Experimental investigation on the mechanical properties of concrete with steel fibers and colloidal nano-silica

Concrete is a commonly used construction material, although it possesses brittle behavior and low tensile resistance. This research evaluates how adding steel fibers and colloidal nano-silica influences the strength characteristics of M30 grade concrete. Concrete specimens were prepared using steel fibers ranging from 0.5% to 2.0% by cement volume along with a constant 2.5% colloidal nano-silica content by cement weight and compared with a control mix. All specimens were cast, cured, and tested in accordance with relevant Indian Standard provisions. Compressive, splitting tensile, and flexural strength tests were performed at 7 and 28 days. The results highlight that use of nano-silica alone increase the 28-day compressive strength by 15% and the splitting tensile strength by 45% compared with the control mix. Adding steel fibers further improved tensile and flexural strength, with a smaller rise in compressive strength. The concrete mix with 2.0% steel fibers and 2.5% colloidal nano-silica exhibited the best overall performance, showing 20% higher compressive strength, 54% higher tensile strength, and 25% higher flexural strength.