Towards the preparation of sustainable superplasticizers for geopolymeric pastes via radiation-induced grafting of sulfonic group-bearing monomers onto corn starch

To address escalating environmental and sustainability concerns of petroleum-based superplasticizers (SPs), this work aims to develop sustainable and eco-friendly starch-based SPs using gamma radiation for maintaining the desired workability of geopolymeric pastes. Specifically, two green SPs were prepared from starch via radiation-induced grafting of two sulfonic group-bearing monomers, namely 2-acrylamido-2-methylpropane sulfonic acid (AMPS) and 4-styrene sulfonic acid sodium salt (Na4SS). The grafting reaction was improved by initial modification of starch with glycidyl methacrylate to insert vinyl groups into the starch backbone. The modified starch samples were characterized by a variety of analytical techniques such as FTIR, ¹H NMR, EDX, SLS, and viscometry. The prepared SPs exhibited high stability in aqueous 5 % NaOH. The effect of the prepared SPs on the fresh properties of GGBFS/MK geopolymer was studied using the mini slump test, zeta potential, adsorption capacity, and setting time. They significantly improved the paste flowability and dispersion compared to the control. Notably, the aromatic Na4SS-grafted starch displayed a comparable enhancement to the commercial PNS, while outperforming the aliphatic AMPS-grafted sample. This emphasizes the potential of these green SPs to address the challenges posed by the petroleum-based SPs and maximize the benefit of using starch as a green renewable resource.