Factors Affecting Compressive Strength of Geopolymer Concrete

Abstract

Geopolymer Concrete is an eco-friendly material that uses source material which is rich in silica and alumina such as Fly Ash, Ground Granulated Ballast Furnace Slag, and Silica Fume, Rice Husk etc. in combination with alkaline liquids such as Sodium Hydroxide /Potassium Hydroxide and Sodium Silicate solution. Since the reaction that takes place here is polymerisation, therefore, the term Geopolymer Concrete was coined. Today one of the major problems that the world is facing is environmental pollution and global warming. While talking about construction industry mainly the production of Ordinary Portland cement (OPC) causes the emission of pollutants in very large amount which results in environmental pollution. The emission of carbon dioxide in huge amount during the production of Ordinary Portland cement is a severe issue because for the production of one ton of OPC approximately one ton of carbon dioxide is emitted into the atmosphere. The Geopolymer Concrete Technology seems to be a promising alternative to conventional OPC concrete. This report will review the factors that affect compressive strength of Geopolymer Concrete along with the basic procedure of casting of Geopolymer moulds. Sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) are the alkaline liquids that will be used in this study. Cube specimens of size 150 x 150 x 150 mm were casted and tested for their compressive strength. Dry Heat Curing was adopted wherever elevated temperature curing is required, rest of the specimens will be cured at ambient temperature. It was found that compressive strength of Geopolymer concrete increased with decrease in content of fly ash and increase in content of GGBS. Further it was also noticed that the compressive strength of Geopolymer concrete increases even after 28 days unlike Portland cement concrete. The method of dry heat curing and rest period are of great significance in Geopolymer concrete which are discussed in detail in later part of the report. For all the specimens the ratio of Na2SiO3: NaOH = 1.8 was kept constant. The super-plasticizer dosage was kept to be 1.5% of FA+GGBS. Extra water, 10% of FA+GGBS was added to improve the workability. Water absorption of aggregates was considered separately. The purpose of the project is to set up optimum values to prepare Geopolymer concrete as per the material readily available in Indian market.