Properties Exhibited by Nanomaterial Based Geopolymers: A Review
Dadi Rambabu, Shashi Kant Sharma, M. Abdul Akbar
Abstract
Heat-cured geopolymers outperform OPC-based concretes in mechanical and durability properties. However, ambient curing conditions cause fly ash-based geopolymer composites to set slowly and have low strength, becoming brittle and porous. Most conventional building method needs concrete to cure at room temperature. These restrictions prevent the extensive use of geopolymer as an OPC binder substitute in structural applications. To uplift the mechanical and physical properties of geopolymer with ambient curing conditions most researchers added binary binders and a high amount of activators. The use of alkaline activators beyond the limit is uneconomical and gives a negative impact on the strength. To avoid these complications, researchers have started incorporating nanomaterials in the binder. Nanomaterials accelerate the reaction between the chemicals within geopolymers and act as filler material. These two properties of nanomaterials make them a better option for geopolymers to increase their conventional properties in cured-in-situ conditions. This study compares and discusses the hardened properties of ordinary geopolymer composites made from different industrial by-products with other geocomposites incorporating nanomaterials like nano-silica, nano-alumina, nano-clay, nano-TiO 2 , carbon nanotubes, and nano-graphene. Studies suggest that the initial measures for improving the hardened properties of geocomposites are; activator precursors of high a aluminate-to-silicate ratio, medium molarity close to 8 M, and a sodium silicate-to-sodium hydroxide ratio close to 2, that yield a compressive strength in the range 35-69 MPa. Nanoparticle incorporation further improved the compressive strength to the range of 25–35 MPa without the need for adding a higher amount of activator solutions. With the addition of 2% nano-silica, nano-alumina, and nano-clay by weight of the binder, the compressive and flexural strength of geopolymer concrete increased by 46.26% & 91.85%, 25.31% and 35.25%, and 46.54% and 48.29%, respectively. Thus, the use of nanomaterials is beneficial, as it imposes no side effect on geocomposites.