Corrosion resistance, sulfur concrete

Sulfur can replace 30-50% of the asphalt in the hlends used for road construction. Road surfaces made from asphalt-sulfur hlends have nearly double the strength of conventional pavement, and it has been claimed that such roads are more resistant to climatic conditions. The impregnation of concrete with molten sulfur is another potential large sulfur use. Concretes impregnated with sulfur have better tensile strength and corrosion resistance than conventional concretes. Sulfur is also used to produce phosphorous pentasulfide, a precursor for zinc dithiophosphates used as corrosion inhibitors. 

Sulfur concretes (SC) are basically simple materials, made by mixing sulfur plus certain additives with heated mineral aggregates. On cooling, SC sets to give a high-strength material with superb corrosion resistance. 

Sulfur concretes can be designed to have compressive and tensile strengths twice or more those of comparable Portland cement concretes (PCC), and full strength is reached in hours rather then weeks. Sulfur concretes are extremely corrosion resistant to many chemicals, including most acids and salts. The metallurgical and fertilizer industries have shown interest in using SC in corrosive enviornments where PCC has a very short lifetime. 

A wide range of applications for sulfur concrete such as SUDICRETE provide many advantages. Included are industrial flooring, electrolytic vats, sumps, catch basins, tanks, sewage and waste impoundment ponds, bridge decks, pipes, etc., all of which can benefit from its extreme corrosion resistance. Rapid... 

Because of its flammability and the potential for oxides of sulfur, it is not normally used for most indoor applications. Table 10.2 provides the resistance of sulfur concrete to atmospheric corrosion. 

Figure 4-9. a) Principle of the simulation device for testing the resistance of concrete and other building materials to biogenic sulfuric acid corrosion, b) View of the open test chamber filled with test blocks. 

A simplification of the polarization resistance technique is the linear polarization technique in which it is assumed that the relationship between E and i is linear in a narrow range around E . Usually only two points ( , 0 are measured and B is assumed to have a constant value of about 20 mV. This approach is used in field tests and forms the basis of commercial corrosion rate monitors. Rp can also be determined as the dc limit of the electrochemical impedance. Mansfeld et al. used the linear polarization technique to determine Rp for mild steel sensors embedded in concrete exposed to a sewer environment for about 9 months. One sensor was periodically flushed with sewage in an attempt to remove the sulfuric acid produced by sulfur-oxidizing bacteria within a biofilm another sensor was used as a control. A data logging system collected Rp at 10-min intervals simultaneously for the two corrosion sensors and two pH electrodes placed at the concrete surface. Figure 2 shows the cumulative corrosion loss (Z INT) obtained by integration of the MRp time curves as ... 

Sulfur replacement of up to 52 wt % of the asphalt in binders has been possible, with no detrimental effects noted to date. Also, sulfur-asphalt concretes are more resistant to the corrosive action of fuels than are normal asphaltic concretes. 

PCs based on epoxy resin binder are resistant to many corrosive environments such as a concentrated solution of caustic soda at 90°C the action of alkali metal salts, alcohols, oils, gasoline and other aliphatic hydrocarbons. The flexural strength of epoxy PC is slightly affected by immersion in a 10% solutions of sulfuric acid and chloride sodium, which is an indicator of the good chemical resistance of this kind of concrete to these aggressive agents [11], However, these polymer concretes are not resistant to a sulfuric acid concentration of 60% and nitric acid concentrations above 70% [12],... 

FIGURE 2.57 Relationship between the RubCon coefficient of chemical resistance and time of corrosion medium exposition (1) water, (2) 30% solution of sulfuric acid, (3) 36% solution of hydrochloric acid, (4) 10% solution of caustic soda, (5) diesel fuel, (6) 5% solution of acetic acids. (Reprinted from Yu. Potapov, Yu. Borisov, V. Chmyhv, and D. Beilin, Research of Polymer Concrete Based on Low Molecular Polybutadiene, Part VIII Chemical Resistance of Polymer Concrete, J. Scientific Israel Technological Advantages 7, nos. 1-2 (2005) 72-78. With permission.)... 

Mansfeld and coworkers [44] used linear polarization to determine polarization resistance, i p, for mild steel sensors embedded in concrete exposed to a sewer environment. One concrete sample was periodically flushed with sewage to remove sulfuric acid produced by sulfur-oxidizing bacteria. Another sample was used as a control. A data logging system collected at 10-min intervals simultaneously for the two corrosion sensors and two additional pH electrodes placed at the concrete surface. Figure 7 [44] shows cumulative corrosion loss, S I NT... 

The choice of the appropriate material is decisive for resistance against microbially influenced corrosion. This means that before the choice of material can be made, what kind of impacts is has to resist needs to be considered. Microbial influencing factors must also be considered. Accordingly, in the presence of volatile sulfur compounds, e.g., in sewage pipelines, it is recommended not to use materials like unprotected concrete which may be destroyed by the end product of the microbial degradation process (in this case, sulfuric acid formed by Thiobacilli). Another example would be the choice of a stainless steel or of an alloy that cannot be attacked under the conditions of a biofllm and the complex metabolic processes occurring underneath it. If, for instance, a material has to be chosen for static reasons, this material has to be protected by a coating or a liner made of an inert material. All these examples are based on the consideration that all attack factors have been identified by a complete inventory. 

Figure 4-10. Two concrete specimens of different resistance from the test chamber after exposure to two test cycles of biogenic sulfuric acid corrosion, where PC is Portland cement (left) and HC is blast furnace cement (right).

---