Bond of reinforcement in concrete with different types of corroded bars
thesisposted on 08.06.2021, 12:19 authored by Assem Adel Abdel Aal Hassan
Repair and rehabilitation of existing structures is becoming a major part of the present construction activities. Corrosion of reinforcement is a major contributing factor to the deterioration of reinforced concrete steel structure. Corrosion of reinforcing steel severely influences the bond at the steel-concrete interface. The aim of this research is to study the effect of corrosion on bond strength using pullout specimens and four different types of concrete having three different types of steel embedded. The study is conducted for four levels of corrosion ranging from uncorroded to severely corroded specimens. The four concrete types used were fly ash concrete mixture, silica fume concrete mixture, normal Portland Cement (NPC) concrete mixture with a water/cement ratio (w/c) of 0.32 and a 0.52 w/c ratio concrete mixture. Each type of these concretes has three different types of steel embedded in them: regular carbon, stainless, and epoxy coated steel bars. The relationship between the bond strength, weight loss and the rib profile loss is studied. The results showed preference for using regular carbon steel bars than stainless steel bars, stainless steel bars exhibited badly damaged shape with lots of voids compared to the regular carbon steel bars. Also, the bond strength for corroded and un-corroded stainless steel bars was lower than that of the regular carbon steel bars. Low levels of corrosion (about 0.5 to 1% of mass loss) were noted to improve the bond strength slightly when using either regular carbon steel bars or stainless steel bars embedded in any type of the concrete mixtures. However, bond strength decreases rapidly with an increase in the corrosion level for both regular carbon and stainless steel bars in any type of the concrete mixtures used. The use of supplementary cementing materials (SCM) such as fly ash and silica fume was very effective in delaying the corrosion process compared to that of NPC concrete with no SCM. Also, the bond performance of any steel bars embedded in NPC concrete with low w/c (0.32) was found to be superior to that of a concrete mexture with high w/c (0.52). However, the bond strength for F.A and S.F concrete was slightly lower than that for the NPC concrete with 0.32 w/c ratio.