Abstract
The use of post-consumer plastics in concrete production is an ideal alternative to dispose of such wastes while reducing the environmental impacts in terms of pollution and consumption of natural resources and energy. This paper investigates different approaches (i.e., reducing water-to-cement ratio and incorporating steel fibers or polymeric latexes) that compensate for the detrimental effect of waste plastics on the drop in concrete mechanical properties including the bond to embedded steel bars. The polyethylene terephthalate (PET) wastes used in this study were derived from plastic bottles that were shredded into small pieces and added during concrete batching at 1.5% to 4.5%, by total volume. Test results showed that the concrete properties are degraded with PET additions, given their lightweight nature and poor characteristic strength compared to aggregate particles. The threshold PET volumetric rates are 4.5% and 3% for concrete made using natural or recycled aggregates, respectively. The reduction of w/c from 0.55 to 0.46 proved efficient to refine the matrix porosity and reinstate the concrete performance. The incorporation of 0.8% steel fibers (by volume) or 15% polymers (by mixing water) were appropriate to enhance the bridging phenomena and reduce the propagation of cracks during the pullout loading of steel bars.
Highlights
Large amounts of waste plastic are generated every year; it is estimated that more than 240 million tons of such wastes were generated in 2016 of which a large part is not recycled [1]
All specimens were immersed in water for 3 days, moist cured at 95% ± 5% relative humidity (RH) and 22 ± 3 ◦ C for testing age after 28 days
The concrete mechanical properties were curtailed with polyethylene terephthalate (PET) additions, given their lightweight nature and poor characteristic strength compared to aggregate particles
Summary
Large amounts of waste plastic are generated every year; it is estimated that more than 240 million tons of such wastes were generated in 2016 of which a large part is not recycled [1]. Numerous studies investigated the possibility of incorporating plastic waste in concrete mixtures, contributing to efficient management and sustainable development of the construction industry. Such wastes often derive from polyethylene terephthalate (PET), polypropylene (PP), polyvinyl chloride (PVC), low- or high-density polyethylene (LDPE, HDPE), polylactic acid (PLA), and other resins [3,4,5]. Choi et al [6] investigated the use of manufactured recycled PET lightweight aggregate as partial replacement of sand on mortar and concrete mechanical properties. Similar conclusions were drawn by Hannawi et al [7], Khatib et al [8], and Saxena et al [9] who studied the use of up to 50% plastic waste as partial replacement of fine aggregates. Liu et al [10]
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