Proceedings of INCOS 05 International Conference on Concrete for Structures

Coimbra, 7-8 July 2005

Department of Civil Engineering

FCTUC, University of Coimbra

PROCEEDINGS EDITORS:

Sérgio Lopes (FCTUC), Isabel Pinto (FCTUC), Luís Bernardo (UBI), Luíz Oliveira (UBI),

Ricardo Carmo (ISEC)

iii

ORGANIZING COMMITTEE Sérgio Lopes, FCTUC (Chairman) Luíz Oliveira, UBI (Vice-Chairman) Paulo Helene, IBRACON Cláudio Sbrighi, IBRACON J. Santos Pato, APEB J. C. Duarte, APEB José Calevera, INTEMAC Jaime Fernandez, INTEMAC

ADVISORY COMMITTEE J. Seabra Santos, Univ. of Coimbra (Rector) Armando Rito, Armando Rito Lda. E. Cansado Carvalho, Grapes, GPEE João Bento, Brisa José Catarino, IOT, ex- Chairman of IEP Júlio Appleton, IST J. Câncio Martins, FCTUC

STEERING COMMITTEE Sérgio Lopes, FCTUC (Chairman) Isabel Pinto, FCTUC José Coutinho, FCTUC Luís Bernardo, UBI Maria José Luís, ACIV Pinto Pereira, IEP Ricardo Carmo, ISEC

SCIENTIFIC COMMITTEE Luís Miguel da Cruz Simões, FCTUC (Chairman) Adelino V. Lopes, FCTUC Ana Maria Sarmento, FEUP António Adão da Fonseca, FEUP António Reis, GRID Arlindo Gonçalves, LNEC Carmen Andrade, Instituto Eduardo Torroja Celestino Quaresma, Ordem dos Engenheiros Cláudio Sbrighi, IBRACON Esteves Ferreira, ATIC J.C.Walraven, TUDelft Jaime Fernandez, INTEMAC João Almeida Fernandes, LNEC João Carlos Duarte, APEB João Henrique Negrão, FCTUC João Paulo Rodrigues, FCTUC Joaquim Figueiras, FEUP Jorge de Brito, IST Jorge Santos Pato, APEB José Calavera Ruiz, INTEMAC José Noronha da Câmara, IST Luís Filipe A. Bernardo, UBI Luíz Oliveira, UBI Manuel Pipa, LNEC Maria Helena Barros, FCTUC Paulo Barbosa Lourenço, U. Minho Paulo Helene, IBRACON Paulo Providência e Costa, FCTUC Paulo Monteiro, University of Berkeley R.N.Swamy, University of Sheffield Ricardo do Carmo, ISEC Rui Faria, FEUP Rui Furtado, FCTUC Said Jalali, U. Minho Sérgio Lopes, FCTUC Silvino Pompeu dos Santos, LNEC Valter Lúcio, UNL

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LOCAL COMMITTEE Alfredo Dias, Coordinator António Freire Carlos Diogo Luís Filipe Jorge Miguel Ferreira Ricardo Costa

STUDENT COMMITTEE Ana Filipa Santos Gabriela Bispo Jacqueline Santos Luís Santos Pedro Santos Ricardo Azeiteiro Rui Pina

v

INDEX

Committees...………………………………………………………………………… iii

Index………………………………………………………………………………… v

TOPIC 1 – CONCRETE, THE MATERIAL

I108 Influence of mineral admixtures in the fresh behaviour of superplasticized concrete mixes A. CAMÕES…………………………………………………………………………..

1

I114 The influence of aggregate size in the risk of spalling in normal and high-strength concrete subjected to hydrocarbon fire A.A. NINCE, A.D. DE FIGUEIREDO……………………………………………….

9

I102 A study on thermal properties of high performance concretes with different types of superplasticizers J.L. CALMON, M. VERONEZ, S.B. DOS SANTOS, M.A.S. ANDRADE…………

21

I105 Adjusted density high-strength concrete using expanded polystyrene beads R. SRI RAVINDRARAJAH, T.F.L. SUBHAN………………………………………

29

I111 The effect of high fly ash content in concrete resistance to acid attack J.J.O. ANDRADE, G.B. LAVARDA, T.R.S. NOBRE………………………………

37

I112 Concrete highway barriers absorbing impact energy: prevention of traumatism in accidents is an example of sustainable development P. BINA, R.P. SCHWARK…………………………………………………………...

