*5.1. Development of GUI*

In order to implement the code for practical purpose, various inputs relating to the weather condition, concrete composition, and cross-section must be retrieved from the user. A web-based interface designed for this purpose will be described in this section.

## 5.1.1. Weather Condition Details

The modeling engine is equipped with weather data for three cities, namely: Dammam, Dhahran, and Jeddah in Saudi Arabia. The data contains temperature and humidity values for the cities for previous years. An algorithm was written to enable extrapolation to future years using the previous years' weather data. A user will choose the city of interest and the exposure zone, whether tidal or splash, using the interface.

#### 5.1.2. Reinforced Concrete Properties and Member Geometric Details

Reinforced concrete properties, including water/cement ratio, cement type, cementitious material type and ratio, admixture type and ratio, aggregate type and content, as well as concrete curing time and exposure date are collected from the user using the interface. The interface is also used to gather data relating to the geometric properties of the exposed reinforced concrete, including the concrete member cross-sectional area and cover to reinforcement.

## *5.2. Modeling Outputs*

The details collected from the user through the interfaces described in the previous section were utilized for the modeling since all the parameters are embedded in the ionic diffusion model described in the previous section. The output of the calculation is the chloride ion concentration at various depths from the member surface to the top of the reinforcement in the concrete member. From Equation (5), it is obvious that the diffusion model is time dependent, and hence, the calculation will continue in time until a specified chloride threshold is attained at which point the calculation will stop. The chloride concentration at this point in time will then be saved together with the total period (in days) before the chloride threshold is reached (known as corrosion initiation time) in the reinforced concrete member. Chloride ion threshold in reinforced concrete member varies depending on the code of practice being adopted. ACI specifies a chloride threshold of 0.5% by weight of concrete member being analyzed. This value was utilized in the current model to produce results similar to Figure 12.

**Figure 12.** Typical modeling results of chloride profile and duration to corrosion initiation.
