Strength and durability of blended geopolymer composite

Abstract

Understanding the presence of huge amount of wastes, priority has been given in Govt. policies of different countries including India, to utilize these wastes. Research on new alternative of cement binder, with considerably lower CO2 emission, is the need of the day. Geopolymer from waste like fly ash is one of such new materials. Research indicates some noticeable drawbacks of fly ash based geopolymer like hardening characteristics, cracking with age, efflorescence, low reactivity level etc. It is observed that dissolution of sodium hydroxide in lower ambient temperature is very low. The optimization of temperature level of activator prior mixing has been done to overcome this problem. Again, the rate of poly-condensation is dependent on the choice of alkali combination for different base and supplementary materials. Slow synthesis may provide sequential development of crystallized compound within the pores which affects the product performance. A program has been designed to investigate the effect of different combination of activators and supplements on the performance of geopolymer. Again, silicate solution consists of more than 65% of water which is essential for primary poly-condensation but responsible for development of semi crystalline phases in geopolymer. The consequence of supplementary reactive silica (silica fume) as an alternative of sodium silicate has been investigated. Studies on the water cured geopolymers, has not received proper attention in the past. Typical alkali activated and water cured new blended product has been investigated. As breed of geopolymer is different from cement based products, new measurement procedures for workability and durability have been explored. Present study is inclined towards the long term performance of geopolymer, optimization of strength, choice of supplementary materials (like GGBS, Lime stone dust, Silica fume, Murram, Borax etc.), choice of combination of oxides (Na2O,K2O) in activator solution, choice of curing profile and aging period etc. This research gives new information based on systematic microstructural and mechanical studies of fly ash based non blended/ blended geopolymer. Tests like SEM, XRD, MIP, FESEM, EDAX and TG/DTA were made for proper scientific interpretations. This research provides pathway to produce high performance geopolymers overcoming present drawbacks.