Banja Luka 10.03.2020 Knowledge FOr Resilient soCiEty KURS CJELOŽIVOTNOG UČENJA PROTIVPOŽARNE GRAĐEVINSKE MJERE SPOLJNI UTICAJ SULFATA NA BETON Doc. Dr Vesna Bulatović The European Commission support for the production of this publication does not constitute an endorsement of the contents which reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein.
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Concrete durability Concrete Microclimate Transport mechanisms quality Capillary Water and Temprature Diffusion Permeability suction aggressive and pressure Cement w/b Curing type Pore connectivity Degree of Porosity binding hydration
Initiation Propagation Accept limit Technical Service Life Damage
Initiation Propagation Accept limit Technical Service Life Damage
Initiation Propagation Accept limit Technical Service Life Damage
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DETERIORATION OF CONCRETE Mechanical Chemical Physical · Impact · Alkali-aggregate · Freeze/thaw · Overload · Thermal reaction · Movement · Aggressive agents · Salt crystallization · Erosion (e.g.settlement) e.g.sulfates,soft · Explosion · Wear water,salts · Vibration · Biological activities
• alkali-silica reaction (ASR) alkali-carbonate reaction (ACR)
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The microstructure of the concrete is changed under this attack. These changes may vary in the type of severity, but they commonly include chemical sulfate attack and physical attack. Common damages: • Cracking, • Expansion • Loss of bond between the cement paste and aggregate . The expansion resulting from sulfate attack is generally attributed to the formation of gypsum and ettringite.
Sulfate attack is categorize into: • Chemical • Physical • Internal • External
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Original cement Liquid Reaction zone Pore solution paste Na + Na + OH - OH - Ca(OH) 2 Ca 2+ CaSO 4 ·2H 2 O SO 42- SO 42- 4CaO·Al 2 O 3 ·SO 3 ·12H 2 O 6CaO·Al 2 O 3 ·3SO 3 ·32H 2 O (ettringite) (monosulfate) Al(OH) -4
Original cement Liquid Reaction zone Pore solution paste Mg(OH) 2 OH - Mg 2+ Mg 2+ Ca(OH) 2 Ca 2+ CaSO 4 ·2H 2 O SO 42- SO 42- 3MgO·2SiO 2 ·2H 2 O C-S-H AFm SiO 2 ·aq AFt
Min cement Class of Min strength Other Max w/c content chemical attack class requirements (kg/m 3 ) XA1 0.55 C30/37 300 XA2 0.50 C30/37 320 Sulfate-resisting cement XA3 0.45 C35/45 360
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Knowledge FOr Resilient soCiEty
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