The effects of dissolved solids in process cooling water and mine water on concrete corrosion.

Abstract

An investigation has been carried out to determine the effects of the dissolved solids in process cooling water (pcw) and mine water (mw) on concrete corrosion. An experimental set up was designed to simulate the process in the cooling towers of Sasol (Pty) Ltd at Secunda. The investigation was carried out using Ordinary Portland Cement (OPC) and Portland Blastfurnace Cement (PBFC). The corrosion process was monitored as a function of time by determining the concentrations of the ions left in solution. This was done using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) and Ion Chromatography (lC). The observation, identification and characterization of the secondary phases formed during the corrosion process were analyzed using the Scanning Electron Microscopy(SEM). Energy Dispersive X-ray Microanalysis (EDX) made it possible to identify the various microstructures and quantify their elemental composition. This made it possible to monitor the penetration of sulphate ions in the mortar. Powder X-ray Diffraction (XRD) qualitative analysis was also performed on the test mortar specimens. The organic constituents in process cooling water were determined using Gas Chromatography coupled with a Mass Spectrometer (GC-MS). The corrosion indices which measures the aggressiveness of water solutions towards cement and concrete were calculated for both process cooling water and mine water. The results of the investigation showed that mine water is more corrosive than process cooling water. This observation has been linked to the presence of the organic compounds in process cooling water. The results also indicated that PBFC was mores resistant to chemical attack than ope.