Unveiling the role of Portland cement and fly ash in pore formation and its influence on properties of hybrid alkali-activated foamed concrete

Aiming to enhance the foam-stability and mitigate the drying shrinkage of alkali activated foamed concrete, the hybrid alkali activated materials are used to prepare foamed concrete. The role of Portland cement and fly ash in pore formation and its influence on performances of hybrid alkali-activated foamed concrete (HAAFC) are studied. Experimental results reveal that the addition of Portland cement promotes the hydration process, decreases the setting time, shortens the evolution time from bubbles to pores and prevents defoaming. In addition, the Portland cement in HAAFC decreases the bubble diameters and enhances the foam stability, which is owing to the increased yield stress of the matrix. The presence of Portland cement and fly ash in HAAFC can increase the crystalline phases and reduce the percentage of mesopores (2 nm <= r <= 50 nm) thus tempering the drying shrinkage of the HAAFC. The HAAFC with 20% cement, 60% GGBS, and 20% FA possesses the low drying shrinkage, high foam-stability and slightly low compressive strength which have the potential to replace alkali activated foamed concrete.