ESTIMATION OF REBAR CORROSION IN CONCRETE USING GROUND PENETRATING RADAR

Abstract

The purpose of this research was to quantitatively relate the amount of rebar corrosion in concrete with the amplitude of electromagnetic waves generated from Ground penetrating radar (GPR). Many studies have been undertaken on qualitative measurement of corrosion, but there are very few studies regarding estimation of rebar corrosion quantitatively. This experiment involved the use of accelerated corrosion by impressed current technique to corrode the rebar inside the concrete and GPR to determine the extent of corrosion, while making a comparison with a stainless steel bar which was used as a cathode to create a galvanic cell action. Rebars were subjected to a constant 15 V power from a DC power supply while being immersed in a 5% NaCl till the corrosion products appeared on the concrete surface. Samples were removed from the tank after being subjected to their respective corrosion period and analyzed for corrosion extents and rebar mass loss. GPR readings were taken at the beginning, after salt water immersion and at the end of their respective corrosion periods. The results indicated the unique value of amplitude of GPR electro- magnetic waves related to different extents of corrosion and rebar mass loss. These results were later on compared with results obtained from a natural corrosion of # 4 (12.7 mm) rebar in bridge deck and percentage error was determined.