This paper describes an investigation of improving the bond strength of mas
onry mortars through the use of polymer additives, so that more efficient u
se of unreinforced masonry may be realized. A brief description of the mech
anisms involved in polymer-modification of cementitious materials is provid
ed as back-ground for the experimental program. Results from a clay brick,
type S cement-lime masonry mortar bond strength testing program investigati
ng various admixtures are presented. The admixture treatments include numer
ous latexes, a defoaming agent, and a superplasticizer. Test specimens were
cured under both moist and dry conditions. Very significant increases in b
ond strength were realized through the addition of several polymers, a plas
ticizer, and combinations of polymers and the plasticizer.