Construction and Building Materials 40 (2013) 659–671

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Construction and Building Materials

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The type of air-entraining and viscosity modifying admixtures and porosity andfrost durability of high performance self-compacting concrete

Beata Łazniewska-Piekarczyk ⇑Silesian Technical University, Faculty of Civil Engineering, Department of Building Processes, Akademicka 5 Str., 44 100 Gliwice, Poland

h i g h l i g h t s

" AEA and VMA type affect the properties of fresh HPSCC." AEA and VMA type affect the properties of hardened HPSCC." AEA and VMA type significantly influence the porosity of HPSCC." AEA and VMA type influence the frost-resistance of HPSCC." AEA and VMA from different sources cannot be used interchangeably.

a r t i c l e i n f o

Article history:Received 18 April 2012Received in revised form 20 November 2012Accepted 22 November 2012Available online 25 December 2012

Keywords:Air-entraining admixture (AEA)Viscosity modifying admixture (VMA)Air-voids parameterFrost-resistanceHigh performance self-compacting concrete(HPSCC)

0950-0618/$ - see front matter � 2012 Elsevier Ltd. Ahttp://dx.doi.org/10.1016/j.conbuildmat.2012.11.032

⇑ Tel.: +48 032 2372294; fax: +48 032 2372737.E-mail address: beata.lazniewska@polsl.pl

a b s t r a c t

The influence of a type of viscosity modifying admixture (VMA) on the air-content, workability of air-entrained high performance self-compacting concrete (HPSCC) is analyzed in the paper. The purpose ofthis study was to examine the influence of type of the admixtures on porosity and pore size distributionof HPSCC at constant water on cement ratio, type and volume of aggregate and volume of cement paste.The parameters of the air-voids and frost-resistance of hardened HPSCC are also investigated. The resultspresented the article demonstrated that admixtures from different sources cannot be used interchange-ably, even if they appear to have a similar chemical composition.

� 2012 Elsevier Ltd. All rights reserved.

1. Introduction

In order to ensure proper resistance to freezing and thawing anartificial air-void system with defined geometric structure is neededin the cement paste to enable it to take up volume extension of thefreezing water without suffering any damage. The stabilization ofmicro air voids is ensured by the use of effective air-entrainingadmixture (AEA) in the mixture [1]. The air-entraining agents aretypically either surfactant that aid in bubble stabilization by reduc-ing the surface tension of water, or substances that produce awater-repellant precipitate when mixed with concrete. Properair-entrainment, with appropriate volume and spacing factor, willdramatically improve the durability of concrete exposed to mois-ture during cycles of freezing and thawing. According to publication[2] air voids should not have a spacing factor larger than 0.2 mm(0.008 in.) for adequate protection of water-saturated concrete in

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a freezing and thawing environment. Research result [1] indicatedthat SCC is frost resistant with spacing factor larger than 0.2 mm.Another factor that must be considered is the size of the air voids.For a given air content, the size of the air voids cannot be too largeif the proper spacing factor is to be achieved without using an unac-ceptable amount of air. The term ‘‘specific surface’’ is used to indi-cate the average size of the air voids. It represents the surface areaof the air voids in concrete per unit volume of air. For adequate resis-tance to repeated freezing and thawing in a water-saturated envi-ronment, the specific surface should be greater than 24 mm2/mm3

[2].Self-compacting concrete is a concrete that is able to flow and

consolidate under its own weight, completely fill the formworkeven in the presence of dense reinforcement, whilst maintaininghomogeneity and without the need for any additional compaction.In case of air-entraining SCC achieving the suitable air void charac-teristics is a difficult task [3–5]. The air-entraining admixtures(AEAs) are required in order to produce the air bubbles dispersedthroughout the concrete, which ultimately provides durability for

660 B. Łazniewska-Piekarczyk / Construction and Building Materials 40 (2013) 659–671

the hardened concrete in freezing and thawing situations. The air-entraining agent is typically either surfactant that aid in bubblestabilization by reducing the surface tension of water, or sub-stances that produce a water-repellant precipitate when mixedwith concrete. Chatterji [6] pointed out that the some type of AEAs,including vinsol resin, sodium adipate, sodium oleate, etc., do notreduce the surface tension of water.

Air bubbles in fresh self-compacting concrete are inherentlyunstable [7,8]. The interfaces between the dispersed air and thesurrounding matrix contain free surface energy, and the thermody-namic tendency is to reduce the interfacial surface areas. Thus, allair bubbles have a lifetime (persistence). If concrete setting is se-verely retarded, lack of small air bubbles in hardened concretemay be expected, which is detrimental to the freeze–thaw resis-tance of concrete. From the point of foam instability, three funda-mental physical mechanisms may lead to the collapse of airbubbles [8,9]:

(1) Diffusion of air from a bubble (small, higher internal pres-sure) to a larger one (lower internal pressure) or into thebulk gas (or solution) surrounding the foam;

(2) Bubble coalescence due to capillary flow leading to ruptureof the lamellar film between the adjacent bubbles (usuallyslower than mechanism 1 and occurs even in stabilizedsystem);

(3) Rapid hydrodynamic drainage of liquid between bubblesleading to rapid collapse.

