The effect of Colloidal Nano-silica on workability, mechanical and durability properties of High Performance Concrete with Copper slag as partial fine aggregate

• Addition of Nanosilica in HPSC improves strength and durability properties.
• Early age strength is enhanced due to the use of nanosilica.
• Good correlation exists between compressive strength with splitting tensile strength and flexural strength.

This study was conducted to investigate the effect of colloidal nanosilica on the properties of High Performance Concrete with copper slag as fine aggregate at a constant replacement level of 40%. Cement mortars and concrete mixes were produced by replacing Portland cement by colloidal nanosilica at 0.5%, 1%, 1.5%, 2%, 2.5% and 3%. Tests on workability, compressive strength, splitting tensile strength, flexural strength, rapid chloride penetration, water absorption, sorptivity and abrasion resistance were conducted on concrete mixes. The results indicate that the water demand increases due to the increase in the percentage of nanosilica owing to its high specific surface area. The amount of super plasticizer was adjusted in each mix to maintain a constant workability. The strength, penetration properties and resistance to abrasion of High Performance Slag Concrete (HPSC) were generally improved with the increment of nanosilica content in the concrete mix. The results denote that the colloidal Nanosilica act as a filler material that improves microstructure as well as an activator to promote Pozzolanic action. The addition of nanosilica enhances the strength characteristics up to 2% replacement level.