Effect of different superplasticizers and activator combinations on workability and strength of fly ash based geopolymer

• Published in: Materials in engineering Vol. 57; pp. 667 - 672
• Main Authors: Nematollahi, Behzad, Sanjayan, Jay
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.05.2014
• Subjects: Activator; Compressive strength; Fly ash based geopolymer; Mini-slump test; Superplasticizer; workability; Mini-slump test; Superplasticizer; workability; Compressive strength; Activator; Fly ash based geopolymer
• ISSN: 0261-3069
• DOI: 10.1016/j.matdes.2014.01.064

This paper evaluates the effect of different commercial superplasticizers (SPs) such as naphthalene, melamine and modified Polycarboxylate based on the workability and strength of a class F fly ash geopolymer paste activated by two different activator combinations, i.e. 8 M sodium hydroxide solution and a multi-compound activator composed of 8 M NaOH solution (28.6%) + Na2SiO3 (71.4%) with a SiO2/Na2O ratio of 2.0. These SPs at a dosage of 1% by mass of fly ash were added to the fresh paste and flowability of the activated fly ash paste was measured via mini slump test and compared with that of the paste without using any SP. The experimental results indicated that the effect of different SPs on the workability and strength of fly ash based geopolymer directly depends on the type of activator and the SP. In the case of using 8 M NaOH solution as the activator, naphthalene based SP was an effective type; whereas modified Polycarboxylate based SP was the most efficient type when the multi-compound activator was used. •Effect of superplasticizers on the fly ash based geopolymer directly depends on the type of activator and the SP.•Naphthalene based SPs is an effective type for the fly ash based geopolymer activated by only NaOH solution.•Modified Polycarboxylates based SP is the most effective type for the fly ash based geopolymer activated by NaOH + Na2SiO3.