Title: Mix-design and Properties of Mortars from Alkali-activated Fly Ashes Containing High Amounts of Unburned Carbon Matter

Author(s): Stefania Manzi , Andrea Saccani, Luca Baldazzi and Isabella Lancellotti

Publication: IJCSM

Volume: 14

Issue:

Appears on pages(s):

Keywords: fly ashes, alkali-activated materials, unburned carbon matter, mortars mix-design, workability, mechanical properties, microstructure

DOI: 10.1186/s40069-020-00435-8

Date: 11/30/2020

Abstract:
Alkali-activated materials are a promising type of binder candidate as a substitute to Portland cement. Fly ashes can be used as binder precursors giving higher environmental benefits. In the present research, fly ashes (Type F) contain-ing different amounts of unburned carbonaceous matter have been used to formulate mortars. Serious problems concerning the workability in the fresh state have been found when high carbon content are reached. An attempt to avoid the preliminary treatments used to eliminate the unburned matter is carried out by exploiting different mix-design receipts obtained by changing the water/binder ratio, the ratio of the alkaline activators and using different types of superplasticizer additives. Data so far collected underline that a high amount of unburned carbonaceous matter can not only compromise the mechanical properties of the materials, but also the rheological ones and under-line the necessity to develop ad hoc additives for this type of binders.