Karolina, Rahmi, Muhammad Abdany Sofran, M.A.P Handana, Syahrizal, and Riza Inanda Siregar. “Geopolymer Concrete Made From Volcanic Ash of Mount Sinabung”. International Journal of Integrated Engineering 12, no. 1 (February 17, 2020): 315–320. Accessed August 7, 2026. https://journal.uthm.edu.my/index.php/ijie/article/view/5732.