FACULTY OF ENGINEERING IN SHOUBRA BENHA UNIVERISITY ASSESSMENT OF FRESH AND HARDENED CONCRETE TREATED WITH CORROSION INHIBITORS BY YASSER ABDELGHANY FAWZY Prof. Dr. Assem M.K.Abdelalim Professor of Properties and Strength of Materials, and The Dean of Faculty of Engineering in Shoubra, Benha University Dr. Gamal Elsayed Abdelaziz Associate Professor of Properties and Strength of Materials, Faculty of Engineering in Shoubra, Benha University SUPERVISED BY

1. To investigate the role of corrosion inhibiting admixtures on cement – phase composition, pore structure and permeation characteristic of OPC matrix and signify the importance of using corrosion inhibiting admixtures on reducing the corrosion activity of reinforcing steel. 2. To clarify the role of corrosion inhibiting admixtures on mechanical properties (compressive, tensile and bond strength) and fresh parameters (setting time, initial flowability, rate of flowability loss and rheology ) of OPC matrix.

3. To clarify the influence of steel coating on corrosion activity of reinforcement, bond strength and microstructure of interfacial zone between steel and concrete. 4. To investigate the corrosion activity of reinforced OPC matrixes made with or without silica fume and fly ash and contaminated with different chloride contents prior to and after the application of MFP and N.

5. To determine the factors affecting the efficiency of adopting MFP and N as remedial treatment and to study the impact of MFP and N on crystal and cement-phase composition of the interfacial zones around reinforcement. 6. To assess the long-term effect of ECE after halting the treatment on corrosion rate of re-passivated reinforcement, i.e. to study the possibility of occurrence of re- diffusion of chloride ions towards reinforcement after halting ECE treatment. 7. To signify the factors controlling the efficiency of ECE treatment and to clarify the effect of ECE on the microstructure of interfacial zone around reinforcement and chloride profile of cover zone.

Calcium nitrit e Sodium benzoate SFFA %40 % Testing Corrosion activity ( potential, rate ) Microstructure (total, capillary porosity, TGA ) OPCSRC 0,2,4,5 % Mechanical (compressive, tensile, bond ) Fresh stateHardened state FlowabilitySetting time InitialFinal Mass transport ( air perm., ISAT, sorptivity ) Figure 2.1 Experimental program of phase I study ( corrosion inhibiting admixtures ).

Zinc richSFFA %40 % Testing Microstructure Corrosion activity Mechanical Corrosion potential Corrosion rateBond SEMXRD Admixed chlorides, % Figure 2.2 Experimental program of phase II study ( steel coating ).

Calcium nitrite SFFA %40 % Testing Microstructure Corrosion activity Mass transport Corrosion potential Corrosion rate ISATSEMXRD 0.6 MFP 5%10 %5 %10 %20 % Sorptivity Cement replacement materials Figure 2.3 Experimental program of phase III study ( corrosion inhibitors as remedial treatment).

Figure 2.4 Experimental program of phase IV study ( ECE treatment ).

Figure 2.5 Specimens used in studying corrosion potential and rate of steel embedded in mortar containing various corrosion inhibitors.

Figure 2.6 Specimens used in studying corrosion potential and rate of steel embedded in mortar treated with corrosion inhibitors as remedial treatment.

Figure 2.7 Half- cell potential apparatus.

Figure 2.8( a) Method of measuring corrosion rate using zero resistance ammeter.

Figure 2.8( b) Schematic drawing of zero-resistance ammeter device.

Figure 2.9 Specimens used for tensile test of mortar containing various corrosion inhibiting admixtures.

Figure 2.10 (a) ECE treatment.

Figure 2.10 (b) Schematic arrangement of ECE treatment.

Table 3.1 Average results of 28 days compressive, tensile and bond strength of OPC mortars containing different contents of CIA, Kg/ cm 2. Bond strength, Kg/ cm 2 Tensile strength, Kg/ cm 2 Compressive strength, Kg/ cm 2 Corrosion inhibitor Code Content Type Control % Calcium nitrite 2 N %4 N %5N % Sodium benzoate 2 B %4 B %55B

Figure 3.1 Flowability of OPC mortar admixed with various corrosion inhibitors.

Figure 3.2 Effect of cement replacement materials on flowability of OPC mortar made with various corrosion inhibitors ( a) calcium nitrite and ( b) sodium benzoate.

