Recycling of dredged sediment as a raw material for the manufacture of Portland cement – Numerical modeling of the hydration of synthesized cement using the CEMHYD3D code

Abstract

Around 56 million m3 of sediments are dredged in France per year to maintain the access to ports and waterways. Sediments are considered as waste according regulations and cause environmental, ecological and economic issues. This paper aims to use dredged sediments as raw material to replace traditional materials in Portland cement production. Two cements were produced at the laboratory: a reference cement made from analytical grade reagents of CaCO3, SiO2, Al2O3 and Fe2O3 and a second cement made from sediment as a partial substitution for traditional materials. The components proportions in the raw meal were adjusted using the cementitious modulus values (LSF, SR and AR). The produced clinkers/cements were characterized by X-ray diffraction; X-ray fluorescence and scanning electron microscopy (SEM-EDS) in order to study their mineralogical and chemical composition as well as their microstructure. The reactivity of the cements was measured by isothermal calorimetry, and by the determination of the degree of hydration and the compressive strength. The CEMHYD3D code was used to numerically model the hydration of cement paste in order to follow the evolution of all phases and to predict the properties of hydrated cements.The results demonstrate that sediments can be used as a raw material in the cement production at a high rate (31 wt%) without affecting the phase assemblage and the hydration behavior.