Behaviour of a Sustainable Concrete in Acidic Environment

Abstract

Sustainability has become one of the most important considerations in building design and construction in recent years. Concrete is susceptible to acid attack because of its alkaline nature. The socioeconomic losses associated with infrastructure deterioration due to acid attack exceed billions of dollars all around the world. An experimental investigation was carried out to study the behaviour of sustainable concrete in 3% sulphuric acid and 1.5% nitric acid environment in which cement was replaced by a combination of fly ash and ultra fine fly ash. It was found that the compressive strength loss of concrete in these acid environments was the minimum in which cement was replaced by 30% fly ash and 10% ultra fine fly ash. This mix also showed the lowest mass loss when exposed to these acids.

Effect of fly ash on the corrosion performance and structural integrity of stainless steel concrete rebars in acid rain and saline environments

“…Furthermore, the detection of chlorine in the surface film of Figs.5(a,b) indicates the formation of salts analogous to the Friedel's salt that may trap Clby chemical and/or physical bonding, hence delaying and/or limiting the aggressive Claccess into the interior of the steel. b) Partial replacement of Ca(OH)2 by supplementary cementitious materials, which decrease the Ca(OH)2 content available for reaction with the AR constituents, in compatibility with [16,17]. c) In the case of the low pH environment, the positive effect of FA is also attributed to the increase in the pH with FA content increasing, as already mentioned.…”

“…These compounds are dissolved in the rainwater, facilitating the ingress of Clto the steel surface). More analytically, this work suggests that the beneficial effect of FA on the corrosion performance of 304L rebars stems from the following reasons: a) Deposition of products of chemical interactions between the involved species (C-S-H, calcium sulfoaluminates, calcium aluminate silicate hydrates) that are more resistant than Ca(OH)2 to aggressive ions [16,33]. Furthermore, the detection of chlorine in the surface film of Figs.5(a,b) indicates the formation of salts analogous to the Friedel's salt that may trap Clby chemical and/or physical bonding, hence delaying and/or limiting the aggressive Claccess into the interior of the steel.…”

“…More specifically, it is generally accepted that the acidic constituents of AR rapidly react with Ca(OH)2 to form hydrated salts soluble in rainwater. (It is recognized that Ordinary Portland Cement (OPC) has minimal resistance to acid (pH ≤ 3) attacks [16]). These solutions penetrate the interior of the concrete through its pores.…”

Durability Issues and Corrosion of Structural Materials and Systems in Farm Environment

“…Inorganic acids have a similar effect on the structural integrity of acidic structures. The impact of the acid attacks on the surface and cross-sectional morphology of the cement microstructure is visualized in the scanning electron micrographs in Figure 5a,b [15]. The decline in strength was proportional to the duration of exposure to acidic environments, as shown in Table 5.…”

“…However, the durability of concrete is the most pertinent factor; timber is used in limited applications because it is susceptible to fungal and insect attacks, discoloration, decay, swelling, and shrinkage [10]. Similarly, metallic structures are more susceptible to corrosion compared to concrete structures [2,11,[13][14][15]. Concrete structures in farm environments are exposed to different forms of corrosive agents such as meal-water mixtures, acids, and bacteria, which suppress the pH and contribute to the accumulation of organic acids such as lactic acid, development of soluble calcium salts and leaching [12].…”