There are various factors that influences the durability of concrete and of which Sulphate and Chloride attack are probably considered the most extensive. The main reasons that make these attacks so harmful to concrete are inherent the concrete itself, to some degree.
Looking at the composition of concrete and what happens to concrete overtime, the older concrete gets, the more susceptible it becomes to these attacks. As concrete ages, it undergoes a process called self-desiccation, where the moisture dries out from the concrete and leaves behind air voids which ultimately leads to a net volume loss – and shrinkage occurs.
These voids and capillaries open up pathways for contaminants such as chlorides and sulphates to enter the concrete where they form harmful chemical reactions with either the cements past or result in the reinforcing steel being corroded. Therefor the main reason why these attacks are so detrimental to the concrete is due to the porous nature of concrete and the only way to stop this type deterioration is to increase the density of the concrete or to reduce the permeability of the concrete.
Sulphate Attack is a process where dissolved sulphates in ground water or other sources enter into the concrete, where it reacts with the minerals found inside of the concrete. These sulphates react with the minerals and in the majority of the time, these reactions are expansive, creating tensile forces which leads to spalling of the concrete.
Chlorides also enter the micro cracks and capillaries in the concrete matrix however they do not always influence the concrete. Chlorides penetrating deep into the concrete will eventually reach the reinforcing steel and combined with moisture and oxygen, will cause the steel to corrode and rust. Rust is an expansive process which will also cause the concrete to spall and accelerating the deterioration by opening up larger and larger cracks within the concrete.
The Penetron® system forms a chemical reaction with the by-products, released during the hydration process between the cement and water, to form insoluble crystals that provide both an increase in density and reduction in permeability.
The testing on the Penetron® System was completed by ÉMI Non-profit Llc. who carry out testing in compliance with domestic and international quality management standards. The ÉMI Non-profit Llc water penetration test practically illustrated the ability of Penetron® treated concrete to resists water penetration and shows a consistently low penetration depth (2mm – 4mm) regardless of its exposure to extreme hydrostatic water pressure (tested up to 20bar or 200m).
Reducing the permeability of any concrete, adding the self-healing ability of the Crystalline system, ensures that the concrete is protected from any contaminants wanting to enter the concrete matrix from the surface.
In closing, the Penetron® Crystalline system has been proven to have the ability to self-heal and close up any cracks, voids and capillaries up to a width of 0,4mm in size within a period of seven days when exposed to moisture (water). This will ensure the concrete structure and reinforcing will be protected, even when exposed to the most severe exposure conditions.