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Behavior of self-compacting concrete made with marble and tile wastes exposed to external sulfate attack
Construction and Building Materials 135 (2017) 335–342
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Behavior of self-compacting concrete made with marble and tile wastes exposed to external sulfate attack Mohsen Tennich a,b, Mongi Ben Ouezdou a,⇑, Abderrazek Kallel a,c a
Université de Tunis El Manar, Ecole Nationale d’Ingénieurs de Tunis, LR03ES05 Laboratoire de Génie Civil, 1002 Tunis, Tunisia Direction Générale des Etudes Technologiques, Institut Supérieur des Etudes Technologiques de Radès, BP 172, 2098 Radès Médina, Tunisia c Prince Sattam bin Abdulaziz University, College of Engineering, Civil Engineering Department, BP 655, 11942 Al-Kharj, Saudi Arabia b
h i g h l i g h t s Effect of marbles wastes and tiles factories on the behavior of SCC under external sulfate attack. The behavior of SCC with Waste is evaluated by mass variation and dynamic elastic modulus. The resistance of SCC with Waste to external sulfate attack is better than the ordinary vibrated concrete.
a r t i c l e
i n f o
Article history: Received 3 October 2016 Received in revised form 29 November 2016 Accepted 29 December 2016
Keywords: Self-compacting concrete (SCC) Waste of marble fillers Waste of tiles fillers Durability External sulfate attack
a b s t r a c t The evaluation of the incorporation of industrials wastes from marbles and tiles factories in the formulation of self-compacting concrete (SCC) usually requires the understanding of their effects on the rheological behavior SCC in the fresh state and on the mechanical performances of these concretes in the hardened state. But, for a long-term behavior, it is imperative to study of their influence on the durability of these types of concrete against chemical degradations that may exist through the waters or aggressive soils. In the present work, samples of different types of self-compacting concretes incorporating wastes from marbles, marble tiles and gravel tiles (SCCWs) were exposed to different forms of external sulfate attack. This study compares the behaviors of these samples to those of a reference self-compacting concrete (SCCR) made with limestone filler SCCR and an ordinary vibrated concrete (OVC). The samples of different concretes were immersed in seawater, in a sodium sulfate solution (liquid form of sulfate attack) and potable water chosen as a reference. Other samples of these concretes were also placed in a vehicle battery charging hall to ensure their exposure to gaseous form in sulfate through the release of sulfur dioxide gas in the hall. To evaluate the behavior of the concrete samples against different forms of external sulfate attack, the change in their masses was monitored as well as the determination of their dynamic elastic modulus by the ultrasonic test was performed. Multiple measurements of these properties were taken for each 60 days of exposure and up to twenty months period. The results of the carried out testing showed that SCCWs have good resistance to external sulfate attack, even in severe exposure to the sulfate with sodium sulfate solution, and especially for the self-compacting concrete made with marble waste. Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction The self-compacting concrete (SCC) is used even in the most complex shapes and can pass through the densest reinforcement without requiring the means of vibration that is to say, it is recommended concrete to use for works of the great projects (buildings, bridges, . . .). The structures of these projects require high mechanical performances and durability of the concrete used. ⇑ Corresponding author. E-mail address: [email protected] (M. Ben Ouezdou). http://dx.doi.org/10.1016/j.conbuildmat.2016.12.193 0950-0618/Ó 2016 Elsevier Ltd. All rights reserved.
The study of incorporation of Tunisian wastes (W1: Waste of marble, W2: Waste of marble tile and W3: Waste of gravel tile) in the SCC, were published in a previous research paper [1]. These wastes were identified and their physical and chemical characteristics were exposed in [1]. Moreover, their particle size distributions and their compactness are given also in the same previous paper. This latter was aimed to the valuation of these industrial wastes dumped in huge quantities in order to find solutions to environmental problems that they pose and also reduce the cost of the cubic meter unit (1 m3) of SCC.
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This valuation requires not only a good formulation of SCC incorporating these industrial wastes (SCCWs) but also to ensure rheological behaviors in fresh state and to obtain sufficient mechanical performances of these SCCWs in the hardened state. To complete this evaluation, we must also consider the longterm durability of these concretes as the exposure to the external sulfate attack, which is the most severe. Indeed, this attack presents a chemical effect on concrete and has negative impacts on its durability. The sulfate ions can have several origins: natural, organic or come from industrial pollution [2–3]. Hence, soils containing gypsum (CaSO42H2O) and hence sulfate, with high concentrations (greater than 5%) can cause degradation of concrete. Similarly clay soils may contain pyrites (FeS2) that oxidize to sulfates in contact with air and moisture to form sulfuric acid (H2SO4). This sulfuric acid strongly attack the concrete slabs that are founded on these soils and causes corrosion and cracking of the slabs and therefore structures stability problems [2]. Furthermore, and as biological origin, the decomposition of organic materials in silos and storage tanks as well as in sanitation sewage can cause the formation of hydrogen sulfide (H2S: very toxic gas). In concretes, anaerobic bacteria convert the sulfate SO2 4 and they produce H2S that is released to the surface. On the surface, the H2S is then decomposed in the form of sulfur by aerobic bacteria. The sulfur is eventually turned into H2SO4, a strong acid and a very corrosive to concrete) [2,3]. Moreover, Chemical industrial pollution, such as battery manufacturing plants for vehicles, may cause the spread in the air of sulfur dioxide (SO2) following the dissolution of sulfuric acid [4]. This gas causes loss of mechanical performance of concrete. In this context, this present study was initiated for a better understanding of the durability of SCCWs incorporating wastes fillers from marbles and tiles factories. The fresh and hardened states properties of these SCCWs were already analyzed in the previous paper [1]. Then, the durability results would be compared to those of a reference of two types of concrete, self-compacting concrete made using limestone filler (SCCR) and ordinary vibrated concrete (OVC). Since the mid 19th century, L. Vicat [5] studied the chemical deterioration of the OVC caused by the presence of sulfate ions in the seawater. He showed that the MgCl2 and MgSO4 magnesium salts are the most aggressive for concrete. Many other studies have been made on the durability of OVC. For SCC which differs from OVC by the existence of some types of additions increasing its volume of paste to ensure its fluidity at fresh state, there are several studies of the durability of this concrete under the effect of external sulfate attack. M.R. Khelifa [4] has studied the durability of concrete exposed of the external sulfate attack. The SCC samples were immersed in a solution dosed with 5% Na2SO4 and subject for six months to a full immersion or different cycles of immersion/drying. The author observed that sample’s degradation by external sulfate attack depends on the type of cement used and also Water/Cement ratio. The experimental results also showed that the damage was more pronounced in the case of immersion/drying cycles than for full immersion of the samples. Y. Senhadji et al. [6] studied the sulfate attack of samples of which the cement is partially substituted by proportions of limestone filler between 10% and 30%. The test results showed that the samples that have highest replacement levels of limestone filler were more susceptible to sulfate attack. S. Boualleg and M. Bencheikh [7] have exposed test samples of paste or mortar cement (pouzzolannique or limestone) to chemical treatments, namely, ammonium nitrate, magnesium sulfate, sodium sulfate, sodium chloride and sulfuric acid for a period of three months. They found that the durability performance of pastes and mortars with pozzolan cement were better than those prepared with limestone.
