MECHANICAL PROPERTIES OF LIGHTWEIGHT CONCRETE WITH RECYCLED EPS AND POLYPROPYLENE FIBERS

Abstract

Lightweight concrete is increasingly utilized in sustainable construction due to its reduced weight and improved thermal performance. However, replacing conventional aggregates with alternative lightweight materials may result in a reduction in concrete strength. To address this issue, fiber reinforcement has been introduced to enhance the concrete’s overall mechanical behavior. This study examines the mechanical properties of concrete mixes incorporating recycled expanded polystyrene (EPS) granules and polypropylene (PP) fibers. The effect of replacing crushed aggregate with EPS was evaluated by comparing a reference mix with mixes including 25 % and 50 % EPS replacement by volume. Additionally, the influence of fiber reinforcement was assessed by comparing a mix with 50 % EPS with mixes containing 0.5 % and 1.0 % fiber by volume. Key properties including density, flexural strength, compressive strength, and dynamic modulus were measured at 7 and 28 days. At 7 days, replacing conventional aggregate with 25 % EPS reduced density by approximately 21 %, flexural strength by 34 %, compressive strength by 57 %, and dynamic modulus by 37 % relative to the reference mix. A 50 % EPS substitution further lowered these properties by approximately 36 %, 54 %, 67 %, and 57 %, respectively. At 28 days, the relative reductions remained consistent. Adding fibers to the 50 % EPS mix improved flexural performance: a 0.5 % fiber dosage increased flexural strength by roughly 10 % at 7 days and 13 % at 28 days, while a 1.0 % dosage increased it by about 28 % at 7 days and 24 % at 28 days. The incorporation of fibers had minimal impact on density, compressive strength, and dynamic modulus.