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Corrosion of Reinforcing Steel in Sabkha Environment
... The exposure of the concrete specimens to the salt solution was cyclic. Each cycle of exposure comprised of wetting the specimens for 24 h followed by drying them for 48 h simulating the wetting and drying of concrete in real-life marine environments [43,44]. After exposing the specimens to the wet-dry cycles for the durations of 6 and 12 months, visual inspection of the specimens were conducted to detect deterioration on the surface, if any. ...
In the present work, effect of inclusion of silica fume on the performance of natural pozzolan-based cement concrete was investigated. Natural pozzolan, obtained from volcanic rocks, was used as the main supplementary cementitious material to partially replace the Portland cement. Silica fume was admixed at an optimum dosage, optimally selected based on the performance of several trial mixtures, in an attempt to improve the performance of the natural pozzolan-based cement concrete. Compressive strength, drying shrinkage, water penetration depth, coefficient of chloride diffusion, carbonation depth, reinforcement corrosion, loss of strength due to exposure to sulfate and salt weathering were measured to evaluate the performance of the concrete mixtures. Inclusion of silica fume to the blend of natural pozzolan and Portland cement significantly improved the performance of concrete. Reduction in the early age compressive strength of natural pozzolan-based cement concrete was compensated for by the addition of silica fume. Inclusion of silica fume to the natural pozzolan-based concrete significantly improved the durability characteristics without significant increase in the shrinkage. Though the addition of silica fume increased the carbonation depth, the increased carbonation depth was much less than the cover thickness normally provided over reinforcing steel, ruling out the possibility of reinforcement corrosion.
Marine, coastal and offshore environments or soils charged with concentrated brines are characterized by high concentrations of chlorides and sulfates. The influence of sulfate ions on chloride-induced corrosion of reinforcing steel in concrete has not been well documented in the literature. An exemplary situation, where these salts exist concomitantly, is the sabkha soil which prevails in many parts of the world. The severity of sabkha environment has resulted in a lot of resources being spent on repair and rehabilitation of the deteriorated concrete infrastructures.
This paper summarizes the results of a comprehensive investigation to evaluate the corrosion performance of reinforced concrete prepared with plain cements (Type I and Type V) and blended cements (made with fly ash, silica fume and blast furnace slag) exposed to sulfate-chloride environments as well as to a “genuine” eastern Saudi sabkha. Several corrosion-related tests were conducted including corrosion potential, corrosion current density and chemical analyses. Based on the results of this investigation, specifications for durable concrete to serve in the aggressive sabkha media are presented and compared with the international codes of practice.
In all published studies of cement carbonation there has been general agreement that it must be considered as a cause of generalised corrosion in reinforcements, but quantitative data have been provided in very few cases. In the present work the intensity of attack has been modified by means of the accelerated carbonation of mortar specimens without additives, with 2% CaCl2, and with 3% NaNO2 It has been shown that a critical level of atmospheric moisture must also be present for considerable attack to occur. The measurement of polarisation resistance (Rp) has been used to evaluate the intensity of corrosion of the reinforcements. This method has already been usefully applied by the authors to investigations of corrosion of steel bars in hardened concrete specimens.