Selected Properties of Self-Compacting Concrete with Recycled PET Aggregate

Concrete production is a major contributor to global carbon emissions. Incorporating waste materials into concrete mixtures is a promising strategy to reduce environmental impact. While prior research has explored the use of recycled aggregates in concrete, the specific effects of polyethylene terephthalate (PET) as a fine aggregate substitute remain unclear. Existing studies have shown that recycled materials can influence flowability and mechanical properties, but the extent of these effects varies. Some work has demonstrated that high percentages of recycled aggregate can compromise structural performance. However, the behavior of PET as a replacement material has not been fully characterized. This gap motivated the current investigation into SCC with PET. The uncertainty around the optimal substitution level for PET in concrete led to this study. No prior work had resolved the specific impact of PET on SCC flow and hardened properties. This research aims to clarify the feasibility of using PET in SCC mixtures.

The study aimed to evaluate the impact of incorporating recycled PET aggregate into self-compacting concrete. The specific problem addressed is the potential use of PET as a fine aggregate substitute in SCC. The motivation stems from the need to reduce construction waste and environmental impact. The study sought to determine the maximum allowable PET substitution without compromising SCC performance. The researchers focused on both fresh and hardened concrete properties. They also aimed to assess the applicability of non-destructive testing methods for quality control. The investigation sought to identify the threshold at which PET negatively affects SCC characteristics. The study aimed to provide data for sustainable concrete formulation guidelines.

The study involved preparing SCC mixtures with varying percentages of recycled PET aggregate. PET was substituted for fine aggregate in increments of 5%, up to 20%. Fresh concrete properties, including flowability, were measured using standard SCC tests. Hardened concrete properties were assessed through compressive and splitting tensile strength tests. The modulus of elasticity and Poisson ratio were also determined. Non-destructive testing methods, such as ultrasound and sclerometric testing, were applied. Correlation curves between non-destructive and destructive test results were developed. The experimental approach combined material substitution with mechanical and non-destructive evaluations.

The results showed a clear decline in flow properties as PET content increased. At 20% substitution, SCC no longer met self-compacting criteria. Compressive strength dropped by nearly 50% at the highest PET level. Splitting tensile strength also decreased with higher PET content. The modulus of elasticity and Poisson ratio were negatively affected. Non-destructive tests revealed consistent correlations with mechanical properties. At 5% substitution, concrete parameters remained largely unchanged. The 5% PET replacement showed minimal impact on SCC performance. The study demonstrated the feasibility of low-level PET substitution in SCC.

The findings suggest that PET substitution above 5% significantly impairs SCC performance. At 20% replacement, the concrete failed to meet SCC requirements. The 5% substitution level appears to be a viable alternative without major performance loss. Non-destructive testing methods proved useful for quality assessment. The study supports the use of low-level PET in SCC mixtures. The results highlight the importance of controlling PET content in SCC formulations. The correlation curves from non-destructive tests could aid in future SCC quality control. The study provides a basis for sustainable SCC mix design with limited PET inclusion.