45

I116 Application of different curing procedures in high performance concrete (HPC) R. DE O. PINTO, A.L.B. GEYER, S.A. BESERRA…………………………………

53

I118 Application of specific mix proportion methods for high performance concretes (HPC) R. DE O. PINTO, A.L.B. GEYER, S.A. BESERRA…………………………………

61

I125 Light-concrete with leather: durability aspects I. PDBAFFA, J. AKASAKI…………………………………………………………..

69

I136 Influence of aggregate type and void content on sound absorption of porous concrete I. MIURA, T. NAKAZAWA, F. IMAI, R. ZHANG…………………………………

79

vi

I137 Experimental evaluation of dry-mix shotcrete with metakaolin A.D. DE FIGUEIREDO, C.S. LACERDA, G. GALLO……………………………...

89

I151 Thermal analysis of large concrete placements H. BARROS, C. FERREIRA, R.A.F. MARTINS……………………………………

97

I120 Service life estimation of concrete nonsatured structures A. GUIMARÃES, P. HELENE……………………………………………………….

105

I143 Chloride ingress data from field and laboratory exposure – influence of salinity and temperature A. LINDVALL………………………………………………………………………..

113

I109 Estimating compressive strength of concrete by mortar testing A. CAMÕES, B. AGUIAR, S. JALALI………………………………………………

121

I129 Bond characteristics of strand in pretensioned concrete C.A. ARBELÁEZ, J.R. MARTÍ, P. SERNA, P. MIGUEL…………………………..

129

I141 Restrained concrete ring test: experimental campaign and numerical simulation M. AZENHA, R. FARIA, J.A. FIGUEIRAS…………………………………………

137

I144 Mechanical behaviour of concrete made with fine recycled concrete aggregates L. EVANGELISTA, J. DE BRITO…………………………………………………...

145

TOPIC 2 – STRUCTURAL CONCRETE

I127 A new criteria to determine experimentally the transmission length of prestressed reinforcement C.A. ARBELÁEZ, J.R. MARTÍ, P. SERNA, M.C. CASTRO……………………….

155

I128 Transmission length of prestressed strand in high strength concrete C.A. ARBELÁEZ, J.R. MARTÍ, P. SERNA, M.A. FERNÁNDEZ………………….

163

I130 A theoretical model to analyze hollow reinforced concrete beams under combined loading J. NAVARRO-GREGORI, P.F. MIGUEL, M.A. FERNÁNDEZ-PRADA………….

171

I131 Bond and bond-slip of fiber reinforced polymer (FRP) reinforcement in concrete Z. SORIC, T. KIŠICEK……………………………………………………………….

179

I133 Experimental analysis of passive reinforcement anchorage in compresion-compresion-tension nodes C. CASTRO-BUGALLO, P.F. MIGUEL-SOSA, M.A. FERNÁNDEZ-PRADA, J.R. MARTÍ-VARGAS……………………………………………………………….

187

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I138 Study of the behaviour of plastic hinge regions in RC elements subjected to axial loads and bending moment A.C. BARRERA, J.L. BONET, M.L. ROMERO, M.A. FERNÁNDEZ, P.F. MIGUEL………………………………………………………………………………

195

I126 A layered finite element for reinforced concrete beams with bond-slip effects R.S. OLIVEIRA, M.R.S. CORRÊA, M.A. RAMALHO……………………………..

203

I121 Management system to concrete engineering structures J.W. LENCIONI, M.G. DE LIMA, F. MORELLI……………………………………

211

I101 Generic retrofitting approach for longitudinal plating reinforced concrete beams and slabs D. OEHLERS, R. SERACINO, I. LIU………………………………………………..

219

I139 Near surface mounted technique for the flexural and shear strengthening of concrete beams J. BARROS, S. DIAS, A. FORTES…………………………………………………..

229

I142 An insight into the flexural behaviour of R.C. beams strengthened with external FRP plates M. HASSANEN, M. RAOOF………………………………………………………...

237

I103 Flexural behavior of post_tensioned segmental beams M.E. TAVARES, J.M. DESIR………………………………………………………..

251

I134 Mechanical behavior assessment of concrete block masonry prisms under compression G. MOHAMAD, P.B. LOURENÇO, H.R. ROMAN………………………………...

261

I148 Behaviour of RC panels under shear R. COSTA, S. LOPES, L. BERNARDO……………………………………………..

269

I150 Torsion in reinforced high-strength concrete hollow beams L. BERNARDO, S. LOPES, L. OLIVEIRA………………………………………….

