Development associate, Dow Chemical Company, Midland, MI
Latexes currently used for modifying portland cement contribute many property improvements to mortar and concrete. Many different polymers are used to make these latexes, but all have one thing in common: they form a film at normal working temperatures. It is the formation of this film that is generally understood to be critical to the performance of these latexes in portland cement and responsible for certain of the property improvements in the hardened mortar and concrete.
Contrary to this accepted understanding, an experimental latex has been developed for use in portland cement that does not form a film at room temperature. Instead, the latex particles maintain their integrity as spheres after the portland cement mixture hardens and still provides property improvement in the hardened mixture. The lack of film-formation also eliminates the stickiness during finishing and the surface crusting from air-drying that are typical of the film-forming latexes used in portland cement.
Tests of this latex were conducted on mortar with ceramic tile and compared to mortars using standard film-forming latexes. Workability, compressive strength, and shear bond of the mortars were evaluated. In addition, flexural bond strength of tile-to-plywood and cement backerboard was measured using a new test procedure.
Paper ID: CCA10146J