What is the difference between mortar and grout?
Good question! I had to pull some books off my shelf because this one peaked my curiosity. There is a fair amount of ambiguity with these terms and I’ve heard them used interchangeably. All of the above responses seem right, but from an engineering perspective, I pulled this information from one of my books. Mortar is used for the following functions: bonding masonry units together, serving as a seating material for the units, leveling and seating the units, and providing aesthetic quality of the structure. Grout is used to fill the cores or voids in hollow masonry units for the purpose of: bonding the masonry units, bonding the reinforcing steel to the masonry, increasing the bearing area, increasing the fire resistance, and improving the overturning resistance by increasing the weight. Using these definitions, grout uses fine gravel in addition to the sand both mixes use. The other ingredients seem similar with minor portioning differences.
