Construction and Building Materials 23 (2009) 2087–2092

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Construction and Building Materials

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An experimental study on the workability of self-compacting lightweight concrete

Zhimin Wu a,*, Yunguo Zhang a, Jianjun Zheng b, Yining Ding a

a State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116023, PR Chinab Faculty of Civil Engineering and Architecture, Zhejiang University of Technology, Hangzhou 310014, PR China

a r t i c l e i n f o

Article history:Received 10 January 2008Received in revised form 31 July 2008Accepted 26 August 2008Available online 8 October 2008

Keywords:Self-compacting lightweight concreteMix proportion designWorkabilityDynamic textStatic test

0950-0618/$ - see front matter � 2008 Elsevier Ltd. Adoi:10.1016/j.conbuildmat.2008.08.023

* Corresponding author.E-mail address: zyg-ncwu@163.com

a b s t r a c t

Numerous investigations have been conducted on self-compacting concrete (SCC) and lightweightaggregate concrete (LWAC), but there are relatively very few studies on self-compacting lightweightconcrete (SCLC). This paper deals mainly with the mix proportion design for SCLC and its workability.By considering the water absorption of lightweight aggregate (LWA), two mix proportions for SCLC aredesigned by the overall calculation method with fixed fine and coarse aggregate contents. The work-ability of the two types of fresh SCLCs is quantitatively evaluated by the slump flow, V-funnel, L-box, U-box, wet sieve segregation, and surface settlement tests. The uniformity of distribution of LWAsalong the specimen is also evaluated by the column segregation test and the cross-section images.Based on the experimental results, a detailed analysis is conducted. It is found that the two types offresh SCLCs have good fluidity, deformability, filling ability, uniform aggregate distribution and mini-mum resistance to segregation. It can be concluded that the two mix proportions for SCLC presentedin this paper satisfy various requirements for workability and can be used for the design of practicalconcrete structures.

� 2008 Elsevier Ltd. All rights reserved.

1. Introduction

Self-compacting lightweight aggregate concrete (SCLC) is a kindof high performance concrete developed from self-compactingconcrete (SCC). SCLC combines the favorable properties of light-weight aggregate concrete (LWAC) and SCC, needs no externalvibration, and can spread into place, fill the formwork and encap-sulate reinforcement without any bleeding or segregation. Asanother advantage, SCLC efficiently reduces the self-weight of thestructure and the on-site noise level and can be used for mainte-nance and repairs of concrete structures.

Workability is a crucial factor that affects the application andphysicomechanical properties of SCLC, since SCLC of practical useis required to have high fluidity, deformability, good filling ability,and moderate resistance to segregation. To ensure that reinforce-ment can be encapsulated and that the formwork can be filledcompletely, a favorable workability is essential for fresh SCLC. Inaddition, aggregate particles in SCLC are required to have uniformdistribution in the specimen and the minimum segregation riskshould be maintained during the process of transportation andplacement.

Various testing and evaluation methods used for SCLC aresimilar to those used for SCC. Extensive investigations on the work-

ll rights reserved.

ability of SCC have been made in North America and Europe [1–3].Khayat et al. reported that the L-box, U-box, and J-ring tests can beused to evaluate the passing ability of SCC and, to a certain extent,the deformability and resistance to segregation [1]. When com-bined with the slump flow test, the L-box test is very suitable forthe quality control of on-site SCC. The visual stability index, wetsieve segregation test, and penetration test are usually used to esti-mate the resistance of SCC to segregation [4].

Although numerous investigations have been made on SCC andLWAC, there are few studies on SCLC so far. Choi et al. [5] designedthe mix proportion for SCLC by adopting a modified method pro-posed by Su and Miao [6]. The slump flow, V-funnel and U-boxtests were then used to evaluate the workability of SCLC. Similarly,Shi and Wu used the slump flow, V-funnel, and L-box tests, and thevisual observation method to study the properties of SCLC [7].Müller and Haist proposed three mix proportions for SCLC and as-sessed their self-compacting properties by the slump flow, J-ring,V-funnel, and L-box tests. It has been found that, compared withSCC, there is no significant difference in the mix proportion designexcept for the aggregate used [8]. According to the current investi-gations on LWAC and the suggestions of EFNARC 2002 [9], thestudy on the resistance of SCLC to segregation is insufficient. Mostof the current investigations on the resistance to segregation areconducted by the visual observation method and the volume sta-bility of SCLC and the uniformity of distribution of aggregate inSCLC are seldom dealt with. Therefore, it is of great practical signif-icance to further study the workability of SCLC.

