Effect of cement alkalinity on pore solution chemistry and chloride-induced reinforcement corrosion

This paper reports the results of a study conducted to evaluate the influence of cement alkalinity on the pore solution chemistry and chloride-induced reinforcement corrosion in ordinary and sulfate resisting Portland cement concretes. To evaluate the influence of cement alkalinity on the pore solution chemistry, cement paste specimens were prepared and admixed with fixed quantity of sodium chloride and various dosages of alkalinity (in the range of 0.4 to 1.4% Na2O equivalent). The pore solution was extracted and analyzed to determine the OH-, Cl- and SO4 -- concentrations. The influence of cement alkalinity on chloride-induced reinforcement corrosion was also assessed by measuring corrosion potentials and corrosion current density at regular intervals. The results indicated that the OH-, Cland SO4 -- concentrations of the pore solution increased with increasing alkali content of the cement. Further, the Cl-/OH- ratio decreased with increasing alkali content up to 0.8% Na2O and then increased with a further increase in the alkalinity. Furthermore, an improvement in the corrosion-resistance of the SRPC and OPC concrete specimens was noted with increasing alkali content of cement. However, the highest improvement was noted when the alkalinity was 0.8% Na2O equivalent

Long-term effect of sulfate ions and associated cation type on chloride-induced reinforcement corrosion in Portland cement concretes

This paper reports the influence of sulfate concentration on chloride-induced reinforcement corrosion in Portland cement concretes (with C3A varying from 3.6% to 9.65%). The concrete specimens were exposed to mixed chloride and sulfate solutions for a period of 1200 days. The chloride was fixed at 5% NaCl for all solutions, while the sulfate concentration was varied to represent that noted in the sulfate-bearing soil and ground water. The study included an assessment of the effect of cation type associated with sulfate ions, namely Na+ and Mg2+, on chloride-induced reinforcement corrosion, an important factor that has received little attention. Reinforcement corrosion was evaluated by measuring corrosion potentials and corrosion current density at regular intervals. The results indicate that the presence of sulfate ions in the chloride solution did not influence the time to initiation of chloride-induced reinforcement corrosion, but the rate of corrosion increased with increasing sulfate concentration. Further, the rate of chloride-induced reinforcement corrosion in the concrete specimens exposed to sodium chloride plus magnesium sulfate solutions was more than that in the concrete specimens exposed to sodium chloride plus sodium sulfate solutions

Effect of sulfate concentration and associated cation type on chloride-induced reinforcement corrosion

Effect of sulfate concentration and associated cation type on chloride-induced reinforcement corrosio

Chloride-induced reinforcement corrosion in blended cement concretes expores to chloride-sulfate environments

This paper reports the results of a study conducted to investigate the influence of sulphate concentration and associated cation type on chloride-induced reinforcement corrosion in blended cement concretes. Reinforced concrete specimens were exposed to chloride plus sulphate solutions for a period of 1200 days. The exposure solutions contained a fixed concentration of 5% sodium chloride and the sulphate concentration was varied from 0 to 4% SO4 2 . The effect of cation type associated with sulphate ions, namely Naþ and Mgþþ, on chloride-induced reinforcement corrosion was also evaluated. Reinforcement corrosion was assessed by measuring corrosion potentials and corrosion current density at regular intervals. The results indicated that the presence of sulphate ions in the chloride solution increased the corrosion current density, but no significant effect on the time to initiation of reinforcement corrosion was noted. Further, the corrosion current density increased with increasing sulphate concentration and the period of exposure. The corrosion current density on steel in the blended cement concrete specimens was much less than that in the plain cement concrete specimens, indicating that the corrosion resistance of blended cements was much better than that of plain cements. The cation type associated with sulphate ions did not significantly influence either the initiation or rate of reinforcement corrosion

CHARACTERISTICS OF THE ARABIAN GULF ENVIRONMENT AND ITS IMPACT ON CONCRETE DURABILITY – AN OVERVIEW

The environmental conditions of the Arabian Gulf that are characterized by high temperature and humidity significantly affect the performance of concrete structures in this region. The daily and seasonal variations in the temperature and humidity further accelerate the rate of concrete deterioration which is predominantly exhibited in the form of reinforcement corrosion, sulfate attack, salt scaling and cracking due to plastic and drying shrinkage. The high humidity provides moisture to concrete that is essential for reinforcement corrosion. Further, the temperature and humidity regimes that are commonly noted in this region are conducive for accelerated carbonation of concrete. The geomorphic conditions in the coastal areas of the Arabian Gulf that are characterized by shallow groundwater table, groundwater and soil contaminated with high concentrations of both chloride and sulfate salts also accelerate the deterioration of concrete mainly due to reinforcement corrosion, sulfate attack and salt weathering. This paper discusses the effect of environmental conditions, namely temperature, humidity, blowing wind, shallow groundwater and high salinity of the groundwater and soil, of the Arabian Gulf, on concrete durability

EFFECT OF CHLORIDE CONCENTRATION IN SOIL ON REINFORCEMENT CORROSION

ABSTRACT This paper presents results of a study conducted to evaluate the effect of chloride concentration in soil on corrosion of reinforcing steel in concrete. Concrete specimens prepared with Type I, Type V and silica fume cements were exposed to soil with a chloride concentration of up to 3%. The effect of chloride concentration in soil on corrosion of reinforcing steel was evaluated by measuring corrosion potentials and corrosion current density. After 18 months of exposure, the concrete specimens were broken and the extent of corrosion of the reinforcing steel was examined and the gravimetric weight loss due to corrosion was assessed. As expected, the degree of corrosion increased with the chloride concentration in the soil. The type of cement also influenced the reinforcement corrosion. For a particular chloride concentration, least reinforcement corrosion was noted in the silica fume cement concrete followed by Type I and Type V cement concrete. Based on the data developed in this study chloride threshold in soil for the three types of cements are suggested