The air bubbles can move more freely in concrete when it ishighly fluid; therefore, there is increased occurrence of bubble coa-lescence and rupturing. To a certain degree, a SCC mixture with ahigh viscosity (usually accompanying a lower slump flow) preventsbubbles from rupturing or coalescing by creating a ‘‘cushion’’ effectfor the air voids to remain unaffected by mixing and other distur-bances [8]. Increasing slump flow increases the demand for AEAto entrain a given volume of air [10,11]. Research results [12]proved that the following three factors primarily influenced theair content and air void characteristics of air-entrained SCC: slumpflow, competition with high range water reducer and viscositymodifying admixture, and type of air-entraining admixture (AEA).The fluidity of SCC affects the generation and stability of air voidsin a concrete matrix by increasing bubble coalescence, and byincreasing interaction between admixtures, which can inhibit theeffectiveness of a given amount of AEA. In terms of AEA type, surfac-tant-type AEAs (i.e. synthetic detergents) secured the best overallair void characteristics, followed by salt-type AEAs containing talloil, and finally salt type AEAs containing Vinsol resin and wood ro-sin. Research results [2] proved that there is a significant differencein behavior between the resulting shells with different AEA admix-tures when the fluid pressure surrounding voids is increased andthen decreased again to atmospheric pressure. Voids made withsynthetic AEA sustain no permanent damage, while voids madewith Vinsol resin and wood rosin crack on depressurization.

In general, greater air-void stability can be obtained when theSCC is proportioned with a higher content of cementitious materi-als and a lower water-cementitious materials ratio (w/c). For mix-tures with a relatively low content of cementitious materials and ahigh w/c, the air-void stability increases when a viscosity-modify-ing admixture is incorporated [7–13]. With such reduction in siteson cement grains it is possible that some of the bubbles becomeless stable and coalesce, thus necessitating greater additions ofAEA [14,15]. The research results in publication show that SCC withslump flow value >700 mm might segregate [16]. While the higherfluidity of SCC can have a destabilizing effect on air voids once theyare formed, the usage of viscosity modifying mixture (VMA) can re-duce the ability of the air-entraining admixture (AEA) to create a

proper air void system. Self-compacting concrete may be classifiedin three types: the powder type, viscosity agent type and the com-bination type [17]:

(1) The powder type SCC is characterized by the large amountsof powder (all material <0.15 mm) which is usually in therange of 550–650 kg/m3. This provides the plastic viscosityand hence the segregation resistance. The yield point isdetermined by the addition of superplasticizer.

(2) In the viscosity type SCC the powder content is lower(350–450 kg/m3). The segregation resistance is mainly con-trolled by a VMA and the yield point by the addition ofsuperplasticizer.

(3) In the combination type of SCC the powder content isbetween 450 and 550 kg/m3 but in addition the rheology isalso controlled by a VMA as well as an appropriate dosageof the superplasticizer.

The results presented in study [12] demonstrated that admix-tures from different sources cannot be used interchangeably, evenif they appear to have a similar chemical composition. The researchresults [18] proved that the admixtures significantly influence onair voids parameters of SCC and consequently affect its frost resis-tance. Thus, it should be examine the effects of the admixtures typein the case of HPSCC.

The main properties of VMA consist in increasing the mix vis-cosity, usually by increasing the viscosity of the water phase[19]. The common VMAs in concrete include microbial polysaccha-rides (such as Welan gum), cellulose derivatives (methyl cellulose),and acrylic polymers [20,21]. The mechanism of action in each caseis different. Some VMAs adsorb on cement particles and increaseviscosity by promoting inter-particle attraction [22–25]. Bury andChristensen [26] had also mentioned two types of VMA, the thick-ening type and the binding type. The first one consists in thicken-ing the concrete and making it very cohesive without affecting thefluidity of the mix, whereas the second type works by binding thewater within the concrete mixture, then increasing the viscosity ofthe mixture. Mailvaganam [27] categorized anti-washout admix-ture and pumping aids into five classes according to their physicalactions in concrete. Kawai [28] classified water-soluble polymersas natural, semi-synthetic, and synthetic polymers [15]. Naturalpolymers include starches and different type of gums, as well asplant protein. Semi-synthetic polymers include: decomposedstarch and its derivatives; cellulose–ether derivatives, such ashydroxypropyl methyl cellulose (HPMC), hydroxyethyl cellulose(HEC), and carboxy methyl cellulose (CMC); as well as electrolytes,such as sodium alginate and propyleneglycol alginate. Finally, syn-thetic polymers include polymers based on ethylene oxide, poly-acrylamide, polyacrylate, and those based on vinyl, such aspolyvinyl alcohol [15]. The thixotropic property increases the sta-bility of the concrete and reduces the risk of segregation after cast-ing. The common VMAs in concrete include microbialpolysaccharides (such as Welan gum), cellulose derivatives(methyl cellulose), and acrylic polymers [20,21]. The mechanismof action in each case is different. Some VMAs adsorb on cementparticles and increase viscosity by promoting inter-particle attrac-tion [22–25]. The mode of action of VMA depends on the type andconcentration of the polymer in use. In the case of welan gum andcellulose derivatives, the mode of action can be classified in threecategories, as follows [15,23]:

(1) Adsorption. The long-chain polymer molecules adhere to theperiphery of water molecules adhere to the periphery ofwater molecules, thus adsorbing and fixing part of the mixwater and thereby expanding. This increases the viscosityof the mix water and that of the cement-based product.

B. Łazniewska-Piekarczyk / Construction and Building Materials 40 (2013) 659–671 661

(2) Association. Molecules in adjacent polymer chains candevelop attractive forces, thus further blocking the motionof water, causing a gel formation and an increase inviscosity.

