| Abstract |
In recent years, the early deterioration of concrete structures has become a major problem. One factor contributing to the deterioration of infrastructure is corrosion of embedded steel in concrete, w...hich is mainly caused by the ingress of aggressive agents (chloride ion and carbon dioxide, CO_2). Concern is growing about the durability of concrete, which depends not only on the quality of the concrete, but also on environmental conditions. Despite the huge amount of data available from a variety of studies, however, only a little real information exists on the long-term performance of concrete. Based on the reason, this study undertook experimental test long-term performance of concrete over 50 MPa in compressive strength. Five level of strength were evaluated in order to measure micro-pore structure associated with the transport of aggressive agent to achieve a certain level of durability, evaluations were also conducted on the prestressed concrete (PC) sheet pile and PC beams exposed in the marine environment for long period, and durability design for Indonesian climate was recommended. The results indicate that micro-pore structure is directly affected by characteristics of materials (type and amount of mineral admixtures, and aggregate quality), W/B and curing time. For PC sheet pile, even high strength concrete, cover depth of 30 mm is not enough for long-term serviceability under marine splash environments, and it is predicted to be only 20-year service life. Besides that, the use of GGBFS shows a significant reduction in the diffusion coefficient, which can provide a good barrier against chloride ingress and able to extend the service period of structures up to 65 years for 50 mm cover depth. Even though carbonation of the concrete did not cause corrosion of the reinforcement, however; it may have contributed to degradation of the cover concrete and indicating severe corrosion conditions for 35 years-old post-tensioned beams with 30 mm cover depth. Increasing in corrosion area of strands caused prestress losses up to 25% and the load bearing capacity dropped by 10%. In each case, it is clear that the quality of concrete and depth of cover to the reinforcement determines the time to corrosion activation. By considering Indonesian climate, a concrete cover of 70 mm with maximum w/c of 0.35 and minimum strength of 50 MPa is recommended if using Portland pozzolan cement (PPC) for a service life of 50 years.show more
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