Metakaolin in ultra-high-performance concrete: A critical review of its effectiveness as a green and sustainable admixture

Mohamed, Abdeliazim Mustafa, Department of Civil Engineering, Prince Sattam Bin Abdulaziz University, Al Kharj, Riyad, Saudi Arabia, Building and Construction Technology Department, Bayan University, Khartoum, Sudan; Tayeh, Bassam A., Department of Civil Engineering, Islamic University of Gaza, Gaza, Palestine, Department of Civil & Environmental Engineering, University of Waterloo, Waterloo, ON, Canada