LOGO “DETERMINATION OF THE APPROPRIATE CONTENT OF CALCIUM NITRITE AS A CORROSION INHIBITOR IN REINFORCED CONCRETE” “DETERMINATION OF THE APPROPRIATE CONTENT OF CALCIUM NITRITE AS A CORROSION INHIBITOR IN REINFORCED CONCRETE” Dr. Le Quang Hung State bureau for Construction quality inspection, Viet Nam Dr. Nguyen Nam Thang Institute for Building Science and Technology, Viet Nam Contents GENERAL 1 RESEARCH RESULTS 3 CONCLUSION 4 MATERIALS AND RESEARCH METHODOLOGY 2 General Overview of reinforced concrete corrosion under the effect of chloride ion The reaction of corrosive process occurs as below: Anode: Fe  Fe 2+ + 2e Cathode: O 2 + 2H 2 O + 4e 2 4 OH - The reinforced concrete structure is corroded very fast under the effect of chloride ion in marine environment The strongly agressivity rate of chloride ion is the main reason causing corrosion, especially in the tropical climate of Vietnam. Han River port Vung Tau port Anode Cathode Cl - Concrete Steel Cua Cam port General Principial protection methods: Calcium nitrite (CN) is used as the most effective inhibitors in preventing reinforced concrete from corrosion.  Primary protection: Compressive strength, water tightness, width of crack, thickness cover of concrete - protecting layer. Secondary protection: Coating surface of structure: Painting Electrochemistry: Cathodic protection Corrosion inhibitors: NO 2 - containing derivatives such as calcium nitrite, sodium nitrite are often used. General The inhibition mechanism of CN A. Oxidation of FeO to form Fe 2 O 3 B. The adsorption on steel surface to tighten passive membrane C. Covering around FeO defected sites D. NO 2 - ion can cover in new particle Fe 2+ fast General Question: Which is the most appropriate ratio [Cl - ]/[NO 2 - ] ? Cement River sand Crush stone Admixture Corrosion inhibitor Materials Material and research methodology Hoang Thanh PCB 30 Nghi Son PCB 40 Sikament R4 Module Mn = 2,5 (Lo river) Dmax = 20mm (Kien Khe field ) 30% of solid calcium nitrite solution Material and research methodology 1.Extract of cement water Testing samples 2. Reinforced concrete samples 1. Extract of cement water Reference extract of cement water (H 0 ) Extract of Cement water with Cl - Extract of Cement water with CN and Cl - Material and research methodology Extract of cement water •water/cement = 0,6 • Cl - : 1,2kg; 2,4kg vµ 6kg • [Cl]/ [NO 2 - ] = 1,6 - 2,6 Material and research methodology 2. Reinfored concrete  Samples with CN and Cl - inside concrete grade 20, 30 and 50 Testing environment: wet and dry cycles, measurement of corrosion rates at the time of: 0, 3, 6, 9, 12, 18 and 24 months. Steel reinforcement: 10 diameter Concrete grade M20, M30, M50, Protection thickness layer: 3,5cm Cl - : 1,2kg; 2,4kg và 6kg/m 3 [Cl] / [NO 2 - ] = 1,6-2,6 Wet and dry cycle: - 3 days in water - 4 days for drying. [...]... Research results Effectiveness of corrosion inhibitor in concrete containing Cl-: Reinforcement corrosion for concrete containing Cl-: Clwill penetrate and destroy the passive membrane, this process happens quite slow after a certain period until corrosion appeared In the samples with same concrete grade, the steel corrosion is increasing by the time and by Cl- content; Higher concrete grade, lower corrosion. .. H21:CW+[Cl/NO2=1,6] Corrosion rate (mm/ year) 0.03 0.02 0.01 H15 H16 H17 H18 H19 H20 H21 0 Time (months) 0 3 6 9 12 Figure 4 Corrosion inhibition ability of CN in cement water extract of (6 kg Cl-) Image 4: Steel sample in cement water extract containing (CN and 6,0 kg Cl-) Research results Effectiveness of corrosion inhibition in extract of cement water containing Cl-: • In H0 extract, steel is maintained in passive... corrosion Effective content of CN is defined as [Cl-]/[NO2-] @ 2 Conclusion 1 CN is an effective