Reusing calcined sediments from Chorfa II dam as partial replacement of cement for sustainable mortar production

Abstract

Dam siltation is an alarming problem that significantly affects the dam's lifetime and water storage capacity. In Algeria, the removal of dredged sediment has become a significant environmental impact and an economic issue. In this context, the utilization of calcined sediments as an artificial pozzolanic material could reduce greenhouse gas emissions in the cement industry. This paper addresses the objective of valorizing calcined sediments in sustainable mortar production on fresh and hardened states of grouts and mortars. Moreover, three dry curing methods were used to accelerate improving the strength of the different mortars at a rate of 5, 15, and 25% by weight of Portland cement (CEM I 42.5 N). The first method was applied at 10 °C, and the other two at 20 °C and 40 °C. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) analysis showed a real advantage of heat treatment at 750 °C of sediments to acquire pozzolanic behavior. A substitution rate of 25% affected the fluidity of cement grouts with calcined sediments at 60 min with a loss of fluidity, even with a high dosage of plasticizer. Indeed, the best mechanical results of the mortars were observed at cure temperatures of 20 °C and 40 °C. With an acceleration of the pozzolanic activity at 90 days for a cure at 40 °C and 180 days at 20 °C, the development of compressive strength is relatively higher than that of the control mortar. In conclusion, the carbon footprint of the final mortars showed that a high substitution rate reduces CO2 emissions, representing a reduction of 3%, 10%, and 17% respectively for the formulation of mortars based on 5%, 15%, and 25% calcined sediment.