Study of the Durability of OPC versus GGBS Concrete on Exposure to Silage Effluent

Abstract

Ordinary Portland cement (OPC) has been traditionally used in the construction of concrete silos in Ireland. However, the aggressive nature of the effluent produced by silage leads to severe degradation of the concrete. GGBS is a common addition to PC composites. It has been demonstrated that GGBS improves the general performance of PC concrete decreasing chloride diffusion and chloride ion permeability; reducing creep and drying shrinkage; increasing sulfate resistance; enhancing ultimate compressive strength and reducing heat of hydration and bleeding. It has also been suggested that GGBS may increase concrete durability in the aggressive environment of silos. In order to investigate this theory, a simulation study was carried out by immersing samples of mortars incorporating increasing amounts of GGBS in a silage effluent solution and a magnesium sulphate solution. Over the course of an experiment consisting of three, 28-day cycles of immersion in the silage effluent, the sample performance was evaluated by testing permeability, porosity, water absorption, capillary suction, compressive strength and mass loss. According to the results obtained, the OPC samples suffered the highest rise in permeability and porosity and the greatest loss in both mass and compressive strength. In addition, the durability of the mortars, when subjected to both salt crystallisation and silage effluent cycles, increased with increasing amounts of GGBS. The significant rise in capillary suction, water absorption and permeability over the course of the experiment indicates that the damage induced by the effluent is not as superficial as previously reported. Loss in mass and increase in permeability were found to be the most reliable indicators of corrosion as they gave the most dramatic and uniform results.

Performance of concrete incorporating GGBS in aggressive wastewater environments

“…The sulfate resisting capabilities of GGBS have been discussed on many occasions [20,21] with much of the benefit being attributed to a denser matrix, decreased permeability and a reduction in calcium hydroxide present in the hydrated system [22,23,24]. Furthermore, with the formation of a secondary C-S-H phase attributable to the long-term hydration of the GGBS, much of the alumina in the system becomes 'locked up' in this product and is not available to form ettringite during a sulfate attack [25].…”

Resistance of geopolymer and Portland cement based systems to silage effluent attack

“…Silage effluent is produced as a result of storing grass as winter feed for livestock [2]. The grass is placed in concrete silos, compacted and sealed.…”

Corrosion Effects on the Strength Properties of Steel Fibre Reinforced Concrete Containing Slag and Corrosion Inhibitor

“…The process of corrosion in fibre reinforced concrete 2 International Journal of Corrosion is phenomenal due to homogenized steel fibre distribution and, hence, more careful attention has to be provided for designing concrete constituents. In this direction, the cement replacements such as fly ash, ground granulated blast furnace slag, and silica fume were typically used in concrete construction to save cost [5][6][7][8]. The addition of such supplementary materials is found to be one choice for reducing the corrosion potential of steel fibre incorporated concrete mixtures.…”