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Concrete deterioration due to sulphate- A case study
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 5 (2018) 17952–17957
www.materialstoday.com/proceedings
ICMPC_2018
Concrete deterioration due to sulphate- A case study Apoorv Choudharyb*, Milind Malikb*, Sachin Tiwaria*,Ankur dubeya ,Urvashi Sharmaa, Ajay Kumara* a
School of Engineering, Gautam Buddha University, Greater Noida 201312, India Department of Civil Engineering, Northern India Engineering College, New Delhi,India
b
Abstract Chemical ions present in the concrete ingredients are major cause of deterioration of the concrete structures, which are in contact of water. Ions like sulphate and chloride present in concrete ingredients or in water causes efflorescence, leaching, corrosion of reinforcement and spalling of concrete. In this paper a case study from Greater Noida region, where a concrete surface near a water tank shown deposition of very fine white crystalline material. Concrete specimens, water from the tank and white crystalline material collected from the different places. The complete water quality analysis was carried out on water samples. XRay Diffraction (XRD) and Scanning Electron Microscope (SEM) tests performed on the concrete and white crystalline samples. X-Ray Diffraction analysis shows that the white crystalline material is sodium sulphate crystallised as thenardite and mirablite crystals. The concrete specimens showed, apart from C-S-H, calcite, and portlandite, ettringite formation was there in the concrete samples by analyzing with the XRD and SEM, which was the major cause of spalling at the site. © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of Materials Processing and characterization. Keywords:Sulphate; Chloride; Mirabilite; Thenardite; Scanning electron microscopy; X-Ray Diffraction
1. Introduction Concrete is the most durable material which are using for structures due to higher compressive strength. Many damages are present in the concrete such as physical, mechanical and chemical damages which causes cracks in the concrete. Chemical damages like pH, sulphate, chloride and exposure condition etc more affects the service life of concrete. Mortar and concrete crumble due to crystallization of soluble salts which are present in porous construction materials [3, 5]. Sodium and chloride soluble salts are present in the soil, aggregates and water which penetrate into concrete during time. * Corresponding author. E-mail address: [email protected]
2214-7853 © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of Materials Processing and characterization.
Sachin Tiwari et al./Materials Today: Proceedings 5 (2018) 17952–17957
17953
Concrete structures damages by sulphate crystals such as thenardite (Na2SO4) and mirabilite (Na2SO4•10H2O) is mainly damaging porous crystals [1, 2, 4, 7]. Three universal dynamic pathways which is the cause of salt crystallization and it is rapid cooling (for porous salts with a divergence in soluble with temperature), rapid drying, and contact between pre-survive finer salts and saturated salt solutions, which is mainly thenardite [6] 1.1 Selection of Tested Area These locations are selected as reinforcement in exposed condition due to spalling of cover or improper mix proportion used. There was seen white efflorescence at chatrapati shahuji hostel water tank slab and water tank walls. Visual cracks were also seen in water tank side walls. Cooling tower platform columns area was badly affected due to water, ingress of chloride so the reinforcement bars were in exposed condition and badly affected due to corrosion. 2. Materials and Methods Materials used in this study: 2.1 XRD sample preparation X –Ray Diffraction patterns of concrete specimens from selected areas obtained on a powder XRD model GBC Emma with CuKα1 radiation (1.54 A0) having a scanning speed of 4°/minute and geometry was used as theta, and two theta. White crystalline sample did not need to preparation of sample because already in a pure crystalline form. Concrete sample passed through 100 micron sieve, prepared by grinding in a mortar and pestle. The sample placed into the sample holder and fixed it with glass slide. It is important that the top of the sample be coplanar with the top of the sample holder. Switch on the GBC machine and chiller. Placed this sample holder into x-ray goniometer as shown in Fig 1 and the angle of x-rays kept fixed 5-80º and name the sample number. Press on x-ray beam button. XRD graph made in between counts and two-theta by using traces software.
Fig.1.Prepared sample holder for testing and X-ray Goniometer
2.2 SEM sample preparation Three samples were taken for the testing. Concrete sample passed through 100 micron sieve, prepared by grinding in a mortar and pestle and white crystalline sample was already as in crystal form so there was no need of grinding. Samples were coated with the thin layer of conducting material such as gold and clicked a various images of the three samples on different magnification and resolution to identify crystalline structures and chemical analysis. 2.3 Water sample 1 litre water sample was taken from three different places of the site to check the pH, conductivity, chloride and sulphate of the water for seeing the effect on concrete structures.
