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Typical crack pattern of the alkali-silica reaction (ASR). The gel exudations through the concrete cracks have a characteristic yellow color and a high pH. The fatty aspect of the exudations imbibing the concrete porosity along the cracks is also a distinctive feature of ASR. The alkali-silica reaction as a chemical cycle process
Oxidation of pyrite in clay formations in contact with concrete – this produces sulfuric acid which reacts with concrete. Bacterial activity in sewers – anaerobic sulfate reduction at work in the organic-rich sludges accumulated under water in the conduits produces hydrogen sulfide gas (H 2 S).
Water loss at this stage aggravates concrete shrinkage and can cause unacceptable cracks to develop in concrete. Cracks form in case of a too short, or too poor, curing when young concrete has not yet developed a sufficient early strength to withstand tensile stress caused by undesirable and premature drying.
When T, or pH, decreases due to the cooling of concrete after setting and hardening, or because of the leaching of the concrete structure by water (immersed concrete component, such as a pile of a bridge), the sulfate ions physically adsorbed onto C-S-H are released (desorption process) into the concrete pore water and become available for the ...
Michigan Concrete Association recommends a regular salt like Morton table salt instead of an ice melter because it’s 100 percent sodium chloride (NaCl). This, however, is recommended for ...
This reaction is expansive, and can disrupt mature concrete. Where concrete is to be placed in contact with, for example, sulfate-laden ground waters, either a "sulfate-resisting" cement (with low levels of tricalcium aluminate) is used, or slag is added to the cement or to the concrete mix. The slag contributes sufficient aluminium to suppress ...
Aluminium sulfate is a salt with the formula Al 2 (SO 4) 3. It is soluble in water and is mainly used as a coagulating agent (promoting particle collision by neutralizing charge) in the purification of drinking water [ 3 ] [ 4 ] and wastewater treatment plants , and also in paper manufacturing.
Corrosion may occur where stale sewage generates hydrogen sulfide gas into an atmosphere containing oxygen gas and high relative humidity. There must be an underlying anaerobic aquatic habitat containing sulfates and an overlying aerobic aquatic habitat separated by a gas phase containing both oxygen and hydrogen sulfide at concentrations in excess of 2 ppm.