277

I147 Inspection and diagnosis tests for structural safety evaluation – a case study P. CUNHA, C. GESTA, F. RODRIGUES, R. VICENTE, H. VARUM……………..

287

I149 Research in timber-LWAC composite structures L. JORGE, S. LOPES, H. CRUZ……………………………………………………..

297

I132 Construction of sava river quay in croatia Z. SORIC, T. KIŠICEK, J. GALIC…………………………………………………...

305

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KEYNOTES

I601 Eurocode 2: basics and backgrounds J. WALRAVEN……………………………………………………………………….

315

I603 Recent research on initial on-site curing, capping and types of concrete specimens J. CALAVERA, J. FERNÁNDEZ-GÓMEZ, C. P. GARAVITO, G. GONZÁLEZ-ISABEL……………………………………………………………………………….

329

I604 Advances in the science and art of concrete: from nanotechnology to the construction of the Los Angeles Cathedral P.J.M. MONTEIRO, D. SILVA………………………………………………………

357

INFLUENCE OF MINERAL ADMIXTURES IN THE FRESH BEHAVIOUR OF SUPERPLASTICIZED CONCRETE MIXES

A. Camões Assistant Professor UM Guimarães, Portugal

ABSTRACT In order to evaluate the effect of the incorporation of mineral admixtures in superplasticized concrete mixes an experimental programme was carried out. Assuming that the characteristics of the fresh paste controls the rheological properties of the fresh concrete, Marsh cone and mini-slump tests were performed in various pastes containing different dosages of fly ash or limestone filler and made with two different types of superplasticizers. The obtained results indicate that: a) the two tests lead to similar overall results; b) the two superplasticizers used showed different effectiveness; c) the behaviour of the different pastes tested was influenced by the presence of the mineral admixture. 1. INTRODUCTION Literature points out three basic physical-chemical phenomena influencing the effect of superplasticizers (dispersion, adsorption and intermolecular repulsion-potential zeta) that result in a deflocculation and dispersion of the cement particles and give them a highly negative electrical charge so that they can repel each other. Usually, in concrete mix design the superplasticizer dosage is fixed determining, this way, the composition of the paste (cement, water, and superplasticizer) with the maximum fluidity for a given water/cement ratio and a given mineral admixture/cement ratio. It is assumed that the characteristics of the fresh paste govern the rheological properties of the fresh concrete and this procedure will yield a concrete with the maximum workability for a given aggregate content.

1

The only variable in this process is the superplasticizer/cement ratio and it is determined using simple and practical tests like Marsh cone or mini-slump. However, when concrete contains mineral admixtures, the following doubt can be established: does the superplasticizer main action of dispersion and deflocculation act only in cement particles or does it also affect mineral admixtures like fly ash or limestone filler? In this context, an experimental programme was carried out. Marsh cone and mini-slump tests were performed in various pastes made with different superplasticizer dosages and containing cement, a given water/powder ratio and different percentages of replacement of cement by fly ash or limestone filler. Two types of superplasticizers were used: copolymer and naphthalene. The obtained results are presented and analysed. 2. MATERIALS AND EXPERIMENTAL TESTS The cement (CEM) used in this research work was Portland cement type CEM I 42.5R. The fly ash (FA) was supplied by Pego Power Plant, Portugal. The limestone filler (LF) used was a commercial one, supplied by a Portuguese company. Table 1 shows the chemical characteristics of CEM, FA and LF used. Table 2 presents the estimated compound composition of CEM using Bogue’s expressions [1]. Table 3 shows some physical characteristics of the referred powder materials. Table 1 – Chemical composition of cement, fly ash and

limestone filler Table 2 – Estimated compound

composition of cement Chemical

Composition CEM - % FA - % LF - % Compound Composition CEM - %

SiO2 19.71 42.16 – 58.46 – C3S 61.61 Al2O3 5.41 21.04 – 32.65 < 0.40 C2S 4.55 Fe2O3 3.34 3.51 – 9.13 < 0.03 C3A 8.69 CaO 61.49 1.67 – 9.18 – C4AF 10.15 MgO 2.58 0.65 – 2.59 – CSH 5.47 SO3 3.22 0.22 – 1.04 – Cl¯ 0.01 0.00 – 0.06 –

CaCO3 – – 99.00 Free Lime 0.81 0 – 0.12 –

Insoluble residue 1.94 – 0.04

Table 3 – Physical characteristics of cement, fly ash and limestone filler Physical Characteristics CEM FA LF Specific weight - kg/m3 3150 2360 2700

