Applications of micro-nanobubble and its influence on concrete properties: An in-depth review

Micro-nanobubbles (MNBs) are tiny bubbles of water used in various industries. The production methods and properties of concrete containing MNBs and the applications of MNBs in different industries are reviewed. Then, the effect of MNBs on the properties of fresh and hardened concrete is described. Next, we assessed the advantages and disadvantages of using MNBs in different types of concretes, environmental and economic impact, and research gaps in the concrete containing MNBs. Even though the presence of MNBs in concrete has an undesirable effect on workability and rheology parameters, the results of workability are in the range of the European Guideline for Self-compacting Concrete regulations and the British Standard for conventional concrete. In contrast, using sulfo-aluminate cement instead of Portland cement and MNBs in concrete improves rheological characteristics. The review also shows that MNBs improve the mechanical properties of concrete by up to 31% for compressive strength, 10–20% for tensile, and 3–34% for flexural strength. Furthermore, concrete containing MNBs has performed better than conventional concrete in terms of durability properties such as electrical resistivity, ultrasonic pulse velocity, chloride penetration resistance, and resistance to freezing–thawing cycles (F-T cycle). MNBs in concrete reduce the porosity by 17% and decrease the size of the holes. Water absorption of MNB concrete at 28 days decreased by 20%, and chloride permeability reduced by 20%. MNBs in concrete help to develop the resistance of cement-based materials improve the elastic modulus at early ages and increase the ability to resist cracking, which can reduce the crack width. Still, it is necessary to carry out more experimental work for workability and durability, especially for SCC. Even though a few studies indicate a slight impact on the environment, environmental and economic effects, and production challenges need more investigations.