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Sachin Tiwari et al./ Materials Today: Proceedings 5 (2018) 17952–17957
3. Results and Discussion 3.1 XRD and SEM Results
100% of silicon oxide quartz cement minerals are present in the CSH concrete sample which are determined by XRD testing. SEM analysis of the samples has been done at various magnification and resolution. CSH gel, calcite and portlandite are present in the sample as shown in Fig. 2 (a-d). a
b
c
d
Fig. 2. X-ray Diffractogram and SEM analysis of CSH concrete sample
78.9% of silicon oxide quartz and 13.5% of calcium carbonate cement minerals which do not affect the concrete quality. 7.6% of sodium aluminium sulphate hydrates alum which accelerates the sulphate attack on concrete. Due to excessive sulphate content is present which causes, ettringite formation in the sample collected from the coolant tower platform column. C-S-H, calcite, portlandite and ettringite crystals are present in this sample which is determined by SEM testing as shown in Fig. 3 (a-d).
Sachin Tiwari et al./Materials Today: Proceedings 5 (2018) 17952–17957
a
c
17955
b
d
Fig. 3.X-ray Diffractogram and SEM analysis of coolant tower platform concrete sample
47.8% of sodium aluminium silicate, 35.6% of sodium sulphate thenardite and 15.6% of sodium sulphate hydrate mirabilite are present in crystalline sample collected from the coolant building which is determined by XRD testing. It can be concluded that all the minerals are having sulphate content which reduces the water content and increases the volume of pores of concrete. SEM testing performs on this sample & thenardite, mirabilite, sodium aluminium silicate crystals and C-S-H gel are present in the samples as shown in Fig.4 (a-d).
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Sachin Tiwari et al./ Materials Today: Proceedings 5 (2018) 17952–17957
a b
c
d
Fig. 4.X-ray Diffractogram and SEM analysis of white crystalline sample
4. Conclusion This work is based on the evaluation and monitoring of concrete samples as a case study by using SEM and XRD.. Following are the conclusions as given below: 1.
2.
There are many crystal phases of cement and sulphate present in the concrete samples. Cement mineral present in the CSH concrete sample which shows that concrete is in good condition. Ettringite phase is present in Coolant tower platform column sample which destroys the C-S-H paste. Concrete will spall in this location continuously due to it and it will damage the structure. Sodium sulphate minerals such as thenardite, mirabilite and aluminium silicate are present in crystalline sample collected from the coolant building. Thenardite (Na2SO4) and mirabilite (Na2SO4.10H2O) come from a saturated sodium sulphate which is present in crystal form on the concrete surface. Thenardite and mirabilite generates high crystallization pressure in concrete pores which are greater damage to porous materials and concrete starts spall..
Sachin Tiwari et al./Materials Today: Proceedings 5 (2018) 17952–17957
17957
Acknowledgments The project is supported by the Gautam Buddha University. References [1]. Charola, A.E. & Weber, J., The hydration-dehydration mechanism of sodium sulphate. In: J.D. Rodrigues, F. Henriques and F.T. Jeremisas (Editors), 7th International Congress on Deterioration and Conservation of Stone, Lisbon Portugal, 1992, Laboratorio Nacionalde Engenharia Civil, Lisbon, Portugal, pp. 581-590. [2]. Doehne, E., In situ dynamics of sodium sulfate hydration and dehydration in stone pores: observations at high magnification using the environmental scanning electron microscope, III International symposium on the conservation of monuments in the Mediterranean basin Venice. 22·1.5 june 1994. [3]. Goudie A.S., Viles H., Salt Weathering Hazards, Wiley, Chichester, 1997. [4]. Grossi, C.M., Esbert, R.M. et al., Acoustic emission monitoring to study sodium sulphate crystallization in monumental porous carbonatestones. Stud. Conserv., 42, 1997, pp. 115-25. [5]. Novak G.A., Colville A.A., Efflorescent minerals assemblages associated with cracked and degraded residential concrete foundations in [6]. Rodriguez-Navarro, C. and Doehne, E. Salt weathering: influence of evaporation rate, supersaturation and crystallization pattern. Earth Surf. Process. Landforms, 24 1999 191–209. [7]. Rodriguez-Navarro, C., Doehne, E. et al., How does sodium sulfate crystallize? Implications for the decay and testing of building materials. Cement and concrete research, 2000, pp. 1527-1534.