(3) Intertwining. At low rates of shear, and especially at highconcentrations, the polymer chains can intertwine andentangle, resulting in an increase in the apparent viscosity.Such entanglement can disaggregate, and the polymerchains can align in the direction of the flow at high shearrates, hence resulting in shear thinning.

The usage of admixtures such as VMA and SP can reduce theability of an air-entraining admixture (AEA) to create a proper airvoid system [7]. The increased VMA content increases the amountof water that can be associated with the polymer. As a result, lessfree water is available to the AEA, and greater additions of AEA arethen needed with increasing VMA contents even in the case ofthose containing no dear eating agents [15,29]. The increased de-mand for AEA in a concrete containing a VMA may also be due inpart to the SP that can reduce the sites on cement particles whereair bubbles can be attached together [15]. The air bubbles formedby hydrophilic surface active compounds should not adhere to ce-ment and grains of aggregate (Fig. 1) [30].

Hwang and Khayat [1] investigated the frost-resistance durabil-ity (ASTM C 666, A) of SCC mixtures proportionate with varioustypes of SP and VMAs, binder compositions, and w/c. Concretemade with 0.35 w/c without VMA necessitated lower AEA dosageto secure a given air volume compared to similar concrete pre-pared w/c of 0.42 and VMA. The research results [24] indicated thatthe air content seems to decrease with the increase of VMA contentin the SCC mixes. This suggests that the incorporation of VMA willprobably necessitate greater additions of air entraining agents tosecure a given air volume. This finding is consistent with that sug-gested by Khayat [3]. Research results [18] showed that VMA influ-ences on air-voids parameters of air-entrained SCC. Chemicaladmixtures generally affect the dosage rate of air-entrainingadmixtures [2]. Admixtures can interfere with the ability of AEAto stabilize air voids in concrete by the way in which they interacton a molecular level. The fluidity of SCC affects the generation and

(a)Fig. 1. (a) Adsorption of the flux molecules framework in the grains of cement and the neand aggregate–cement–water arrangement, with the use of air-entraining mean (surfac

Table 1The chemical and physical properties of CEM I 42.5 R.

Chemical analyses (%) Specific surfaBlaine (cm2/

SiO2 CaO Al2O3 Fe2O3 MgO Na2Oe SO3

21.61 64.41 4.46 2.24 1.25 0.4 3.1 3830

stability of the air voids in a concrete matrix by increasing bubblecoalescence, and by increasing interaction between admixtures,which can inhibit the effectiveness of a given amount of AEA[12]. Many inorganic electrolytes and polar organic materials influ-ence the foaming ability of surfactants [8]. Because of the complex-ity of modern AEAs and other chemical admixtures, it is impossibleto generalize the effects of their interactions with surfactants onthe air entrainment.

The article presents the development of HPSCC with differenttypes of AEA and VMA. The main objective of the research is todetermine the influence the admixtures on the rheological aspect,air-content in fresh concrete mixture, porosity characteristics andfrost resistance of HPSCC. A study was then carried out on the freshand hardened properties of different HPSCC at constant water oncement ratio, type and volume of aggregate, volume of cementpaste.

2. Materials and description of the tests

The experimental investigation was carried out in two phases.In Phase 1, tests were carried out on fresh high performance self-compacting concrete with different type of AEA. The Phase 2 inves-tigated the properties of the hardened HPSCC.

2.1. Examined material

2.1.1. Cement, mineral additives and aggregatesA type CEM I 42.5 R cement was used. Chemical and physical

properties of cement are shown in Table 1. The chemical and phys-ical properties of a silica fume (SF) are shown in Table 2. Local nat-ural sand, fine and 8 mm maximum size gravel aggregates, wereused in concrete mix, respectively. The properties of sand and grav-el aggregate are presented in Tables 3 and 4. Fig. 2 presents thegrading of fine and coarse aggregates. Water was used accordingto EN 1008.

2.1.2. Chemical admixturesThe properties of admixtures are presented in Tables 5–7. SP 1

and SP 2 composed of different type of polycarboxyl ether, having

(b)

AEA+SP

SP

SP

gative effect of the anion final group; (b) diagram of arrangement of cement–watere active anion substance) [31].

ceg)

SpecificGravity (g/cm3)

Compressivestrength (MPa)

Setting time, Vicat test (min)

Initial setting Final setting

3.1 69.3 175 –

Table 2The chemical and physical properties of silica fume.

Chemical analyses (%) Specific surface (m2/kg)

SiO2 CaO Al2O3 Fe2O3 MgO Na2O SO3 K2O

92.8 0.7 0.6 0.3 1.32 0.3 0.8 0.5 18,000

Table 3The chemical and physical analysis of sand 0/2 mm.

Parameters Result

SiO2 >99.3%Fe2O3 300 ppm MaxAl2O3 2500 MaxCaO 250 ppm MaxMgO 50 ppm MaxClay 0.3% MaxCaCo3 0.5% MaxMoisture <0.1% MaxLoss on ignition <0.3% MaxpH NeutralDensity 2.65 gm/cc

Table 4The properties of sand and gravel.

Property Sand 0/2 mm Gravel 2/8 mm

The content of mineral dust 0.67%, category f3 0.48%, category f3

The content of organic substances Absence AbsenceBulk density qnz 1.74 kg/dm3 1.69 kg/dm3

Flatness index – 6.2%, category FI10

Absorptivity – 0.62%

Table 5The properties of superplasticizer.

