A Study on the Bond Characteristics of Steel Bars in Concrete Containing Polypropylene (PP) Plastic Particles as Fine Aggregate

The use of plastic in modern society has resulted in a considerable amount of environmental contamination, largely due to the inherent chemical composition of the material. This poses a significant risk to the surrounding environment, particularly in terms of its impact on soil, air, and water quality. The use of recycled plastic in concrete is becoming increasingly prevalent within the construction industry due to its potential to mitigate environmental contamination from plastic waste. The objective of this study was to evaluate the performance of concrete incorporating recycled Polypropylene (PP) plastic as a fine aggregate. The two critical factors under examination were the quantity of PP plastic granules used as a proportion of fine aggregate (ranging from 0% to 30%) and the water-cement (w/c) ratio, which could be 0.45 or 0.55, in conjunction with a 1.5% plasticizer. The samples were subjected to a pull-out test to evaluate the parameters of bond stress behavior, failure mode, and bond-slip behavior. The findings indicated that an increase in the proportion of PP plastic granules used as a substitute for fine aggregate resulted in a notable reduction in bond strength, which was further amplified when the w/c ratio was diminished. The incorporation of 10% PP plastic granules led to a reduction in bond stress by 13.4% and 11.56%, respectively, in samples with w/c ratios of 0.45 and 0.55. Consequently, at a low w/c ratio, the predominant failure mode is considered to be splitting, while a higher w/c ratio increases the probability of pull-out splitting failure.