Non-structural Performance of Pastes and Mortars Fabricated from Alkali Activated Electric Arc Furnace Slag

With the implementation of legislation on waste management in the European Union, which sets objectives in terms of promoting the re-use and recycling of products, the industry and the academic community have been making additional efforts in order to develop solutions that aim to use industrial by-products as raw materials, more specifically, in the study of alternative binders to Portland cement. In this work, an extensive experimental campaign is carried out to characterise, from the non-structural point of view, a set of alkali activated mixtures fabricated with electric arc furnace slag (EAFS) and phosphate sludge (PS) as the precursor, and two different activators (a commercial solution composed by sodium hydroxide and sodium silicate, and a solution used to clean the sand moulds from the aluminium processing industry). Results reveal that the mixtures based on EAFS present some handicaps in terms of shrinkage and workability, and that these properties are influenced by the nature of the activator and the presence of the PS.

Keywords:Electric arc furnace slag; Phosphate sludge; Alkali activated mortars; Non-structural behaviour

List of Abbreviations:

CS – solution used to clean the sand moulds from the Portuguese aluminium processing industry; EAFS – electric arc furnace slag; FS – flexural strength tests; HS – solution containing commercial sodium hydroxide and sodium silicate; LVDT – linear variable differential transformer; PS – phosphate sludge; PSD – particle size distribution; UCS – uniaxial compressive strength tests

List of Notations

Cm is the coefficient of water absorption for mortars other than renovation mortars

Cr is the coefficient of water absorption for renovation mortars

f is the factor of molarity

m is the mass of the sample

M0 is the dry mass of the specimen

M1 is the mass of the specimen after soaking for 10 minutes

M2 is the mass of the specimen after soaking for 90 minutes

M3 is the mass of the specimen after soaking for 24 hours

md is the dry weight of the specimen

mh is the immersed weight of the specimen

ms is the saturated weight of the specimen

p0 is the open porosity of the specimen

Rf is the flexural strength

Rc is the compressive strength

V1 is the sample titre of 0.1 M ammonium thiocyanate solution

V2 is the blank titre of 0.1 M ammonium thiocyanate solution

ρb is the bulk density of the specimen

ρrh is the water density

% Cl is the percentage chloride