Table 2Physical properties and grading of expanded shale aggregate

Apparentdensity(kg/m3)

24-h waterabsorption(%)

Crushstrength(MPa)

Aggregate volume fraction (%)

1363 4 6.0 <5 mm 5 – 10 mm 10 – 16 mm >16 mm16.6 43.6 25.7 14.1

2088 Z. Wu et al. / Construction and Building Materials 23 (2009) 2087–2092

2. Materials and mix design

2.1. Materials

An ordinary Portland cement produced in Dalian, China was used in this study.Class I fly ash with apparent density of 2.7 g/cm3 was added as a viscous admixture.Sica 3301 polycarboxylate-based high-range water reducer (HRWR) with specificgravity of 1.1 was used to adjust the workability of SCLC. An expanded shale asshown in Fig. 1 was used as coarse aggregate. The maximum aggregate diameterwas 20 mm. River sand was used as fine aggregate. The physical properties of thecement and expanded shale are shown in Tables 1 and 2, respectively.

2.2. Mix proportions

Considering the water absorption of LWA, the mix proportions for SCLC weredetermined by the overall calculation method with fixed fine and coarse aggregatecontents [10,11]. In the experiment, two series of concrete specimens, denotedrespectively by SCLC1 and SCLC2, were cast. The coarse and fine volume fractionswere 0.520 and 0.206 for SCLC1 and 0.510 and 0.211 for SCLC2, respectively. Thewater to binder ratio w/b was determined by

w=b ¼ mðwÞmðcþ fÞ ¼

1fcu;p=ðAfceÞ þ B

ð1Þ

where m(w) is the mass of water, m(c+f) is the total mass of cement and fly ash, fcu,p

is the cube compressive strength of SCLC, is the compressive strength of cement, andA and B are two regression coefficients. According to [12], A = 0.48 and B = 0.52 forcrushed aggregate. The volume fraction of water was given by

Vw ¼Vcp � V0

1þ ½fcu;p=ðAfceÞ þ B�=½qcð1� /Þ þ /qfð2Þ

where Vcp is the volume fraction of cement paste, V0 is the volume fraction of air, u isthe substitution rate of fly ash for ordinary Portland cement, and qc and qf are thedensity of cement and fly ash, respectively. The value of u was taken to be equalto 0.30 [6,7]. Thus, the mix proportions for SCLC1 and SCLC2 were determined asshown in Table 3.

3. Workability tests

To better evaluate the workability of SCLC, both dynamic andstatic stability tests are usually required [1,2]. Dynamic stabilityis concerned with the properties of SCLC during the process of mix-ing, transportation, and casting, while static stability deals with theproperties of SCLC during the period from casting to initial set.

Fig. 1. Expanded shale LWA.

Table 1Physical properties of cement

No. MgO (%) SO3 (%) Specific surface(m2/kg)

Percentage retainedon 80 lm sieve (%)

It

P42.5 65.0 63.5 >290 63.0 P

3.1. Dynamic stability tests

3.1.1. Slump flow testSince the slump test is not suitable for the analysis of the fluid-

ity of SCLC, the slump flow test is adopted. The testing apparatusconsists of a normal slump cone and a steel plate with dimensionsof 900 � 900 mm. With this apparatus, the time for SCLC to spreadto 500 mm in diameter, T500, and the final slump flow diametersand D2 in the two orthogonal directions as shown in Fig. 2 can bemeasured.

According to EFNARC [9], for class 1 SCC the slump flow diam-eter is 550 – 650 mm and T500 6 2 s; for class 2 SCC the slump flowdiameter is 600 – 750 mm and T500 P 2 s; for class 3 SCC the slumpflow diameter is 760 – 850 mm, but no specification for T500 is gi-ven. To further examine how the fluidity of SCLC is changed withtime, the slump flow was measured at 0, 10, and 30 min, respec-tively. The results are shown in Table 4.

3.1.2. V-funnel testThe apparatus for the V-funnel test is shown in Fig. 3. With this

apparatus, the total time for SCLC to flow through the V-funnel, canbe measured. The V-funnel flow test is to evaluate the fluidity ofSCLC and the ability for SCLC to change its path and to pass througha constricted area. According to EFNARC [9], for class 1 SCC TV issmaller than 8 s and for class 2 SCC TV is 9 – 25 s. The measuredvalues of TV are shown in Table 5.

