The role of synthesis parameters on the workability, setting and strength properties of binary binder based geopolymer paste. (30th December 2017)

• Record Type: Journal Article
• Authors: Yaseri, Sajad; Hajiaghaei, Ghazal; Mohammadi, Farnaz; Mahdikhani, Mahdi; Farokhzad, Reza
• Is Part Of: Construction & building materials. Volume 157(2017)
• Page Start: 534
• Page End: 545
• Publication Date: 2017-12-30
• Subjects: Binary binder -- Geopolymeric products -- Mini slump flow time -- Geopolymer paste -- Microstructure -- Geopolymerization -- N-A-S-H gel phase; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2017.09.102
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: Influence of increased Si/Al ratio in different B/S ratios can be various. By increasing B/S ratio compressive strength increased and mini slump and setting time were reduced. By increasing Si/Al ratio geopolymerization increased and setting time of geopolymer paste decreased. IR spectra demonstrated that, when Si content increased in the system, SiOT bond shifted to the higher wave number. Adding an optimum percentage of silica fume improves strength. Abstract: In this paper the effect of different binder to solution ratio (B/S) and different Si/Al molar ratio in the synthesis of binary binder based geopolymer paste on their workability, setting and compressive strength is investigated. Geopolymer paste was prepared by combination of metakaolin (MK) and silica fume (SF) as aluminosilicate source with a mixture of sodium hydroxide with concentration of 14M and sodium silicate as alkaline activator solution having constant H2 O/Na2 O and Na2 O/SiO2 molar ratio. For having different Si/Al ratio, metakaolin has been replaced partially by silica fume in precursor. Workability of fresh paste was measured by mini-slump test. Compressive test at the ages of 1, 3 and 7 days, setting time, FTIR and XRD analysis were used to characterize the geopolymer paste. Results show that the combination of MK and SF can be used as the aluminosilicate source materials for making geopolymer. Also, results concluded both B/S and Si/Al ratios had a significant effect on workability, setting time and strength. By increasing B/S and decreasing Na2 O/binder ratio in the system the compressive strength increased, also, in constant B/S = 1.2, 1.4 ratio, by increasing Si/Al ratio in binder growth compressive strength was obtained, but in B/S = 1.6, 1.8 with high Si/Al ratio increases, the strength will be reduced. XRD analysis showed that geopolymer has an amorphous to semi-crystalline phase which, by increasing Si/Al ratio, will decrease the intensity of crystalline phases. FTIR spectra results illustrate that when both B/S and Si/Al ratio increase in the system, SiOT bonds will shift to higher wave number.