Investigation of the Pore Structures and Water Absorbency of Foamed Alkali-Activated Binders

Water absorbency of foamed alkali-activated binders (FAABs) with various pore distributions were investigated in this study, where the pore structures were characterized and analyzed quantitatively to expound the mechanism of water absorption. Initially, workability consisting of fluidity and the aerating procedure of fresh FAABs pastes were studied, which revealed the fluidity evolution of the pastes and volume development with respect to time. On this basis, the effect of hydrogen peroxide (H2O2) dosages on pore distributions was elaborated and a numerical model was proposed to assess the porosity in the kernel part of a sample. Two bubble stabilizers, sodium dodecyl sulfate (SDS) and calcium stearate (CS), were employed to improve the pore structures of FAABs. It was found that the fractions of small pores increased in the bubble stabilizer-modified FAABs and the fractions of independent pores increased markedly. Tests on water absorption indicated that CS was able to decrease the moisture content attributed to its hydrophobicity as well as the redistribution of pores in the FAABs. However, SDS failed to control the water absorption of the FAABs due to the difference in chemical properties.