An article published in Materials Today: Reviews examined concrete mixing with magnesia (MgO) nanoparticles from a durability perspective.
Study: Study of the reliability of nano-concrete at different levels of a nano-filler. Image Credit: Bannafarsai_Stock/Shutterstock.com
Concrete – can it keep up with advanced constructions?
Concrete is a mixture of coarse and fine aggregates held together with a cement paste that hardens over time.
Abundant supplies, great flexibility and well-established production procedures make concrete the most ubiquitous building material in the factory.
Many different types of mortars can be constructed by mixing the constituents in the appropriate amounts. Despite the development of modern cementitious composites, conventional mortar production techniques are no longer suited to meet the needs of advanced multi-purpose structures.
Advanced structures present more difficult challenges for concrete. Therefore, there is a pressing need for practical and advanced concrete solutions.
The role of nanomaterials in improving the durability of cementitious materials
Durability is one of the most critical and challenging issues facing the construction industry.
The development of nanomaterials has fueled efforts to use more environmentally friendly materials. Nanomaterials are characterized by their large outer surfaces and better strength and tribological properties compared to conventional materials.
Many ceramic compounds have significant cementitious reactions with calcium oxides, leading to the generation of additional silicates. This ultimately helps to improve the structural characteristics and durability of cementitious materials.
Fiber-like materials improve the tensile properties of mortar by bridging cracks and preventing further crack growth through their needle-like operation.
The question of anti-splinter coatings
Recently, cementitious supplements have been widely explored to produce concrete slabs.
These additives increase the interracial transit zones between the cement and the agglomerates and help generate dense crystallites, indicated by the improved physical properties.
However, when exposed to temperature extremes, these tight structures react in unpredictable ways, resulting in spall coatings.
Spall coatings occur due to inadequate permeability for pressure distribution, thermal fluctuations, or the build-up of thermal gradients.
The fibers are thermodynamically unstable; therefore, they combine at around 300 degrees Celsius and generate air pockets. The presence of these air pockets affects the life of the composite.
Can nanoparticles strengthen concrete?
Concrete mixes are susceptible to fractures and lack desirable qualities as they are generally semi-brittle. The incorporation of nanomaterials into concrete mixes is hailed as the solution to these problems.
Ceramic nanoparticles, carbon nanoparticles and metallic nanoparticles have been shown to improve the structural and physical properties as well as the service life of concrete mixes at room temperature.
The corrosive atmosphere of cementitious composites is caused by the oxidative activity produced during the hydration process and the deposition of additional CSH inside the porous architecture. This ultimately improves the mechanical properties of cementitious materials.
Nanomaterials appear to have a strong filling effect, yielding significant binding and precipitation involvement at the nanoscale, which ultimately promotes an accelerated hydration process.
Due to the transition from an inactive corrosive phase to a highly active corrosive phase, countless microscopic cracks begin to grow. To overcome this problem, it is essential to include nanowires that use the nanoscale stiffness of the CSH hydrogel to limit the propagation of nanoscale fractures.
Conclusions of the study
The effect of MgO nanoparticle content on the durability properties of conventional concrete was investigated in this research using 6%, 4% and 2% mass fractions of MgO nanoparticles.
When the dosage was kept within a small range, MgO nanoparticles significantly increased the fracture toughness, sorptivity, and porosity of cementitious composites.
The fracture transmission, sorptivity and moisture permeability of concrete were all significantly reduced by increasing the mass fraction of MgO nanoparticles.
However, if the mass fraction of MgO nanoparticles in cementitious composites exceeded a specific limit, the mortar would become less reliable.
When a 4% mass fraction of MgO nanoparticles was added to a standard cement mortar, it improved the moisture permeability depth by approximately 45%. Additionally, adding a 3% mass fraction of MgO nanoparticles to the cementitious mixture reduced sorptivity by about 30% and fracture length per unit area by about 83%.
The ideal dosage of MgO nanoparticles has been recommended at 4% to positively affect the fracture, permeability and sorptivity parameters of the cementitious composite.
Neeraja, VS, Mishra, V., Ganapathy, CP, Sunagar, P., Kumar, DP and Parida, L. (2022). Study of the reliability of nano-concrete at different levels of a nano-filler. Materials Today: Reviews. Available at: https://www.sciencedirect.com/science/article/pii/S2214785322053512?via%3Dihub