Abstract
Large amounts of sediments are dredged each year to ensure navigation. These materials, classified as waste, seem to be promising alternatives to conventional construction materials. Dredging operations, carried out by the Territorial Directorate of the Seine Basin (DTBS), generate an annual volume of sediments of about 150,000 m3, of which nearly 50% are fine sediments (<80 μm). For these fine sediments, it is necessary to look for possible ways of valorisation, knowing that the coarse sediments, sands and gravels are already easily reused in concrete. The valorisation of fine sediments, such as concrete with 30% sand, has already been evaluated. However, it was found to significantly affect concrete performance; it extends setting time from 3 to 18 h, decreases compressive strength by an average of 50% and increases shrinkage deformation up to 200%. This paper seeks to evaluate the effects of ten different fine sediments, used as substitutes for 10% of cement by volume, on physico-chemical and mechanical properties. The experimental results show that fine sediments marginally affect concrete properties. The main peak of the released heat flux is delayed to less than 4 h, the compressive strength is decreased by 8% on average and the increase in shrinkage deformation does not exceed 17%, except for in two fine sediments. This incorporation method also has an environmental advantage over substituting 30% of concrete with sand, as it reduces CO2 emissions by almost 10% (instead of 0.2%).
Highlights
Concrete is one of the most consumed materials in the world, which has an effect on the natural material deposits that are used directly in the manufacture of concrete
The results of this study showed that as the fine sediment content increases from 0 to 20 wt %, the flow gets reduced by 50% and the compressive strength is slightly affected
Several studies dealing with the effect of the incorporation of calcined sediments on the rheology of cementitious materials have shown that the substitution of cement by calcined sediments induces a noticeable loss of fluidity, which means that the calcined sediments potentially retain water and the water does not contribute to the fluidity of the mixture [14,18,34]
Summary
Concrete is one of the most consumed materials in the world, which has an effect on the natural material deposits (sand, aggregates, limestone, etc.) that are used directly in the manufacture of concrete. Due to modern lifestyles, the progress of industry and technology has led to a significant increase in the amount and type of waste, such as demolition concrete, waste foundry sand and glass These wastes could be recycled and used as alternative sources of aggregates or cement to produce concrete and meet the challenge of reducing the depletion of raw materials [1,2,3,4,5,6]. Dredging operations carried out on the waterways of the Paris region generate approximately 150,000 m3 annually These sediments require valorisation or storage in waste storage facilities. 190,000 m3 (25%) of the sediments dredged over the period between 2014 and 2018 were directly stored in Inert Waste Storage Facilities (ISDI) at a cost between 5 and 11 EUR/ton [8] (based on 2012 data; current data may be much higher). National and international regulations concerning sediments are increasingly demanding and, in the future, the cost of their current management could be greatly increased
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