Synthesis of new defoamer agents and characterization of cementitious formulations

Abstract

The production of cementitious formulations involves the addition of chemical additives essential for the optimization of many properties. Superplasticizers are considered additives of great interest but when mixed with concrete they lead to an undesirable increase of air content, with the consequent development of foam. This can adversely affect both mechanical properties and workability, therefore, the use of an antifoam agent is also necessary which should be able to prevent or destroy the foam. This work aims to synthesize esters derived from the reaction of glycine betaine with saturated and unsaturated fatty alcohols of different chain lengths. The reaction products were analyzed by 1H NMR analysis, and the stability of antifoam agents in a superplasticizer solution was studied through foaming tests according to the Ross-Miles method. At the same time, their effectiveness in the cementitious systems was evaluated through flow Table tests. Finally, the effectiveness of the antifoam agents was quantified through an image analysis software, Image J, which allowed the investigation of the contents of the bubble in concrete samples. All synthesized antifoams showed properties superior to the commercial product, especially defoamers containing saturated fatty alcohols. It has been found that alcohols with too small or too long carbon chains were not effective. In particular, it was verified the optimal range of carbon atoms number contained in the antifoam chain which included between 12 and 14.

Keywords

• Sustainable materials
• pH-responsive esters
• Cementitious formulations
• Antifoams
• Bubbles reduction