Property SP

Main base Polycarboxyl etherSpecific gravity at 20 �C, g/cm3 1.05 ± 0.02pH-value at 20 �C 6.5 ± 1.5Chloride ion content, % mass 1.3Alkali content (Na2O eqiv.), % mass 1.3

662 B. Łazniewska-Piekarczyk / Construction and Building Materials 40 (2013) 659–671

total solid content of 30.0% were used. The chemical compositionof SP, VMA and AEA is a proprietary commercial patent.

2.2. Mix proportion and its preparation

Twenty-six high performance self-compacting concrete mix-tures (Tables 8–10) were made to study the effect of type of SP,VMA and AEA on the properties of HPSCC. The proportion of ce-ment, silica fume, water, coarse aggregate and sand was kept con-stant (Table 8).

The following admixtures were used (Tables 9 and 10): SP2(without air-entraining side effect), AEA1, AEA2, VMA1, VMA2and VMA3.

The concrete was produced in a horizontal pan mixer withcapacity of 0.070 m3. The sand and coarse aggregate were firstmixed for 1 min. Then, cement and fly ash were added with thewater. After mixing for 10 min, the SP was introduced and allowedto mix for an additional 5 min. Finally, remaining admixtures(according to Tables 8–10) were added and mixed for the addi-tional 3 min.

0.0 0.46.9

26.1

0

20

40

60

80

100

0 0.125 0.25 0.5

%

m

Fig. 2. The grain size distribution of aggregate. The boundary curv

2.3. Methodology of test of properties of HPSCC

2.3.1. Tests on fresh HPSCC propertiesThe main aim of this step of the research is to compress the

influence of type of admixtures on workability and air volume offresh HPSCC. The slump flow test [33] was used to evaluate the freedeformability and flowability of SCC. Slump flow value representedthe mean diameter (measured in two perpendicular directions) ofconcrete after lifting the standard slump cone. The upper and low-er limits of slump-flow classes (SF) are the following [33]:SF1-slump flow from 500 to 650 mm, SF2-slump flow from 660to 750 mm, SF3-slump flow from 760 to 850 mm. While the upperand lower limits of viscosity classes (VS) are the following [33]:VS1–T500 less than or equal to 2 s, VS2–T500 greater than 2 s. Theair content in fresh HPSCC was measured by the pressure methodaccording to EN 12350-7 [34].

2.3.2. Tests on hardened HPSCC propertiesThe temperature and relative humidity were respectively 20 �C

and 100% (in water). After 28 days, the tests were conducted todetermine the freeze–thaw resistance, durability coefficient DFand air-voids parameters of HPSCC.

The entrained air void distribution in hardened concrete wasdetermined using a computer-driven system of automatic imageanalysis. Tests were performed using polished concrete specimens100 � 100 � 20 mm cut from cube specimens. The automatic mea-surement procedure was designed to comply with the require-ments imposed by EN 480-11 [35]. Results of measurementswere available as a set of standard parameters for air void micro-structure characterization: spacing factor (mm), specific surface a(1/mm), air content A (%), content of air voids with diameter lessthan 0.3 mm A300 (%), air void diameters distribution.

The freeze-proof resistance was investigated according to PN-88/B-06250. After 28 days, concrete samples (150 � 150 � 150 mm)were freezing for three hours in temp.�20 �C and thawing in water

41.253.8

76.5

98.2 100.0

1 2 4 8 16m

es according to [32]. Sand content in the aggregate is 44.4%.

Table 6The properties of air-entraining admixtures.

Property AEA1 AEA2

Main base Syntheticsurfactants

Saponified acidresin

Specific gravity at 20 �C, g/cm3 1.01 ± 0.02 1.00pH-value at 20 �C 8.8 10–12Chloride ion content, % mass 60.1 Not availableAlkali content (Na2O eqiv.), % mass 61.0 Not available

Table 8The components of HPSCC.

CEM I 42.5R(kg/m3)

Silicafume (%)

Sand 0/2 mm

Gravel 0/8 mm

Volume ofpaste

w/c w/b

581.0 65.0 710.1 887.6 40.0 0.31 0.28

Table 9The dosage of SP and AEA by weight of total binder,%.

Symbol SP AEA1 AEA2

HA1 4.49 0.27 –HA2 3.16 – 1.58

HA1-SP + AEA1, HA2-SP + AEA2.

Table 10The dosage of SP, AEA and VMA by weight of total binder,%.

Symbol SP AEA1 AEA2 VMA1 VMA2 VMA3

HA1V1 4.66 0.27 – 0.27 – –HA1V2 4.58 0.26 – – 0.71 –HA1V3 5.96 0.26 – – – 0.07HA2V1 5.33 – 0.91 0.26 – –HA2V2 3.25 – 1.32 – 0.71 –

HA1V1-SP + AEA1 + VMA1, HA1V2-SP + AEA1 + VMA2, HA1V2-SP + AEA1 + VMA3,HA2V1-SP + AEA2 + VMA1, HA2V2-SP + AEA2 + VMA2.

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for three hours in temp. +20 �C. Four cycles per day were performed.After 300 freeze–thaw cycles the compressive strength and mass de-crease of the concrete specimens were tested. According to thisnorm, concrete is frost-resistant when its decrease of compressivestrength is lower than 20% after n cycles and weight loss is lowerthan 5%.