Figure 4.11 Corrosion potential of OPC mortar made with various corrosion inhibitors ( a) calcium nitrite and ( b) sodium benzoate. Figure 4.11 Corrosion potential of OPC mortar made with various corrosion inhibitors ( a) calcium nitrite and ( b) sodium benzoate. Figure 3.3 ( a) Corrosion potential of OPC mortar made with for calcium nitrite.

Figure 3.3 (b) Corrosion potential of OPC mortar made with sodium benzoate.

Figure 3.4 (a) Corrosion rate of OPC mortar made with calcium nitrite.

Figure 3.4 (b) Corrosion rate of OPC mortar made with sodium benzoate.

Table 4.1 Bond strength at 28 days for ordinary and coated steel, Kg/ cm 2. Bond strength, Kg/ cm 2 Code 44.7Ordinary steel 30.36Coated steel

Figure 4.1(a)Relationship between corrosion potential and exposure time for ordinary and coated steel at 0% chloride contents.

Figure 4.1(b) Relationship between corrosion potential and exposure time for ordinary and coated steel at 0.6 % chloride content.

Figure 4.1( c ) Relationship between corrosion potential and exposure time for ordinary and coated steel at 1.2 % chloride content.

Figure 5.1(a) Corrosion potential of reinforcement embedded in OPC mortar treated with various concentrations of MFP, contaminated with 0.6 % sodium chloride.

Figure 5.1(b) Corrosion potential of reinforcement embedded in OPC mortar treated with various concentrations of MFP, contaminated with 1.2 % sodium chloride.

Figure 5.1( c) Corrosion potential of reinforcement embedded in OPC mortar treated with various concentrations of MFP, contaminated with 2.4 % sodium chloride.

Figure 5.2 (a) Corrosion potential of reinforcement embedded in OPC mortar treated with various concentrations of N, contaminated with 0.6 % sodium chloride.

Figure 5.2 (b) Corrosion potential of reinforcement embedded in OPC mortar treated with various concentrations of N, contaminated with 1.2 % sodium chloride.

Figure 5.2 ( c) Corrosion potential of reinforcement embedded in OPC mortar treated with various concentrations of N, contaminated with 2.4 % sodium chloride.

Table 6.1 Effect of ECE treatment using various impressed current density (I) for treatment period (TP) on corrosion rate of reinforcement. I = 2 A/ m 2 I = 1 A/ m 2 Corrosion current density (Icorr), µ A/cm 2 TP=4 weeks TP= 8 weeks TP= 4 week s TP= 2 weeks 1.25 Prior to ECE application (Icorr1) Immediately after halting ECE (Icorr2) After 4 weeks from halting ECE (Icorr3)

Table 6.2 Effect of electrolyte type used in ECE treatment on corrosion rate of reinforcement embedded in treated OPC specimens with ECE. Electrolyte type Corrosion current density (Icorr), µ A/cm 2 Calcium hydroxide Water 1.25 Prior to ECE application (Icorr1) Immediately after halting ECE (Icorr2) 0.01 After 4 weeks from halting ECE (Icorr3)

Table 6.3 Effect of content of admixed chloride on corrosion rate of reinforcement embedded in treated OPC specimens with ECE. Admixed chloride content Corrosion current density (Icorr), µ A/cm 2 2%1% Prior to ECE application (Icorr1) Immediately after halting ECE (Icorr2) After 4 weeks from halting ECE (Icorr3)

Table 6.4 Effect of external chloride content on corrosion rate of reinforcement embedded in treated OPC specimens with ECE. External chloride contentCorrosion current density (Icorr), µ A/cm 2 5%3% Prior to ECE application (Icorr1) 6.25 Immediately after halting ECE (Icorr2) After 4 weeks from halting ECE (Icorr3)

Table 6.5 Corrosion rate of reinforcement embedded in treated OPC and SRC specimens with ECE ( 1 A/m 2 for 4 weeks ). Specimen type Corrosion current density (Icorr), µ A/cm 2 SRCOPC 1.25 Prior to ECE application (Icorr1) Immediately after halting ECE (Icorr2) After 4 weeks from halting ECE (Icorr3)

Figure 6.1 Corrosion current density (Icorr) of reinforcement embedded in OPC specimens treated with ECE using various impressed current density (I).

Figure 6.2 Corrosion current density (Icorr) of reinforcement embedded in OPC specimens treated with ECE using an impressed current density of 1 A/m2 for different periods.