3.1.3. L-box testThe L-box test is used to evaluate the fluidity of SCLC and the

ability for SCLC to pass through steel bars. The L-box consists ofa ‘‘chimney” section and a ‘‘channel” section as shown in Fig. 4.With the L-box, the height of concrete in the chimney, h1, theheight of concrete in the channel section, h2, and the time for SCLCto reach 400 mm from three steel bars, T400, can be measured.According to EFNARC [9], when the ratio of h2 to h1 is larger than0.8, SCC has good passing ability. However, no specification forT400 is given in EFNARC or other codes. In most previous studieson SCC, T400 is used to estimate the flow velocity of SCC. The mea-sured values of h2/h1 were respectively 0.84 and 0.97 for SCLC1 andSCLC2, and the values of T400 are shown in Table 5.

3.1.4. U-box testThe U-box test is used to evaluate the filling ability and passing

ability of SCLC in congested reinforcement. The main parameter tobe measured is the height difference of concrete between the twoboxes, Dh. The apparatus for the U-box test is shown in Fig. 5.According to EFNARC [9], when the height difference of concreteis smaller than 30 mm, SCC has good filling and passing ability.

nitial settingime (min)

Final settingtime (min)

3-Day compressivestrength (MPa)

28-Day compressivestrength (MPa)

100 6330 P25 P46

Fig. 2. Slump flow test.

Fig. 3. V-funnel test.

Table 5Values of Iseg, SR, TV, T500, and T400 for SCLC1 and SCLC2

No. Iseg (%) SR (%) TV (s) T500 (s) T400 (

SCLC1 2.9% 4.4% 23.3 5.9 7.5SCLC2 4.2% 5.6% 17.8 4.2 6.3

Fig. 4. L-box test.

Table 3Mix proportions for SCLC1 and SCLC2

No. Cement (kg/m3) Fly ash (kg/m3) Sand (kg/m3) LWA (kg/m3) Water (kg/m3) HRWR (kg/m3) 28-Day compressive strength (MPa) Bulk density (kg/m3)

SCLC1 397 170 780 416 187 6.2 42.6 1879SCLC2 425 182 787 408 176 10.9 50.1 1920

Table 4Variations of T500, D1, and D2 with time

No. 0 min 10 min 30 min

T500 (s) D1 � D2

(mm)T500 (s) D1 � D2

(mm)T500 (s) D1 � D2

(mm)

SCLC1 5.9 760 � 740 6.0 710 � 680 9.2 680 � 690SCLC2 4.2 780 � 800 4.8 780 � 800 6.6 780 � 770

Z. Wu et al. / Construction and Building Materials 23 (2009) 2087–2092 2089

s)

Fig. 5. U-box test.

The measured height differences of concrete were 6 and 3 mm forSCLC1 and SCLC2, respectively.

3.2. Static stability tests

3.2.1. Wet sieve segregation testThe wet sieve segregation test as shown in Fig. 6 was first devel-

oped in France. It can be used to quantitatively evaluate the resis-tance of SCLC to segregation. The test procedure is as follows. First,10 l of fresh SCLC is filled in a sealed container. After the samplestands still for 15 min, 5 kg of SCLC is taken out of the containerand then poured from a height of 500 mm onto a perforated metalsieve with aperture 5 mm. After 2 min, the mass of SCLC thatpasses through the sieve is recorded. Finally, the mass percentageof the sample passing through the sieve is calculated as the segre-gation ratio (SR) of SCLC. Obviously, the smaller the value of SR is,the larger the resistance of SCLC to segregation is. According toEFNARC [9], the value of SR should not exceed 15% for SCC to meetthe requirement of resistance to segregation. The measured valuesof SR are shown in Table 5.

3.2.2. Surface settlement testThe surface settlement test is used to measure the rate of

settlement at the top surface of SCLC in a plastic stage to evaluate

Fig. 6. Wet sieve segregation test. Fig. 8. Column segregation test.

2090 Z. Wu et al. / Construction and Building Materials 23 (2009) 2087–2092

its volume stability. The rate of settlement (expressed as relativesettlement per hour) can be expressed as follows [13]

Settlementrateð%=hÞ ¼ f½Stð%Þ � St�5ð%Þ�=5ðminÞg=60ðminÞ ð3Þ

where St is the settlement value at a given time t (in minutes), St�5

is the settlement value at time of t minus 5 min. The apparatus forthe surface settlement test is made of a polyvinyl chloride pipe withdiameter 200 mm and height 700 mm. A circular polypropylenecolophony plate is placed on the top of the polyvinyl chloride pipeto monitor the height change of SCLC as shown in Fig. 7. Hwanget al. found that the volume stability of SCC decreases with the in-crease of the volume fraction of cement [13]. According to their sug-gestions, when the settlement rate at 30 min is smaller than 0.16%per hour and the maximum settlement is smaller than 0.5%, SCC hasgood volume stability. The measured settlement rate at 30 min andmaximum settlement after 5.5 h were 0.086% per hour and 0.22%for SCLC1 and 0.080% per hour and 0.16% for SCLC2, respectively.

