Ensuring good quality water for the population is an effective health protection measure. However, in the Republic of Congo, drinking water shortages are particularly acute in the cities of Pointe-Noire and Brazzaville, where the populations concerned are forced to build underground reinforced concrete tanks for the storage of large quantities of water, thus helping to alleviate this shortage. However, water stored in reinforced concrete tanks, which are porous in nature, installed in wetlands and polluted, is likely to be crossed by an aggressive diffuse current caused by pollution of the surrounding environment due to human activities, untreated landfills, or other types of pollution. Entropic activities and untreated garbage dumps significantly alter wet sites, thus promoting the dissolution and migration of pollutants to groundwater at depth by gravity and through the underlying soils.
This weakness constitutes preferential routes for the diffusion via the capillary and porous network of aggressive substances dissolved in the water table, which is flush with the natural ground (soil), thus altering the quality of the water stored inside the reservoir. This has a negative impact on the durability of the storage tank. The problem of optimizing the durability of the concretes constituting the underground tank in relation to external influences and the tightness of the walls then becomes a recurring problem. This durability induced by the transfer properties is also evident for all structures subjected to aggressive environments, which can lead to premature degradation of the concrete material. For these concrete tanks, this durability is not only based on their self-stability in view of the stresses caused by external actions, but also on their ability to prevent exchanges between the surrounding (aggressive) environment and the interior of the structure, thus avoiding the deterioration of the quality of the stored water.
Recent studies conducted by Chen courant (2011) show that the permeability of concrete represents the ability of porous material to be crossed by a fluid under a pressure gradient. It depends strongly on the porous network, its possible cracking and the water content of the material. This permeability is commonly used to assess the durability of concrete structures, especially when they are exposed to harmful environments. Also, in the case where the concrete structure is in contact with water, depending on the constitution of the cementitious matrix, permeability can be understood as the ability of the porous medium to allow a fluid to pass through it and completely fill the interconnected pores.
In this perspective, a study based on the physico-chemical analysis of water stored in underground reservoirs was carried out in order to assess the mineral pollution of water stored under the influence of the external environment. The aim is to highlight the lack of reliability in terms of waterproofing, reinforced concrete walls and, ultimately, the problem of transferring pollutants through the walls of the underground tank.