On the possibility of using sands with high chloride content in reinforced concrete structures

Abstract

Introduction . The sand of many deposits, especially in the far east of our country, contains a large amount of chlorides, which makes it unsuitable for use in reinforced concrete. This is because chloride ions are the most aggressive corrosive agent for steelreinforcement. The Laboratory of Corrosion and Durability of Concrete and Reinforced Concrete Structures at the A.A. Gvozdev Research Institute of Concrete and Reinforced Concrete Structures conducted research on the corrosion of steel reinforcement in concrete and cement-sand mixtures that contained sand with a high chloride content. Aim . To determine the possibility of using sand from the Kamchatka Territory deposits in concrete mixtures in terms of corrosion aggression to steel reinforcement. Materials and methods. The studies were conducted on a model cement-sand mixture (CPM) and concrete with smooth rod reinforcement of 6 mm in diameter. The sand contained 0.08 % by mass (based on chlorine ion) of water-soluble chlorides and 0.55 % by mass (based on chlorine ion) of total chlorides in the sand. An electrochemical method was used to accelerate the determination of the corrosion effect of the environment on steel reinforcement. The method is based on obtaining the dependence of the electric current density on the electric potential of the steel reinforcement, which is known as the potential-dynamic method. Results show that sand with a high content of water-insoluble chlorides does not cause corrosion of steel reinforcement when the samples are in a non-aggressive (neutral) environment. In the initial state and exposure in the humidification – drying mode for 3, 6 months, neither in the cement-sand mixture samples nor in the concrete samples, the current density at a potential of plus 300 mV did not exceed 10 μA/ cm2, as well as the potential after (60 ± 5) s after the current was turned off did not drop below + 5mV. Conclusions. Sand with a high content of water-insoluble chlorides can be recommended for use in reinforced concrete structures that are guaranteed to be free from aggressive environments even during operation.