The results of the dynamic elastic modulus test are presented interms of the durability factor DF [36] (ASTM C666), which is de-fined by [37]:

DF ¼ RDMUPTT;n � N=M

where RDMUPTT,n is the relative dynamic modulus (the measuredvalue divided by the value determined before any freeze–thaw cy-cling); N is the number n of freeze–thaw cycles for RDMUPTT,n; M isthe total number of freeze–thaw cycles.

If RDMUPTT,n (measured according to (CEN/TR 15177, 2006) on100 � 400 � 400 mm concrete specimens) falls to a value lowerthan 60% of its pre-freeze–thaw value, then the test is terminatedand DF is calculated. If the number of the freeze–thaw cyclesreaches 300 before RDMUPTT,n falls to less than 60% of itspre-freeze–thaw value, then the test is stopped and DF is calcu-lated. If there is no change in the dynamic elastic modulus, thenDF = 100%. If P falls to less than 60% of its pre-freeze–thaw value,then DF = 60%. Any concrete test specimen with a DF = 60% is oftenconsidered nondurable or frost-damage susceptible. However,other higher levels of DF may be more desirable as critical values.The concrete test specimen with a DF P 80% is often considereddurable [36].

3. Test results and its discussion

3.1. The research results of fresh HPSCC

In general, salt-type AEAs react immediately with the ions in ce-ment pastes, creating insoluble water-repellant precipitates that,when caught in the water–air interfaces, tend to remain partiallydry [38]. The salt-type AEAs are not considered surfactants, andtherefore are not generally adsorbed by the cement or other parti-cles within the concrete, but rather the surface tension of waterholds the AEA precipitate in the air–water interface. In contrast,synthetic detergent AEAs are pure surfactants that are typicallyform a film at the air–water and air–water–cement interfacesand reduce the surface tension of water [12,38]. The reduction ofsurface tension of water prevents the air voids from coalescing intolarger air voids through the combined Gibbs–Marangoni effect,

Table 7The properties of viscosity modifying admixtures.

Property VMA1

Main base Synthetic copolymerSpecific gravity at 20 �C, g/cm3 1.0–1.02pH-value at 20 �C 6–9Chloride ion content, % mass <0.1Alkali content (Na2O eqiv.), % mass Not available

thus stabilizing them throughout the fresh concrete. The bubble-stabilizing capability of a synthetic detergent AEA is highly depen-dent on the amount of admixture in the bulk liquid phase [8,12].The research results in Table 10 show that VMA1 is about 2.5 moreefficient in action than VMA2. Due to the fact that mixtures con-tained more VMA than AEA by volume, the additional VMA re-duced the free water content, thus necessitating increasedamounts of the synthetic detergent AEA to entrain the sameamount of air.

The test results of the properties of the air-entrained HPSCC aresummarized in Table 11. The analysis of the results suggests thatthe type of AEA is very important, because both of the consistency,and the effect of the air entrainment of HPSCC.

AEA2 is less effective in action than AEA1 (about six times lesseffective than AEA1, see Table 9). The source AEA1 is a syntheticdetergent AEA, whereas sources AEA2 is wood-derived acid salts,which utilize different mechanisms to entrain air, and thus reactdifferently with the other mixture constituents (i.e. cement, flyash and admixtures) [12].

In general the incorporation of a VMA can increase sharply theAEA demand for achieving a given air content. However, a properair-void system can still be produced provided that a proper dos-age of AEA is used [15]. According to publication [39] the newVMA have no adverse interaction with air entraining admixtures.The test results of the properties of the air-entrained HPSCC withdifferent type of VMA are summarized in Table 12. The results ofthe research carried out by Khayat [3] suggest an adverse effectof VMA on the air entrainment of concrete. The research results

VMA2 VMA3

Silica Methylcellulose1.30 Not available9.5 Not availableNot available Not availableNot available Not available

Table 11Properties of fresh air-entrained HPSCC.

Symbol SF (mm) T500 (s) Slump-flowclasses

Viscosityclasses

Ac (%)

HA1 580 3 SF1 VS2 6.4HA2 500 4 SF1 VS2 10.5

HA1-SP + AEA1, HA2-SP + AEA2.

Table 12Properties of fresh air-entrained HPSCC with different type of VMA.

Symbol SF (mm) T500 (s) Slump-flowclasses

Viscosityclasses

Ac (%)

HA1V1 570 4 SF1 VS2 5.2HA2V1 630 5 SF1 VS2 3.5HA2V2 570 4 SF1 VS2 9.0HA1V2 530 5 SF1 VS2 9.5HA1V3 500 10 SF1 VS2 7.0

HA1V1-SP + AEA1 + VMA1, HA1V2-SP + AEA1 + VMA2, HA1V2-SP + AEA1 + VMA3,HA2V1-SP + AEA2 + VMA1, HA2V2-SP + AEA2 + VMA2.

Table 13The air-voids characteristics of air-entrained HPSCC.

Symbol A (%) a (mm�1) L (mm) A300 (%)

HA1 6.37 31.02 0.16 4.54HA2 8.18 28.63 0.16 3.85

HA1-SP + AEA1, HA2-SP + AEA2.

Table 14The air-voids characteristics of air-entrained HPSCC with different type of VMA.

