The fabrication and research of pH-responsive cement-based materials with switchable wettability

Abstract

Recently, intelligent responsive materials have received increasing attention due to the controllability of their wettability. However, research has primarily focused on the surface properties of materials such as sponges and copper meshes, with a notable lack of investigation into cement-based materials in this regard. Currently, multi-functionality has become an inevitable trend in the development of cement-based materials. The controllable and adjustable wettability of cement-based materials can further expand their application scope. In this article, saturated fatty acids and dicarboxylic acids were selected to modify cement-based materials, fully utilizing their rich hydroxyl characteristics. Firstly, the feasibility of developing pH-stimuli-responsive surfaces on cement-based substrates with chosen raw materials was rapidly verified using the immersion method. When the mass fraction of dicarboxylic acid in the modifier is between 60 % and 80 %, the modified substrate surface exhibits hydrophobicity towards neutral liquids and hydrophilicity towards alkaline liquids. Based on this, the corresponding sodium salts of organic acid were synthesized and used as additives, which were then mixed with cement to prepare modified cement-based materials with switchable wettability. Through acid solution treatment, the modified hardened cement paste can transform from initially hydrophilic to hydrophobic, and the conversion angle can reach 90°. This study broadens the application field of intelligent response surfaces and enriches the functionality of cement-based materials.