Effects of a fine smoothing mortar layer in the prevention of chemical floor covering deterioration

摘要

This paper examines how a fine smoothing mortar (FSM) layer affects the moisture state and performance of covered concrete slabs, and discusses ion and pore water transport through the FSM layer from the concrete slab to the adhesive and overlaying floor covering materials. Similarly, changes in the pH value of the FSM due to ageing and moisture content are also discussed. In order to obtain a fast floor covering time and to ensure that the moisture content under the floor covering does not impair quality, a thin FSM layer should be installed fairly soon after casting and after necessary curing it should be allowed to dry uncovered for few days to several weeks. It has been confirmed that a low-alkali smoothing mortar layer can hinder the destruction of adhesives and floor covering materials caused by high moisture content, alkalinity and high OH~- ion contents in the pore water of concrete. However, where the mortar layer has cracked, it has also been found that the performance and quality of the covering material can be reduced even when a low-alkali smoothing mortar layer is used. Cracks in the smoothing mortar layer can cause moisture and reactive ions to penetrate the adhesives and floor covering layers. The destruction of some adhesives can take place also in a low pH and high RH environment, and the adhesion between concrete and the FSM layer can be lost due to high pH at the concrete surface.