Effects of corrosion on tension stiffening and cracking behaviour of reinforced Engineered Cementitious Composite and concrete

As a kind of ductile fiber-reinforced cementitious composite, Engineered Cementitious Composite (ECC) has great crack width control ability and improved durability.However, there are only limited studies on the durability of steel reinforced ECC (R/ECC) members.This makes the service life quantification of R/ECC members lack of research data.The present study investigates the interaction behaviour between steel rebar and ECC after corrosion exposure.Results from four R/ECC and four reinforced concrete (RC) ties with the dimension of 7575600 mm and corrosion levels up to about 5% were reported herein.Corrosion-induced cracks were recorded during accelerated corrosion tests.After corrosion, the corroded ties were tested under uniaxial tension together with the uncorroded ties.Steel strain distributions of specimens during tension were monitored by distributed optical fiber sensors (DOFS) to examine the stress transfer mechanism between rebar and matrix.The impacts of steel corrosion on the tension-stiffening behaviour of R/ECC specimens were compared with those of RC ones.It was found that the corrosion-induced cracking degree in ECC was much smaller than that in concrete.Moreover, corrosion improved tension-stiffening effect in all R/ECC ties and decreased in all RC ties from the load-average strain curves.The number of transverse major cracks in corroded R/ECC ties was kept similar as in the uncorroded tie, but the microcracks number decreased.In the group of RC ties, the transverse major cracks were only seen in the uncorroded specimen whereas several secondary cracks emerging from longitudinal cracks appeared in corroded specimens.Further, DOFS data displayed that steel reinforcement in ECC generally exhibited more uniform deformation than that in concrete.The strain distributions in corroded R/ECC ties were not changed apparently, and the steel strains in the corroded R/ECC ties are slightly larger than those in the uncorroded R/ECC tie at similar average corrosion level.This implies that bond strength can be well maintained in uncorroded R/ECC.The distance of strain peaks in corroded RC ties increased compared to that in the uncorroded RC tie, which reflected a decrease of bond strength in corroded RC ties for the investigated corrosion levels.The results from this study reveal that R/ECC members are less impaired by steel corrosion compared to concrete.