The coalescence of polymer particles (continuous polymer film formation) in powdered polymer-modified mortars (PPMMs) and aqueous polymer-modified mortars (APMMs) was evaluated and compared. Polymer-modified mortars (PMMs) using various redispersible polymer powders (powdered cement modifiers) and polymer dispersions (aqueous cement modifiers) were prepared by varying the polymer-cement ratio (P/C) and were characterised by SEM after curing for 28 days. It was concluded that mortar constituents of unmodified mortar (UMM) are loosely joined with each other due to the absence of polymer films, thus having a structure with comparatively lower strength and durability. By contrast, mortar constituents in PPMMs and APMMs are compactly joined with each other due to the presence of interweaving polymer films, thereby forming a monolithic structure with improved strength and durability. However, the results confirm the poor coalescence of polymer particles or development of inferior quality polymer films in PPMMs compared to APMMs. Moreover, PPMMs show a less uniform distribution of polymer films. Different powdered cement modifiers have different film-forming capabilities. However, such a difference is hardly recognised in aqueous cement modifiers. The polymer films in PPMMs and APMMs may acquire different structures. They may appear as mesh-like, thread-like, rugged, dense or fibrous with fine or rough surfaces. Development of coherent polymer films is not well pronounced at a P/C of 5% in PPMMs, whereas sometimes coherent polymer films are seen at a P/C of 5% in APMMs. At a P/C of 10% or more, fully developed, coherent polymer films are seen in both PPMMs and APMMs. 16 refs.
Primary author(s): Afridi M U K; Ohama Y; Demura K; Iqbal M Z
Dadabhoy Construction Technologies (Pvt) Ltd.; Nihon,University; Lahore,University of the Punjab