K. Behfarnia and O. Farshadfar [8] studied the effects of various pozzolanic binders such as fumed silica, zeolite and metakaoline on SCC’s durability in a magnesium sulfate environment. The results of their tests showed that SCCs with metakaoline and zeolite are more durable than those with silica fume. H. Siad et al. [9] studied the effects of mineral additives (limestone filler, fly ash and natural pozzolan) on the behavior of SCCs immersed in a sodium sulfate solution. According to their findings, natural pozzolan is the most beneficial additive for an SCC in a rich sodium sulfate environment. R. Deepthy and M P. Mathews [10] studied the durability of SCC based fly ash as an additive through the immersion of samples in solutions with different proportions of sulfate ions and chloride. The experimental results show that the compressive strengths of immersed samples decreases with increasing concentration of sulfate and chloride solutions. Similarly, there are weight losses of these samples and they’re proportional to the duration of exposure. Recently, Boudali S. et al. [11] have studied the attack of sulfate of the mixtures incorporating recycled concrete aggregates and fines; their results show that they have a better behavior for sulfate attack than those with natural aggregates and natural pozzolana. In this paper, three different forms of external sulfate attacks testing of concretes samples prepared in advance were realized. The first type of these tests was to immerse the samples in seawater, while for the second type, the samples were immersed in a sodium sulfate solution (5% Na2SO4), and for the third type, the samples were exposed to the polluted environment of sulfur dioxide (SO2) from a battery charging hall. The evaluation of the behavior of SCCWs exposure to external sulfate attack is monitored through tracking the change in mass of the samples and the change in the dynamic elastic modulus determined by the ultrasonic test. Parallel to these external sulfate attack tests, a reference test was also completed by immersing the same types of samples in potable water at a temperature 20 ± 2 °C to facilitate the interpretation of results. 2. Experimental procedures 2.1. Materials The major materials that were used in this research are: – A Portland cement CEM I 42.5 produced by the factory CAT – Jebel Jeloud in Tunis according to standard NT47.30 [12]. – A gravel provided by the crushing quarry of Jebel Ressas in Tunis with a maximum nominal size 16 mm and alluvial silica sand from a the quarry Borj Hfaiedh with a maximum size of 4 mm. These concretes aggregates characteristics are defined in the standard NT 21.30 [13] and their specifications are the same as in the previous paper [1]. – The additives used are: The limestone filler (LF) produced by the group ‘‘Omya” that is chosen to make the control or Reference Self-Compacting Concrete (SCCR). The industrial wastes fillers provided by two Tunisian factories of marble and tiles. These are classed of three types (W1: Waste of marble, W2: Waste of marble tile and W3: Waste of gravel tile). Their chemical characteristics are presented in Table 1. – A superplasticizer, high water reducer polyvalent (SIKA VISCOCRETE TEMPO 12).
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M. Tennich et al. / Construction and Building Materials 135 (2017) 335–342 Table 1 Chemical composition of fillers. Filler
LF (Limestone)
W1 (Marble)
W2 (Marble tile)
W3 (Gravel tile)
Calcium oxide (lime): CaO (%) Aluminum oxide (alumina): Al2O3 (%) Iron oxide: Fe2O3 (%) Silicon dioxide (silica): SiO2 (%) Magnesium oxide: MgO (%) Sulfur trioxide: SO3 (%) Potassium oxide: K2O (%)
55.44 0.02 0.01 1.09 0.38 0.07 0.02
49.46 0.46 0.66 7.36 0.23 0.08 0.11
47.09 0.58 0.06 3.78 4.62 0.41 0.09
53.08 0.66 0.10 4.28 0.10 0.29 0.08
The values in bold is to show the importance of the % of the Aluminium oxide present in W1, W2, and W3 and their effect under the sulfate attack.
– The waters used are potable water, chosen as a reference to assist in interpreting sample behaviors for the other tests, the distilled water used to prepare the sodium sulfate solution (5% Na2SO4, 10H2O) and the seawater (from Tunis). Their chemical characteristics are summarized in Table 2. 2.2. Mixture proportions Three types of self-compacting concrete (SCCW) incorporating one of the three industrial wastes (W1, W2 and W3) were prepared for evaluation their resistance to external sulfate attack. The durability of these SCCWs was compared to a reference self-compacting concrete made using limestone filler (SCCR) and a reference ordinary vibrated concrete (OVC). The formulation of these concretes is realized by using ‘‘Concrete Lab Pro2” software and adjustment by tests in the fresh state [1,14]. The five optimized compositions chosen are presented in Table 3 that have characteristics within standard EFNARC [15] and are in good agreement with the values given by the French Association of Civil Engineering AFGC [16]. 2.3. Samples The samples used in this research are of cubic shape (70 70 70 mm), obtained after sawing prismatic specimens (70 70 280 mm). Before sawing, these specimens were manufactured and cured in water maintained at 20 ± 2 °C for 28 days. After sawing, the samples were dried at a temperature of 60 °C. 2.4. Exposure and testing For each exposure test, three samples were prepared for each type of concrete and exposed to external sulfate attack. The following types of tests were performed: – The attack by sulfate in liquid form. The samples were immersed in seawater and in the sodium sulfate solution (5% Na2SO4, 10H2O) which is considered as a severe condition of external sulfate attack for concrete.
