Crack self-healing of cement-based materials by microorganisms immobilized in expanded vermiculite

Cement-based materials were the most widely used building materials in the world, among which light-weight aggregate could be used in the fields of heat preservation and fire resistance, and had a great development prospect. In this paper, crack self-healing of cement-based materials by microorganisms immobilized in expanded vermiculite was studied. First of all, the adsorption and immobilization of microorganisms by expanded vermiculite was effective, and the microorganisms could be revived and had strong activity after immobilization. Secondly, the expanded vermiculite was wrapped by different methods, such as silicone hydrophobic agent, aqueous epoxy resin and composite paste. The best treatment method was wrapped by composite paste in terms of water absorption rate, and water absorption rate was only 62.7%. The high alkaline environment was not conducive to the survival of microorganisms, and the carrier could provide effective protection for microorganisms. Finally, the mechanical properties of cement-based materials and the effect of crack self-healing were confirmed. Compared with the initial expanded vermiculite specimens, the mechanical properties of the expanded vermiculite specimens wrapped by composite paste were significantly improved. The replaced rate of expanded vermiculite should not be higher than 20% to ensure the mechanical properties of cement-based materials. The effect of cracks repair in cement-based materials gradually improved with the extension of curing age. The cracks with the width of 400 um were basically repaired after curing for 28 days. The mineralized products were identified as calcite, and they not only blocked the cracks surface, but also filled a certain depth. (C) 2020 Elsevier Ltd. All rights reserved.