File 705 Derabla Etal Ace2012

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10th International Congress on Advances in Civil Engineering, 17-19 October 2012

Middle East Technical University, Ankara, Turkey

Effect of Steam Curing on the Properties of Slag-Cement

Concrete in Seawater Environment

R. Derabla1, M. L. Benmalek

2, F. Sajedi

3

1Department of Civil Engineering, University of 20 August 1955, Skikda, Algeria, [email protected] 2Department of Civil Engineering, University of 8 May 1945, Guelma, Algeria, [email protected] 3Department of Civil Engineering, Islamic Azad University, Ahvaz, Iran, [email protected]

Abstract

This study deals with the use of ground granulated slag in substitution to cement (up to 40% of by weight) to

produce slag-cement concrete. The physical and mechanical properties (water absorption capacity, porosity andcompressive strength) of specimens prepared with elaborated cements was investigated under two curingconditions, i.e. standard and steam curing and two storage environments as freshwater and seawater.

It was proved that using slag in substitution of cement leads to produce a heat-treated-concrete resistant to

chlorides and sulfates existing in the marine environment by either:

- Combining 20% of slag, with the use of water reducing plasticizer admixture and w/c rate limited to 0.3, or

- Using 40 % of slag, without admixture and a w/c slightly higher, equal to 0.5.

Keywords: slag, heat treatment, concrete, seawater, porosity

1 Introduction

The needs of the modern world demand to produce more, faster, sustainable and less costly, and such as theconcrete is the building material most used today, but requiring a long time to acquire its optimal capacities, we

have tried to accelerate his setting and his hardening to become compatible with the requirements of industrial production. This objective can be obtained using heat treatment which occupies an important place amongvarious possible methods.

In order to minimize the final cost of cement, to reduce the energy consumption of its production (Trenkwalderand Ludwig, 2001) and as a result the reduction of the environmental impacts and using rationally and

economically of local materials, we are usually directed towards the use of mineral additions. Among theseadditions there is the blast furnace slag, but the rapid cooling which makes granulated confers its latent hydraulic properties, which requires the use of an activating agent to ensure its hydration. Due to the latent hydraulicreaction of slag, its incorporation into the cement leads to a decrease in mechanical performance especially atearly ages. To improve these performances, three methods of activation are usually followed as thermalactivation (Chabi et al., 2004) and (Sajedi. and Abdul-Razak, 2010), chemical activation (Gifford and Gillott,1997) and (Rompaey, 2006) and (Sajedi. and Abdul-Razak, 2010), and mechanical activation (Sajedi, 2012).

The aspect of durability which has a great importance, especially for structures located in aggressiveenvironments containing sulphates and chlorides such as the marine environments; in case, we must establish a

concrete properly formulated and cured to make it as impermeable and as compact as possible in order to acquirehigh resistance against seawater and therefore ensuring a longer life for the building works in question.

1

mailto:[email protected]








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The approach taken in this work is to substitute part of cement with slag at levels of 0% for APC, 20% for CPCand 40% for BFC. It will then make concretes that will be studied under different treatment conditions (standardto 20 ° C and thermal with the cycle as shown in Figure 1) and storage conditions (freshwater and seawater) inorder to know the effect of the heat treatment and slag content on the physical and mechanical properties ofelaborated concretes. They are the porosity (P), the water absorption capacity (WAC) and the compressivestrength at the ages of 2, 7, and 28 days.

2 Raw materials

2.1 Aggregates

A crushed sand 0/4 and gravel with the fractions of 4/8, 8/16 and 16/25 from the quarry of COJAAL located atDidouche Mourad (wilaya of Constantine) were used. The grain size distribution of aggregates used is presentedin Figure 2.

Figure 1. Heat treatment cycle0

10

20

30

40

50

60

70

80

90

100

31.52520161412.51086.34210.50.250.1250.063

undersize(%)

sieve size (mm)

Sand 0/4 Gravel 4/8 Gravel 8/16 Gravel 16/25

Figure 2. Granulomertric curves

The results of characterization tests, carried out in laboratory of COJAAL, are presented in Tables 1 and 2 as below.

Table 1. Specification of sand according to XP P 18-545

Sand

equivalent

%

Methylene

Blue

%

Fineness

modulus

%

Absolute

Density

g/cm3

Coefficient of

absorption%

Sable 0/4 49 1.00 2.98 2.84 1.16

Table 2. Specification of gravels according to XP P 18-545

Los

Angeles

%

Micro

Deval

%

Aplatissement

%

Absolute

Density

g/cm3

Coefficient of

absorption

%

G 4/8

26 13

7 2.71 2.00

G 8/16 5 2.73 1.98

G 6/25 6 2.73 1.95

2.2 Admixture

A water reducer plasticizer (VISCOCRETE 3045) was used as an admixture. It is based on polycarboxylatesmodified, no chlorinated (Cl- ions content ≤ 0.1%) and ready to use it in mixes in conformity with NF EN 934-2.

