In situ Determination of the Chloride Content of Portland Cement Concrete Bridge Decks

摘要

The objective is to develop an instrument and test procedure for rapid, local, in situ determination of chloride content in PCC bridge decks or other reinforced concrete members at the level of the outermost mat of reinforcing steel. In Phase I (report FHWA-RD-77-26) a dual measurement method, employing thermal neutron prompt gammas and thermal neutron activation, was shown to be feasible for non-destructive monitoring of chloride content below the surface. In Phase II the prototype instrument, a self-contained vehicle, has been developed and has undergone laboratory evaluation and field trials. Laboratory chloride determinations, made on over 100 concrete test specimens show insensitivity to water/cement ratio; moisture content; reinforcing bar location and pattern; aggregate type, and presence of overlays or membranes (unless they contain PVC). Field trials were conducted on 5 bridges in Texas. They confirmed that up to six non-destructive chloride measurements per hour can be made with enough sensitivity to permit on-the-spot decisions regarding bridge deck repair or maintenance.