Shrinkage, Creep, and Thermal Expansion

Kawanol found that, compared to ordinary cement mortar, a reduction in the drying shrinkage of latex-modified mortars is mainly due to the effects of the surfactants and antifoamers contained in the latexes. 

Conflicting data exist on the creep behavior of latex-modified mortar and concrete. The creep characteristics of SBR- and PAE-modified concretes reported by Ohamal l are represented in Fig. 4.40. Like ordinary cement concrete, the relationships between loading time (t) and creep strain (ec) or creep coefficient ( )) (i.e., creq) strain/elastic strain ratio) of the latex-modified concretes fit approximately the expression  

By contrast, SolomatovI found that the creep deformation in flexure of poly(vinyl acetate-dibutyl maleate)-modified mortar was several times larger than that of unmodified concrete at 20°C, and its catastrophic deformation occurred at 50°C since the polymer developed a high plasticity above its glass transition temperature. 

In general, the coefficient of thermal expansion of latex-modified mortar and concrete is directly influenced by that of the aggregates used, as in ordinary cement mortar and concrete. Latex-modified mortar and concrete usually have coefficients of thermal expansion equal to or slightly larger than that of ordinary mortar and concrete. Table 4.6l gives the coefficient of linear thermal expansion of SBR- and PVDC-modified mortars with variation of polymer-cement ratio. 

---