Flexural strength of beam concrete with PET plastic addition and 30% copper slag Mochamad Firmansyah Sofianto, Meity Wulandari, Muhammad Imaduddin and Dedy Yusuf E3S Web Conf., 513 (2024) 02012 Published online: 24 April 2024 DOI: 10.1051/e3sconf/202451302012