Table 2 Chemical composition of waters. Elements (Mg/l)
Potable water of natural tap
Seawater
Cl Na Mg SO4 Ca K HCO3 Br B CO3 Sr F pH
240 187 27.8 253 92.7 0.9 143 – – 0 – – 7.60
19367.09 10783.95 1283.27 2712.58 411.09 394.30 107.48 67.14 4.37 17.55 8.21 1.31 6.57
– The attack by the sulfate in gas form. The samples were exposed to the polluted environment of sulfur dioxide (SO2) from a battery charging hall. The samples were similarly immersed in potable water. All waters and the solution used were renewed every 30 days and timing measurements of mass change and the evolution of the sound propagation velocity [17] in concrete were taken every 60 days up to twenty months of exposure. The Dynamic Elastic modulus was measured by the ultrasound testing and is given directly by the apparatus. In this trial period, there was the appearance of degradations in some test samples. 3. Experimental results and discussion 3.1. Potable water immersion test The results of the variation of the mass of the samples for the different concretes are presented in Fig. 1. This figure shows the % of mass variation as a function the exposure period up to 600 days (about 20 Months). The results of samples immersion in potable water show an increase of their masses until the age of 4 months (about 120 days); this increase is mainly due to absorption of water by immersion and the variations are in the range 2.81–4% of the initial mass. Beyond this age, we observed that the samples of all concretes are nearly saturated and the gain of the mass is very small. The results of the evolution of the dynamic elastic modulus of the samples immersed in potable water for the different studied concretes are presented in Fig. 2. Although some variations in measured values were initially observed, beyond the age of 4 months however, the change in the dynamic elastic modulus is low and all measured values remain above 30 GPa for all the studied concretes. 3.2. Seawater immersion test From the chemical analysis of waters, presented in Table 2, it is found that the used sea water is loaded with dissolved salts: chlorides (sodium chloride NaCl, and magnesium chloride MgCl2) and sulfates (magnesium sulfate: MgSO4). According to L. Vicat [5], both magnesium salts (MgSO4 and MgCl2) are the most aggressive for cement. Hence, the attack of concrete by this seawater is the result of more or less simultaneous reactions between sulfates and chlorides and the cement components. The observed variations of the mass of the samples for different concretes, being evaluated, are presented in Fig. 3 (similar to Fig. 1). The results show an increase of the mass of the samples until the age of 4 months. Between the 5th month (150 days) and the 10th month (300 days), some mass reductions were observed for all samples except for the OVC that continued to increase. Beyond one year, we observed that all the samples have a mass gain. Those
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Table 3 Compositions of concretes with various fillers. Components
Concrete type
Sand (kg/m3) Gravel (kg/m3) Cement (kg/m3) Limestone filler: LF (kg/m3) Marble waste: W1 (kg/m3) Marble tile waste: W2 (kg/m3) Gravel tile waste: W3 (kg/m3) Water (kg/m3) Dosage of super-plasticizer (%)
OVC
SCCR
SCCW1
SCCW2
SCCW3
737.9 1119.4 350 – – – – 180.9 0.4
791.3 800.2 350 250 – – – 180.1 1.0
789.7 798.6 350 – 200 – – 175.1 1.2
800.8 809.8 350 – – 200 – 190 1.3
808.7 817.7 350 – – – 150 180.2 1.0
5
OVC
SCCR
SCCW1
SCCW2
SCCW3
% Mass Variaon
4
3
2
1
0
0
100
200
300
400
500
600
Exposure period (days) Fig. 1. Evolution of mass of different concretes samples (Potable water).
50
Dynamic elasc modulus (GPa)
45 40 35 30 25 20
OVC
0
100
SCCR
200
SCCW1
SCCW2
300
400
SCCW3
500
600
Exposure period (days) Fig. 2. Evolution of dynamic elastic modulus of the different concretes (Potable water).
mass gains are greater than those observed for potable water immersion test and their values are in the range of 3% for SCCR to 4.5% for OVC. We also noted that the OVC samples are the most attacked ones by seawater. According to P.-C. Aïtcin [18], the reaction of seawater salts with Portlandite (Ca(OH)2) of the cement results initially in the substitution of Mg2+ by Ca2+ (Eq. (1) and Eq. (2)) for calcium chloride
(CaCl2).This salt reaction with the non-hydrated tricalcium aluminate (C3A), represents a positive modification of the microstructure of the concrete, but it is unstable. In the presence of sulfates, monochloro-aluminates give: C3A3CaSO432H2O and causes swelling, which explains the mass gain of all samples.
MgCl2 þ CaðOHÞ2 ! CaCl2 þ MgðOHÞ2
ð1Þ
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5
OVC
SCCR
SCCW1
SCCW2
SCCW3
% Mass Variation
4
3
2
1
0
0
100
200
300
400
500
600
Exposure period (days) Fig. 3. Evolution of mass of different concretes samples (Seawater).
CaCl2 þ C 3 A þ 10H2 O ! C 3 A CaCl2 10H 2 O
ð2Þ
The results of the evolution of the dynamic elastic modulus of the samples immersed in seawater for the different studied concretes are presented in Fig. 4. We observed that there is a decrease in dynamic elastic modulus of most concretes studied beyond the age of 4 months but up to 20 months of the exposure by seawater, their values remain above 25 GPa.A swelling caused by monochloro-aluminates [18] can explain the mass gain of the samples and the decrease of dynamic elastic modulus for the different concretes.
3.3. Immersion test in a sodium sulfate solution The samples immersed in sodium sulfate solution did present any sign of alteration up to 7th month. Some damage was observed starting from the 8th month on the OVC, SCCW3 and SCCW2 concretes samples (Fig. 5). After immersion for 20 months in a solution of Na2SO4, the OVC samples have been cracked with swelling. These results can be explained by the action of sulfate on the aluminates contained in the paste (cement or cement with industrial waste containing more alumina than limestone filler). The sulfate
reaction results in the formation of ettringite which causes swelling and consequently cracking of the concrete [2,4]. The results of the variation of mass of the samples immersed in a sodium sulfate solution are presented in Fig. 6. Some mass gain was observed for all concretes for the first four months and the changes varies from 2.2% for the SCCW1 to 3% for the SCCW3; this mass gain is due to water absorption by the samples and is smaller than those of the samples immersed in the potable water (Fig. 1) except for the OVC. That is to say that the water absorption for the different concretes is influenced by Na2SO4 solution even before the 4th month. Beyond of 4 months of exposure, we observed that the mass gain becomes more important (Fig. 6) for the samples of OVC and SCCW3 with simultaneous decrease of the dynamic elastic modulus (Fig. 7). For SCCW1 and SCCR, the mass gain and the decrease of dynamic elastic modulus are generally low until 20 months of exposure. From the physical characteristics and grain size analysis of the wastes presented in the previous paper [1], it is clear that the third waste (gravel tiles) which is coarser and with less specific Blaine surface was more sensitive to sulfate attack. These results may also be, in part, explained by the action of sulfate on the aluminates, increasing the amount of C3A in the
50
Dynamic elasc modulus (GPa)
45 40 35 30 25 20
OVC
0
100
SCCR
200
SCCW1
300
SCCW2
400
SCCW3
500
Exposure period (days) Fig. 4. Evolution of dynamic elastic modulus of the different concretes (Seawater).
600
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M. Tennich et al. / Construction and Building Materials 135 (2017) 335–342
SCCR
formed causes swelling in the paste of concrete and therefore cracking of concrete attacked.
OVC
CaðOHÞ2 þ Na2 SO4 þ 2H2 O ! CaSO4 2H 2 O þ 2NaOH
SCCW3
SCCW2
ð3Þ
The ettringite formation may be obtained by two ways: First, from the residual anhydrous C3A reaction with the secondary gypsum formed in Eq. (3) (Eq. (3)) reacts according to the following equation (Eq. (4)):
SCCW1
C 3 A þ 3CaSO4 2H2 O þ 26H2 O ! C 3 A 3CaSO4 32H 2 O
ð4Þ
Or the second way from hydrated aluminates (Eq. (5)):
C 3 A CaSO4 18H2 O þ 2CaðOHÞ2 þ 2SO4 þ 12H2 O ! C 3 A 3CaSO4 32H 2 O
ð5Þ
3.4. Exposure test in battery charging hall Fig. 5. Samples damaged for the concretes OVC, SCCW3 and SCCW2 after immersion for two years in a solution of Na2SO4.
paste (only cement with industrial wastes that contain high amount of aluminates compared to the limestone filler). These results are consistent with the findings of M. Regourd [3] that explains that the sulfate reaction by the formation of ettringite after a secondary gypsum formation (Eq. (3)). This ettringite 12
OVC
SCCR
The gas form a sulfate external attack is under the effect of the propagation of the sulfur dioxide (SO2) in the air after the dissolution of sulfuric acid (H2SO4) in the battery charging hall (Eq. (6)).
