed for about 4 min+ The water and superplasticizer used are then added and mi&ed for about @ min+

'ubse1uently, steel fibers, if necessary, is added and mi&ed for another @ min+ The entire mi&ing

 process takes about A min before the mi& is ready to cast+

Table 1 Chemical and physical properties of cement, ', U) and ''Cement 'ilica fume 'teel slag Ultra-fine fly ash

Chemical composition ($

'i7# #4+4 2+B 4+A A+B

Ca7 AB+@ +4 ""+4 4+B

)l#74 B+# + #+A 4#+

e#74 4+ +% #+% @+

*g7 +B + A+2 +

'74 4+ +#

9oss in ignition 4+#4 +#

 f -Ca7 +B Physical properties

'pecific density (kgm4 4+ #+# 4+2 #+AA

>laine surface area (m#kg "#B # A" @A2

Compressi!e strength of cement (*Pa

4 days 4B+#

#% days @+B

Table 2 *i&ing proportions of UHPCs (by weight ratio 

 ?o+ C U) '' ' 'and ;ater 

  'P

'teel fibers# 

$

'%# +AA +# +% +A

+ +@ +@ #'B +A% + +B +A

'@@ +A# +@ +@ +@6 5ncluding water from 'P:#6 Dolume fraction of steel fiber is #$+

or chloride ion permeability, freeze-thaw and sulfate attack resistance test, specimens

(EFA-mm, "F"F@-mm and FF"-mm respecti!ely are kept in water with the

temperature of about # 3C for 4 days after demolded, and then are cured in 2 3Cwater (T2 for

another 4 days+ or mercury porosimetry , specimens ("F"F@-mm are kept in # 3Cwater for 4days after demolded, and then are cured in 4 conditions6 # 3C water, @ 3C water and 2 3C water

(abbr+ T#,T@ and T2 for a gi!en period ( day or 4 days respecti!ely+

Chloride ion permeability test. The chloride ion penetration coefficient is used for e!aluate the

chloride ion permeability of UHPCs in this paper+ The chloride ion penetration coefficients are

in!estigated through rapid chloride ion migration test (.C* and samples are prepared according to

Table # e&pect without steel fibers+

The test procedure of chloride ion penetration coefficients has been described pre!iously /", A0+ To

 perform the .C*, a saturated -mm diameter, A-mm long UHPC sample is placed in a slee!e and

then set in the test apparatus as shown in ig+ + 7n one side of the sample, the solution contains

chloride ions, while the other is chloride free+ )n electrical potential with !oltage of 4G" D is then

applied such that the chloride ions are dri!en into the concrete for gi!en time+ >oth the current and

temperature of the upper solution during the test are recorded+ )nd the chloride ion penetration depth

in cylinder specimen can be attained through sil!er nitrate ()g?74 solution after the test+ Two

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replicates ha!e been done for each specimen and the a!erage depth is taken as the chloride ion

 penetration depth of the specimen+ )nd then, the chloride ion penetration coefficient ( D RCM  of each

specimen can be obtained by the following e1uations /@06

t 

 x xTh

 D

d d 

 RCM 

(

%B#+#

@   α −

×=  −

+ (

;here T  is the a!erage temperature of the initial and final temperature of the anode solution (, h is

the height of specimen (m, xd  is the penetration depth of chloride ion (m, t  is the time of the testing

current duration (s, α is defined as Th444%+4   −

×=α  +

igure 1 .C* set-up /A0

ree!e"tha# and sul$ate attac% resistance+ The mi&ing proportions of specimens for freeze-thaw

and sulfate attack resistance are shown in table #+ The reeze-thaw resistance of specimens is tested

according to I*ethod for fast reezeJ 8>K%#-%A+ Three prism specimens (FF"-mm are

cast for each mi&ture and are placed in a T.-T<. machine for rapid freezing and thawing after theend of heat treatment+

The sulfate attack resistance is tested as follows6 'pecimens ("F"F@-mm are cured in water

and A$ sodium sulfate solution (by weight respecti!ely+ The sulfate attack resistance is denoted by

mass loss rate and the anti-erosion coefficient for compressi!e strength, i+e+  K c, of specimens+

