| The porosity of High Performance Concrete (HPC) especially when silica fume is added, is much lower than conventional mixes. It is, therefore, assumed that HPC provides significantly better protection against corrosion of reinforcing steel than conventional concrete.;As part of environmental protection efforts, the construction of effluent treatment vessels is of interest to the pulp & paper industry. An investigation of the durability of steel reinforced HPC, cast conventionally and precast, in this application is, therefore, particularly relevant.;A field exposure program is underway with cast-in-place and pre-cast samples, containing embedded reinforcing steel probes exposed to pulp & paper industry effluent at two locations on Vancouver Island, B.C., Canada. The cast-in-place samples were loaded in three-point bending prior to exposure to initiate cracks in the location of the steel probes. Probes were also embedded in uncracked areas of the slabs. To provide a basis of evaluating the HPC, one lower quality concrete, one industrial standard quality concrete, one HPC and one HPC containing silica fume were included in the test matrix. Parallel laboratory corrosion studies were conducted on cast-in-place concrete specimens exposed to a simulated effluent.;The reinforcing steel corrosion was evaluated using linear polarization resistance (LPR) and electrochemical noise measurement technology. Electrochemical noise was suitable to detect, but not quantify, corrosion of embedded reinforcing steel.;The initial results of the field exposure are also present. A lower water to cementitious ratio of the concrete was found to better protect the reinforcing steel from corrosion damage, both in the uncracked and cracked state. For laboratory samples, the use of silica fume drastically reduced the corrosion protection capabilities of HPC in the cracked state. Lower pH in the crack in this type of concrete is the probable cause of the poor performance of the cracked silica fume HPC. (Abstract shortened by UMI.). |
