Characterization of Fly Ashes for Sulfate Resistance

Dhole, Rajaram; Folliard, Kevin J.; Drimalas, Thano

doi:10.14359/51685530

Cited by 2 publications

(2 citation statements)

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“…Additionally, 5% silica fume (SF) was used as part of a ternary blend with 35% HC fly ash. The HC fly ash had a CaO = 28.98% and is known to be susceptible to sulfate attack [6,7,[21][22][23]. The chemical composition of the cementitious materials, as well as the phase composition of the cements used is presented in Tables 1 and 2, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…The results suggest that the chemical composition of the mixtures prior to sulfate exposure could be affecting the performance. This is likely attributed to the reactive glassy phases and aluminates available to react in the fly ash mixture thus favoring the formation of ettringite at later ages [22]. Santhanam et al [33] modeled the effects of sodium sulfate concentrations on small mortars.…”

Section: C2 Mixturesmentioning

confidence: 99%

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Deterioration of Mortar Bars Using Binary and Ternary Mixtures Immersed in Sodium Sulfate Solutions

Aguayo

Nodehi

2022

Ceramics

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In this study, the performance of several binary and ternary mixtures containing high-calcium fly ash and other pozzolans, such as Class F fly ash and silica fume, were investigated for their sulfate resistance using different sodium sulfate solutions. The mortar bars were placed in a similar sulfate solution as per modified ASTM C 1012/1012M (33,800 ppm SO42−) with a less severe sulfate solution (6000 ppm SO42−) has been tested to resemble actual field performance for a duration of 18 months. The phase composition of the mortar samples was investigated using X-ray diffraction and scanning electron microscope coupled with energy dispersive spectroscopy (SEM/EDS). Results show that the mortar bars placed in the moderate sulfate concentration experience less expansion and deterioration than the same bars placed in the higher sulfate concentration. Storage in sodium sulfate solutions resulted in the formation of ettringite and gypsum in both sulfate concentrations. Replacement of cement by high-calcium fly ash showed significantly higher amounts of ettringite formation, especially for the mortar bars stored in the higher sulfate concentration. SEM analysis revealed ettringite to be the primary cause of disruption and deterioration observed in the mortar bars.

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Section: Methodsmentioning

confidence: 99%

Section: C2 Mixturesmentioning

confidence: 99%