Effect of drying temperature on the properties of alkali-activated binders - Recommendations for sample preconditioning

Alkali-activated binders (AABs) stand out as a promising alternative to replace ordinary Portland cement (OPC) due to the possibility of using by-products and wastes in their manufacturing. This paper assessed the potential of weathered bottom ash (WBA) from waste-to-energy plants and PAVAL® (PV), a secondary aluminium recycling process by-product, as precursors of AABs. WBA and PV were mixed at weight ratios of 98/2, 95/5, and 90/10. A mixture of waterglass (WG) and NaOH at different concentrations (4 and 6 M) was used as the alkaline activator solution. The effects of increasing NaOH concentration and PV content were evaluated. Alkali-activated WBA/PV (AA-WBA/PV) binders were obtained. Selective chemical extractions and physicochemical characterization revealed the formation of C-S-H, C-A-S-H, and (N,C)-A-S-H gels. Increasing the NaOH concentration and PV content increased porosity and reduced compressive strength (25.63 to 12.07 MPa). The leaching potential of As and Sb from AA-WBA/PV exceeded the threshold for acceptance in landfills for non-hazardous waste.

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Effect of CaSO4 Incorporation on Pore Structure and Drying Shrinkage of Alkali-Activated Binders

Materials ◽

10.3390/ma12101673 ◽

2019 ◽

Vol 12 (10) ◽

pp. 1673 ◽

Cited By ~ 3

Author(s):

Hyeongmin Son ◽

Sol Moi Park ◽

Joon Ho Seo ◽

Haeng Ki Lee

Keyword(s):

Fly Ash ◽

Pore Structure ◽

Drying Shrinkage ◽

Phase Changes ◽

X Ray Diffraction ◽

Activated Slag ◽

Capillary Tension ◽

Alkali Activated Binders ◽

Internal Pore Structure ◽

Alkali Activated

This present study investigates the effects of CaSO4 incorporation on the pore structure and drying shrinkage of alkali-activated slag and fly ash. The slag and fly ash were activated at a 5:5 ratio by weighing with a sodium silicate. Thereafter, 0%, 5%, 10%, and 15% of CaSO4 were incorporated to investigate the changes in phase formation and internal pore structure. X-Ray Diffraction (XRD), thermogravimetry (TG)/derivative thermogravimetry (DTG), mercury intrusion porosimetry (MIP), nuclear magnetic resonance (NMR), and drying shrinkage tests were carried out to find the correlation between the pore structure and drying shrinkage of the specimens. The results showed that CaSO4 incorporation increased the formation of thenardite, and these phase changes affected the pore structure of the activated fly ash and slag. The increase in the CaSO4 content increased the pore distribution in the mesopore. As a result, the capillary tension and drying shrinkage decreased.

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Influence of different curing methods on mechanical and durability properties of alkali activated binders

Construction and Building Materials ◽

10.1016/j.conbuildmat.2021.123963 ◽

2021 ◽

Vol 299 ◽

pp. 123963

Author(s):

V.S. Athira ◽

A. Bahurudeen ◽

M. Saljas ◽

K. Jayachandran

Keyword(s):

Durability Properties ◽

Curing Methods ◽

Alkali Activated Binders ◽

Alkali Activated

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Leaching, carbonation and chloride ingress in reinforced alkali-activated fly ash mortars

MATEC Web of Conferences ◽

10.1051/matecconf/201819902025 ◽

2018 ◽

Vol 199 ◽

pp. 02025 ◽

Cited By ~ 1

Author(s):

Gregor J. G. Gluth ◽

Petr Hlaváček ◽

Steffi Reinemann ◽

Gino Ebell ◽

Jürgen Mietz

Keyword(s):

Fly Ash ◽

Visual Inspection ◽

Electrochemical Behaviour ◽

Transport Coefficients ◽

Chloride Penetration ◽

Chloride Ingress ◽

Reaction Products ◽

Steel Bars ◽

Alkali Activated Binders ◽

Alkali Activated

Alkali-activated fly ash mortars were studied with regard to durability-relevant transport coefficients and the electrochemical behaviour of embedded carbon steel bars on exposure of the mortars to leaching, carbonation and chloride penetration environments. The transport coefficients differed considerably between different formulations, being lowest for a mortar with BFS addition, but still acceptable for one of the purely fly ash-based mortars. Leaching over a period of ~300 days in de-ionized water did not lead to observable corrosion of the embedded steel, as shown by the electrochemical data and visual inspection of the steel. Exposure to 100 % CO2 atmosphere caused steel depassivation within approx. two weeks; in addition, indications of a deterioration of the mortar were observed. The results are discussed in the context of the different reaction products expected in highand low-Ca alkali-activated binders, and the alterations caused by leaching and carbonation.

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