Development of a new ecological material based on Moroccan industrial waste for road construction

Currently, the recovery of industrial waste to reduce their quantities and their impact on the environment is one of
the problems to be tackled in research. The Phosphogypsum (PG) is an industrial waste produced by the attack of
sulfuric acid on natural phosphate. PG contains harmful elements to the ecosystems and human health, in particular
heavy metals and radionuclides [1]. The electric steel is a growth industry worldwide, in particular in the United States,
it raised from less than 50% in 2000 to more than 68% in 2018 (Létard, 2019). This growth is accompanied by a
significant increase in slag waste. In Morocco, OCP (Jorf Lasfar) generates more than 15 million tonnes per year of
and the steel company (SONASID) produces slag waste (SC) 150,000 tonnes per year. Adding this waste to concrete
may increase its mechanical strength. The Aim of this study is to incorporate these wastes with Bentonite of deposit
Trebia (Nador, Morocco) stabilized by Lime to assess stabilization effect of bentonite in the presence of water (W).
For this purpose the mixtures (BLW), (BL-PG-W) and (BL-PG-Ss-W), cured for 3, 7, 15 and 28 days, were analyzed by
X-ray diffraction (XRD), infrared (IR), thermal analysis (DTA/TGA or DSC/TGA), scanning electron microscopy (SEM)
and unconfined compressive strength (UCS).
The kinetics setting and hardening of B-L and B-L-PG mixtures are slow. The addition of PG to the mixture (B-L)
allows ettringite formation after 7 days of hydration and stratlingite after 28 days. The Slag accelerates the setting of
the mixture and activates the pozzolanic reactions of bentonite. Mechanical strength is accelerated for the mixture
(B-L-PG-Ss) comparable to other mixtures; it increases only after 3 days of setting. This improvement was confirmed
for other curing times. The presence of Ye’elimite and other hydraulic binder phases present in slag could explain the
increased hardening showed for B-L-PG-Ss mixture