<p>The introduction of moderate foam has been shown to improve the fluidity, shrinkage resistance, and freeze–thaw durability of alkali-activated materials (AAM). However, because of the inherently high alkalinity and ionic strength of AAM, conventional chemical surfactants generally fail to generate and stabilize foam within this system. In this study, the biosurfactant rhamnolipid (RL) was employed to systematically evaluate its surface activity and foaming behavior in sodium-silicate-based activator solutions, as well as its influence on AAM performance. The results demonstrate that RL maintains pronounced surface activity at pH 14, effectively lowers surface tension, mitigates the charge-shielding effect caused by Na⁺ ions, and increases the absolute zeta potential, thereby facilitating the formation of stable foam. At the macroscopic scale, the incorporation of 0.05 wt.% RL prolonged the initial and final setting times of AAM by 32.6% and 44.2%, respectively, while increasing fluidity by approximately 26.2%. In addition, RL-induced foam significantly enhanced the freeze–thaw resistance of AAM by optimizing pore structure and reducing the proportion of fine pores, thereby alleviating shrinkage-related cracking. Overall, RL enables stable foam generation and performance enhancement in highly alkaline, high-ionic-strength AAM systems, offering an effective strategy for foam regulation and property optimization. </p>