Blaine specific surface - m2/kg 358.4 387.9 – Fineness - % (µm) 1.7 (>90) 14.1 – 31.6 (>45) ; 5.60 – 18.9 (>75) 18.0 (>80) Loss on ignition 2.52 5.60 – 9.28 43.61

Water demand - % 28.0 29.7 –

2

One of the superplasticizer (SP) used had a chemical composition based on naphthalene sulphonate formaldehyde condensates. The other was a last generation copolymer based SP. Table 4 shows some characteristics of the SP used. Table 4 – Main characteristics of copolymer (CP) and naphthalene (NS) superplasticizers used

Characteristics CP NS Solid content - % 20 ± 2 40 ± 2

Relative density (20 ºC) 1.05 ± 0.02 1.2 ± 0.02 PH 7 ± 1 7.1 ± 0.5

Chloride content - % < 0.1 0 Appearance brown liquid brown liquid

60

297

98

Ø = 8.3

148

Figure 2: Mini-slump test

Figure 1: Marsh cone used in the tests (dimensions in mm)

The Marsh cone and the mini-slump tests have been used previously to determine the saturation dosage of the SP and the compatibility between CEM and SP [2]. The Marsh cone used in the present study is shown in Figure 1. During the test the cone was filled with 1000 ml of paste and it was measured the time needed for 500 ml of the paste to flow through. The longer the flow time the lower the fluidity. After the Marsh cone tests the pastes were subjected to mini-slump tests. The method requires a truncated cone with the following dimensions: 57 mm of height; 19 mm of top diameter; 38 mm of bottom diameter. After filling the mini-slump cone to the top with the paste, the slump cone was lifted and two perpendicular diameters of the spread flow were measured (Figure 2). The result of the test is the average value of the measured spreads. The longer the spread flow the higher the fluidity.

3

Since the rheological behaviour of the fresh paste depends on the mixing action, sequence and time, these aspects haMoreover, the use of the same mixing sequence and tpreparation can be assumed to yield a paste that is simithis study, all the mixes were produced using a 5-liter pdifferent velocities: low (60 rpm) and high (120 rpm)was chosen based on other studies [3]: the CEM, water alow speed for 2 minu ; then, the mineral admixtures (FA or LF) were added and the paswas mixed for 4 more minutes at h , 1/3 of the SP was added and the

he study was divided in three steps. First, the tests were conducted in pastes containing CEM,

3.0; 4.0 %

ve to be maintained constant during the experimental programme. ime in this step as in the concrete

lar to the paste phase of the concrete. In lanetary blender. The mixer had two

. The following mixing sequence used nd 1/3 of the SP were first mixed at

tes te igh speed; in the third stage

paste was mixed for 2 more minutes at low speed; and in the last stage, the remaining 1/3 of the SP was added and the paste was mixed for 2 more minutes at high speed. In order to determine the optimum SP dosage, to compare the performance of different SP or to evaluate the effect of the addition of different quantities of FA and LF, various pastes were prepared and subjected to Marsh cone and mini-slump tests. In all the compositions the water/powder ratio (powder = CEM + FA + LF) was maintained constant and equal to 0.945 in volume, which correspond to 0.30 in weight for the composition made without mineral admixtures. The quantity of water that the SP contains was also considered in the mix design of the pastes. Tcopolymer SP (CP) and FA. Then, it was used CEM, naphthalene SP (NS) and FA. Finally, the tests were performed in pastes made with CEM, CP, and LF. Table 5 shows the different studied mixes.

Table 5 – Pastes mix design studied CEM + FA/(CEM + FA) = 0; 20; 40; 60; 100 % + CP/(CEM + FA) = 0.15; 0.25; 0.50; 1.0; 2.0;

CEM + FA/(CEM + FA) = 0; 40; 100 % + NS/(CEM + FA) = 3.0; 4.0 % 0.15; 0.25; 0.50; 1.0; 2.0;

CEM + LF/(CEM + LF) = 0; 40; 100 % + CP/(CEM + LF) = 0.15; 0.25; 0.50; 1.0; 2.0; 3.0; 4.0 %

As it can be seen in Table 5, the variables studied were: percentage of CEM replacement by FA (in volume); percentage of e); type of SP (CP or NS); do f e powder (CEM 3. CO ST

he Marsh cone test and the corresponding mini-slump test results are represented in Figure 3.

