Evaluation of Durability Index for Medium Strength Concrete
Keywords:
Concrete, Durability index, Oxygen permeability, Sorptivity, Chloride conductivity.Abstract
Durability of concrete can be defined as the ability of a structure to perform its intended function over a specified period of time under the influence of agents anticipated in service. It is considered as durable material and will retain its quality and serviceability in its original form when exposed to environment.
In the design of reinforced concrete structures, the strength requirement is considered as mainly governing criterion. If cube strengths are OK, then concrete in the structure is fine, and it is considered that concrete will take care of itself. But reality is different. The aspect of the durability of the concrete was not given as much attention. Many structures have shown signs of deterioration earlier than expected for their service life, which has resulted in the need for repair and rehabilitation of these structures, often at great cost. This implies that the durability is related to the material performance and environment and cannot be thought of as being an inherent property of the concrete.
In present work, durability index for medium strength concrete containing M20, M40 and M50 with plain OPC and with replacement of OPC by fly ash by 30% are evaluated. Total 60 no. of cubes were casted, 10 for each type of mix. For durability index, three tests Oxygen Permeability, Water Sorptivity and Chloride Conductivity as per South African Durability Index Approach were carried out. From the Water Sorptivity and Chloride Conductivity results the concrete mixes were found to be of good category while found poor category from oxygen permeability.
