Yes, in the scenario you've described, the concept of sandwich leave would be applicable.
Here's why:
You are taking leave on consecutive working days, which are the 16th, 17th, and 18th of August. The weekend (19th and 20th of August) falls between these leave days. You return to work on Monday, the 21st of August. Since the leave is taken between two non-working days (weekend) and the employee returns to work on the next working day (Monday), this situation aligns with the concept of sandwich leave. This means that the employee is essentially "sandwiching" their leave days between two non-working days. However, please keep in mind that the application of sandwich leave can vary based on company policies and practices. It's advisable to consult your organization's HR department or refer to your company's leave policy to ensure that you are following the correct leave procedure.