F. S. Khalid, Z. Zaki , S. M. Saadin , S. Shahidan , J.M. Irwan , M.H. Wan Ibrahim , N.S Ghadzali , N. A. A. Guntor. 2020. “Effect of Water to Cement Ratio and Replacement Percentage of Recycled Concrete Aggregate on the Concrete Strength”. International Journal of Advanced Science and Technology 29 (6s), 1625 -35. http://sersc.org/journals/index.php/IJAST/article/view/9312.