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R. Derabla, M. L. Benmalek, F. Sajedi

2.3 Cement

Three types of cement were used as an artificial Portland cement (APC CEM I 42.5) sulphate-resisting (C3A: 2.8

to 3.2%) of the cement factory of M'Sila, a compound Portland cement (CPC 42.5) containing 20% of slag produced by the cement factory of Hdjar Soud, and a blast furnace cement (BFC) containing 40% of slag, which

was prepared by adding 20% of slag to the second type of cement, CPC 42.5.

The chemical and mineralogical compositions of the three cements used are presented in Tables 3 and 4respectively:

Table 3. Chemical Composition of APC, of CPC and of slag

APC CPC Slag

SiO2 21.94 ± 0.14 22 - 28 34.41

Al2O3 3.78 ± 0.05 5 - 6 8.17

Fe2O3 4.82 ± 0.01 3 - 3.6 4.15

CaO 63.11 ± 0.21 55 - 65 40.69

MgO 2.12 ± 0.02 1 - 2 0.10K 2O 0.46 ± 0.01 0.3 - 0.6 0.10

Na2O 0.17 ± 0.02 0.1 - 0.16 0.89

SO3 1.87 ± 0.03 1.8 – 2.5 -

Free CaO 0.915 ± 0.010 0.8 – 1.8 -

Cl- 0.01773 ± 0.00079 0 – 0.1 0.36

Insoluble Residues 0.89 ± 0.15 - -

Loss on ignition 1.370 ± 0.004 - -

Table 4. Mineralogical Composition of cements

Clinker % Gypsum % Slag % C4AF % C3A % C2S % C3S %

APC 95 5 0 13 - 15 2.8-3.2 17- 21 55- 59CPC 75 5 20

9 - 13 8 - 12 10- 25 55- 65BFC 55 5 40

2.4. Slag

The granulated slag of the blast furnaces of El Hadjar (wilaya of Annaba) was used after it was crushed to thefineness of 3138 cm2/ g (similar to CPC) using a laboratory-type ball mill in the laboratory of Civil Engineeringat the University of Annaba. Its chemical compositions are given in Table 3 as mentioned above.

The activity index, i.e. M b, determined using the following formula (1), indicates that it is basic (Dreux and

Festa, 1998):

10,96OAl%%SiO

%MgO%CaO

322

b ≈=

+

+

=M (1)

3 Concrete mix design

Two mixes design of concrete determined using the method of Dreux-Gorisse were made, the dosages are

presented in Table 5. To achieve the envisaged test program, six concrete mixes were prepared by the use of thethree types of cement (APC, CPC and BFC) and the two mixes design as mix design 1 with w/c = 0.5 and mixdesign 2 with w/c = 0.35+ admixture. The study examined the influence of storage medium (freshwater and

seawater) and the heat treatment process for 2, 7 and 28 days.

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Table 5. Concrete mix design

DosageCement

(kg)

S 0/4

(kg)

G 4/8

(kg)

G 8/16

(kg)

G16/25

(kg)

Water

(l)

Admixture

(%)w/c

Slump

(mm)

Mix design 1 375 757 128 478 534 192 - 0.5 80Mix design 2 400 681 144 491 527 140 2.0 0.35 180

4 Results and discussion

4.1. Physical properties

To determine the porosity (equation 2) and the WAC (equation 3) of the concrete specimens (reference and heattreated concretes) at the age of 28 days, specimens were weighed after drying and total elimination of moisture(an oven dried at 105 ° C) and then immersion in water up to saturation.

100(%) ×

−

=

t

drysat

V

mmP (2)

%100×

−

=

dry

drysat

m

mmWAC (3)

msat: mass of specimen saturated with watermdry: mass of dried specimenVa: apparent volume of specimen

The values of P and WAC are presented on in Figure 3 and 4 as below.

0

2

4

6

8

10

12

14

APC

(0.5) APC

(0.35+Adm) CPC

(0.5) CPC

(0.35+Adm) BFC

(0.5) BFC

(0.35+Adm)

Reference (Se aw at er ) He at treated (Seawater)

Reference

(Fresh

w at er ) He at

treated

(Fresh

water)

P(%) (*)= (w/c)

Adm=Admixture

0

1

2

3

4

5

6

APC

(0.5) APC

(0.35+Adm) CPC

( 0. 5 ) C PC

(0.35+Adm) BFC

(0.5) BFC

(0.35+Adm)

Reference

(Se aw at er ) He at

treated

(Seawater)

Reference

(Fresh

w at er ) He at

treated

(Fresh

water)

WAC(%) (*)=

(w/c)

Adm=Admixture

Figure 3. Porosity of concretes Figure 4. WAC of concretes

4.1.1. Effect of storage medium

- The concretes stored in fresh water have a higher porosity than those stored in seawater.

