Abstract

Rapid industrial development causes serious problems all over the world such as the depletion of natural aggregates and creates an enormous amount of waste material from construction and demolition activities. One of the ways to reduce this problem is to utilize recycled concrete aggregate (RCA) in the production of concrete. The present study involves an experimental work and numerical application for the behavior of reinforced concrete piers using recycled aggregate concrete as green concrete. The experimental work included a test of thirteen reinforced concrete piers with different types of mix and reinforcement. Each pier has the same dimensions of (200 mm width, 400 mm height, and 600 mm total length) with column dimensions of 200×300 mm and 200 mm for depth. The experimental parameters were: concrete mix types, using recycled aggregate as green concrete (GC) at 50% replacement ratio instead of normal concrete (NC), recycled steel fiber with 2% volumetric ratio to be added to the GC mix in different areas of the pier   and using of  green high strength in different areas of the pier. The study involves using carbon fiber reinforced polymer (CFRP) bars and glass fiber reinforced polymer (GFRP) bars for reinforcing pier cap and the top two layers of pier cap. The load was applied to each pier by two points of loading, and the deflection was measured under the load and the average value was taken.

The results showed that using green concrete with 50% replacement ratio decreases the ultimate load by 2.41% and increases deflection by 18.5 %. The ultimate carrying capacity of GC pier has been increased when adding recycled steel fiber to the green concrete mix as it led to an increase in the ultimate load at rate reach to 8.95% than the ultimate load of GC. It was also found that using green high strength concrete mix has improved the ultimate load at rate reach to 36.76% than GC pier specimen. Furthermore, changing the reinforcement type with CFRP has a positive influence on pier characteristics as it led to an increase in the ultimate load at rate reach to 6.86 as compared with GC pier. Using of GFRP bar led to a decrease in the ultimate load to 6.96% as compared with GC pier specimen. Moreover, the use of GFRP as stirrups for pier cap has led to an increase in the ultimate load by 0.95.

Three-dimensional finite element analysis by ANSYS program (version 17.2) was used to investigate the behaviour of reinforced concrete piers. Fully bonding was assumed between concrete and steel reinforcement. Concrete was represented by SOLID65, and the reinforcement by LINK180, while the steel plates of loading and supports were represented by SOLID185. The results of the numerical application showed an acceptable degree of variation with the experimental results.