CEM replacement by LF (in volumsage of SP (in volume) expressed in terms o

+ FA + LF) volume. SP solid content and as a percentage of th

MARSH NE AND MINI-SLUMP TE RESULTS

TIn order to take into account the effect of the density of the different pastes in their flow times, the results of the Marsh cone tests are expressed through a factor, Kflow, which represents better the rheology of pastes with different densities [4]. Kflow is the product of the paste flow time by the corresponding specific weight.

4

10 50

7520

30

40

50

g/l.s

)

60

70

0.0% 1.0% 2.0% 3.0% 4.0%solid CP/(CEM+FA) (%)

Kflo

w (k

FA=0FA=20%FA=40%FA=60%FA=100%

100

125

150

(mm

)

175

225

0.0% 1.0% 2.0% 3.0% 4.0%solid CP/(CEM+FA) (%)

Flow

spr

ead

200

FA=0FA=20%FA=40%FA=60%FA=100%

Figure 3: Marsh cone and mini-slump test results (first step of the experimental work)

As it can be seen in Figure 3, the fluidity of the different pastes does not increase significantly beyond a certain dosage of SP. This value, known as the saturation dosage, may be taken as the maximum SP dosage. It can be noticed that both tests lead to a similar value of the saturation dosage in all the pastes: 0.5%. However, the results of the Marsh cone test seems to be easier to read and more consistent than the ones of the mini-slump. In addition, the overall results show that: the presence of FA is beneficial, increasing the fluid les, cting on the FA particles too; the rheological behaviour of the mixes made with FA contents

pastes can be obtained with the ddition of a very small quantity of CP SP.

ity of the pastes; it seems that the action of the SP is not limited to the CEM particagreater than 60% are different from the others. In these pastes, the Marsh cone test results does not show a saturation dosage and for FA = 100% and for SP contents greater than 2.0% the Marsh cone fluidity decrease significantly. However it is interesting to notice that the plain FA paste does not flow thought the cone if any SP are used. Based on this observation, it appears that the maximum fluidity of FA = 60% and FA = 100%a

10

20

50

75

10030

40

50

60

70

)

0.0% 1.0% 2.0% 3.0% 4.0%solid NS/(CEM+FA) (%)

Kflo

w (k

g/l.s

FA=0

FA=40%

125

150

175

200

225

m)

0.0% 1.0% 2.0% 3.0% 4.0%solid NS/(CEM+FA) (%)

Flow

spr

ead

(m

FA=0FA=40%FA=100%

Figure 4: Marsh cone and mini-slump test results (second step of the experimental work)

5

The results obtained in the second step of the experimental work are presented in Figure 4. In this phase, the CP SP was replaced with a NS SP and only pastes with 0, 40% and 100% of CEM replaced by FA were studied. In these tests, pastes with SP solid content less than 1.0% does not flow thought Marsh cone and does not have mini-slump spread. Pastes made with FA = 100% does not flow thought Marsh cone and with SP equal to 4.0% does not spread in mini-slump test to. With the NS the SP saturation dosage is higher than the obtained with CP. Both Marsh cone and mini-slump tests show that the optimum SP dosage is near 2.0%. This NS SP seems to be less effective in FA particles than the CP, once the incorporation of FA tends to decrease the fluidity of the tested pastes made with NS SP. However, good performance results were obtained with plain CEM pastes made with NS SP quantities near or greater than the saturation dosage.

astes incorporating 40% and 100% of CEM replaced by LF and CP SP were also tested. PResults are indicated in Figure 5.

50

40

50

60

200

225

LF=0LF=40%

LF=100%

75

100

125

150

ow s

prea

d (m

m)

175

0.0% 1.0% 2.0% 3.0% 4.0%

Fl0

10

20

30

Kflo

w (k

g/l.s

)

LF=0

LF=40%

LF=100%

0.0% 1.0% 2.0% 3.0% 4.0%solid CP/(CEM+LF) (%)solid CP/(CEM+LF) (%)

Figure 5: Marsh cone and mini-slump test results (third step of the experimental work)

Results obtained in LF pastes indicate that: the incorporation of LF increases significantly the fluidity of the pastes; it seems that the action of the SP is effective on the LF particles; the rheological behaviour of the mixes made with LF is different from the plain CEM paste. In LF pastes, the Marsh cone test results does not show a saturation dosage but the mini-slump indicates that for LF = 40% the saturation SP dosage is near 0.5%. However, like in FA plain pastes, the flow thought the Marsh cone is only possible if pastes contain a certain amount of SP. So, it seems that with LF particles, pastes can acquire the maximum fluidity with a very small amount of CP SP. 4. LOSS OF FLUIDITY WITH TIME The in ethis ing

crease of workability is one of the major benefits of the use of SP in concrete. Howevincrease is of relatively short duration, and may last from 30 to 60 minutes follow

r,

6

which the concrete reverts back to its origin nsistency [5]. In this context, the loss of

es were mixed for one minute at 60 rpm and then the Marsh cone ow time was measured.

