Once mixed with water, hydraulic cement sets and hardens in just a few minutes. Hot water quickens the setting time, while cold water slows it down. It can be used on horizontal surfaces like floors as well as vertical ones like basement walls. And it doesn’t shrink, rust, or corrode. It’ll remain intact even if it’s submerged in water.
Be aware that exposure to hydraulic cement can be toxic, though, so you need to wear protective gear. And you need to work quickly since the mortar only remains workable for about 10 minutes once mixed. Also, it doesn’t work on frozen surfaces, so be sure to make your repairs before the winter.