Synthesis of Lignosulfonate-Based Dispersants for Application in Concrete Formulations

Abstract

Lignosulfonates (LS) are products from the sulfite pulping process that could be applied as renewable environmentally-friendly polymeric surfactants. Being widely used as plasticizers and water-reducing admixtures in concrete formulations LS compete in the market with petroleum-based superplasticizers, such as naphthalene sulfonate formaldehyde polycondensate (NSF) and copolymer polycarboxylate ethers (PCE). In this work, different chemical modification strategies were used to improve LS performance as dispersants for concrete formulations. One strategy consisted in increasing the molecular weight of LS through different approaches, such as laccase and polyoxometalate-mediated polymerization, glyoxalation, and reversible addition-fragmentation chain transfer (RAFT) polymerization. The other strategy consisted of preparing LS-based non-ionic polymeric dispersants using two different epoxidized oligomer derivatives of poly(ethylene glycol) (PEG) and poly(propylene glycol) (PPG). Modified LS were used to prepare cement pastes, which were examined for their fluidity. Results revealed that the most promising products are PPG-modified LS due to the introduction of PPG chains by reaction with phenolic moieties in LS. The enhanced dispersant efficiency of the ensuing products is probably related not only to electrostatic repulsion caused by the sulfonic ionizable groups in LS but also to steric hindrance phenomena due to the grafted bulky PPG chains.

A Green Cement Plasticizer from Softwood Kraft Lignin

“…5−7 However, these plasticizers are mostly petroleum-based and thus environmentally unfriendly. 8 Alternatively, lignosulfonate (LS) has been used commercially as a biobased cement plasticizer. 9 The LS is the byproduct of the sulfite pulping process.…”

“…They are used in the concrete admixture to increase its dispersibility by decreasing the agglomeration of the hydrating cement materials , and reduce its water requirement by maintaining its strength . Commercial plasticizers, such as hydroxycarboxylic acid and sulfonic naphthalene acid, have carboxylate and sulfonate groups that create electrostatic repulsions in the cement paste and increase the fluidity of the cement paste. − However, these plasticizers are mostly petroleum-based and thus environmentally unfriendly …”

Evaluation of the influence of sodium and magnesium lignosulfonates on the hydration kinetics of cementitious paste

“…Among several types, water reducers/plasticizers are those with the highest consumption volume [2]. Because they are more environmentally friendly, lignosulfonate-based admixtures form the highest percentage among water-reducing/retarding admixtures used in the concrete industry [3,5]. Lignosulfonates are complex anionic polymers obtained together with cellulose during acid sulfite or bisulfite pulping of wood [6].…”

“…Lignosulfonates have high molecular masses, in the order of 20,000-30,000 g/mol, with wide molecular weight distribution and varying degrees of sulfonation. Despite some divergences [15], there is a consensus that the adsorption and water-reducing capacity of lignosulfonates increase with their molecular weight [5][6][7]. The main mechanism of action of lignosulfonate is attributed to the phenomenon of adsorption on cement particles, which is a characteristic of sulfonated polymers, neutralizing surface charges and causing electrostatic repulsion in the cement paste.…”

A study on investigating the effect of lignosulfonate-based com-paction aid admixture dosage on the properties of roller com-pacted concrete

“…In this experimental study, a lignosulfonate-based admixture was preferred in production of roller compacted concrete because it helps compaction, provides technical advantages and is cost-effective. Furthermore, it has been reported that lignosulfonate-based admixtures have been used as water-reducers and plasticizers in concrete since the 1930s, as they have been used for a long time, many studies have been conducted on them and they can improve concrete properties with their working mechanisms (Scripture, 1937;Swenson and Thorvaldson, 1959;Magina et al, 2021).…”