ScienceDirect Materials Today: Proceedings 5 (2018) 17952–17957
www.materialstoday.com/proceedings
ICMPC_2018
Concrete deterioration due to sulphate- A case study Apoorv Choudharyb*, Milind Malikb*, Sachin Tiwaria*,Ankur dubeya ,Urvashi Sharmaa, Ajay Kumara* a
School of Engineering, Gautam Buddha University, Greater Noida 201312, India Department of Civil Engineering, Northern India Engineering College, New Delhi,India
b
Abstract Chemical ions present in the concrete ingredients are major cause of deterioration of the concrete structures, which are in contact of water. Ions like sulphate and chloride present in concrete ingredients or in water causes efflorescence, leaching, corrosion of reinforcement and spalling of concrete. In this paper a case study from Greater Noida region, where a concrete surface near a water tank shown deposition of very fine white crystalline material. Concrete specimens, water from the tank and white crystalline material collected from the different places. The complete water quality analysis was carried out on water samples. XRay Diffraction (XRD) and Scanning Electron Microscope (SEM) tests performed on the concrete and white crystalline samples. X-Ray Diffraction analysis shows that the white crystalline material is sodium sulphate crystallised as thenardite and mirablite crystals. The concrete specimens showed, apart from C-S-H, calcite, and portlandite, ettringite formation was there in the concrete samples by analyzing with the XRD and SEM, which was the major cause of spalling at the site. © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of Materials Processing and characterization. Keywords:Sulphate; Chloride; Mirabilite; Thenardite; Scanning electron microscopy; X-Ray Diffraction
1. Introduction Concrete is the most durable material which are using for structures due to higher compressive strength. Many damages are present in the concrete such as physical, mechanical and chemical damages which causes cracks in the concrete. Chemical damages like pH, sulphate, chloride and exposure condition etc more affects the service life of concrete. Mortar and concrete crumble due to crystallization of soluble salts which are present in porous construction materials [3, 5]. Sodium and chloride soluble salts are present in the soil, aggregates and water which penetrate into concrete during time. * Corresponding author. E-mail address: [email protected]
2214-7853 © 2018 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of Materials Processing and characterization.
Sachin Tiwari et al./Materials Today: Proceedings 5 (2018) 17952–17957
17953
Concrete structures damages by sulphate crystals such as thenardite (Na2SO4) and mirabilite (Na2SO4•10H2O) is mainly damaging porous crystals [1, 2, 4, 7]. Three universal dynamic pathways which is the cause of salt crystallization and it is rapid cooling (for porous salts with a divergence in soluble with temperature), rapid drying, and contact between pre-survive finer salts and saturated salt solutions, which is mainly thenardite [6] 1.1 Selection of Tested Area These locations are selected as reinforcement in exposed condition due to spalling of cover or improper mix proportion used. There was seen white efflorescence at chatrapati shahuji hostel water tank slab and water tank walls. Visual cracks were also seen in water tank side walls. Cooling tower platform columns area was badly affected due to water, ingress of chloride so the reinforcement bars were in exposed condition and badly affected due to corrosion. 2. Materials and Methods Materials used in this study: 2.1 XRD sample preparation X –Ray Diffraction patterns of concrete specimens from selected areas obtained on a powder XRD model GBC Emma with CuKα1 radiation (1.54 A0) having a scanning speed of 4°/minute and geometry was used as theta, and two theta. White crystalline sample did not need to preparation of sample because already in a pure crystalline form. Concrete sample passed through 100 micron sieve, prepared by grinding in a mortar and pestle. The sample placed into the sample holder and fixed it with glass slide. It is important that the top of the sample be coplanar with the top of the sample holder. Switch on the GBC machine and chiller. Placed this sample holder into x-ray goniometer as shown in Fig 1 and the angle of x-rays kept fixed 5-80º and name the sample number. Press on x-ray beam button. XRD graph made in between counts and two-theta by using traces software.
Fig.1.Prepared sample holder for testing and X-ray Goniometer
2.2 SEM sample preparation Three samples were taken for the testing. Concrete sample passed through 100 micron sieve, prepared by grinding in a mortar and pestle and white crystalline sample was already as in crystal form so there was no need of grinding. Samples were coated with the thin layer of conducting material such as gold and clicked a various images of the three samples on different magnification and resolution to identify crystalline structures and chemical analysis. 2.3 Water sample 1 litre water sample was taken from three different places of the site to check the pH, conductivity, chloride and sulphate of the water for seeing the effect on concrete structures.
