Deterioration of PVC flooring due to alkaline moisture: 5-year follow-up study

In-situ cast concrete slabs with high moisture content and elevated pH levels (approximately pH 12.5) create optimal conditions for hydrolysis reactions, leading to the degradation of PVC flooring adhered to these slabs. To mitigate this issue, solutions identified in the 1990s include either installing floor coverings on sufficiently dry concrete (with a relative humidity limit of 85% as recommended by most floor covering manufacturers) or placing a layer of low-alkali material, typically a self-levelling screed, between the concrete slab and the floor covering. This paper presents a 5-year follow-up study on the degradation (measured by VOC emissions) of PVC floorings containing the contemporary plasticizer di(isononyl) cyclohexane-1,2-dicarboxylate (DINCH), installed under varying conditions of concrete relative humidity and the pH of the underlying material. The findings indicate that both the pH and the type of screed material significantly influence the degradation process and VOC emissions. Specifically, lower pH levels of the material in contact with the flooring result in reduced VOC emissions. The critical pH threshold is identified around pH 12; materials with higher pH levels lead to a substantial increase in emissions. Additionally, there are notable temporal variations in the occurrence of different emission compounds.