inhibitor to enable minimizing steel corrosion in concrete 2 Determine the appropriate content of calcium nitrite as 1 2 Extract of Cement water : Concrete grade M20, M30,M50: -W/C = 0,6; pH = 12,2 -[Cl-]: 1,2kg; 2,4kg and 6kg /m3 -Thickness of protective layer: 3,5cm -[Cl-]: 1,2kg; 2,4kg and 6kg /m3 [Cl-]/... Steel corrosion rate in concrete grade M20 containing different contents of Cl- Image 5: Reinforcement in concrete grade M20containing different contents of Cl- Research results 0.04 B02: M30 B22: 1,2kg Cl 0.03 B29: 2,4kg ion Cl Corrosion rate (mm/year) B36: 6,0kg ion Cl 0.02 0.01 Time (months) B0-2 0 0 3 6 9 12 15 18 21 Figure 6 Steel corrosion rate in concrete grade M30 containing different contents of. .. steel is maintained in passive state and not corroded • The extract containing Cl-: corrosion rate is continuously increased with the time and with Clratios • At [Cl-]/[NO2-] 2,2; corrosion rate was very small Research results 2 Case of reinforced concrete 0.04 B01: Reference sample M20 (mm/ year) B1: 1,2kg Cl 0.03 B8: 2,4kg ion Cl B15: 6,0kg ion Cl B01 Corrosion rate 0.02 B1 B8 B15 0.01 Time (months)... Image 6: Reinforcement in concrete grade M30 containing different contents of Cl- Research results 0.04 B 03 : M50 B61: 1,2kg Cl 0.03 B68: 2,4kg ion Cl Corrosion rate (mm/year) B75: 6,0kg ion Cl 0.02 0.01 Time (months) B0-3 0 0 3 6 9 12 15 18 21 B61 B68 B75 24 Figure 7 Steel corrosion rate in concrete grade M50 containing different contents of Cl- Image 7: Reinforcement in concrete grade M50 containing...Research results 1 Case of extract of cement water 0.06 0.05 Corrosion rate (mm/year) 0.04 0.03 0.02 0.01 Time (months) H0 0 0 3 6 9 H0: CW H8 12 H1: CW+1,2kg ion Cl H8: CW+2,4kg ion Cl H1 H15: CW+ 6,0kg ion Cl Figure 1 Steel corrosion rate in extracte of cement water containing Cl- Image 1: Steel sample in cement water extract containing Cl- H15 Research results 0.06 H1:CW+1,2kg... contents of Cl- Research results 0.04 B1: 1,2kg Cl B2: [Cl/NO2=2,6] B3: [Cl/NO2=2,4] 0.03 B4: [Cl/NO2=2,2] B5: [Cl/NO2=2,0] Corrosion rate (mm/year) B6: [Cl/NO2=1,8] 0.02 B7: [Cl/NO2=1,6] 0.01 Time (months) B1 B2 0 0 3 6 9 12 15 18 21 Figure 8 Steel corrosion rate in concrete grade M30 containing of Cl and CN B3 B4 B5 B6 B7 24 Image 8: Reinforcement in concrete grade M30 containing Cl- and CN Research... [Cl/NO2=2,0] Corrosion rate (mm/year) B13: [Cl/NO2=1,8] 0.02 B14: [Cl/NO2=1,6] 0.01 B8 Time (months) 0 0 3 6 9 12 15 18 21 Figure 9 Corrosion inhibition ability of CN in concrete grade M20 containing 2,4 kg Cl-/ m3 B9 B10 B11 B12 B13 B14 24 Image 9: Reinforcement in concrete grade M20 containing CN and 2,4 kg ion Cl- Research results 0.04 B15: 6,0kg Cl B16: [Cl/NO2=2,6] B17: [Cl/NO2=2,4] 0.03 Corrosion rate... [Cl/NO2=2,0] Corrosion rate (mm/year) B34: [Cl/NO2=1,8] 0.02 0.02 Corr osio n rate (mm /yea r) B35: [Cl/NO2=1,6] 0.01 B66: [Cl/NO2=1,8] B67: [Cl/NO2=1,6] Time (months) 0.01 Time (months) 0 0 0 3 6 9 12 15 18 21 24 Figure 12 Corrosion inhibition ability of CN in concrete grade M30 containing 2,4 kg Cl-/ m3 0 3 6 9 12 15 18 21 24 Figure 13 Corrosion inhibition ability of CN in concrete grade M50 containing 1,2 . LOGO DETERMINATION OF THE APPROPRIATE CONTENT OF CALCIUM NITRITE AS A CORROSION INHIBITOR IN REINFORCED CONCRETE DETERMINATION OF THE APPROPRIATE CONTENT OF CALCIUM NITRITE AS A CORROSION INHIBITOR. Cl - ) Effectiveness of corrosion inhibition in extract of cement water containing Cl - : • In H 0 extract, steel is maintained in passive state and not corroded • The extract containing Cl - : corrosion rate is continuously. strongly agressivity rate of chloride ion is the main reason causing corrosion, especially in the tropical climate of Vietnam. Han River port Vung Tau port Anode Cathode Cl - Concrete Steel Cua Cam