Principle and Performance of Latex-modified Mortars

Synopsis: The paper is a review of principle and performance of latex modified mortars.When latex (i.e. a polymer dispersion in water) is added to a cement based mortar, the polymer particles will partly adhere to the cement grains and improve the rheology, and after setting when liquid water is reduced by hydration the polymer particles are brought closer together and finally they will coalesce to a polymer film providing that the minimum film forming temperature (MFT) of the polymer is lower than ambient temperature. Then a true organic-inorganic composite is formed with continuous films of polymer (providing high enough dosage) and continuous cementitious binder.A system is discussed for elucidating the effect of polymer based on volume replacement of cementitious binder keeping w/c constant rather than comparing mortars of equal flow (and thereby improvement by lower w/c achievable by cheaper means).The effect of latex on mechanical properties (e.g. flexural strength) is briefly discussed with emphasis on curing conditions and moisture state.More importantly, the influence of latex on durability is reviewed, like chloride ingress, carbonation, capillary suction of water etc.