17954
Sachin Tiwari et al./ Materials Today: Proceedings 5 (2018) 17952–17957
3. Results and Discussion 3.1 XRD and SEM Results
100% of silicon oxide quartz cement minerals are present in the CSH concrete sample which are determined by XRD testing. SEM analysis of the samples has been done at various magnification and resolution. CSH gel, calcite and portlandite are present in the sample as shown in Fig. 2 (a-d). a
b
c
d
Fig. 2. X-ray Diffractogram and SEM analysis of CSH concrete sample
78.9% of silicon oxide quartz and 13.5% of calcium carbonate cement minerals which do not affect the concrete quality. 7.6% of sodium aluminium sulphate hydrates alum which accelerates the sulphate attack on concrete. Due to excessive sulphate content is present which causes, ettringite formation in the sample collected from the coolant tower platform column. C-S-H, calcite, portlandite and ettringite crystals are present in this sample which is determined by SEM testing as shown in Fig. 3 (a-d).
Sachin Tiwari et al./Materials Today: Proceedings 5 (2018) 17952–17957
a
c
17955
b
d
Fig. 3.X-ray Diffractogram and SEM analysis of coolant tower platform concrete sample
47.8% of sodium aluminium silicate, 35.6% of sodium sulphate thenardite and 15.6% of sodium sulphate hydrate mirabilite are present in crystalline sample collected from the coolant building which is determined by XRD testing. It can be concluded that all the minerals are having sulphate content which reduces the water content and increases the volume of pores of concrete. SEM testing performs on this sample & thenardite, mirabilite, sodium aluminium silicate crystals and C-S-H gel are present in the samples as shown in Fig.4 (a-d).
17956
Sachin Tiwari et al./ Materials Today: Proceedings 5 (2018) 17952–17957
a b
c
d
Fig. 4.X-ray Diffractogram and SEM analysis of white crystalline sample
4. Conclusion This work is based on the evaluation and monitoring of concrete samples as a case study by using SEM and XRD.. Following are the conclusions as given below: 1.
2.
There are many crystal phases of cement and sulphate present in the concrete samples. Cement mineral present in the CSH concrete sample which shows that concrete is in good condition. Ettringite phase is present in Coolant tower platform column sample which destroys the C-S-H paste. Concrete will spall in this location continuously due to it and it will damage the structure. Sodium sulphate minerals such as thenardite, mirabilite and aluminium silicate are present in crystalline sample collected from the coolant building. Thenardite (Na2SO4) and mirabilite (Na2SO4.10H2O) come from a saturated sodium sulphate which is present in crystal form on the concrete surface. Thenardite and mirabilite generates high crystallization pressure in concrete pores which are greater damage to porous materials and concrete starts spall..
Sachin Tiwari et al./Materials Today: Proceedings 5 (2018) 17952–17957
17957
Acknowledgments The project is supported by the Gautam Buddha University. References [1]. Charola, A.E. & Weber, J., The hydration-dehydration mechanism of sodium sulphate. In: J.D. Rodrigues, F. Henriques and F.T. Jeremisas (Editors), 7th International Congress on Deterioration and Conservation of Stone, Lisbon Portugal, 1992, Laboratorio Nacionalde Engenharia Civil, Lisbon, Portugal, pp. 581-590. [2]. Doehne, E., In situ dynamics of sodium sulfate hydration and dehydration in stone pores: observations at high magnification using the environmental scanning electron microscope, III International symposium on the conservation of monuments in the Mediterranean basin Venice. 22·1.5 june 1994. [3]. Goudie A.S., Viles H., Salt Weathering Hazards, Wiley, Chichester, 1997. [4]. Grossi, C.M., Esbert, R.M. et al., Acoustic emission monitoring to study sodium sulphate crystallization in monumental porous carbonatestones. Stud. Conserv., 42, 1997, pp. 115-25. [5]. Novak G.A., Colville A.A., Efflorescent minerals assemblages associated with cracked and degraded residential concrete foundations in [6]. Rodriguez-Navarro, C. and Doehne, E. Salt weathering: influence of evaporation rate, supersaturation and crystallization pattern. Earth Surf. Process. Landforms, 24 1999 191–209. [7]. Rodriguez-Navarro, C., Doehne, E. et al., How does sodium sulfate crystallize? Implications for the decay and testing of building materials. Cement and concrete research, 2000, pp. 1527-1534.