Production of Bio-Based Concrete Water Reducer from Crude Cellulose derived from Woody Biomass
Abstract
Concrete water reducers are chemical ingredients added to concrete before or during mixing to reduce the required quantity of water, which produces increased workability and flowability in freshly mixed concrete and improved mechanical strength, and durability in hardened concrete. Recently, there has been a growing interest in bio-based concrete water reducers because they are renewable, abundant, and simple to source and produce. Also, the increased awareness of the deleterious environment and health impacts of producing and using petroleum-based concrete water reducers has further increased the demand for bio-based water reducers. In the present study, a new bio-based concrete water reducer is produced from the dual consecutive esterification (with maleic anhydride, MA) and sulphonation (with sodium sulphite, SS) of crude cellulose (CC) obtained from fractionated pinewood sawdust. The effects of various reaction conditions on the Degree of Substitution (DS), product yield and Sulfonation Degree (SD) were investigated to optimize the process conditions. The optimal reaction conditions of the esterification process have been determined as: 140oC, 5h, 3:1 MA/CC molar ratio, 4% ZnCl2 catalyst loading, using N, N Dimethylformamide (DMF) as solvent in a solvent/substrate ratio of 60:40 (w/w), where the obtained crude cellulose maleate (CC-MA) product has a DS of 1.3 and 90% yield. The CC-MA was further functionalized by a sulphonation reaction with sodium sulphite (SS) performed at room temperature overnight, or at 60-70 oC for 2h, with an SS/CC-MA molar ratio of (0.95´DS):1 using water as solvent at a solvent/substrate ratio of 70:30 (w/w) to produce crude cellulose-based water reducers. The crude cellulose-based water reducer derived from the CC-MA 1.3DS (denoted as 1.3WR) demonstrated better and comparable plasticizing and mechanical properties relative to the commercial lignin-based product. At a dose of 0.6 wt.% of cement weight, the 1.3WR sample showed better performance in cement fluidity and concrete slump than the commercial lignin-based water reducer and comparable performance in setting time and compressive strength measurements.