Pre-Industrial Manufacturing Tests on Construction Blocks Composed of Magnesium Slags

The aim of this study is the valorization of magnesium slags in order to recycle them in construction block form. Two kinds of slag with hydraulic properties are obtained according to a 1/3-2/3 ratio: powdered slag similar to cement, and granulated slag similar to sand. A previous laboratory study was carried out in order to obtain sufficient mechanical strength for construction blocks and setting kinetics compatible with an industrial process. The present paper deals with the consecutive implementation of life size tests on an industrial scale. Two pre-industrial tests were carried out in extremely different temperature conditions: 7 degrees C for the first test and 22 degrees C for the second one. Furthermore, the second test benefited from the new casting conditions resulting from updating of the manufacturing unit. The first test showed that the laboratory study permitted to adjust the set kinetics to a level adequate for industrial casting, whereas the mechanical strength obtained was lower than expected when the powdered slag was used as a substitute for cement. The second test enabled the authors to obtain enough mechanical strength for mixtures entirely composed of magnesium slags and proved the possibility of total and simultaneous enhancing value of magnesium slags as construction blocks. More generally, these industrial tests show how difficult the transfer to the industrial scale is.