The Evaluation Effect of Copper Fibre Diameter on Enhancing Compressive Strength of Pure Gypsum oleh Arshad Nadhom Shubber, Firas Saeed Abbas, Hayder Mohammed AL-Taweel, Sinan Khaleel Ibrahim, Ali Al-Balhawi, Yasir M. Al-Badran, Layth Sahib Dheyab, Ahmed S.D. Al-Ridha