Long-Term Behavior of Cracked SFRC Elements Exposed to Chloride Solutions

摘要

The design of Steel-Fiber-Reinforced-Concrete (SFRC) pavements is mainly controlled by requirements in terms of serviceability limit states (short and long-term deformation, cracking, durability) and only marginally by requirements in terms of ultimate limit states. Despite that, experimental data on the behavior of SFRC under serviceability loads, especially as far as creep and durability are concerned, is nowadays still very limited. This paper describes the first results of an experimental campaign aimed at investigating the long-term behavior of cracked SFRC beams-with dimensions defined in order to be representative of a pavement strip-exposed to chloride solutions. In order to represent serviceability conditions where environmental actions act while structural elements are under loading a specific test procedure was developed. In the first stage of the procedure the specimens (two beams) were pre-cracked up to a chosen crack-opening value, then they were unloaded and subsequently reloaded with a fraction of the load corresponding to the flexural tensile-strength of the cracked cross section (previously reached). This reduced load was then kept constant, in a four-point bending scheme. During this stage of the test one of the beams was exposed to drying-wetting cycles in a 5% NaCl solution while the other beam was left unexposed. This long-term test lasted for about 8 months and was performed in a climate-controlled room. The mid-span deflection and the crack opening of the beams were monitored for the entire length of the test. At the end of the long-term test the beams were loaded up to failure. The results obtained show that the effects of the exposure to the aggressive environment are limited on both the long-term behavior and the residual flexural tensile-strength of the SFRC beams.