Portland Cement Types

Here's a silly way to remember the types of cement, but it helped me: It is like you are climbing a hill.

Type I, normal cement: you haven't started climbing yet. you feel normal.
Type II, moderate sulfate resistant cement: you are halfway up the hill and feeling moderately resistant to continuing. You are losing salt in your sweat (sulfate is a salt).
Type III, High early strength cement: you are at the top of the hill. You got to the height of the journey early and feel strong.
Type IV, Low heat of hydration cement: Coming down the hill so you are losing elevation. You are hot and try to stay hydrated. 
V, High sulfate resistant cement: You made it to the bottom of the hill. You are highly resistant to doing that again due to salt loss.