Figure 6.3 Corrosion current density (Icorr) of reinforcement embedded in OPC specimens treated with ECE using different electrolytes.

Figure 6.4 ( a) Corrosion current density (Icorr) of reinforcement embedded in OPC specimens attacked by admixed chlorides and treated with ECE.

Figure 6.4 ( b) Corrosion current density (Icorr) of reinforcement embedded in OPC specimens attacked by external chlorides and treated with ECE.

Figure 6.5 Corrosion current density (Icorr) of reinforcement embedded in OPC and SRC specimens treated with ECE, using 1 A/m 2 for four weeks.

1. The initial flowability of OPC matrix is inversely affected by increasing the dosage of sodium benzoate. Inclusion of sodium benzoate in OPC mortar mixes has led to reducing its initial flowability and this effect would increase with increasing sodium benzoate content. While, calcium nitrite has an insignificant role on initial flowability. On the other hand, the rate of flowability loss is significantly increased when calcium nitrite is utilized in the mix, compared to sodium benzoate effect. 2. The inclusion of calcium nitrite in OPC mixes can lead to a significant modification in its microstructure and permeation related characteristics. Increasing the dosage of calcium nitrite resulted in enhancing the degree of hydration and amount of CSH, and reducing the amount of interconnected pores and rate of fluid transport, Meanwhile, sodium benzoate had a little effect on cement-phase composition when compared to calcium nitrite.

3. The tensile and bond strength are significantly improved as a result of admixed calcium nitrite in OPC mix and the amount of improvement increases with increasing its content. On the other hand, the studied mechanical properties (compressive, tensile and bond strength) have been degraded when sodium benzoate was used. 4. Compared to uncoated steel using coated steel has lead to altering the corrosion potential behavior of reinforcement. 5. The use of either sodium monofluro phosphate (MFP) or calcium nitrite ( N ) as a remedial corrosion inhibitor has a reasonable beneficial effect on increasing the resistance of reinforcement against corrosion, through lowering its corrosion potential and corrosion current density and altering its corrosion state from active to passive.

6. The beneficial role of sodium monofluro phosphate (MFP) in controlling the corrosion activity of reinforcement was significantly augmented with increasing the dosage of MFP and prolonging period of MFP treatment till a certain period (14 weeks), at which no more reduction in the corrosion activity produced as a result increasing the period of treatment afterward. However, increasing the amount of chloride ions in reinforced OPC matrix has led to diminish such beneficial role. Whereas, increasing the period of calcium nitrite ( N ) treatment more than a period (26 weeks) is essential to alter the corrosion activity of reinforcement from active to passive state. 7. Both calcium nitrite (N) and sodium monofluro phosphate (MFP) are efficient in delaying/stopping corrosion processes of reinforcement embedded in OPC/SF matrix than that embedded in pure OPC matrix. Where, the corrosion potential and corrosion current density of reinforcement embedded in treated OPC matrix with either N or MFP was significantly reduced as a result of inclusion of silica fume in OPC matrix. On the other hand, the treatment of reinforced fly ash mortars with either N or MFP was shown to be ineffective, from corrosion potential point of view.

8. Electrochemical chloride extraction (ECE) has been confirmed to be a successful temporary remedial treatment of reinforcement corrosion. It can leads to a reasonable decrease in the chloride profile of the cover zone and a substantial reduction in the corrosion rate of reinforcement, thus transforming the state of reinforcement corrosion from active to passive. 9. Assessment of the short-term efficiency of ECE on the corrosion activity of corroded reinforcement is preferable to be carried out after a short period from halting ECE process (about 4 weeks) and not immediately after halting ECE treatment.

10. The long-term efficiency of ECE on the corrosion activity of reinforcement after halting ECE treatment was reasonably improved with increasing the amount of impressed current charges and using of water as an electrolyte. However, the source and content of chloride ions and type of cement had insignificant effect on the long-term efficiency of ECE. On the other hand, all above-mentioned parameters had a slight effect on improving short-term efficiency of ECE, compared to their effects on the long-term efficiency of ECE. 11. Re-diffusion of chloride ions towards reinforcement after halting ECE can be possibly reduced with increasing the amount of impressed current considered in ECE treatment, prolonging the period of ECE treatment and using of water as an electrolyte. Reduction of the amount of re-migrated chloride ions can leads to reducing the rate of reinforcement corrosion and hence extending the time for reinforcement to re-corrode again.