Symbol A (%) a (mm�1) L (mm) A300 (%)

HA1V1 5.97 24.67 0.210 2.83HA2V1 2.57 8.52 0.798 0.33HA2V2 6.36 22.26 0.203 2.26HA1V2 6.10 32.01 0.170 4.26HA1V3 7.17 26.11 0.164 4.26

HA1V1-SP + AEA1 + VMA1, HA1V2-SP + AEA1 + VMA2, HA1V2-SP + AEA1 + VMA3,HA2V1-SP + AEA2 + VMA1, HA2V2-SP + AEA2 + VMA2.

664 B. Łazniewska-Piekarczyk / Construction and Building Materials 40 (2013) 659–671

(Table 12) indicate that VMA1 decreases intentionally the air-entrainment (as a result of AEA1 and AEA2 acting) of the high per-formance self-compacting concrete mixture (compare Tables 11and 12). The same amount of AEA1 in case of H2A and HA1V1was used (Tables 9 and 10). VMA2 and VMA3 do not reduce theair entrainment of HPSCC. On the contrary, VMA3 and VMA2 causean increase in entrainment of HPSCC with AEA1. VMA2 does notcause significant change in the air content of HPSCC with AEA2.In conclusion, the analysis of the results in Table 12 shows that

Fig. 3. The air voids diamet

the type of AEA and VMA influences the air entrainment and con-sistency of HPSCC.

In the research [12] following types of VMAs were tested: aque-ous solution of polysaccharides, naphthalene sulfonate and welangum, dispersed carbohydrate and methyl isothiocyanate and sulfo-nated naphthalene and melamine polymer. With an increased dos-age of VMA, more water was absorbed, providing less free waterfor the AEA to bond with water, resulting in a greater demand ofAEA to secure 6% air [29]. Moreover, several cellulose derivativesand synthetic polymers, such as polyethylene oxide, can entraplarge volumes of air and are used in conjunction with deareatingagents [15].

A general factor that could cause greater demand of the AEA inVMA concrete is the increased viscosity of the cement paste thatincreases internal pressure in air bubbles and reduce their stability[7]. This can led to a collapse of some of the air bubbles and reduc-tion of air content [40]. The performance of SCC made with fourair-entraining admixtures and four liquid-based VMAs (incorpo-rated to secure stable air-void system and adequate segregationresistance) were investigated in study. The research [40] resultsproved that the low air content of SCC can be due to the low viscos-ity and possible use of defoaming admixtures in some VMA prod-ucts. The moment of introduction of AEA in relations to the VMAcan have an effect on the AEA demand. Incorporation of AEA inconcrete after the introduction welan gum and a naphthalene-based SP was shown to result in a more effective air-void systemthan when the AEA is introduced prior to the VMA-SP dispersion[14,15]. However, unlike the former SCC, the introduction theAEA was more efficient when carried out prior to the addition ofthe SP and welan gum [15].

3.2. The research results of hardened HPSCC

In Tables 13 and 14 and in Figs. 3–13, the air voids parametersresearch results are presented. The research results proved thatadmixtures type is very important to the values of the HPSCCair-voids parameters.

The results of the determination of the air voids parameters ofthe air-entrained HPSCC are summarized in Table 13. AEA2 has asmaller efficiency than AEA1 (Table 9). The analysis of the resultsin Table 13 shows that the type of AEA is very important becauseof the air content in HPSCC. Other parameters of porosity of HPSCCwith AEA1 and AEA2 are similar. However, the air voids have asmaller diameter in case of HPSCC with AEA1 (compare Figs. 3–6).

Owing to the lack of significant hydrophobic constituents, we-lan gum has little activity at the air–water interface, and thusnot generates foam or entraps large volume of air [29]. The effectof incorporating a VMA and SP on the air-void system (EN 480-11) is for concrete made with various welan gum content andtwo dosages of AEA was analyzed in publication [15]. The higherdosage of AEA was necessary to secure an adequate air-void spac-ing factor (L) in the VMA concrete.

ers distribution in HA1.

Fig. 4. The air voids diameters distribution in HA2.

Fig. 5. The view of the air voids in HA1. The scale indicates length of 0.5 mm.

Fig. 6. The view of the air voids in HA2. The scale indicates length of 0.5 mm.

Fig. 7. The air voids diameters distribution in HA1V1.

Fig. 8. The air voids diameters distribution in HA2V1.

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Fig. 9. The air voids diameters distribution in HA2V2.

Fig. 10. The air voids diameters distribution in HA1V2.

Fig. 11. The air voids diameters distribution in HA1V3.

Fig. 12. The view of the air voids in HA1V1. The scale indicates length of 0.5 mm.

Fig. 13. The view of the air voids in HA1V2. The scale indicates length of 0.5 mm.

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μ

Fig. 14. Relations between spacing factor and durability coefficient [14].

Fig. 15. Relationship between the volume of air voids and compressive strength decrease of HPSCC after 300 freeze–thawing cycles.

α

Fig. 16. Relationship between specific surface of the air voids and compressive strength decrease of HPSCC after 300 freeze–thawing cycles.

