Study of the impact of sediments on the mechanical behavior of concrete and towards the penetration of carbon dioxide

Abstract

Dam reservoirs are exposed to a loss of water storage capacity due to the phenomenon of siltation. This particularity can be expressed by the siltation of reservoirs and the entrainment of particles transported by watercourses. Siltation of reservoirs is a critical state which causes a reduction in the storage capacity of dams. Algeria is characterized by a semi-arid climate, which annually loses a considerable volume of water storage. The carbonation of concrete is influenced by a number of parameters which accelerate its kinetics. These parameters are the porosity of the concrete, the quantity of lime contained in the cement, the concentration of CO2 in the atmosphere and the humidity of the environment. It should be noted that, water being the vector for moving aggressive agents, carbon dioxide can only diffuse through the concrete if the latter is not completely saturated and not perfectly dry at the same time. Another factor increasing the permeability of concrete is the amount of limestone added to the cement during its manufacture at the factory. This permeability allows the diffusion of CO2 or other aggressive agents in the concrete. The addition of limestone to cement must therefore be used with caution. The objective is to propose economically competitive and easy-to-implement formulations which allow the valorization of these materials in the making of ordinary concrete by partial substitution of cement (10, 20 and 30%) and its influence on the progress of long-term carbonation after six years of curing in the open air. The sediment is treated by calcination at 750°C to make it active. Natural carbonation tests were carried out on the study concretes in order to evaluate their durability. The results obtained confirmed the possibility of producing concretes incorporating calcined sludge at dosages of up to 30% without compromising the quality of these concretes from the point of view of behavior in the face of attacks by the dissolution of carbon dioxide from the air in the interstitial solution of concrete, meeting economic, ecological and technological objectives.