Lightweight concrete elements are well known for its reduced weight and excellent thermal insulation properties. The study focused on investigating the behavior of lightweight concrete beams developed using lightweight expanded clay aggregate (LECA) and polyethylene terephthalate (PET) flakes. The natural coarse aggregate was replaced by 70% of LECA and 15% of PET and the load-deflection behaviour was determined. Lightweight beams of size 800x150x100 mm were cast to determine the properties such as compressive strength, split tensile strength, water absorption, density, rapid chloride penetration test etc. The experimental test results were compared with the analytical results obtained by finite element analysis using Ansys.