Effect of potassium humate as humic substances from river sediments on the rheology, the hydration and the strength development of a cement paste

Abstract

Dredged river sediments may contain various types of organic matter that can affect the properties of a cement matrix, with the most representative part of such organic matter consisting of humic substances (HS). This work seeks to investigate the effects of humic substances on the rheology, the hydration and the strength development of a cement paste with different curing times, ranging from 1 to 90 days. Results show that adding organic matter to the cement paste offers greater workability by decreasing the yield stress. This addition also serves to retard the hydration of cement particles. Setting times increase to beyond one week when raising the amount of humic substances in the mixture, while the heat released ultimately reaches values comparable to those of the reference cement paste. Therefore, the addition of organic matter negatively affects strength development of the paste, especially at an early age; no resistance at 1-day has been noticed for HS content greater than 1%. Nevertheless, that there was no significant reduction in the compressive strength up to 20% for HS content less than 1% at 90-day. In parallel, a study on pastes containing calcium lignosulfonate (water reducer) is carried out and the same effects are observed.

Reuse potential of dredged river sediments in concrete: Effect of sediment variability

“…For example, concrete incorporating CF6 fine sediments exhibits a longer hydration delay and a lower compressive strength at 3 days, while its compressive strength at 28 days is close to that of other concretes incorporating fine sediments. This finding is consistent with the effects of soluble humic substances, as reported in (Beddaa et al, 2019). In contrast, since sediment sands and sediment gravels do not generate a significant effect on cement hydration, their effect on both early-term and long-term compressive strength remains the same.…”

“…Soluble humate substances can adsorb on cement particles and extend this delay to several days. More precisely, the delay depends on the amount of soluble humic substances per weight of cement (Beddaa et al, 2019). From Table 3, the delay in the main peak is not proportional to the rate of organic matter.…”

“…Consequently, the fine fraction of sediments contains a higher amount of organic matter than the other granular classes. Since organic matter is known to delay the setting, hydration and the development of compressive strength of concrete (Beddaa et al, 2019;EN12620+A1, 2008); these properties are expected to be altered as organic-rich sediments are substituted for conventional concrete aggregates.…”

“…Nevertheless, these sediments contain organic matters, shells and fines that may affect the concrete properties. For instance, organic matter is known to delay setting and hinder the development of cement paste strength (Beddaa et al, 2019;Chen and Wang, 2006;Clare and Sherwood, 2007;Saride et al, 2013;Tremblay et al, 2002). Moreover, shells reduce concrete strength owing to their flattened shapes and poor adhesion to cement paste (Martínez-García et al, 2017;Nguyen et al, 2013bNguyen et al, , 2017Rica, 2017;Yang et al, 2010).…”

Effect of the amount of river sediment on the basic properties of cement mortars

“…Dredging water bodies, including lakes, rivers or ports, is a common process. It helps to restore their natural depth and prevents, among other things, flooding, and, in the case of ports, ensures that ships have a sufficient draft [1]. Deposition of sediment on the bottoms of water bodies is either a natural process (so-called endogenous origin) or frequently is due to human activity (so-called exogenous origin).…”