1 SO2 ðgÞ þ O2 þ H2 O ! H2 SO4 ¼ HSO4 þ Hþ 2
SCCW1
SCCW2
SCCW3
% Mass Variation
10 8 6 4 2 0
0
100
200
300
400
500
600
Exposure period (days) Fig. 6. Evolution of mass of different concretes samples (Solution of Na2SO4).
Dynamic elastic modulus (GPa)
50
OVC
SCCR
SCCW1
SCCW2
SCCW3
45
40
35
30
25
0
100
200
300
400
500
Exposure period (days) Fig. 7. Evolution of dynamic elastic modulus of the different concretes (Solution of Na2SO4).
600
ð6Þ
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0
Exposure period (days) 0
100
200
300
400
500
600
% Mass Variation
-0,5
-1
-1,5
-2 OVC
SCCR
SCCW1
SCCW2
SCCW3
-2,5 Fig. 8. Evolution of mass of different concretes samples (Battery charging hall).
50 OVC
SCCR
SCCW1
SCCW2
SCCW3
Dynamic elastic modulus (GPa)
45
40
35
30
25
0
100
200
300
400
500
600
Exposure period (days) Fig. 9. Evolution of dynamic elastic modulus of the different concretes (Battery charging hall).
No cracking was noticed for samples studied but we have found alterations in powder form on the samples facets. These alterations are increasing for a year of testing and justify the results of the loss of sample mass for the different studied concretes as presented in Fig. 8. Beyond a year of samples exposure, a mass gain for all types of concretes was noticed. This behavior can be explained by the attack of sulfate inside the samples and not on their external facets. According to I. Mouallif et al. [19], the sulfate reaction results in the formation of secondary ettringite (Eq. (4)) following the formation of secondary gypsum (Eq. (7)). This ettringite causes swelling and hence increase the sample mass under the effect of humidity in the battery charging hall.
CaðOHÞ2 þ H2 SO4 ! CaSO4 2H 2 O
ð7Þ
The results of the variation in samples of dynamic elastic modulus for different concretes studied are presented in Fig. 9. The OVC was found to be the most concrete attacked by dissolving sulfuric acid in the battery charging hall, resulting in the decrease in its dynamic elastic modulus below 25 GPa after 10 months of exposure. Considering the SCCWs, the SCCW1 was noticed to be the most resistant to this external sulfate attack. The dynamic elastic modulus of all SCCWs remained above 25 GPa after 20 months of exposure in the battery charging hall.
4. Conclusion The present research demonstrated the following main findings: – The immersion of concrete samples in a solution of Na2SO4 demonstrated, that the self-compacting concretes (SCCWs) incorporating industrial wastes have sufficient resistance to severe chemical degradation. The observed mass gain for the SCCWs was between 5% and 7% for 20 months of exposure in comparison to the OVC one, which was greater than 10%.Similarly, the dynamic elastic modulus of the SCCWs remained above 25 GPa until 14 months of exposure (for SCCW3) while for the OVC it decreased below 25 GPa after only 8 months of exposure. The SCCW1 samples showed the most resistance to external sulfate attack in liquid form while the OVC samples were completely degraded. – The chemical degradation by sulfate in liquid form appears to be influenced by the amount of aluminates existing in the concrete paste. The SCCWs (incorporating wastes from marbles and tiles factories: W1, W2 and W3), were more attacked by the
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sulfate than the SCCR because these industrials wastes contain higher amount of alumina (Al2O3) than the limestone filler used in the SCCR. – Exposure of concretes samples to external sulfate attack in gas form at a battery charging hall showed that the SCCWs are more resistant than the OVC for attack by sulfur dioxide (SO2) in the air. The decrease of their dynamic moduli of elasticity varies from 15% to 35% for a 20 months exposure period while for OVC; this decrease was 43.8% after only 5 months of exposure in the battery charging hall. – The effect of seawater on the concretes samples was slower than the external sulfate attacks observed from the two other tests (immersion in solution of Na2SO4 and exposure in a battery charging hall). Thus, the concentration level of sulfate in the solution or in the air affects the attack rate and severity of the concretes samples. – Incorporation of industrials wastes fillers from marbles and tiles factories in the formulation of SCC have a positive effect on the durability of SCCWs. By increasing the compactness and reducing the pores interconnection in the SCCWs, they reduce the ions penetration of sulfates that can exist in air, in waters and aggressive soils.
Acknowledgments The authors express their gratitude to the Tunisian SIKA and for the factories of marble and tile COGEMAC and SICAS – Sejoumi – Tunis for their continuous supply of superplasticizer and industrial wastes for the testing for this research. References [1] M. Tennich, A. Kallel, M. Ben Ouezdou, Incorporation of fillers from marble and tile wastes in the composition of self-compacting concretes, Constr. Build. Mater. 91 (2015) 65–70.
