Alkali-activated foamed concrete (AFC) emerges as a promising cement-free building insulation material, but its design and fabrication methods, particularly regarding the selection of surfactants compatible with the highly alkaline, ion-rich environment of the one-part alkali-activated slag system, remain unclear. This work compared four types of surfactants, including sodium dodecyl sulfate (SDS), sodium olefin sulfonate (40 K), cetyltrimethylammonium bromide (CTAB), and Triton X-100 (Triton), to elucidate how surfactant chemistry governs foam film stability and shapes pore-network structure of foamed alkali-activated slag (AAS). The results showed that cationic CTAB exhibited superior interfacial behavior, maintaining high interfacial availability under alkaline, calcium-rich conditions, which stabilized foam films and promoted a uniform, closed-cell pore network, yielding higher compressive strength and lower thermal conductivity. In contrast, the SDS lost 75% foamability and formed calcium dodecyl sulfate; 40 K generated moderate foam with short-lived films; Triton foamed abundantly but collapsed rapidly. This work suggests that effective surfactants for AFC are those that resist precipitation in alkaline, ion-rich environments, preserve foam stability during paste formation, and maintain a relatively low and stable surface tension (approximately 35–40 mN/m) in pore solution, providing a quantitative criterion for surfactant selection. • Surfactant survivability under alkaline ionic fluctuations governs foam stability. • A 50–55 mN/m surface tension criterion informs surfactant selection. • Cationic CTAB preserves interfacial availability in foamed one-part AAS paste.
Yang et al. (Wed,) studied this question.