1. School of Environmental Engineering; Universiti Malaysia Perlis, Pusat Pengajian Jejawi 3, 02600 Arau; Perlis Malaysia
2. Center of Excellence Geopolymer & Green Technology (CEGeoGTech) School of Materials Engineering; Universiti Malaysia Perlis, P.O. Box 77, D/A Pejabat Pos Besar 01000 Kangar; Perlis Malaysia
3. School of Materials and Mineral Resources Engineering; Engineering Campus Universiti Sains Malaysia, Seri Ampangan 14300 NibongTebal, Seberang Perai Selatan; Penang Malaysia