6 and 7. The results are expressed by the percentage f loss of Kflow related to the initial one (∆Kflow).

al cofluidity with time of the pastes is one of the most important parameters that must be studied. The effect of the incorporation of FA and LF should be evaluated and also the influence of the type of SP (CP or NS). After the realization of Marsh cone and mini-slump tests the pastes containing the optimum dosage of SP (0.5% for CP and 2.0% for NS) were maintained in a recipient and were again subjected to Marsh cone test later than 15, 30 and 60 minutes. One minute before the referred times of the new tests the pastfl The obtained results are shown in Figures o

0

5

10

∆Kflo

w (%

)

15

20

25

0 10 20 30 40 50 600

300

0 10 20 30 40 50 60

400

500FA=0FA=20%FA=40%FA=60%FA=100%

FA=0FA=40%

SP: NS(2.0%)

100

200

Kflo

w (%

)

SP: CP(0.5%)

time (min.)time (min.) Figure 6: Loss of fluidity with time of pastes incorporating FA and optimum dosage of CP SP

and NS SP

0

5

10

15

20

25

0 10 20 30 40 50 60

∆Kflo

w (%

)

time (min.)

LF=0LF=40%

LF=100%

SP: CP(0.5%)

Figure 7: Loss of fluidity with time of pastes incorporating LF and optimum dosage of CP SP

7

Figures 6 and 7 show that FA and LF incorporation reduces significantly the loss of fluidity with time, even for the smallest dosage used (20% of FA and 40% of LF). Paste made with NS SP and no CEM replacement showed much higher values of loss of fluidity with time than that with CP SP. Only after 15 minutes of the first flow through Marsh cone, the plain CEM paste containing NS SP exhibits a loss of fluidity of about 22%. This value was similar to the one registered in CP SP paste after 60 minutes. After 30 minutes the loss of fluidity of the NS SP paste was about 100% and 470% at 60 minutes. However, the paste made with NS SP and 40% of CEM replaced by FA exhibits a loss of fluidity with time similar than that registered with CP SP. 5. CONCLUSIONS

saturation dosage of CP SP was around 0.5% of the powder content (in volume) and e NS SP about 2.0%. Increased amounts of FA improved the fluidity of CP SP pastes and

of NS SP pastes. So it seems that the CP SP is more efficient in FA P. The NS SP plain CEM paste showed a very high loss of fluidity with

in, P.-C. – High-Performance Concrete. Modern Concrete Technology 5, E & FN

Based on the results obtained, it seems that the saturation dosage of SP can be determined bysimple tests either by Marsh cone or mini-slump. However, the Marsh cone test results appears easier to read and, as a whole, more consistent. The presence of mineral admixtures (FA or LF) affects the rheological behaviour of pastes and the SP saturation dosage must be determined considering their presence, i.e., the amount of SP must be referred as a function of the powder content and not only as a percentage of cement content. The two different SP used (CP and NS) showed considerable different effectiveness. The solid ontent c

thdecrease the fluidity

articles than the NS Sptime. This aspect was not noticed in pastes made with CP SP. However, pastes incorporating FA or LF and CP SP or NS SP showed similar values of loss of fluidity with time and their addition reduces significantly this time dependent effect. 6. REFERENCES [1] Bogue, R.H. – Chemistry of Portland Cement. Reinhold, New York, 1955. 2] Aïtc[

Spon, London and New York, 1998. [3] Carbonari, B.T..– “A Synthetic Approach for the Experimental Optimization of High

Strength Concrete”. 4th International Symposium on Utilization of High-Strength / High-Performance Concrete, Paris, 1996, p. 161-167.

[4] Camões, A. – High-Performance Concrete Incorporating Fly Ash. Doctoral thesis. University of Minho, Guimarães, 2002, 456 p. (in Portuguese).

[5] Ramachandran, V.S., Malhotra, V.M., Jolicoeur, S. and Spiratos, N. – Superplasticizers: Properties and Applications in Concrete. CANMET, Canada, March, 1998, 404 p.

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