- The concrete based on APC has a lower porosity in seawater because of its nature (Sulfate resisting cement)and its characteristics (permeability and better resistance in aggressive environments containing sulphates).

- The incorporation of 20% slag makes the concrete (based on CPC and with admixture) having a porosity lessthan that containing 40% of slag, and consequently more resistant to penetration of chlorides and sulfates. Thisresult was also obtained by (Jau and Tsay, 1998) and (Binici et al., 2008) who estimated that 20% of slag inconcrete is an optimum against chloride penetration especially in the marine environment.

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4.1.2. Effect of mix design

The use of plasticizer water reducer (case of mix design 2) is very beneficial. According to (Markestad, 1986)

the water-reducer admixture is responsible for 60% or more of the gain of strength at 28 days, and in our case ithas allowed to obtain porosity rate lower than that of made without admixture (case of mix design 1). Thisfinding is even more significant with more slag which reduces the diameter of continuous pores (Aldea et al.,

2000).

4.1.3. Effect of heat treatment process

In fresh water, the porosity is higher in reference concretes than in heat treated concretes for both the APC and

CPC, as well as for the BFC with mix design 1. This result is the opposite of concrete obtained with BFC mixdesign 2 duo to the slag needs more water and time to react.

In seawater, the porosity is higher in reference concretes than in heat treated concretes for the two mixes designwith the APC and CPC with mix design 1, but the opposite for the remaining. This allows to conclude that 20%of slag with sufficient water (w/c = 0.5) is more advantageous for a heat-treated concrete intended to be used in

marine environments.

According to the results obtained for the porosity and the WAC, a proper relationship can be seen between P andWAC as a high porosity corresponds to a high WAC relating to the same reasons mentioned as above.

4.2. Compressive strength

The compressive test was carried on cubic specimens of concrete with side lengths of 150 mm. The influence ofthe factors studied is discussed at the ages of 2, 7 and 28 days.

4.2.1. Effect of heat treatment process

4.2.1.1. Concrete based on APC

It can be seen from the Figure 5 that, on the one hand, the concretes prepared with mix design 2 were able toacquire the highest strength by the two modes of treatment (standard and thermal) and in the two storagemedium because of the use of the plasticizer water-reducing which helped to limit the amount of mixing water(w/c), and on the other hand has the highest steamed concrete strength at early ages compared to the reference

concrete, allowing a fast demoulding at short term and consequently a high productivity. This strength gain iseven more important when the temperature is higher, but at long term, the reference concrete has higher strengthsince the negative effect of heat treatment appears at this stage; here is discussed about the porosity whichincreases due to evaporation of water, of course, whenever the sealing conditions are not adequate (loss ofmoisture).

At long term (28 days and above), the loss of strength of heat treated concretes compared to the referenceconcrete are predictable; in this research they are within 5 and 8 %.

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Figure 5. Compressive strength of concretes based on APC

4.2.1.2. Concrete based on CPC

The results relating to mechanical activation are presented in Figure 6. The strengths are the highest for thespecimens prepared with mix design 2, and the heat treatment of concrete allows having excellent values mainlyat early ages.

Figure 6. Compressive strength of concretes based on CPC

In the long terms, it may be noted that:

- In fresh water: the strength of steamed concrete (w/c=0.35+admixture) exceeds that of the reference concretewith a gain nearby 9.5%. This represents an excellent result compatible with that obtained by (Baoju et al.,

2001). ]. The strength of the heat treated concrete (w/c= 0.5) has a loss of 3.2% compared to the concrete without

using treatment.

- In sea water: the loss of strength of steamed concrete with admixture is of about 4.1%. It is practically nil for

the concrete made with the use of second mix design.

4.2.1.3. Concrete based on BFC

Similar to the two previous cases, at early ages, the steamed concrete is always predominant, beyond it can be

said that (Figure 7):

- In standard medium: The strength of steamed concrete containing admixture is higher as 11.2%, probably dueto the high slag content in BFC, i. e. 40%.

- In the marine environment: the strength of the heat treated concrete (without admixture) substantially increasesuntil it reaches the strength of reference concrete with admixture, it can be explained by the beneficial effect of

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high replacement level of slag and its good response with temperature (thermal activation) in seawater. This wasexpected due to good behavior of slag and its high affectivity in aggressive environments such as in sea water(chlorides, sulfates), when it was subjected to thermal activation.

Figure 7. Compressive strength of concretes based on BFC

4.2.2. Effect of slag

4.2.2.1. Concrete made with mix design 1

For the reference concrete, from the early ages, the higher strength is related to the concrete based on APCfollowed by the concrete based on CPC, but with time increasing, the strength of the concrete based on BFC

increases considerably (Figure 8). Globally, using CPC, interesting compressive strengths at 28 days are reached.

