Modelling Methods for Protection of RCC Structures

Anil Kumar Pillai, GM, Ramco Cements, discusses two major softwares (Life 365 and DuraCrete), used in the industry for protection of RCC structures.

The common design approach is faulty because we consider only the loading aspect, whereas the environmental aspect is equally important. This is because we have seen structures failing only due to environmental impacts on the structure, and not because of overloading.

There are number of models available online free of charge which gives an idea of various factors.

Life 365
Life 365 software helps predict how the structure fails. It divides the corrosion aspect into two time periods: the initiation period (ti) and the propagation period (tp). The following inputs are required to predict the initiation period:

• geographical location
• type of structure
• nature of exposure
• depth of clear cover
• protection strategy scenarios
• water-cement ratio
• type and quantity of supplementary cementitious materials
• corrosion inhibitors
• type of steel
• coatings
• type and properties of membranes and sealers.

There are tabs for project details like wall, column, slab as well as tabs for environmental factors to be considered and treatment tab to select mode of treatment opted. It can give you the probable causes of failure for a certain specified period of the life of the structure. It can also estimate life-cycle cost based on the initial concrete and other protection costs and future repair costs.

DuraCrete
The DuraCrete approach overcomes the shortcomings of Life 365 and provides a greater calculation accuracy towards prediction of structures which can get affected by chlorides. In this method, the following durability limit states have been identified regarding service life:

• depassivation of reinforcement
• cracking of concrete cover
• spalling of concrete cover
• collapse of the structure.

(The above information is sourced from the online technical discussion Design Life and Life Expectancy of RCC structures with respect to the deteriorating effect of environmental agents like chlorides and sulphates on the structure. The webinar was conducted by SQVe consultants).