Reinforced concrete corrosion

The danger of corrosion is in general greater for pipelines in industrial installations than in long-distance pipelines because in most cases cell formation occurs with steel-reinforced concrete foundations (see Section 4.3). This danger of corrosion can be overcome by local cathodic protection in areas of distinct industrial installations. The method resembles that of local cathodic protection [1]. The protected area is not limited, i.e., the pipelines are not electrically isolated from continuing and branching pipelines. 

Cathodic protection of reinforcing steel with impressed current is a relatively new protection method. It was used experimentally at the end of the 1950s [21,22] for renovating steel-reinforced concrete structures damaged by corrosion, but not pursued further because of a lack of suitable anode materials so that driving voltages of 15 to 200 V had to be applied. Also, from previous experience [23-26], loss of adhesion between the steel and concrete due to cathodic alkalinity [see Eqs. (2-17) and (2-19)] was feared, which discouraged further technical development. 

The decision to cathodically protect reinforced concrete structures depends on technical and economic considerations. Cathodic protection is not an economic process for small area displacements of the concrete due to corrosion of the reinforcing steel arising from insufficient concrete covering. On the other hand, the... 

Since stray current corrosion damage can occur after only a few years, the economy of stray current protection measures is obviously not questionable [12], In Fig. 22-3 the effect of stray currents is shown by curve 2 [14]. Without there being firm evidence, it is apparent that the shape of the corrosion damage curve in steel-reinforced concrete (see Sections 10.3.6 and 4.3) is similar to that for stray current corrosion [15]. 

Treadaway, K. W. J., Cox, R. N. and Brown, B. L., Durability of corrosion resisting steels for reinforced concrete. Proceedings of the Institute of Civil Engineers (in press)... 

Reinforced concrete structures that are fully immersed or buried in a corrosive environment may generally be protected using conventional cathodic... 

Plastics provide different performance requirement in providing protective liners in many different applications such as building foundations, pipe and tank liners containing corrosive liquids, etc. As an example Fig. 4-13 shows an RP stack liner being inspected prior to installation in a 682 ft. high reinforced concrete chimney (background) of the 1,500-megawatt Intermountain Power Project near Delta, Utah (1985). 

The protection of steel reinforcements. Concrete produces a layer of passivity at the steel/concrete interface and any breakdown of this can increase the chance of reinforcement corrosion. In addition, it is important that concrete be maintained in a state of low permeability to minimize the passage of moisture and air to the steel. 

There has been controversy over the use of calcium chloride in concrete containing embedded metal in view of the possibility of corrosion, particularly where the concrete is of a porous nature. Many countries have made provision in the relevant codes of practice to prevent or limit its use where steel reinforcement is present. This has renewed interest in chloride-free accelerators as replacements for calcium chloride in reinforced concrete. However, calcium chloride remains a most effective material for use in unreinforced concrete for economic production under winter conditions and its effects on concrete, whether beneficial or undesirable, are well researched and quantified. In some areas the newer non-chloride materials, although shown to reduce the likelihood of reinforcement corrosion, have not been widely studied and their other effects on concrete are less known. 

Latex-modified mortars and concretes have become promising materials for preventing chloride-induced corrosion and for repairing damaged reinforced concrete structures. In Japan and the USA, latex-modified mortar is widely used as a construction material in bridge deck overlays and patching compounds, and for finishing and repairs [99]. Polymer-cement hydrate-... 

Griffin, D.F. (1975). Corrosion Inhibitors for Reinforced Concrete, Corrosion of Metals in Concrete, ACI SP-49, American Concrete Institute, Detroit, 95-102. 

The liquid waste is stored for at least 6 y prior to solidification to reduce the decay heat (Fig. 16.8) by a factor of 10 or more. The first U.S. military fuel reprocessing wastes were stored as neutralized waste in mild steel tanks at the Hanford reservation in eastern Washington. These steel-lined, reinforced-concrete tanks were 500,000-1,000,000 gal in capacity with provisions for removal of waste heat and radiolysis products. Corrosion of several tanks occurred with the release of waste. Fortunately, the soil around these tanks retarded nuclide transport. A better (and more expensive) design for storage tanks was implemented at the Savannah River site in South Carolina consisting of a second steel tank inside of a Hanford-style tank. The storage of acid waste in these tanks has not encountered the corrosion problems seen with the Hanford tanks. 

F. J. Ansuini and J. R. Dimond, Long-term stability testing of reference electrodes for reinforced concrete , Corrosion 94, Paper No. 295, NACE, Houston, TX, USA, 1994. 

The inhibitors considered thus far are either liquids or solids dissolved in solvents. Other useful type of inhibitors are vapor-phase corrosion inhibitors. These are used to minimize corrosion in electronics, packaging, processing industries, reinforced concrete,... 

Chloride contents must be kept low to avoid corrosion of steel in reinforced concrete (Section 12.3) and formation of kiln rings and preheater deposits. Contents below 0.02% are preferred, though higher ones can be acceptable if a sufficient proportion of the kiln gases is bypassed or in less energy-efficient (e.g. wet process) plants. 

The hydration reactions of alinite cements do not appear to have been reported, but it may be surmised that they are similar to those of Portland cements, with the probable addition to the products of CjA CaCK-lOHjO and possibly also of Ca2Cl2(0H)2 H20. The Cl is, however, not wholly and permanently combined in these or other hydration products. In tests on reinforced concrete, serious corrosion had occurred within 5 years, showing the cement to be unsuitable for such use (L51). 

Metal or steel reinforced concrete structures which are not in themselves inert to chemical attack (corrosion) from the environment in which they are designed to serve can very rarely be protected by a metallic surfacing. The normal protection under such conditions will be supplied by a nonmetal, often a coating. Each nonmetal so used has its own limitations—chemical or thermal—which must be considered. Therefore, in many cases, a combination of two or more nonmetals is required to provide the necessary ultimate protection to the steel or concrete. 

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