By using heat treatment and a sufficient amount of mixing water, the concrete based on BFC stored in seawater presents the strength results of 28-day greater than of based on APC and on CPC. This result shows once againthe contribution of the slag in the marine environment as affirmed by (Binici et al., 2008) and in the field ofacceleration of concrete hardening using heat treatment process which joins the opinion of the authors (Yazici,2010).

Figure 8. Compressive strength of concretes made with mix design 1

4.2.2.2. Concrete made with mix design 2

For the reference concrete, at 28 days, the strengths of the fluid concretes based on APC and on CPC which arestored in seawater are much higher than those stored in the fresh water (Figure 9).

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Figure 9. Compressive strength of concretes made with mix design 2

For the heat-treated concrete and as noted above, the slag concretes have more reactions using heat treatment(activation), but with the use of water reducing admixture and a w/c = 0.35, concrete steamed elaborated with

CPC has generally the highest resistant, and hence the most economical. This is in accordance with the resultsobtained by other researchers (Binici et al., 2008), (Jau and Tsay, 1998) and (Aldea et al., 2000).

5 Conclusions

The concrete made with mix design 2 gave better results using heat treatment especially at early ages, where the

strengths can reach 55% of the strength of reference concrete at 28 days, the increase of slag increases thecompressive strength of concrete subjected to heat treatment with a gain of around 11%.

These promising results allow us to demould the formwork of concrete elements quickly (after some hours),reinforced or pre-stressed concrete (especially in precast industry), resulting in a gain of time, money and high productivity.

Using slag, it is possible to make a heat-treated concrete, resistant to marine salts by combining 20% of slag with

an w/c limited to 0.35 and the use of a water-reducing plasticizer, or with 40% of slag and a w/c limited to 0.5.

A microscopic study and extended for maturities greater than 28 days (90 days and above) can probably clarifythe effectiveness of steel waste more, i. e. slag, thermally activated in aggressive environments, especially inseawater.

References

Aldea, C.M., Young, F., Wanga, K. and Shah, S.P. (2000). Effects of curing conditions on properties of concrete

using slag replacement. Cement and Concrete Research. Vol. 30, pp. 465-472.Baoju, L., Youjun, X., Shiqiong, Z. and Jian, L. (2001). Some factors affecting early compressive strength of

steam-curing concrete with ultrafine fly ash. Cement and Concrete Research. Vol. 31, pp. 1455–1458.Binici, H., Aksogan, O., Bahsude, E., Kaplan, H. and Bodur, M.N. (2008). Performance of ground blast furnace

slag and ground basaltic pumice concrete against seawater attack. Construction and Building Materials.Vol.22, pp. 1515–1526.

Chabi, S., Mezghiche, B. and Guettala, H. (2004). study of the influence of actives mineral additions on the

mechanical behavior of cements et mortars. E-Knowledge n°5, university of Biskra, pp. 03-08.Dreux, G. and Festa, J. (1998). New guide of concrete and its components. Eyrolles edition.

Gifford, P.M. and Gillott, J.E. (1997). Behavior of mortar and concrete made with activated blast furnace slagcement. Canadian Journal Civil Engineering. Vol. 24, pp. 237-247.

Jau, W.C. and Tsay, D.S. (1998). Study of the basic engineering properties of slag cement concrete and itsresistance to seawater corrosion. Cement and Concrete Research. Vol. 28, pp. 1363–1371.

Markestad, S.A. (1986). A study of the combined influence of condensed silica fume and a water reducingadmixture on water demand and strength of concrete. Materials and Constructions. Vol. 19, pp. 39-47.

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Sajedi, F. and Abdul-Razak, H. (2010). Thermal activation of ordinary Portland cement-slag mortars. Materials

and Design. Vol. 31, pp. 4522-4527.Sajedi, F. and Abdul-Razak, H. (2010). The effect of chemical activators on early strength of ordinary Portland

cement-slag mortars. Construction and Building Materials. Vol. 24, pp. 1944-1951.Sajedi, F. (2012). Mechanical activation of cement-slag mortars. Construction and Building Materials. Vol. 26,

pp. 41-48.

Trenkwalder, J. and Ludwig, H.M. (2001). Producing slag cements by separate grinding and subsequent mixingat the Karlstadt works. Zkg International. Vol. 54, pp. 480-491.

Rompaey G.V. (2006), Study of the reactivity of cements rich in slag at low temperature and short time without

chlorinated adding, doctorate thesis PhD, Free university of Brussels.Yazici, H., Yardimci, M.Y., Yigiter, H., Aydin, S. and Türkel, S. (2010). Mechanical properties of reactive

powder concrete containing high volumes of ground granulated blast furnace slag. Cement and Concrete

Composites. Vol. 32, pp. 639–648.

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