3.2.3. Uniformity test of coarse aggregate distributionCompared with normal aggregate concrete, LWAs in SCLC are

easier to float up, resulting in segregation. A preferable SCLC shouldnot only have good fluidity, deformability, and filling ability, butalso have uniform aggregate distribution and minimum resistanceto segregation. In this study, the column segregation test was con-ducted to examine the uniformity of distribution of LWA. As shownin Fig. 8, the circular steel column consists of four short columnswith diameter 200 mm and height 165 mm. The fresh SCLC wasfilled in the circular steel column. After 30 min, the four short col-umns were removed one by one from the top. The SCLC in each

Fig. 7. Surface settlement test.

short column was poured onto a sieve with aperture 5 mm andthen washed by water. The mass of coarse aggregate in each shortcolumn was finally weighed. The ratio of the mass of coarse aggre-gate in each short column to the total mass of coarse aggregate inthe four short columns are used to evaluate the uniformity of dis-tribution of coarse aggregate. With the four ratios, the coefficient ofvariation can be calculated as the aggregate segregation index Iseg.Obviously, the smaller the value of Iseg is, the more uniform the dis-tribution of coarse aggregate is. The measured values of Iseg areshown in Table 5.

4. Analysis of experimental results

4.1. Dynamic stability test

In this study, the compressive strength and density of SCLCwere also measured. The measured 28-day compressive strengthand density were 42.6 MPa and 1879 kg/m3 for SCLC1 and50.1 MPa and 1920 kg/m3 for SCLC2, respectively. Therefore, theyare of high-strength lightweight concrete.

The variations of T500, D1, and D2 with time are shown in Table4. As can be seen from Table 4, SCLC1 and SCLC2 have very high flu-idity. It is also noted that, although T500 increases and the slumpflow diameter decreases with the increase of time, they still satisfythe requirements for class 2 SCC. Therefore, SCLC1 and SCLC2 are ofhigh self-compacting ability.

The results from the L-box, V-funnel, and U-box tests are shownin Figs. 9 and 10. In Fig. 9, the dashed line denotes the critical valueof h2/h1 suggested by EFNARC and the domain of h2/h1 > 0.8 iscalled the self-flow zone. It can be seen from Fig. 9 that SCLC1

SFZ

0

2

4

6

8

10

0 0. 2 0. 4 0. 6 0. 8 1 h 2/h 1

T40

0 [s

]

SCLC1SCLC2

Fig. 9. Relationship between T400 and h2/h1.

SFZ

0

5

10

15

20

25

30

0 8 16 24 32 40Δ h [mm]

T V [s

]

SCLC1SCLC2

Fig. 10. Relationship between TV and Dh.

0

0.4

0.8

1.2

1.6

2

0 1 2 3 4 5 6Time [h]

Surf

ace

sett

lem

ent [

mm

]

SCLC1SCLC2

Fig. 13. Variation of surface settlement of SCLC with time.

Z. Wu et al. / Construction and Building Materials 23 (2009) 2087–2092 2091

and SCLC2 satisfy the workability requirement for SCC based on theL-box test. In Fig. 10, the domain surrounded by 0 6 Tv 6 2 s and0 6Dh 6 30 mm is called the self-flow zone. It can be seen fromFig. 10 that SCLC1 and SCLC2 also satisfy the workability require-ment for SCC based on the V-funnel and U-box tests. Therefore,SCLC1 and SCLC2 are of good fluidity, deformability, passing ability,and filling ability.

4.2. Static stability test

As can be seen from the results on the column segregation testshown in Fig. 11, the minimum and maximum aggregate contentsare 23.9% and 25.4% for SCLC1 and 24.1% and 26.5% for SCLC2,respectively. This shows that the distribution of coarse aggregateparticles along specimens have good uniformity, which is also con-firmed by the cross-section images shown in Fig. 12.

