CHLORIDE CONTAMINATION OF CONCRETE BY INTERACTION WITH PVC COMBUSTION

Chloride contamination of concrete by interaction with PVC combustion gases has been studied in a small-scale testing chamber, which allows simulating the conditions probably prevailing in PVC fires of differen t magnitude through variation of the quotient between mass of burnt PV C and exposed concrete surface (PVC/S). In all cases, a steep gradient of chloride concentration with depth is found after the fire: most ch loride is detected in the outermost layer at depths below 5 mm. Surfac e chloride contents (within 5 mm) for prestressed and reinforced concr etes, tested with a high (PVC/S) ratio, are as high as 2.5 and 5% by w eight of cement, respectively. Chloride concentrations in concrete nea r the steels are below the corrosion thresholds after the fire, but th ey can rise by diffusion to values able to induce rebar corrosion, esp ecially if concrete is exposed to a humid atmosphere. (C) 1998 Elsevie r Science Ltd.