The Effect of Different Types of Aggregate on the Durability of Concrete : Carbonation

Abstract

Highly desirable durability requirement for concrete is not always achieved in practice due to various environmental factors. Corrosion of reinforcement in concrete is a common cause of deterioration in many RC structures. One of the main cause of corrosion of reinforcement in concrete is Carbonation, which is the result of the chemical reaction between carbon dioxide gases in the atmosphere and alkaline hydroxides in the concrete. This paper investigates the durability of concrete specimens made with different locally available coarse aggregate through carbonation testing in accelerated condition using a carbonation chamber. To investigate the fresh and hardened properties of concrete, four different coarse aggregates such as black stone (a type of crushed stone), shingles (round shaped stone), brick aggregate and recycled brick aggregates were used. Several tests such as specific gravity, absorption capacity, unit weight, and abrasion resistance were performed for coarse aggregate. Cylindrical concrete specimens of diameter 100 mm and length 200 mm were made with different sand to total aggregate volume ratio (s/a) (0.44), W/C ratio (0.45, 0.50). OPC, PCC Type II B-M, PCC Type II B-S, PCC Type II B-S (40% OPC – 60 % Slag) are the four different binder types used with cement content (340 kg/m3 and 400 kg/m3). A total of 42 different cases were considered and a total of 672 concrete specimens were made for testing. The specimens have been tested for compressive strength, split tensile strength test at 28 days and 2 months. Non-destructive tests such as Ultrasonic Pulse Velocity (UPV) was also performed. The results have revealed that black stone and OPC are the two aggregate and cement type that produced highest compressive and tensile strength for the concrete specimens at 28 days. UPV test showed higher values for stone aggregates compare to brick and recycled brick aggregates. Besides, correlation between compressive strength with other properties like young’s modulus, tensile strength and UPV were also explored .Our main goal was to find the effect of different aggregates types and the mechanical properties they produced on the durability of concrete by assessing the carbonation depth found in the specimens. But due to time limitation the carbonation testing could not be completed. Further analysis based on the data collected and carbonation depth will be made as soon as the data are available. This analysis will help us to reach a vii conclusion on how different aggregates and cement types affect the carbonation process in concrete.