Abstract: This research explores the development of sustainable, lightweight, and thermally efficient building materials through the combination of Expanded Polystyrene (EPS) beads and Surkhi.EPS is well-known for its low density and excellent insulation properties, which help reduce the weight and energy consumption of construction materials. The EPS beads are coated with cement in a 1:1 ratio.Surkhi, a recycled byproduct obtained from crushed bricks or burnt clay, acts as a natural pozzolanic material that improves the compressive strength, durability, and water resistance of concrete. When combined, these materials offer a cost-effective and environmentally friendly alternative to traditional fine aggregates, supporting circular economy principles and reducing the ecological footprint of the construction industry.This composite approach aims to address growing concerns about the depletion of natural resources, material waste, and energy efficiency in modern construction. The study was conducted in two phases: first, Surkhi was used to partially replace fine aggregates at rates of 10%, 15%, 20%, and 25%; next, EPS beads were added at levels of 1%, 3%, 5%, and 7%. Various mix combinations were tested for compressive strength, density, and water absorption to determine the most effective formulation. Ultimately, the top-performing block was compared to a commercially available AAC (Autoclaved Aerated Concrete) block to evaluate its suitability in terms of structural performance, weight, insulation, and cost. The results highlight the potential of the EPS–Surkhi block as a sustainable choice in contemporary construction.

Keywords: Surkhi, Expanded Polystyrene (EPS), Expanded Polystyrene Pozzolana block (EPP), Autoclaved Aerated Concrete (AAC) block, Compressive strength, Block density, Water absorption.

| DOI: 10.17148/IARJSET.2025.12730