Effect of Combination of Waste Glass Powder and Fine Plastic Aggregate on Structural Behaviour of Reinforced Concrete Beams

Abstract

In this work, an investigation was conducted in two stages to examine the benefits of using post-consumer waste material. Glass and plastic are two examples of materials that must be appropriately disposed of or repurposed to protect our environment. The current work focused on investigating the mechanical and structural behavior of mixes containing crushed waste plastic (CWP) resulting from the manufacture of safety valves of cooking gas bottles by ratios of (0%, 10%, 20%, and 30%) as a partial alternative of fine aggregate, with 15% waste glass powder (WGP) from the broken windows as a partial alternative of cement. The experimental program was separated into two parts: fresh and hardened characteristics of concrete specimens and structural behavior of reinforced concrete beams. It was found that the 30% plastic caused a decline in the concrete mechanical properties so, this percentage was excluded, and only 10% and 20% of waste plastic were adopted to combine with 15% glass powder. The results indicated that the replacement of 15% of glass powder instead of cement improved concrete properties comparison to control mix. On the other hand, samples that contained plastic showed ability to absorb higher energy than the control sample. The second part of this research was carried out to investigate the structural behavior of reinforced concrete beams incorporating 0% and 15% waste glass powder combined with (0, 10, and 20%) of plastic aggregate. Fifteen beams were tested with (150 mm) depth, (150 mm) wide, and (900 mm) length. These beams were strengthened by different longitudinal steel ratios 0.0056 (2Ø8), 0.0125 (2Ø12), and 0.023 (2Ø16) with two ratios of shear reinforcement (stirrup at every 60 mm and 150 mm). To understand the structural behavior clearly, the results were displayed based on four parameters: the effects of waste glass powder, crushed waste plastic, longitudinal and transverse reinforcement. Experimental results showed an improvement in the structural behavior of beams incorporating these wastes. The higher ultimate load was 158 kN, recorded for beam that was reinforced longitudinally by 2Ø16 mm and transversely by stirrups Ø6 mm at a space of 60 mm between them and contained 15% glass powder with 10% plastic aggregate. Studying the effect of 15% waste glass powder on the structural II behavior clarified an increase of 30.49%, 83.83%, and 39.28% in the maximum deflection, ductility index, and total absorbed energy of the tested beam, respectively compared to the control beam. Regarding the influence of crashed waste plastic, the increase in the proportion of added plastic caused a rise in the maximum deflection, ductility index, and total absorbed energy for 20% plastic aggregate by 47.26%, 13.84%, 49.04%, respectively compared to the control beam. In contrast, these characteristics values were decreased up to 80.89%, 82.21%, and 54.57%, respectively with increasing the tensile steel ratio to 0.023 (2Ø16) compared to the beam that was reinforced by 2Ø8 mm with the same content of glass and plastic. There was around 39.22%, 57.05%, and 44.56% reduction in the previous structural properties with increasing the space between stirrups (S) to 150 mm compared to beam with S=60 mm with the same conditions of glass powder and plastic content. According to this work, replacing 15% of cement with waste glass powder and replacing 10% of fine aggregate with crushed fine waste plastic gave the best loading capacity and acceptable properties for structural concrete. Using this proposed method can save 72.9 kg and 85.2 kg of cement and sand, respectively, per cubic meter of concrete. These replacements reduced the cost of producing concrete by 25 %, at the same time, reduced the consumption of natural resources. Also, replacing 15% of cement with glass can reduce carbon dioxide emissions by 15%. So, reusing these wastes will bring health benefits to humanity by reducing the accumulation of this waste and its harmful effects on society.