Mechanical Performance Optimization of Concrete Using Combined Nano-Silica and Nano-Alumina

Concrete remains the most widely used construction material in the world, owing to its cost-effectiveness and durability. However, the brittle nature of concrete and its propensity for cracking limit those applications that involve high tensile/flexural strength. Incorporation of nanomaterials like nano-silica (nS) and nano-alumina (nA) will improve the mechanical properties of concrete through filler and pozzolanic effects. This work investigates the influence of adding nS and nA at replacement levels from 0 to 4% on certain important characteristics of concrete belonging to the M30 grade: compressive strength, split tensile strength, flexural strength, and modulus of elasticity. The test results indicated that all the aforementioned properties improved when the dosage was optimized to 4% nS + 1% nA, which generated maximum enhancement in compressive strength, split tensile strength, flexural strength, and elastic modulus by about 36%, 25%, 22%, and 21%, respectively. The refinement of microstructure and interfacial transition zones brought about the increases. In contrast, excessive nano addition decreased the overall strength, while nS and nA enhanced properties, and offered sustainability benefits through an extended structural service life. More studies on optimizing nano-dosages are recommended.