Sustainable Concrete Using Seawater, Recycled Aggregates, and Non Corrosive Reinforcement

Abstract

Using seawater and recycled concrete aggregate (RCA) in a concrete mix is potentially advantageous from a sustainability perspective. However, the high chloride levels expected in such a concrete mix demands the use of non-corrosive reinforcement in lieu of normal black steel to avoid corrosion problems. Glass fiber reinforced polymer (GFRP) is considered promising as an alternative reinforcement owing to its corrosion resistance and acceptable mechanical properties that minimize maintenance and repairs and extend service life. Yet, the relatively high initial cost of GFRP bars may mitigate its potential use. In view of that, the current thesis is aimed at verifying the safe and economic utilization of seawater, recycled concrete aggregate, and GFRP reinforcement to produce sustainable and efficient concrete structures. The main body of the thesis consists of five key studies. In the first study, an extensive experimental program was conducted to compare the fresh and hardened properties of freshwater- and seawater-mixed concretes. In the second study, the performance of concrete mixed with seawater and recycled coarse aggregates (at 100% replacement level) was experimentally investigated. The third study was carried out to experimentally examine the flexural performance of seawater-mixed recycled aggregate GFRP-reinforced concrete beams. In the fourth study, a life cycle cost analysis (LCCA) was performed (considering 100-year analysis period) to verify the cost performance of structural concrete combining seawater, RCA, and GFRP reinforcement for high-rise buildings as compared to the traditional reinforced concrete (i.e., with freshwater, natural aggregates, and black steel reinforcement). The fifth study evaluates the cost effectiveness of different reinforcement alternatives in a concrete water chlorination tank using LCCA: a comparison was established between four concrete reinforcing materials, namely, black steel, epoxy-coated steel, stainless steel, and GFRP through a 100-year analysis period. The results of these five studies suggest the potential use of the proposed combination (seawater + RCA + GFRP reinforcement) to produce safe and economic concrete structures.