Lasco, Jonathan David, Marish Madlangbayan, and Marloe Baclayon Sundo. “Compressive Strength and Bulk Density of Concrete Hollow Blocks (CHB) With Polypropylene (PP) Pellets As Partial Replacement for Sand”. Civil Engineering Journal 3, no. 10 (November 4, 2017): 821–830. Accessed June 28, 2025. https://www.civilejournal.org/index.php/cej/article/view/459.