Mechanical Performance and Microstructural Characterization of PET-Modified Cement Mortars with Metakaolin

Area of Science:

• Materials Science
• Civil Engineering
• Sustainable Construction

Background:

• Plastic waste utilization in construction materials is key for sustainability.
• Incorporating plastic waste, like polyethylene terephthalate (PET), often compromises mechanical properties due to poor interfacial bonding.
• The interfacial transition zone (ITZ) is critical for the performance of these composite materials.

Purpose of the Study:

• To investigate the impact of metakaolin on the ITZ and mechanical properties of cement mortars containing PET flakes.
• To evaluate metakaolin's effectiveness in mitigating the negative effects of PET on mortar performance.
• To explore the microstructural changes in PET-modified mortars with metakaolin addition.

Main Methods:

• Preparation of cement mortars with varying metakaolin content (10% and 50% as cement replacement) and a fixed PET flake content (5% as sand replacement).
• Testing of mechanical properties, including compressive and flexural strength, after 28 days of curing.
• Microstructural analysis using Scanning Electron Microscopy (SEM) focusing on the ITZ.

Main Results:

• PET flake incorporation reduced mechanical properties due to a porous and weak ITZ.
• 10 wt% metakaolin addition significantly enhanced mechanical properties, making PET-modified mortars comparable to the reference mix.
• SEM analysis confirmed that metakaolin refined the ITZ microstructure and reduced porosity, improving interfacial bonding.

Conclusions:

• Metakaolin effectively counteracts the detrimental effects of PET incorporation in cement mortars.
• The addition of 10 wt% metakaolin improves the ITZ characteristics, leading to enhanced mechanical performance.
• Metakaolin is a viable additive for developing high-performance, sustainable cement-based composites utilizing plastic waste.