Co-valorization of sediments incorporating high and low organic matter with alkali-activated GGBS and hydraulic binder for use in road construction

Abstract

This study investigates the valorization of dredged sediments containing high and low organic matter (OM) content with alkali-activated ground granulated blast furnace slag (GGBS) and conventional hydraulic binders (HB). The objective is to develop a sustainable material with the necessary qualities for road construction. Research is conducted on dredged sediments from the French port of Cherbourg (CHER-ALL sediments) and the dam in the Maurienne Valley of France (MOR-ALL sediments), with high and low levels of OM content, respectively. After the determination of physico-chemical and mineralogical characteristics, high organic CHER-ALL sediments were first valorized using conventional HB and then co-valorized using low carbon footprint alkaline activated byproducts (AAB). The alkali activation of the byproduct (GGBS) was performed with a chemical activator named NeoliX. AAB and HB were utilized to treat the dredged sediments to compare their mechanical performances as well as environmental impacts. In terms of mechanical performance, the obtained results revealed that AAB outperformed traditional HB, and concerning the environmental impacts, byproducts have no carbon footprint except for their transportation. As a consequence, AAB has also been utilized to co-valorize the sediments from the Maurienne dam (MOR-ALL sediments) as well. AAB co-valorization of these two sediments (CHER-ALL and MOR-ALL) with varying degrees of OM content facilitates an understanding of the effects of OM concentration on mechanical properties. The high OM content of the CHER-ALL sediment (>17%), regardless of the proposed mixing with traditional HB, proved to impede the valorization, since the 28-day UCS did not exceed 1 MPa. The CBR as well as ultimate tensile strength (UTS) testing confirms the reported trends from the UCS experiments. In addition, the presence of a high OM concentration significantly decreased the mechanical properties of dredging sediments co-valorized with AAB. However, depending on the mass percentage of sediment (wt%) in the mix design, it was achievable to attain the required minimum strength value of 1 MPa with 30% and 70% of CHER-ALL and MOR-ALL sediments, respectively. Even if the OM content of sediments is high, alkaline activation can be employed to co-valorize them, as demonstrated by these encouraging results. The quantity of sediment to be co-valorized is depend upon their OM content.