The variation of the surface settlement of SCLC with time isshown in Fig. 13. From Fig. 13, it can be seen that the surface set-tlement basically tends to be stable after 3.5 h, which is consistent

22

23

24

25

26

27

1st 2nd 3rd 4thShort columns' No.

Aag

greg

ate

cont

ent [

%]

SCLC1SCLC2

Fig. 11. Variation of aggregate content along circular steel column.

Fig. 12. Distribution of coarse aggregates on three cross-sections.

with the finding by Assaad et al. [2]. The measured maximum sur-face settlement were respectively 0.22% and 0.16% for SCLC1 andSCLC2, both of which are smaller than 0.5%, a critical value sug-gested by Assaad et al. [2]. Therefore, SCLC1 and SCLC2 have goodvolume stability.

Among these physical quantities shown in Table 5, Iseg and SRare used to evaluate the resistance of SCLC to segregation, andTV, T500, and T400 measure the shear flow velocity of SCLC. It canbe seen from Table 5 that, compared with SCLC1, the value of TV,T500, or T400 is smaller for SCLC2. This shows that SCLC2 has smallershear yield stress and therefore larger shear flow velocity thanSCLC1. On the other hand, since the value of Iseg or SR for SCLC2is larger than that for SCLC1, SCLC1 has larger resistance to segre-gation. Since the binder content in SCLC2 is larger than that inSCLC1, the shear flow velocity increases but the resistance to seg-regation decreases with the increase of the binder content.

5. Conclusions

In this paper, two mix proportions for SCLC have been pre-sented. Based on various tests, the workability of SCLC and the uni-formity of distribution of LWAs along the specimen have beenevaluated in a quantitative manner. The conclusions of this studyare summarized in the following points:

1. Considering the water absorption of LWA, two mix proportionsfor SCLC have been designed by the overall calculation methodwith fixed fine and coarse aggregate contents.

2. The good workability of the two types of fresh SCLCs has beendemonstrated by the slump flow, V-funnel, L-box, U-box, wetsieve segregation, and surface settlement tests.

3. The good uniformity of distribution of LWAs along the speci-men has been verified by the column segregation test and thecross-section images.

4. The shear flow velocity increases but the resistance to segrega-tion decreases with the increase of the binder content.

References

[1] Khayat KH, Assaad J, Daczko J. Comparison of field-oriented test methods toassess dynamic stability of self-consolidating concrete. ACI Mater J2004;101(2):168–76.

[2] Assaad J, Khayat KH, Daczko J. Evaluation of static stability of self-consolidating concrete. ACI Mater J 2004;101(3):207–15.

[3] Ding YN, Liu SG, Zhang Y, Thomas A. The investigation on the workability offibre cocktail reinforced self-compacting high performance concrete. ConstrBuild Mater 2008;22(7):1462–70.

[4] Bartos P. Testing-SCC toward new European for fresh SCC. In: 1st InternationalSymposium on Design, Performance and Use of Self-Consolidating Concrete.Changsha, China: 2005. p. 25–44.

[5] Choi YW, Kim YJ, Shin HC, Moon HY. An experimental research on the fluidityand mechanical proprieties of high-strength lightweight self-compactingconcrete. Cem Concr Res 2006;36(9):1595–602.

2092 Z. Wu et al. / Construction and Building Materials 23 (2009) 2087–2092

[6] Su N, Miao B. A new method for the mix design of medium strengthflowing concrete with low cement content. Cem Concr Compos2003;25(2):215–22.

[7] Shi CJ, Wu YZ. Mixture proportioning and properties of self-consolidatinglightweight concrete containing glass powder. ACI Mater J 2005;102(5):355–363.

[8] Müller HS, Haist M. Self-compacting lightweight concrete – technology anduse. Concr Plant Precast Technol 2002;71(2):29–37.

[9] European Project Group. Specification and guidelines for self-compactingconcrete. UK: EFNARC; 2002.

[10] Chen JK, Wang DM. New mix design method for HPC-overall calculationmethod. J Chin Ceram Soc 2000;28(2):194–8 [in Chinese].

[11] Japanese Ready-Mixed Concrete Association. Manual of producing highfluidity (self-compacting) concrete. Japan: Japanese Ready-Mixed ConcreteAssociation; 1998 [in Japanese].

[12] JGJ55-2000. Specification for the mix proportion design of ordinaryconcrete. China: Ministry of Construction; 2000 [in Chinese].

[13] Hwang SD, Khayat KH, Bonneau O. Performance-based specifications of self-consolidating concrete used in structural applications. ACI Mater J2006;103(2):121–9.