[2] R. Gagné, Durabilité et réparations du béton, in: Course guide, GCI-714, Université de Sherbrooke, 2000, pp. 160–185. [3] M. Regourd, Durability, physico-chemical and biological processes related to concrete, Durability of Concrete structures, in: CEB-RILEM International Workshop, Copenhagen, 1983, pp. 49–71. [4] M.R. Khelifa, Effet de l’attaque sulfatique externe sur la durabilité des bétons autoplaçants Thèse de Doctorat, U. de Constantine et U. d’Orléans, 2009. [5] L. Vicat, Recherches sur les causes physiques de destruction des composés hydrauliques par l’eau de mer, Bulletin de la société d’encouragement pour l’industrie nationale, 1857. [6] Y. Senhadji, M. Mouli, H. Khelafi, A.S. Benosman, Sulfate attack of Algerian cement-based material with crushed limestone filler cured at different temperatures, Turk. J. Eng. Environ. Sci. 34 (2010) 131–143. [7] S. Boualleg, M. Bencheikh, Effets des milieux agressifs sur les propriétés des matrices cimentaires, in: INVACO2 Conference, Rabat – Maroc/23–25 Novembre 2011, n°: 4P–079. [8] Kiachehr Behfarnia, Omid Farshadfar, The effects of pozzolanic binders and polypropylene fibers on durability of SCC to magnesium sulfate attack, Constr. Build. Mater. 38 (2013) 64–71. [9] H. Siad, S. Kamali-Bernard, H.A. Mesbah, G. Escadeillas, M. Mouli, H. Khelafi, Characterization of the degradation of self-compacting concretes in sodium sulfate environment: Influence of different mineral admixtures, Constr. Build. Mater. 47 (2013) 1188–1200. [10] R. Deepthy, M.P. Mathews, Durability study of self-compacting concrete using manufactured sand, Int. J. Res. Eng. Technol. 2 (9) (2014) 45–50. [11] S. Boudali, D.E. Kerdal, K. Ayed, B. Abdulsalam, A.M. Soliman, Performance of self-compacting concrete incorporating recycled concrete fines and aggregate exposed to sulfate attack, Constr. Build. Mater. 124 (2016) 705–713. [12] Norme NT 47.30, Ciments – Détermination des résistances mécaniques, INNORPI, 1991. [13] Norme NT 21.30, Granulats – Définitions, conformités, spécifications, INNORPI, 2002. [14] F. De Larrard, T. Sedran, Logiciel Béton lab Pro2, Laboratoire Central des Ponts et Chaussées, Centre de Nantes. [15] EFNARC, The European Guidelines for Self-compacting Concrete: Specification, Production and Use, European Federation for Specialist Construction Chemicals and Concrete Systems, 2005. [16] AFGC, Bétons autoplaçants: Recommandations provisoires, Annales du bâtiment et des travaux publics, 2000. [17] CONTROLS, Instruction manual-auscultation sonique, Rev: 02/01, N°: 58E0049/A, p. 25. [18] P-C. Aïtcin, ‘‘Bétons haute performance”, édition Eyrolles, ISBN 2-212-01323X, 2001. [19] I. Mouallif, S. Lasfar, A. Latrach, M. Chergui and N. Barbe, Influence du vieillissement sulfatique sur la résistance mécanique et la microstructure du béton, in: 21ème Congrès Français de Mécanique, Bordeaux, 2013, pp. 26–30.
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Behavior of self-compacting concrete made with marble and tile wastes exposed to external sulfate attack Mohsen Tennich a,b, Mongi Ben Ouezdou a,⇑, Abderrazek Kallel a,c a
Université de Tunis El Manar, Ecole Nationale d’Ingénieurs de Tunis, LR03ES05 Laboratoire de Génie Civil, 1002 Tunis, Tunisia Direction Générale des Etudes Technologiques, Institut Supérieur des Etudes Technologiques de Radès, BP 172, 2098 Radès Médina, Tunisia c Prince Sattam bin Abdulaziz University, College of Engineering, Civil Engineering Department, BP 655, 11942 Al-Kharj, Saudi Arabia b
h i g h l i g h t s Effect of marbles wastes and tiles factories on the behavior of SCC under external sulfate attack. The behavior of SCC with Waste is evaluated by mass variation and dynamic elastic modulus. The resistance of SCC with Waste to external sulfate attack is better than the ordinary vibrated concrete.
a r t i c l e
i n f o
Article history: Received 3 October 2016 Received in revised form 29 November 2016 Accepted 29 December 2016
Keywords: Self-compacting concrete (SCC) Waste of marble fillers Waste of tiles fillers Durability External sulfate attack
a b s t r a c t The evaluation of the incorporation of industrials wastes from marbles and tiles factories in the formulation of self-compacting concrete (SCC) usually requires the understanding of their effects on the rheological behavior SCC in the fresh state and on the mechanical performances of these concretes in the hardened state. But, for a long-term behavior, it is imperative to study of their influence on the durability of these types of concrete against chemical degradations that may exist through the waters or aggressive soils. In the present work, samples of different types of self-compacting concretes incorporating wastes from marbles, marble tiles and gravel tiles (SCCWs) were exposed to different forms of external sulfate attack. This study compares the behaviors of these samples to those of a reference self-compacting concrete (SCCR) made with limestone filler SCCR and an ordinary vibrated concrete (OVC). The samples of different concretes were immersed in seawater, in a sodium sulfate solution (liquid form of sulfate attack) and potable water chosen as a reference. Other samples of these concretes were also placed in a vehicle battery charging hall to ensure their exposure to gaseous form in sulfate through the release of sulfur dioxide gas in the hall. To evaluate the behavior of the concrete samples against different forms of external sulfate attack, the change in their masses was monitored as well as the determination of their dynamic elastic modulus by the ultrasonic test was performed. Multiple measurements of these properties were taken for each 60 days of exposure and up to twenty months period. The results of the carried out testing showed that SCCWs have good resistance to external sulfate attack, even in severe exposure to the sulfate with sodium sulfate solution, and especially for the self-compacting concrete made with marble waste. Ó 2016 Elsevier Ltd. All rights reserved.
1. Introduction The self-compacting concrete (SCC) is used even in the most complex shapes and can pass through the densest reinforcement without requiring the means of vibration that is to say, it is recommended concrete to use for works of the great projects (buildings, bridges, . . .). The structures of these projects require high mechanical performances and durability of the concrete used. ⇑ Corresponding author. E-mail address: [email protected] (M. Ben Ouezdou). http://dx.doi.org/10.1016/j.conbuildmat.2016.12.193 0950-0618/Ó 2016 Elsevier Ltd. All rights reserved.
The study of incorporation of Tunisian wastes (W1: Waste of marble, W2: Waste of marble tile and W3: Waste of gravel tile) in the SCC, were published in a previous research paper [1]. These wastes were identified and their physical and chemical characteristics were exposed in [1]. Moreover, their particle size distributions and their compactness are given also in the same previous paper. This latter was aimed to the valuation of these industrial wastes dumped in huge quantities in order to find solutions to environmental problems that they pose and also reduce the cost of the cubic meter unit (1 m3) of SCC.
