Synthesis and properties of different alkyl alcohol polyethers as the defoamers for concrete

In this study, we report the synthesis and properties of different alkyl alcohol polyethers as the defoamers for concrete. A series of alkyl alcohol polyethers with the same ethylene oxide unit amount (8 EO) but different alkyl chain lengths (C14~22) were obtained. The surface activities and defoaming properties of them in aqueous solutions were studied. Using them as the concrete defoamers, the defoaming properties in both fresh and hardened cement mortars were investigated, and the structure-property relationships of the polyethers were fully discussed. The results indicate that the C14 polyether showed obvious air-entraining property and the C16~22 polyethers showed effective defoaming property. As the alkyl chain length increases, the HLB value of polyether decreases (hydrophobicity increases), and the defoaming effect of polyether increases in both solutions and mortars. The results also indicate that the polyether containing longer alkyl chain length improved the mechanical performance of the hardened mortar more effectively. The study found great potential of alkyl alcohol polyethers for the practical applications as high performance defoamers.