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In the research [12] indicated that synthetic detergent AEA pro-duced the smallest and most closely spaced air voids, followed bywood-derived acid salts. Both the AEA1 and SP are surfactants,relying on adsorption to the cement particles to both stabilize airbubbles and to fluidize the cement paste. Therefore, the increaseddosage of SP at the higher slump flows competed with the AEA foradsorption to the cement surface area, resulting in a poorer air voidsystem [7]. Additionally, synthetic detergent AEAs are influencedby increased fluidity due to their primary location at the air–waterinterface [8]. While these air voids have been known to adsorb tocement particles, the use of a SP in all probability decreases thelikelihood, allowing the bubbles to move about freely in the matrix.Therefore, the bubbles created by synthetic detergent AEA weremore likely to coalesce than the bubbles produced by salt-type

AEAs. The salt-type AEAs produced relatively similar trends in airvoid characteristics when compared to those generated by syn-thetic detergent AEA. The air voids generated by salt-type AEAsare adhered to water-repellant precipitates (which are productsof an immediate reaction between the AEA and calcium ions inconcrete), resulting in similar air void characteristics regardlessof slump flow [41]. The mass of the precipitate acts like an anchorto disperse the air bubbles throughout the matrix and reduce thetendency of large air bubbles to float to the surface, regardless ofthe paste viscosity and fluidity [8].

The research results of publication [24] indicated that VMA de-creases the air-entrainment (as a result of AEA action). The re-search results of the porosity characteristics of the air-entrainedHPSCC with VMA1, VMA2 and VMA3 are summarized in Table

Fig. 17. Relationship between the air voids spacing factor and compressive strength decrease of HPSCC after 300 freeze–thawing cycles.

Fig. 18. Relationship between A300 and decrease of compressive strength of HPSCC after 300 freeze–thawing cycles.

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14. The analysis of the results shows that the VMA, depending onits type, is reducing or increasing the air content in HPSCC.VMA1 adversely affects the HPSCC air entrainment (Fig. 8). VMA2causes the smallest change in the values of the air voids parame-ters of HPSCC with AEA1. Also in the case of the HPSCC withVMA2 and AEA2 the porosity parameters are similar to the airvoids parameters of HPSCC without VMA2. VMA3 causes an in-crease in the content of the air pores in HPSCC, while the remainingporosity parameters are not significantly changed (Fig. 11). There-fore, from the viewpoint of the frost resistance of HPSCC use ofVMA3 seems to be most beneficial (compare Tables 13 and 14).

The relationships between the measurements of the total vol-ume of fresh and hardened air content as reported by severalresearchers [34]. The comparison of data in Tables 12–14 suggeststhat it is possible to predict the air-content in air-entrained HPSCCon the basis of the air-content in high performance self-compact-ing concrete mixture.

The research results of the frost-resistance of HPSCC with AEA1and AEA2 are presented in Figs. 15–22. The research result indi-cates that the type of AEA is important for frost-resistance ofSCC. The air-entrained HPSCC with both type of AEA is frost-resistant (decrease of compressive strength of freeze–thawedHPSCC is lower than 20% and decrease of mass is lower than 5%).The analysis of results suggests that the type of AEA is very impor-tant due to the reduction of strength HPSCC subjected to freeze–thaw cycles.

Khayat [15] reported Yamato et al. [42] research results thatproved that concrete made with 0.45 w/c and either cellulose-

based agents or a polyacrylamide VMA can exhibit poor frost dura-bility (ASTM C 666, Procedure A) compared with concrete madewithout any VMA. The durability factor of such VMA concretewas found to vary between 10% and 50% compared with 90% forthe non-VMA concrete. Mixtures containing the polyacrylamide-type VMA had better frost resistance than those made with thecellulose-based VMA. The lack of frost durability was partiallyattributed to the higher L values of the VMA concrete that variedbetween 120 lm and 420 lm compared with 250 lm for thenon-VMA concrete. The VMA mixtures were reported to havegreater capillary porosity that the non-VMA concrete, particularlyfor pores with apparent diameters larger than 10 nm [42]. Khayat[43] investigated the effect of the sequence of adding an air-entraining admixture, two commonly used VMAs, namely, welangum and hydroxypropyl methylcellulose, and a superplasticizeron the frost durability and scaling resistance of fluid concrete mix-tures. He concluded that regardless of the air-spacing factor andpresence of the VMA, such fluid concrete mixtures can have poorsurface scaling resistance, which was attributed to the relativelyhigh porosity of the skin of concrete.

The research results in Figs. 15–22 proved that VMA type signif-icantly affects the strength reduction of freeze–thawed HPSCC. Theanalysis of the influence of synthetic copolymer based agents(VMA1) on frost-resistance of HPSCC demonstrates that both, incase of AEA1 and AEA2, VMA1 increases strength reduction ofHPSCC after 300 cycles of freezing–thawing. While the impact ofVMA2 (silica based agents) in this regard significantly dependson the type of AEA. The combination of AEA2 and VMA2 is the most

Fig. 19. Relationship between the volume of air voids and mass decrease of HPSCC after 300 freeze–thawing cycles.

α

Fig. 20. Relationship between specific surface of the air voids and mass decrease of HPSCC after 300 freeze–thawing cycles.

Fig. 21. Relationship between the air voids spacing factor and mass decrease of HPSCC after 300 freeze–thawing cycles.

