Preparation of Concrete Water Reducer via Fractionation and Modification of Lignin Extracted from Pine Wood by Formic Acid

Abstract

In this work, a lignin-based concrete water reducer was prepared through organic solvent fractionation and chemical modification of lignin extracted from pine wood with formic acid. The fractionated lignin with different molecular weight was modified via oxidation–sulfomethylation (OS), and the effects of fractionation on the performance of lignin-based concrete water reducer were investigated. It was found that the sulfonation degree (SD) of the fractionated lignin after OS was clearly higher compared to the unfractionated lignin, and the SD of fractionated lignin was linearly correlated with its workability (i.e., the fluidity of cement paste) based on the results obtained. By adding the same quantity of modified lignin-based concrete water reducer, the fluidity of cement paste with the fractionated lignin (by pure acetone) after OS modification was 21% higher than the sulfonated FAL (M-FAL) without fractionation. The organic solvents used in this study could be easily recovered and reused. Thus, the whole fractionation process was sustainable. In addition, the structure changes of lignin samples before and after fractionation and OS modification were characterized by gel permeation chromatography, FTIR, and 1H NMR, respectively.

Lignin-Based Hybrid Admixtures and their Role in Cement Composite Fabrication

“…The hybrid materials used in the tests as admixtures for the mortar resulted in a final increase of the slump result (23.5–25.0 cm, depending on the quantities of mortar and biopolymer used). The results show clearly that the addition of biopolymers or of hybrid systems containing biopolymers makes it possible to increase the final slump result of cement mortar, indicating that they act as plasticizers, as has also been confirmed by other authors [15,16,17,18].…”

“…Those authors conducted a series of experiments on an aluminum plate, and the results clearly indicated the high potential of coatings with a high lignin content as anti-corrosive agents. There are also several literature reports that describe the direct use of lignin as an agent reducing the amount of mixing water for the production of cement mixtures [15,16] or as a plasticizing agent [17,18].…”

Tuning Lignin Characteristics by Fractionation: A Versatile Approach Based on Solvent Extraction and Membrane-Assisted Ultrafiltration

“…Variations in these characteristics due to different lignin origins and processing/extraction methods can cause significant alterations in the performance of the final product [24]. A critical dependence on lignin properties was found for several high-value applications [25][26][27][28], such as the production of polymers [16], antioxidants [29], aromatic compounds [30], the synthesis of vanillin [31], and the development of high-performance concrete water-reducing agents [32]. The availability of effective fractionation processes for obtaining lignins with tailored physico-chemical properties and a defined molecular weight distribution is therefore a key requirement to effectively cope with both the upstream material variability and the downstream application requirements.…”

Biopolymer-Based Hybrids as Effective Admixtures for Cement Composites

“…The authors of publications [40][41][42][43] also observed an increase in the plasticity of mixtures with the addition of lignin or its derivatives. Kalliola et al [40] reported a beneficial effect of the admixture of oxidized lignin on the flow rate for pastes, mortars and concretes.…”

“…Moreover, in their tests, it was confirmed that this admixture had no negative impact on the compressive strength of the mature concrete and the aeration of the mix. In their study, Li et al [41] obtained lignin from pinewood, and then subjected it to a series of solvent modifications to obtain a lignin-based water reducer. The authors showed the influence of the sulfonation degree of the obtained lignin on the workability of pastes, including their plasticity.…”