1-6. Admixtures. Besides the four basic ingredients (Figure 1-1), any other materials added to the
mortar are called admixtures. The most common admixtures are accelerants and retardants.
Figure 1-1. Ingredients of mortar
1-7. Accelerants. An accelerant is an agent that speeds up the curing time of mortar. One such
accelerant is calcium chloride. This is sometimes used when working conditions are very cold (40
degrees Fahrenheit or below) and there is a danger of the mortar freezing before it is completely set.
However, since calcium chloride corrodes metal, its use is discouraged by most building codes. Instead,
heating devices and Type III cement are recommended.
1-8. Retardants. Retardants are admixtures that slow down the curing time of mortar. These may be
specified when conditions are very hot and dry, causing the mortar to set too rapidly and never attain its
strength. However, most building codes discourage the use of retardants when other means of retarding,
such insulation, may be used.