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disadvantageous due to the frost resistance of HPSCC. The impactof VMA3 (cellulose-based VMA) on the frost resistance of the air-entrained HPSCC is the most beneficial. Also the DF research results(Table 15) proved that air-entrained HPSCC with cellulose-basedagents (VMA3) and also with a synthetic copolymer based agents(VMA1) or a silica based agents (VMA2) can exhibit good frostdurability. Khayat [14] investigated the impact of incorporatinghydroxypropyl methyl cellulose (HPMC) and welan gum on frostdurability of concrete with various w/c (0.32–0.50). An effectivesynthetic detergent was used for the AEA. The result clearly

showed that, providing an adequate air-void system is secured,concrete made with welan gum or HPMC can exhibit adequatefrost durability similar to that of conventional concrete. As showedin Fig. 14, regardless of the presence of a VMA, concrete with0.45 w/c and L less than 400 lm exhibited a frost durabilitycoefficient greater that 75%. Such coefficients were in excess of100% in the case of similar concrete made with w/c ratio 0.32and 0.40. Such mixtures had L and specific surface of air-voids val-ues ranging between 150 and 380 lm and 31 and 15 mm�1,respectively [14].

Fig. 22. Relationship between A300 and decrease of mass of HPSCC after 300 freeze–thawing cycles.

Table 15The research results of DF coefficient measurements after freezing–thawing ncycles,%.

Symbol 0 25 75 100 150 250 300

HA1 100 101 101 105 105 109 110HA2 100 101 103 103 106 108 109HA1V1 100 100 100 99 97 97 96HA2V1 100 100 102 102 103 105 105HA2V2 100 100 100 99 97 95 95HA1V2 100 100 100 101 101 102 102HA1V3 100 100 101 101 103 103 106

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The research results [44] proved that the use of a VMA inhigh-volume replacement SCC seemed to enhance its resistanceto deicing salt surface scaling. Whether this result can be consis-tently obtained or whether it is a particular occurrence in thisstudy needs further investigation.

According to European standards (EN 206-1, Austrian StandardÖNORM B 4710-1, Danish Standard DS. 2426, German Federal Min-istry of Transport ZTV Beton-StB 01) recommended values of air-voids parameters are following: A = 3.5–5.5%, L ¼ 0:18—0:20mm,A300 = 1.05–1.8%. The research results in Tables 13 and 14 indicatethat the air-entrained HPSCC and VMA-modified air-entrainedHPSCC are frost-resistant and the values of the parameters of airvoids are consistent with the recommendations of these standards.On the other hand, no correlation was found between the values ofthe parameters of the air voids (with the exception of the specificsurface of air voids) and values of decrease of compressive strengthof the air-entrained HPSCC (Figs. 15–22, Tables 13–15).

The data in Table 14 indicate the negative influence of VMA2 onvalues of the air-voids parameters regardless of air-entrainedHPSCC frost-resistance (HA2V1, compare data in Tables 13 and14). Nevertheless, HA2V1 is frost-resistant, which is also indicatedby the DF research results (Table 15). Moreover, the decrease of thecompressive strength after 300 freeze–thawing cycles of HA2V1 isthe smallest .

4. Final remarks

The research proved that VMA and AEA type significantly affectsthe characteristic of porosity and frost-resistance HPSCC. There is alarge variability of the composition of the additives. Therefore, it isimpossible to generalize about their impact on the analyzed prop-erties HPSCC. It is recommended to determine the effects of mod-ification of air-entrained HPSCC by VMA. The effects of admixturesactions may influence the air-voids parameters and frost resistanceof concrete. The relationship between the parameters and frost

resistance may be different under the influence of the admixtures.The results presented the article demonstrated that admixturesfrom different sources cannot be used interchangeably. The influ-ence of VMA also depends on the type of SP used in case HPSCC.The parameters of HPSCC air voids are characterized by very differ-ent values, depending on what kind of SP and VMA was used. Dueto the complexity of modern AEAs and VMAs, it is impossible togeneralize the effects of their interactions with surfactants on theair entrainment. While the higher fluidity of SCC can have a desta-bilizing effect on air voids once they are formed, the usage of VMAhas a variable effect on air void system. One type of VMA reducesthe air content in HPSCC, while another type of VMA increases theair content in HPSCC. Thus the choice of VMA type for frost resis-tant HPSCC cannot be rushed.

5. Conclusions

In the range of investigation of the HPSCC, used admixtures andreceived research results it was indicated that:

(1) The type of SP is very important because of the size param-eters of HPSCC air pores. In case of HPSCC with ‘‘air-entrain-ing’’ SP, the content of the air pores is not much higher butthe specific surface of the air voids, air voids spacing factorand content of the air voids with a diameters less than300 lm are much higher.

(2) The type of AEA is very important because of the air contentin HPSCC. Synthetic surfactants AEA produce the smallestand most closely spaced air voids, followed by saponifiedacid resin AEA. Other parameters of porosity of HPSCC withboth AEA are similar. However, the air voids have a smallerdiameter in case of HPSCC with synthetic surfactants AEA.

(3) Type of VMA cause increase/decrease of air content. Syn-thetic copolymer VMA adversely affects the HPSCC airentrainment. Silica VMA causes the smallest change in thevalues of the air voids parameters of HPSCC with syntheticsurfactants AEA. Also in the case of the HPSCC with silicaVMA and saponified acid resin AEA the porosity parametersare similar to the air voids parameters of HPSCC without sil-ica VMA. Methylcellulose VMA causes an increase in thecontent of the air pores in HPSCC, while the remainingporosity parameters are not significantly changed.

(4) VMA and AEA type significantly affects the strength reduc-tion of freeze–thawed HPSCC. However, the frost-resistanceand the durability coefficient research results proved thatair-entrained HPSCC with VMA can exhibit good frostdurability.

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(5) The research results also indicate that HPSCC is frost-resis-tant even though the values of air-voids parameters are dif-ferent from recommendations of European standards.

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