Sustainable Hybrid Lightweight Aggregate Concrete Using Recycled Expanded Polystyrene

Area of Science:

• Materials Science
• Civil Engineering
• Environmental Science

Background:

• Ordinary Portland cement (OPC) production is resource-intensive and environmentally concerning.
• Expanded polystyrene (EPS) waste presents significant ecological challenges.
• Lightweight concrete (LWAC) offers potential for reduced structural weight and improved insulation.

Purpose of the Study:

• To investigate the mechanical behavior of LWAC incorporating recycled EPS and a hybrid cementitious matrix.
• To evaluate the performance of LWAC using a blend of OPC and alkali-activated cement (AAC).
• To assess the potential of this sustainable LWAC for structural applications.

Main Methods:

• LWAC was formulated with 35% lightweight aggregates (LWA) (EPS and expanded clays) and 65% normal-weight aggregates.
• The cementitious matrix consisted of 30% OPC and 70% AAC (fly ash and lime-based).
• Compressive strength, density, X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy were analyzed after 28 days of curing.

Main Results:

• A 48.8% improvement in compressive strength was observed, exceeding ACI 213R-03 standards.
• A 21.5% reduction in density was achieved, indicating potential cost savings and enhanced insulation.
• XRD and FTIR confirmed the formation of C-S-H, C-(A)-S-H, and N-A-S-H gels, though anhydrous products suggested a slower reaction rate.

Conclusions:

• The developed hybrid LWAC demonstrates potential as a sustainable structural material, effectively utilizing waste EPS.
• The material meets requirements for structural lightweight concrete, offering benefits in strength, density reduction, and insulation.
• Further research on activator solution dosage and curing conditions is recommended to optimize mechanical performance.