)nti-erosion coefficient for compressi!e strength is defined as6

,

,

,

a

 sodiuma

ac R

 R K    = + (#

;here Ra,sodium is the compressi!e strength of specimens after the specimens had been curing in A$

sodium sulfate solution for a gi!en period, and Ra,0 is the compressi!e strength of specimens whichwere cured in water and had the same age+ The strengths (compression and fle&ure of specimens were

tested according to 8>TB@B-222+

Mercury porosimetry. Porosimetric measurements are carried out on a P7.L*)'TL. 44-@

 porosimeter+ 'amples are splinters taken from specimens and are o!en-dried at @ 3C for #" h+ Those

specimens are prepared according to mi&ture 'B e&cept without steel fibers (Tab+ # and ha!e

 been curing in 4 conditions, i+e+ T#, T@ and T2 for a gi!en period respecti!ely after demolded+

&esults and 'iscussions

'urability.  The results of chloride ion permeability, freeze-thaw and sulfate attack resistance of

UHPC specimens are shown in table 4, " and A+The result shown in Table 4 demonstrates the e&cellent resistance to chloride ion penetration of

UHPC specimens+ 5t is generally agreed that the resistance to chloride ion penetration of concrete

depends mainly on pore structure, especially the amount of capillary and their degree of connecti!ity+

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*oreo!er, the type of cement and mineral admi&tures both ha!e significant effect on the resistance to

chloride ion penetration /#, @0+ Thus, the results shown in table 4 imply that UHPCs ha!ing high

!olume of '' and U) ha!e a !ery dense microstructure, a low porosity and a small capillary

diameter, which would be !erified by pore structure analysis+ Table " shows that UHPCs prepared in

this paper ha!e e&cellent resistance to freeze-thaw6 )ll specimens ha!e no mass loss while the relati!e

dynamic elastic modulus reaches 22$ after A freeze-thaw cycles: )fter 4 freeze-thaw cycles, themass loss is less than +A$ and the relati!e dynamic elastic modulus still e&ceeds 22$+ urthermore,

table A indicates the e&cellent resistance of UHPCs to sulfate attack+

Table ( Chloride ion penetration coefficient ( D RCM  of UHPC specimens 

'ample '%# 'B '@@

 D RCM (F-4m#s +A4 +A +A@

Talbe ) reeze-thaw resistance of UHPC specimens 

Cycles

'ample

*ass loss $ .elati!e dynamic elastic modulus$

A # 4 A # 4

'%# +# +4@ 22+B 22+@ 22+

'B +" +4# 22+2 22+B 22+4

'@@ +4 +" 22+@ 22

Table * 'ulfate attack resistance of UHPC specimens (A$ ?a#'7" 

'ample

*ass loss $)nti-erosion coefficient for

compressi!e strength, K c $

4 d @ d 2 d %d 4 d @ d 2 d %d'%# #+ #+2 4+4 @+"

'B +A #+A 4+B A+A

'@@ +# #+" #+2 "+4

Mercury porosimetry. The mercury porosimetry results of sample 'B (without steel fiber

cured in 4 different conditions for a gi!en period (d and 4d are shown in Table @+

Table + Pore structure of sample 'B cured in 4 conditions respecti!ely for a gi!en period

 ?o+ Porosity(mlg

The most

 probable pore

diameter(nm

Pore diameter distribution($

#G(nm G#(nm #G(nm G#(nm M#(nm

T#,ageNAd +4"# 2+" A2+4 @+# +" +%4 #+@2

T@-d,ageNA

d+## B+B @A+B "+2 2+#A %+B# #+"

T2-d,ageNA

d+#B @+A @2+4A 4+4" %+24 @+2A +"4

T#,ageNBd +4# %+ @A+@# "+%B +"B B+B +2B

T@-4d,ageNB

d+2 A+B @B+B@ @+A% %+2@ A+4 +42

T2-4d,ageNB

d +BB 4+2 B"+2 "+4# B+4B 4+#B +2A

)s shown in Table @, the maOor portions of pores e&isted in those samples belong to the innocuous

 pores or the harmless pores /#0, and the proportion of the harmful pores (by the total !olume of pore

