Abstract
The research concentrated on the corrosion resistance of reinforced self-consolidating concrete (SCC), lightweight SCC (LWSCC), fiber reinforced LWSCC (FRLWSCC), Engineered cementitious composite (ECC) and composite (ECC-SCC/LWSCC) beams. The performance of corroded beams were analyzed based on current measurements, half-cell potential readings, crack pattern/width, rebar mass loss and diameter reduction from accelerated corrosion tests. Corroded and their companion uncorroded beams were tested to failure under four-point loading to evaluate load-deflection response, crack pattern, 1st flexure/diagonal cracking load, failure load and failure modes. Composite beams with higher ECC layer thickness exhibited superior corrosion resistance than their lower thickness counterparts and full depth SCC or LWSCC counterparts as well as performance of beams with ECC wrap was better than those with layer. Overall, ECC beams can be a superior alternative of their conventional counterparts and ECC can be used as layer or wrapping in conventional/LWSCC beams to enhance corrosion resistance and structural performance
Highlights
Introduction and Mix designCivil infrastructures are always subject to multi-hazards such as earthquakes, fires, the wind, storm surges
Packing density concept is a technique of concrete mix design that has been successfully utilized in lightweight SCC (LWSCC) by determining the best cement to aggregates packing voids ratio (Lotfy et al.,2015).The objective of LWSCC mix design are to minimize the voids volumes related to the coarse aggregate, maximize the density of the cementitious materials, minimize the water to cement ratio and (d) optimize the flowability requirements of the fresh concrete (Kaffetzakis & Papanicolaou, 2012)
The performance of corroded full-depth self-consolidating concrete (SCC)/Engineered cementitious composite (ECC)/LWSCC/fiber reinforced LWSCC (FRLWSCC) and layered or fully enclosed composite beams was evaluated based on current measurement, half-cell potential measurement, mass loss, crack pattern, bar diameter degradation, strength loss, load deflection response and mode of failure compared to their non-corroded counterparts
Summary
The natural tendency of steel is to undergo corrosion reactions, concrete contains a high level of the alkaline environment (pH of 12 to 13), which provides the corrosion protection of steel. The Adsorption Theory - Chloride ions grasp the rebar surface in competition with dissolved O2 or hydroxyl ions At this moment chloride ion encourages the hydration of the iron ions and helps the corrosion of steel. 3. The Transitory Complex Theory – The chloride ions become combine in the passive film replacing some of the hydroxides. The Transitory Complex Theory – The chloride ions become combine in the passive film replacing some of the hydroxides This mechanism raising the both conductivity and solubility of the passive layer. According to Daczko (2012), “Self-compacting concrete (SCC) is an innovative concrete that does not require vibration for placing and compaction. It can flow under its own weight, and full compaction possible in congested reinforcement.
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