Sodium polyacrylate experiment

This is my experiment I did today I had no clue what would happen the only thing I did was put spoonfuls of water in a cup full of  sodium  polyacrylate expanded until the come was overflowing and then we put salt in and their slowly sunk in and turned the top into water and the turned into more concentrated sodium polyacrylate .I learnt what sodium polyacrylate was and what people use it for. If you know what sodium polyacrylate is and what it does?