Electrolytes' influence on foamability and foam stability of cement suspensions

In this work, the foamability and foam stability of two Air-Entraining Agents (AEAs), an anionic and an amphoterous, were evaluated in cement suspensions. The anionic agents are the most used AEAs for cementitious materials, mainly due to their low cost. However, they may displays sensitivity in suspensions with high electrolytes concentration, as when mixed into cements. Amphoterous agents are known to be less sensitive, but their complex synthesis make them more expensive. Foamability and foam stability tests were performed in water and in aqueous suspensions with electrolytes from hydrated Ordinary Cement Portland (OPC) to investigate the air-entraining capacity of these AEAs. The AEAs performance were also tested regarding the addition of the alkali-catch Al-Anodizing Waste (AAW) as an air-entrainment adjuvant into cement suspensions. The AEAs were firstly characterized by FT-IR and surface tension tests. Chemical and physical features of AAW and OPC were determined by XRF, particle size and surface area analyzes. The electrolytes' influence and chemical interactions between materials were investigated by foaming tests, surface tension analysis, electrical conductivity and atomic absorption. The results demonstrated that the anionic agent is strongly affected mainly by Ca and also by K electrolytes. On the other hand, the amphoterous agents are unaffected. AAW showed high reactivity with electrolytes from hydrated cement and its alkali-catch ability may help sensitives AEAs to improve their air-entraining capacity.