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is only "G$+ 5n addition, table @ also shows that a high curing temperature or a long curing duration

leads to a low porosity and a high proportion of the innocuous pores as well as a small diameter of the

most probable pore+ The reason is that during the process of heat treatment, the pozzolanic reaction of

', '' and U) is acti!ated and takes place se1uentially /4,B0, which continuously consume

Ca(7H# produced by cement hydration+ )s a result, most of Ca(7H# are transformed into a type of

gel product (C-'-H gel and these product fill some pores in hardened paste /40+ Thus, the porediameter and the total porosity of hardened paste decrease and the microstructure of paste becomes

increasingly compact, which would definitely impro!e the durability of UHPC+

>ased on these abo!ed-studies, it is thought in this paper that the e&cellent durability of UHPCs

mainly comes from the following factors6 irstly, the UHPC compound system has a !ery low

water-binder ratio (+@ as well as a high packing density /%0+ Thus, the paste has a low porosity as

well as a small pore diameter and its microstructure is !ery compact+ *oreo!er, the strength of

hardened paste is prominent /40, so the ability of resistance to attack is !ery wonderful+ 'econdly, the

UHPC specimens contain a large amount of '', U) and '+ <uring the process of heat treatment,

the pozzolanic reaction of those mineral admi&tures is acti!ated and takes place se1uentially, which

would impro!e the microstructure of UHPCs+

Conclusions

The results show that UHPCs ha!ing high !olume of '' and U) ha!e e&cellent resistance to

chloride ion permeability, freeze-thaw and sulfate attack+ *ercury intrusion porosimetry indicates

that a high curing temperature or a long curing duration results in a low porosity and a high proportion

of the innocuous pores as well as a small pore diameter in UHPCs whose most probable pore diameter

does not e&ceed nm+ This porous structure of UHPCs would definitely enable the material ha!e

e&cellent durability+

Ac%no#ledgements

This research work was financially supported by the .esearch 'tart-up und of China Three

8orges Uni!ersity (?o+ K#2>@# and the key technology .< program of th i!e-Qear Plan

of China (?o+ #4>)@A#C+

&e$erences

/0 P+ .ichard and *+ Cheyrezy6 Cement and Concrete .esearch, Dol+ #A (22A, ?o+B, p+ A

/#0 R+ ;u, H+ 9ian6 High performance concrete (China .ailway Press, 222 (in Chinese

/40 Q+ Peng, '+ Hu, S+ <ing6 Kournal of ;uhan Uni!ersity of Technolotgy, *aterials 'cience

Ldition, Dol+#A (#, p+ 4"2

/"0 '+ Hu, Q+ Peng and S+ <ing, in6  Proceedings of the First Internationa Conference on

 Microstructure Reated Dura!iit" of Cementitious Composites, ?anOing, China, .59L*

Publications '+)+.+9+ (#%, p+ "4B

/A0 + 'tanish, .+ <+ Hooton, *+ <+ )+ Thomas6 Cement and Concrete .esearch, Dol+ 4" (#",

 ?o+, p+ A

/@0 K+ 8eng6 The .esearch on the <eteriorated *echanisms of .einforced Concrete in 'tray Currents

and Chloride 5on Coe&isted Corrosion Ln!ironment /<0, ;uhan6 ;uhan Uni!ersity of

Technology, #% (in Chinese

/B0 Q+ Peng6 'tudy on Composition, 'tructure and Properties of .eacti!e Powder Concrete

Containing 'teel 'lag Powder /<0, ;uhan6;uhan Uni!ersity of Technology, #2 (in Chinese

/%0 Q+ Peng, '+ Hu and S+ <ing6 Particuology, Dol+B (#2, ?o+A, p+422

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Advances in Civil Engineering, CEBM 2011 

10.4028/www.scientific.net/AMR.255-260 

Durability and Microstructure of Ultra-High Performance Concrete Having High Volume of Steel Slag

Powder and Ultra-Fine Fly Ash 

10.4028/www.scientific.net/AMR.255-260.452 

DOI References

[3] Y. Peng, S. Hu, Q. Ding: Journal of Wuhan University of Technolotgy, Materials Science Edition, Vol. 25

(2010), p.349.

http://dx.doi.org/10.1007/s11595-010-2349-0