EFFECT OF SUPERPLASTICIZER ON CORROSION VULNERABILITY OF REINFORCED HPC

Abstract

The present study investigates the corrosion effect on reinforcing steel in reinforced HPC elements by three types of superplasticizers viz. modified lignosulphate(SP1), sulfonated naphthalene formaldehyde condensate(SP2) and polyether polycarboxylates(SP3). Beam specimens of size 100mmxl50mmxl200 mm were cast using high strength concrete mixes of M60 with 10% silica fume. After 56 days of moist curing, ponds were constructed on the tension side of these beams, and the specimens were subjected to ponding using 5% NaCl solution. Specimen beams of type SP3 were subjected to four points bending at 40% ultimate load. Half cell potential readings were taken to monitor the time taken for corrosion initiation. After corrosion initiation, an external current was applied to these specimens to accelerate the corrosion process. The residual loading capacity of the beams was found at the end of the durability exposure tests. The results indicate that the use of three types of superplasticizers with varying dosages have significant effects on reinforced HPC in both corrosion initiation and corrosion propagation as well as on residual flexural capacity as compared to plain concrete.