Effects of Plastic Waste on the Heat-Induced Spalling Performance and Mechanical Properties of High Strength Concrete

Abstract

This paper investigates a potential application of hard-to-recycle plastic waste as polymeric addition in high strength concrete, with a focus on the potential to mitigate heat-induced concrete spalling and the consequent effects on the mechanical properties. The waste corresponds to soft and hard plastic, including household polymers vastly disposed of in landfills, although technically recyclable. Mechanical and physical properties, cracking, mass loss, and the occurrence of spalling were assessed in high strength concrete samples produced with either plastic waste or polypropylene fibers after 2-h exposure to 600 °C. The analysis was supported by Scanning Electron Microscopy and X-Ray Computed Tomography images. The plastic waste is composed of different polymers with a thermal degradation between 250 to 500 °C. Polypropylene (PP) fibers and plastic waste dispersed in concrete have proved to play an essential role in mitigating heat-induced concrete spalling, contributing to the release of internal pressure after the polymer melting. The different morphology of plastic waste and polypropylene fibers leads to distinct mechanisms of action. While the vapor pressure dissipation network originated by polypropylene fibers is related to the formation of continuous channels, the plastic waste seems to cause discontinuous reservoirs and fewer damages into the concrete matrix. The incorporation of plastic waste improved heat-induced concrete spalling performance. While 6 kg/m3 of plastic increased the mechanical performance after exposure to high temperature, the incorporation of 3 kg/m3 resulted in mechanical properties comparable to the reference concrete.

Performance of Different Concrete Types Exposed to Elevated Temperatures: A Review

“…This reaction improves the bond between constituents improving performance of the HSC resisting higher temperatures. Additionally, results presented in Figure 14 [ 5 , 68 , 77 ] show that adding metakaolin or ground pumice proved to yield the best results [ 68 ]. In fact, it could maintain at least 70% of its strength at 500 °C [ 68 ].…”

“…Furthermore, High Performance Micro Concrete (HPMC) which relies only on fine aggregates could retain 30% of its tensile strength at 1000 °C after being subjected to cooling [ 67 ]. In addition, Figure 17 [ 77 ] shows the behavior of HSC after incorporating plastic waste. It was found that they could be better than using PP fibers as long as they are used as 3 kg/m 3 or 6 kg/m 3 quantities.…”

“…This is mainly due to the increased pore content that is created at higher temperatures by the deteriorating PP fibers. In addition, the vapor pressure network created by the continuous channels of PP fibers could damage the concrete matrix [ 77 ]. Other types of constituents such as plastic waste could be better as they create a discontinuity in the vapor network and in turn yield better results.…”

“…Other types of constituents such as plastic waste could be better as they create a discontinuity in the vapor network and in turn yield better results. Plastic waste also proved to reduce heat-induced concrete spalling due to their lower thermal conductivity; therefore, it was able to yield a better tensile strength at 600 °C than PP fibers [ 77 ]. Surely, HSC can be better than NSC in terms of its post-fire properties; however, it all depends on the type of constituents used and their amounts.…”

Performance of concrete containing recycled masks used for personal protection during coronavirus pandemic

“…On the other hand, recycled plastic wastes can also improve selected properties of cement-based material, e.g. reduce its plastic shrinkage [10] or enhance the performance in fire [11] , [12] . The latter case is possible due to the decomposition of polypropylene, which is a common compound of plastic wastes, beginning around 200°C.…”