Effects of naphthalene superplasticizer on geopolymers activated by calcium carbide residue and Glauber's salt

Poor fluidity limits the large-scale applicability of geopolymers. This study aims to improve the fluidity of onepart geopolymer by naphthalene superplasticizer. Three types of systems were utilized as geopolymer precursors: fly ash (90 wt%), fly ash: silica fume (86 wt%: 4 wt%), and fly ash: flue gas desulfurization gypsum (85 wt%: 5 wt %). Then, activators comprising 5 wt% calcium carbide residue and 5 wt% Glauber's salt were used to prepare geopolymer composites. The resulting fluidity and mechanical strength of the developed geopolymer systems were evaluated. The 0.4 wt% naphthalene superplasticizer was found to have the optimal effect in the activated fly ash system, and the corresponding fluidity and strength increased by 17.2% and 22.8%, respectively. The results indicate that the increase in fluidity is attributed to the electrostatic repulsion between the naphthalene superplasticizer and the precursor particles. Further, the enhancement in compressive strength can be attributed to the increased gel formation resulting from intensified ion dissolution in the precursor due to the presence of the naphthalene superplasticizer, resulting in a denser microstructure with fewer pores.