Influence of Crystallization Admixture on Mechanical Parameters and Microstructure of Polymer-Cement Mortars with Waste Limestone

Abstract

Many years of experience in practice not only in the Czech Republic but also around the world have shown that crystallising waterproofing technology (mortars, coatings) improves the water and water-vapor impermeability of the treated structures and thus positively affects the durability of concrete. The sealing of pores, capillaries and cracks also prevents degradation due to physical and mechanical structural actions (e.g. the effects of ice and salts in pores, etc.). In the presented research, the influence of different crystallization admixture (CA) contents on the mechanical properties of polymer-cement mortar with 24% cement substitution by waste limestone was investigated. The crystallization admixture (CA) was added in different amounts at 0.8, 1.6 and 2.4% of the cement content in the mix. It was determined that the mechanical properties, namely the compressive and flexural strengths were not significantly influenced by the CA addition, with the highest difference recorded in the compressive strength (7%). The cohesion with the base concrete containing different amounts of limestone was sufficient, and the bond of the mortar to concrete was also closely examined using scanning electron microscopy (SEM). Through the SEM investigation it was determined that the presence of waste limestone of particle size below 250 μm did not affect the formation of crystals during the proper hydration process, in a climatic chamber at a high relative humidity (99%).