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This valuation requires not only a good formulation of SCC incorporating these industrial wastes (SCCWs) but also to ensure rheological behaviors in fresh state and to obtain sufficient mechanical performances of these SCCWs in the hardened state. To complete this evaluation, we must also consider the longterm durability of these concretes as the exposure to the external sulfate attack, which is the most severe. Indeed, this attack presents a chemical effect on concrete and has negative impacts on its durability. The sulfate ions can have several origins: natural, organic or come from industrial pollution [2–3]. Hence, soils containing gypsum (CaSO42H2O) and hence sulfate, with high concentrations (greater than 5%) can cause degradation of concrete. Similarly clay soils may contain pyrites (FeS2) that oxidize to sulfates in contact with air and moisture to form sulfuric acid (H2SO4). This sulfuric acid strongly attack the concrete slabs that are founded on these soils and causes corrosion and cracking of the slabs and therefore structures stability problems [2]. Furthermore, and as biological origin, the decomposition of organic materials in silos and storage tanks as well as in sanitation sewage can cause the formation of hydrogen sulfide (H2S: very toxic gas). In concretes, anaerobic bacteria convert the sulfate SO2 4 and they produce H2S that is released to the surface. On the surface, the H2S is then decomposed in the form of sulfur by aerobic bacteria. The sulfur is eventually turned into H2SO4, a strong acid and a very corrosive to concrete) [2,3]. Moreover, Chemical industrial pollution, such as battery manufacturing plants for vehicles, may cause the spread in the air of sulfur dioxide (SO2) following the dissolution of sulfuric acid [4]. This gas causes loss of mechanical performance of concrete. In this context, this present study was initiated for a better understanding of the durability of SCCWs incorporating wastes fillers from marbles and tiles factories. The fresh and hardened states properties of these SCCWs were already analyzed in the previous paper [1]. Then, the durability results would be compared to those of a reference of two types of concrete, self-compacting concrete made using limestone filler (SCCR) and ordinary vibrated concrete (OVC). Since the mid 19th century, L. Vicat [5] studied the chemical deterioration of the OVC caused by the presence of sulfate ions in the seawater. He showed that the MgCl2 and MgSO4 magnesium salts are the most aggressive for concrete. Many other studies have been made on the durability of OVC. For SCC which differs from OVC by the existence of some types of additions increasing its volume of paste to ensure its fluidity at fresh state, there are several studies of the durability of this concrete under the effect of external sulfate attack. M.R. Khelifa [4] has studied the durability of concrete exposed of the external sulfate attack. The SCC samples were immersed in a solution dosed with 5% Na2SO4 and subject for six months to a full immersion or different cycles of immersion/drying. The author observed that sample’s degradation by external sulfate attack depends on the type of cement used and also Water/Cement ratio. The experimental results also showed that the damage was more pronounced in the case of immersion/drying cycles than for full immersion of the samples. Y. Senhadji et al. [6] studied the sulfate attack of samples of which the cement is partially substituted by proportions of limestone filler between 10% and 30%. The test results showed that the samples that have highest replacement levels of limestone filler were more susceptible to sulfate attack. S. Boualleg and M. Bencheikh [7] have exposed test samples of paste or mortar cement (pouzzolannique or limestone) to chemical treatments, namely, ammonium nitrate, magnesium sulfate, sodium sulfate, sodium chloride and sulfuric acid for a period of three months. They found that the durability performance of pastes and mortars with pozzolan cement were better than those prepared with limestone.
K. Behfarnia and O. Farshadfar [8] studied the effects of various pozzolanic binders such as fumed silica, zeolite and metakaoline on SCC’s durability in a magnesium sulfate environment. The results of their tests showed that SCCs with metakaoline and zeolite are more durable than those with silica fume. H. Siad et al. [9] studied the effects of mineral additives (limestone filler, fly ash and natural pozzolan) on the behavior of SCCs immersed in a sodium sulfate solution. According to their findings, natural pozzolan is the most beneficial additive for an SCC in a rich sodium sulfate environment. R. Deepthy and M P. Mathews [10] studied the durability of SCC based fly ash as an additive through the immersion of samples in solutions with different proportions of sulfate ions and chloride. The experimental results show that the compressive strengths of immersed samples decreases with increasing concentration of sulfate and chloride solutions. Similarly, there are weight losses of these samples and they’re proportional to the duration of exposure. Recently, Boudali S. et al. [11] have studied the attack of sulfate of the mixtures incorporating recycled concrete aggregates and fines; their results show that they have a better behavior for sulfate attack than those with natural aggregates and natural pozzolana. In this paper, three different forms of external sulfate attacks testing of concretes samples prepared in advance were realized. The first type of these tests was to immerse the samples in seawater, while for the second type, the samples were immersed in a sodium sulfate solution (5% Na2SO4), and for the third type, the samples were exposed to the polluted environment of sulfur dioxide (SO2) from a battery charging hall. The evaluation of the behavior of SCCWs exposure to external sulfate attack is monitored through tracking the change in mass of the samples and the change in the dynamic elastic modulus determined by the ultrasonic test. Parallel to these external sulfate attack tests, a reference test was also completed by immersing the same types of samples in potable water at a temperature 20 ± 2 °C to facilitate the interpretation of results. 2. Experimental procedures 2.1. Materials The major materials that were used in this research are: – A Portland cement CEM I 42.5 produced by the factory CAT – Jebel Jeloud in Tunis according to standard NT47.30 [12]. – A gravel provided by the crushing quarry of Jebel Ressas in Tunis with a maximum nominal size 16 mm and alluvial silica sand from a the quarry Borj Hfaiedh with a maximum size of 4 mm. These concretes aggregates characteristics are defined in the standard NT 21.30 [13] and their specifications are the same as in the previous paper [1]. – The additives used are: The limestone filler (LF) produced by the group ‘‘Omya” that is chosen to make the control or Reference Self-Compacting Concrete (SCCR). The industrial wastes fillers provided by two Tunisian factories of marble and tiles. These are classed of three types (W1: Waste of marble, W2: Waste of marble tile and W3: Waste of gravel tile). Their chemical characteristics are presented in Table 1. – A superplasticizer, high water reducer polyvalent (SIKA VISCOCRETE TEMPO 12).
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M. Tennich et al. / Construction and Building Materials 135 (2017) 335–342 Table 1 Chemical composition of fillers. Filler
LF (Limestone)
W1 (Marble)
W2 (Marble tile)
W3 (Gravel tile)
Calcium oxide (lime): CaO (%) Aluminum oxide (alumina): Al2O3 (%) Iron oxide: Fe2O3 (%) Silicon dioxide (silica): SiO2 (%) Magnesium oxide: MgO (%) Sulfur trioxide: SO3 (%) Potassium oxide: K2O (%)
55.44 0.02 0.01 1.09 0.38 0.07 0.02
49.46 0.46 0.66 7.36 0.23 0.08 0.11
47.09 0.58 0.06 3.78 4.62 0.41 0.09
53.08 0.66 0.10 4.28 0.10 0.29 0.08
The values in bold is to show the importance of the % of the Aluminium oxide present in W1, W2, and W3 and their effect under the sulfate attack.
– The waters used are potable water, chosen as a reference to assist in interpreting sample behaviors for the other tests, the distilled water used to prepare the sodium sulfate solution (5% Na2SO4, 10H2O) and the seawater (from Tunis). Their chemical characteristics are summarized in Table 2. 2.2. Mixture proportions Three types of self-compacting concrete (SCCW) incorporating one of the three industrial wastes (W1, W2 and W3) were prepared for evaluation their resistance to external sulfate attack. The durability of these SCCWs was compared to a reference self-compacting concrete made using limestone filler (SCCR) and a reference ordinary vibrated concrete (OVC). The formulation of these concretes is realized by using ‘‘Concrete Lab Pro2” software and adjustment by tests in the fresh state [1,14]. The five optimized compositions chosen are presented in Table 3 that have characteristics within standard EFNARC [15] and are in good agreement with the values given by the French Association of Civil Engineering AFGC [16]. 2.3. Samples The samples used in this research are of cubic shape (70 70 70 mm), obtained after sawing prismatic specimens (70 70 280 mm). Before sawing, these specimens were manufactured and cured in water maintained at 20 ± 2 °C for 28 days. After sawing, the samples were dried at a temperature of 60 °C. 2.4. Exposure and testing For each exposure test, three samples were prepared for each type of concrete and exposed to external sulfate attack. The following types of tests were performed: – The attack by sulfate in liquid form. The samples were immersed in seawater and in the sodium sulfate solution (5% Na2SO4, 10H2O) which is considered as a severe condition of external sulfate attack for concrete.
