An employee completed a repair job on an expansion joint that had a known leak. The employee then went through decontamination and removed his personal protective equipment (PPE). The employee placed his decontaminated PPE on the ground and proceeded to finish cleaning up the work area. Once done, he picked up the discarded PPE to take it to the appropriate disposal bin. He carried the PPE under his right arm. By the time he reached the bottom of the stairway to exit the unit, he felt a burning sensation under his arm. The employee sustained chemical burns.