https://www.researchgate.net/publication/361912570_Study_of_Nanotechnology_in_Concrete_Compounds_and_Properties_when_Adding_Polypropylene_Fibers_to_Design_a_Concrete_Mix
https://www.researchgate.net/publication/361912570_Study_of_Nanotechnology_in_Concrete_Compounds_and_Properties_when_Adding_Polypropylene_Fibers_to_Design_a_Concrete_Mix