The proposal of the British Standard for mortars is that all ingredients of mortars should be specified by weight proportions of the total dry weight of the mortar. In the case of lime:sand mortars it also is suggested that the “available lime content,” as specified by ASTM Method C 25-65, is used to determine the active lime in the mortar.
In the first part of this investigation the effects of varying the available lime content on the physical properties of mortars have been studied. It has been shown that using one sand and one hydrated lime the physical properties of the plastic mortars are related to the available lime content, and that when hydrated lime mortars are aged for 24 h as a mortar the test methods are more reproducible.
In the second part of this investigation a number of different types of limes have been tested in the form of lime:sand mortars and gaged with portland cement. From the results of the second series of tests it was shown that controlling the amount of lime in a mortar by its available lime content is a useful form of standardization, but that the physical properties of different types of lime do affect the final properties of the mortar.
The proposed British Standard methods of testing mortars were found to give reasonably satisfactory results and capable of classifying types of building mortars.