Microstructure of Selected Mortars Undergoing Long-term Influence of External Environment

Abstract

A facial wall is defined as an element used outside or inside which should have an attractive look. It is built from attractive wall elements using standard way of execution and joints filled with mortar appropriate for this type of wall element. From the point of view of durability, the mortar is a wall element which not only binds bricks but also takes part in humidity transport. It is associated with mortar microstructure which in comparison to clinker is characterized with high percentage of pores causing capillary flow and wall drying abilities. Mortars belong to the group of chemically active materials for which both internal as external factors are essential. The reason for internal corrosion are mortar components (binder, sand, water, additions). External corrosion includes all cases where mortar is threatened with external factors (CO2 gas, acid rain, temperature changes exceeding zero point, solution of soluble mineral salts originating from surrounding elements). The factors mentioned essentially influence mortar microstructure changes. This process is distributed in time. This work concerns the analysis of changes in quantity and distribution of pores resulting from many years of functioning of mortar in facial wall threatened with external factors. The researches were performed on a field test station localized in area of the University of Science and Technology in Bydgoszcz (Poland). Three facial walls with different mortars were chosen: Portland cement based mortar CEM I, Portland cement based mortar CEM I with plasticizer and cement-lime mortar. During construction of walls, standard beams were formed from mortars in order to perform basic tests and microstructure tests after 28 days of hardening.