Final answer:
Portland cement increases the mortar's cohesiveness by enhancing the bond between mortar ingredients.
Step-by-step explanation:
Portland cement increases the mortar's cohesiveness. Cement is a binder that sets, hardens, and adheres to other materials to bind them together. When mixed with sand and gravel, it produces mortar for masonry. Portland cement is a common type of cement used in construction and is known for its ability to enhance the bond between mortar ingredients, thereby increasing cohesiveness.