This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
(1) Lime Mortar. As previously stated in section 88, a barrel of unslaked lime should be mixed with about 8 1/2 cubic feet of water. This will make about 9 cubic feet of lime paste. Mixing this with a cubic yard of sand will make about 1 cubic yard of 1:3 lime mortar. This means approximately 1 volume of unslaked lime to 8 volumes of sand.
(2) Cement Mortars. The volume of cement depends very largely on whether it is loosely dropped in a pile, shaken together, or packed. The practical commercial methods of obtaining a mixture of definite proportions will be given later under "Concrete," section 94. Natural cement mortars are usually mixed in the 1: 2 ratio, although a 1:1 mixture would probably be used for tunnel work or bridge abutments where natural cement would be used at all. Portland cement will be used to make 1: 3 mortar for ordinary work, and 1:2 mortar for very high-grade work. As previously stated, a small percentage of lime is sometimes substituted for an equal volume of cement in order to make the mortar work better.