Effect of stagnant rainwater on a concrete element

This study investigates the degradation of a reinforced concrete slab caused by stagnant rainwater during the winter period. Visible signs of damage include whitish surface traces and deposits (stalactites) forming beneath the slab, potentially linked to the concrete leaching by the stagnant rainwater. An investigation into the concrete material of the passageway slab of the university employed various laboratory techniques, including Thermal Gravimetric Analysis (TGA), Differential Thermal Analysis (DTA), microscopic analysis using Scanning Electron Microscopy (SEM), and physical analysis using mercury porosimetry. Visual observations suggest a variation in the degradation level throughout the slab thickness. This is likely due to microstructural phenomena and physico-chemical mechanisms such as the dissolution of the concrete paste especially the existing hydrates and the formation and precipitation of new ones like ettringite and additionally, there is the dust grain descent caused by the water that follows within the concrete slab, potentially leading to self-clogging and a form of self-repair within the concrete.