Performance of fly ash based geopolymer pastes under chemical environment

Title: Performance of fly ash based geopolymer pastes under chemical environment
Author(s): B. Singh, Sarika Sharma, M.Gupta and S.K. Bhattacharyya
Paper category : conference
Book title: International RILEM Conference on Advances in Construction Materials Through Science and Engineering
Editor(s): Christopher Leung and K.T. WAN
ISBN: 978-2-35158-116-2
e-ISBN: 978-2-35158-117-9
Publisher: RILEM Publications SARL
Publication year: 2011
Pages: 877 - 884
Total Pages: 8
Nb references: 13
Language: English

Abstract: Class F fly ash was activated with sodium hydroxide and sodium silicate solution in a ratio of 1:2.5 using different Na2O concentrations. The properties of geopolymer pastes were optimized at 18 molar activator concentrations in terms of their compressive strength and microstructure. Performance of these pastes was studied in the acidic and sulphate environments for a period of 4 months. It is observed that the loss of compressive strength was 26% in Na2SO4 and 50% in MgSO4 solutions. The samples were cracked in the mixed solution of Na2SO4 and MgSO4 after 30 days. Under acidic environment, the samples exhibited strength loss to an extent of 39% in HCl and 54.2% in H2SO4 solutions respectively. It is noted that the loss of geopolymer strength in deionized water was ~ 25%. The exposed samples gained 1.4% and 3% weight in acidic and sulphate environments respectively. The difference in strength of the fresh and exposed samples could be explained on the basis of their microstructural features such as leaching of sodium ion, dealumination and deposition of precipitates, fissures in the gel structure, crystalline zeolites and porosity. EDAX analysis indicates that in sulphate solution, Si/Al ratio increases and Na/Al ratio decreases whereas in HCl solution, Si/Al and Na/Al ratio decreased in the exposed samples when compared with the control sample. The maximum deteriorating effect in the geopolymer pastes was obtained in a mixed sulphate solution and H2SO4 solution.

Online publication: 2011-10-31
Publication type : full_text
Public price (Euros): 0.00