Search results
Results From The WOW.Com Content Network
Sulfate attack typically happens to ground floor slabs in contact with soils containing a source of sulfates. [2] Sulfates dissolved by ground moisture migrate into the concrete of the slab where they react with different mineral phases of the hardened cement paste. The attack arises from soils containing SO 2−
The thaumasite form of sulfate attack (TSA) is a particular type of very destructive sulfate attack. C-S-H are the "glue" in the hardened cement paste filling the interstices between the concrete aggregates. As the TSA reaction consumes the silicates of the "cement glue", it can lead to a harmful decohesion and a softening of concrete ...
A less common, but very severe, form of ESA is the thaumasitic form of sulfate attack (TSA) when concrete is exposed to an external source of sulfate in the concomitant presence of carbonate, HCO − 3 ions, or CO 2. [24] It preferentially occurs in clay formations exposed to air oxygen by excavation works and in which pyrite has been oxidized.
Unlike conventional sulfate attack, in which the calcium hydroxide (portlandite) and calcium aluminate hydrates react with sulfates to form gypsum and ettringite (an expansive phase) respectively, in the case of the thaumasite form of sulfate attack (TSA) the calcium silicate hydrates ensuring the cohesion in the hardened cement paste are also ...
GGBS cement is routinely specified in concrete to provide protection against both sulfate attack and chloride attack. GGBS has now effectively replaced sulfate-resisting Portland cement (SRPC) on the market for sulfate resistance because of its superior performance and greatly reduced cost compared to SRPC.
Biogenic sulfide corrosion is a bacterially mediated process of forming hydrogen sulfide gas and the subsequent conversion to sulfuric acid that attacks concrete and steel within wastewater environments. The hydrogen sulfide gas is biochemically oxidized in the presence of moisture to form sulfuric acid.
Sulfate attacks, an hat appellation covering different concrete degradation mechanisms: Delayed ettringite formation (DEF), also known as internal sulfate attack (ISA) when the temperature of fresh concrete exceeds 65 °C during its setting and hardening; External sulfate attack (ESA), and; Thaumasite form of sulfate attack (TSA).
As the concentration increases, the attack on the Portland cement can begin. For buried structures such as pipe, this type of attack is much rarer, especially in the eastern United States. The sulfate ion concentration increases much slower in the soil mass and is especially dependent upon the initial amount of sulfates in the native soil.