Chemischer Angriff auf verpresste Anker und Pfähle

Chemical Attack on Grouted Piles and Anchors A Numerical Prognosis of Durability

With the aid of numerical simulation, the degradation of grouted piles and anchors in presence of high amounts of ammoniumions (up to 150 mg/L NH4+) and chloride-ions (up to 2500 mg/L Cl-) was calculated. Given these environmental conditions it can be assumed, that the grout (cement paste with high w/b) is dissolved by the ammonium-ions, and the steel of the piles and anchors is corroded because of the reduction of the pH-value and the attack of the chloride-ions. Until now there is not one technical rule or a code that deals with the durability of piles and anchors that suffer from chemical attack due to ammonium or chloride or both combined. The designers are not sure how to establish the durability in that case. Due to this fact a numerical calculation of combined chemical attack of ammonium-ions and chloride-ions is performed for real environmental conditions. For that purpose the numerical model Transreac is used. This model combines the calculation of transport processes in porous materials and the calculation of chemical reactions. The numerical prognosis shows that the grout is not likely to degenerate within 100 years by reason of the attack of ammonium-ions. Furthermore, there will not be a considerable consumption of steel in the anchor within the given conditions, neither from the decrease in the pH-value nor from the chloride.