Table 2 Chemical composition of waters. Elements (Mg/l)
Potable water of natural tap
Seawater
Cl Na Mg SO4 Ca K HCO3 Br B CO3 Sr F pH
240 187 27.8 253 92.7 0.9 143 – – 0 – – 7.60
19367.09 10783.95 1283.27 2712.58 411.09 394.30 107.48 67.14 4.37 17.55 8.21 1.31 6.57
– The attack by the sulfate in gas form. The samples were exposed to the polluted environment of sulfur dioxide (SO2) from a battery charging hall. The samples were similarly immersed in potable water. All waters and the solution used were renewed every 30 days and timing measurements of mass change and the evolution of the sound propagation velocity [17] in concrete were taken every 60 days up to twenty months of exposure. The Dynamic Elastic modulus was measured by the ultrasound testing and is given directly by the apparatus. In this trial period, there was the appearance of degradations in some test samples. 3. Experimental results and discussion 3.1. Potable water immersion test The results of the variation of the mass of the samples for the different concretes are presented in Fig. 1. This figure shows the % of mass variation as a function the exposure period up to 600 days (about 20 Months). The results of samples immersion in potable water show an increase of their masses until the age of 4 months (about 120 days); this increase is mainly due to absorption of water by immersion and the variations are in the range 2.81–4% of the initial mass. Beyond this age, we observed that the samples of all concretes are nearly saturated and the gain of the mass is very small. The results of the evolution of the dynamic elastic modulus of the samples immersed in potable water for the different studied concretes are presented in Fig. 2. Although some variations in measured values were initially observed, beyond the age of 4 months however, the change in the dynamic elastic modulus is low and all measured values remain above 30 GPa for all the studied concretes. 3.2. Seawater immersion test From the chemical analysis of waters, presented in Table 2, it is found that the used sea water is loaded with dissolved salts: chlorides (sodium chloride NaCl, and magnesium chloride MgCl2) and sulfates (magnesium sulfate: MgSO4). According to L. Vicat [5], both magnesium salts (MgSO4 and MgCl2) are the most aggressive for cement. Hence, the attack of concrete by this seawater is the result of more or less simultaneous reactions between sulfates and chlorides and the cement components. The observed variations of the mass of the samples for different concretes, being evaluated, are presented in Fig. 3 (similar to Fig. 1). The results show an increase of the mass of the samples until the age of 4 months. Between the 5th month (150 days) and the 10th month (300 days), some mass reductions were observed for all samples except for the OVC that continued to increase. Beyond one year, we observed that all the samples have a mass gain. Those
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Table 3 Compositions of concretes with various fillers. Components
Concrete type
Sand (kg/m3) Gravel (kg/m3) Cement (kg/m3) Limestone filler: LF (kg/m3) Marble waste: W1 (kg/m3) Marble tile waste: W2 (kg/m3) Gravel tile waste: W3 (kg/m3) Water (kg/m3) Dosage of super-plasticizer (%)
OVC
SCCR
SCCW1
SCCW2
SCCW3
737.9 1119.4 350 – – – – 180.9 0.4
791.3 800.2 350 250 – – – 180.1 1.0
789.7 798.6 350 – 200 – – 175.1 1.2
800.8 809.8 350 – – 200 – 190 1.3
808.7 817.7 350 – – – 150 180.2 1.0
5
OVC
SCCR
SCCW1
SCCW2
SCCW3
% Mass Variaon
4
3
2
1
0
0
100
200
300
400
500
600
Exposure period (days) Fig. 1. Evolution of mass of different concretes samples (Potable water).
50
Dynamic elasc modulus (GPa)
45 40 35 30 25 20
OVC
0
100
SCCR
200
SCCW1
SCCW2
300
400
SCCW3
500
600
Exposure period (days) Fig. 2. Evolution of dynamic elastic modulus of the different concretes (Potable water).
mass gains are greater than those observed for potable water immersion test and their values are in the range of 3% for SCCR to 4.5% for OVC. We also noted that the OVC samples are the most attacked ones by seawater. According to P.-C. Aïtcin [18], the reaction of seawater salts with Portlandite (Ca(OH)2) of the cement results initially in the substitution of Mg2+ by Ca2+ (Eq. (1) and Eq. (2)) for calcium chloride
(CaCl2).This salt reaction with the non-hydrated tricalcium aluminate (C3A), represents a positive modification of the microstructure of the concrete, but it is unstable. In the presence of sulfates, monochloro-aluminates give: C3A3CaSO432H2O and causes swelling, which explains the mass gain of all samples.
MgCl2 þ CaðOHÞ2 ! CaCl2 þ MgðOHÞ2
ð1Þ
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5
OVC
SCCR
SCCW1
SCCW2
SCCW3
% Mass Variation
4
3
2
1
0
0
100
200
300
400
500
600
Exposure period (days) Fig. 3. Evolution of mass of different concretes samples (Seawater).
CaCl2 þ C 3 A þ 10H2 O ! C 3 A CaCl2 10H 2 O
ð2Þ
The results of the evolution of the dynamic elastic modulus of the samples immersed in seawater for the different studied concretes are presented in Fig. 4. We observed that there is a decrease in dynamic elastic modulus of most concretes studied beyond the age of 4 months but up to 20 months of the exposure by seawater, their values remain above 25 GPa.A swelling caused by monochloro-aluminates [18] can explain the mass gain of the samples and the decrease of dynamic elastic modulus for the different concretes.
3.3. Immersion test in a sodium sulfate solution The samples immersed in sodium sulfate solution did present any sign of alteration up to 7th month. Some damage was observed starting from the 8th month on the OVC, SCCW3 and SCCW2 concretes samples (Fig. 5). After immersion for 20 months in a solution of Na2SO4, the OVC samples have been cracked with swelling. These results can be explained by the action of sulfate on the aluminates contained in the paste (cement or cement with industrial waste containing more alumina than limestone filler). The sulfate
reaction results in the formation of ettringite which causes swelling and consequently cracking of the concrete [2,4]. The results of the variation of mass of the samples immersed in a sodium sulfate solution are presented in Fig. 6. Some mass gain was observed for all concretes for the first four months and the changes varies from 2.2% for the SCCW1 to 3% for the SCCW3; this mass gain is due to water absorption by the samples and is smaller than those of the samples immersed in the potable water (Fig. 1) except for the OVC. That is to say that the water absorption for the different concretes is influenced by Na2SO4 solution even before the 4th month. Beyond of 4 months of exposure, we observed that the mass gain becomes more important (Fig. 6) for the samples of OVC and SCCW3 with simultaneous decrease of the dynamic elastic modulus (Fig. 7). For SCCW1 and SCCR, the mass gain and the decrease of dynamic elastic modulus are generally low until 20 months of exposure. From the physical characteristics and grain size analysis of the wastes presented in the previous paper [1], it is clear that the third waste (gravel tiles) which is coarser and with less specific Blaine surface was more sensitive to sulfate attack. These results may also be, in part, explained by the action of sulfate on the aluminates, increasing the amount of C3A in the
50
Dynamic elasc modulus (GPa)
45 40 35 30 25 20
OVC
0
100
SCCR
200
SCCW1
300
SCCW2
400
SCCW3
500
Exposure period (days) Fig. 4. Evolution of dynamic elastic modulus of the different concretes (Seawater).
