Investigation on the influence of fibre reinforcement on chloride induced corrosion of RC structures

Paper in proceeding, 2016

Corrosion of reinforcement is the main cause of deterioration of RC structures located in marine environments or subjected to de-icing salts. In order to delay the ingress of chlorides, such structures require the use of thick, dense concrete covers and strict crack width limitations. Given the crack limiting effect provided by fibres, it would be of interest to incorporate fibre reinforcement to conventionally reinforced concrete structures. Nevertheless, whereas fibre reinforcement might delay the penetration of detrimental agents into the concrete through crack control, there are other aspects which need to be addressed to determine whether fibres can improve the overall durability of RC structures. Several experiments were conducted within the present project, parts of them still ongoing, to investigate some of these aspects, namely: (i) the effect of fibres on the diffusivity of uncracked concrete; (ii) whether fibres may affect the corrosion onset of rebars for any crack width; (iii) whether steel fibres, due to their conductive nature, might influence the resistivity and consequently the corrosion rate of embedded rebars; and (iv) whether there is a risk of galvanic corrosion between steel fibres and rebars. Obtained results from chloride migration and bulk diffusion tests showed that fibres had no significant influence on the diffusion coefficient of concrete. Results from experiments in which RC beams were subjected to different loading conditions and thereafter naturally corroded through exposure to highly concentrated salt solution, showed a trend for earlier corrosion initiation with increasing crack width. Concrete mixes incorporating fibres exhibited similar or delayed corrosion onset compared to their plain concrete counterparts. While resistivity of FRC was consistently lower than resistivity of plain concrete measured under AC at 1 kHz, corrosion rate measurements based on the galvanostatic pulse technique showed no clear correlation between the presence of fibres and the corrosion rate.