Effect of redispersible polymer powder on setting time of thin-bed mortars

Abstract

The aim of work is to describe and to complement the existing knowledge on the effect of redispersible polymer powder on the setting time of cement mortar as measured by means of ultrasonic apparatus. The mortars were simple mixtures of filler in the form of quartz sand, Portland cement CEM I 42.5 R as binder and methyl hydroxyethyl cellulose. The mortar additives were two commercially available redispersible polymer powders in an amount of 0-5% of total weight. The chosen polymers had different chemical structure: styrene-acrylic copolymer (SA), vinyl acetate-ethylene copolymer (ET), and minimum film forming temperature (MFFT). The amount of water was constant and equal to 20% of the total weight of the mortar. Conclusions: - even the small amount of redispersible polymer powder added to the cement mortar has a significant influence on mortar's initial and final setting time and this effect strongly depends on the percentage of the additive, - the chemical structure of the studied redispersible polymer powders did not influence the behaviour of the whole chemical system, - the further studies on technical properties, such as mechanical strength and permeability are planned in order to find more information on the structure of hardened mortar.