600
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SCCR
formed causes swelling in the paste of concrete and therefore cracking of concrete attacked.
OVC
CaðOHÞ2 þ Na2 SO4 þ 2H2 O ! CaSO4 2H 2 O þ 2NaOH
SCCW3
SCCW2
ð3Þ
The ettringite formation may be obtained by two ways: First, from the residual anhydrous C3A reaction with the secondary gypsum formed in Eq. (3) (Eq. (3)) reacts according to the following equation (Eq. (4)):
SCCW1
C 3 A þ 3CaSO4 2H2 O þ 26H2 O ! C 3 A 3CaSO4 32H 2 O
ð4Þ
Or the second way from hydrated aluminates (Eq. (5)):
C 3 A CaSO4 18H2 O þ 2CaðOHÞ2 þ 2SO4 þ 12H2 O ! C 3 A 3CaSO4 32H 2 O
ð5Þ
3.4. Exposure test in battery charging hall Fig. 5. Samples damaged for the concretes OVC, SCCW3 and SCCW2 after immersion for two years in a solution of Na2SO4.
paste (only cement with industrial wastes that contain high amount of aluminates compared to the limestone filler). These results are consistent with the findings of M. Regourd [3] that explains that the sulfate reaction by the formation of ettringite after a secondary gypsum formation (Eq. (3)). This ettringite 12
OVC
SCCR
The gas form a sulfate external attack is under the effect of the propagation of the sulfur dioxide (SO2) in the air after the dissolution of sulfuric acid (H2SO4) in the battery charging hall (Eq. (6)).
1 SO2 ðgÞ þ O2 þ H2 O ! H2 SO4 ¼ HSO4 þ Hþ 2
SCCW1
SCCW2
SCCW3
% Mass Variation
10 8 6 4 2 0
0
100
200
300
400
500
600
Exposure period (days) Fig. 6. Evolution of mass of different concretes samples (Solution of Na2SO4).
Dynamic elastic modulus (GPa)
50
OVC
SCCR
SCCW1
SCCW2
SCCW3
45
40
35
30
25
0
100
200
300
400
500
Exposure period (days) Fig. 7. Evolution of dynamic elastic modulus of the different concretes (Solution of Na2SO4).
600
ð6Þ
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0
Exposure period (days) 0
100
200
300
400
500
600
% Mass Variation
-0,5
-1
-1,5
-2 OVC
SCCR
SCCW1
SCCW2
SCCW3
-2,5 Fig. 8. Evolution of mass of different concretes samples (Battery charging hall).
50 OVC
SCCR
SCCW1
SCCW2
SCCW3
Dynamic elastic modulus (GPa)
45
40
35
30
25
0
100
200
300
400
500
600
Exposure period (days) Fig. 9. Evolution of dynamic elastic modulus of the different concretes (Battery charging hall).
No cracking was noticed for samples studied but we have found alterations in powder form on the samples facets. These alterations are increasing for a year of testing and justify the results of the loss of sample mass for the different studied concretes as presented in Fig. 8. Beyond a year of samples exposure, a mass gain for all types of concretes was noticed. This behavior can be explained by the attack of sulfate inside the samples and not on their external facets. According to I. Mouallif et al. [19], the sulfate reaction results in the formation of secondary ettringite (Eq. (4)) following the formation of secondary gypsum (Eq. (7)). This ettringite causes swelling and hence increase the sample mass under the effect of humidity in the battery charging hall.
CaðOHÞ2 þ H2 SO4 ! CaSO4 2H 2 O
ð7Þ
The results of the variation in samples of dynamic elastic modulus for different concretes studied are presented in Fig. 9. The OVC was found to be the most concrete attacked by dissolving sulfuric acid in the battery charging hall, resulting in the decrease in its dynamic elastic modulus below 25 GPa after 10 months of exposure. Considering the SCCWs, the SCCW1 was noticed to be the most resistant to this external sulfate attack. The dynamic elastic modulus of all SCCWs remained above 25 GPa after 20 months of exposure in the battery charging hall.
4. Conclusion The present research demonstrated the following main findings: – The immersion of concrete samples in a solution of Na2SO4 demonstrated, that the self-compacting concretes (SCCWs) incorporating industrial wastes have sufficient resistance to severe chemical degradation. The observed mass gain for the SCCWs was between 5% and 7% for 20 months of exposure in comparison to the OVC one, which was greater than 10%.Similarly, the dynamic elastic modulus of the SCCWs remained above 25 GPa until 14 months of exposure (for SCCW3) while for the OVC it decreased below 25 GPa after only 8 months of exposure. The SCCW1 samples showed the most resistance to external sulfate attack in liquid form while the OVC samples were completely degraded. – The chemical degradation by sulfate in liquid form appears to be influenced by the amount of aluminates existing in the concrete paste. The SCCWs (incorporating wastes from marbles and tiles factories: W1, W2 and W3), were more attacked by the
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sulfate than the SCCR because these industrials wastes contain higher amount of alumina (Al2O3) than the limestone filler used in the SCCR. – Exposure of concretes samples to external sulfate attack in gas form at a battery charging hall showed that the SCCWs are more resistant than the OVC for attack by sulfur dioxide (SO2) in the air. The decrease of their dynamic moduli of elasticity varies from 15% to 35% for a 20 months exposure period while for OVC; this decrease was 43.8% after only 5 months of exposure in the battery charging hall. – The effect of seawater on the concretes samples was slower than the external sulfate attacks observed from the two other tests (immersion in solution of Na2SO4 and exposure in a battery charging hall). Thus, the concentration level of sulfate in the solution or in the air affects the attack rate and severity of the concretes samples. – Incorporation of industrials wastes fillers from marbles and tiles factories in the formulation of SCC have a positive effect on the durability of SCCWs. By increasing the compactness and reducing the pores interconnection in the SCCWs, they reduce the ions penetration of sulfates that can exist in air, in waters and aggressive soils.
Acknowledgments The authors express their gratitude to the Tunisian SIKA and for the factories of marble and tile COGEMAC and SICAS – Sejoumi – Tunis for their continuous supply of superplasticizer and industrial wastes for the testing for this research. References [1] M. Tennich, A. Kallel, M. Ben Ouezdou, Incorporation of fillers from marble and tile wastes in the composition of self-compacting concretes, Constr. Build. Mater. 91 (2015) 65–70.
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