萘系高效减水剂对赤泥基胶凝材料性能的影响机理OA

Objectives Red mud is a bulk industrial solid waste generated during alumina production,char-acterized by huge annual output and low utilization efficiency.Its stockpiling not only occupies large areas of land but also poses potential risks of alkali pollution to surrounding soil and water environments.More-over,its fine particle size and strong water absorption significantly deteriorate the fluidity and mechanical properties of cement-based materials,thereby limiting large-scale and resource-efficient utilization.Meth-ods A naphthalene-based superplasticizer(NSF)was used as a chemical admixture.The effects of NSF on the rheological behavior,mechanical properties,and microstructure of red mud-cement pastes with differ-ent red mud contents were systematically investigated.The underlying mechanisms governing these effects were analyzed.Results The results show that an optimal NSF dosage of 0.5％significantly improved the flu-idity of the cement paste,and effectively reduced slump loss at 30 and 60 min.Meanwhile,plastic viscos-ity and shear stress were decreased,indicating improved dispersion of red mud and cement particles.At red mud contents of 0％and 25％,the compressive strength of NSF-modified pastes was higher than that of the control samples at 1,3,7,and 28 days.This improvement can be attributed to the accelerated hydra-tion of C2S and C3S induced by NSF.The C―S―H gels exhibited fibrous and reticular morphologies in all samples,while Ca(OH)2 showed a plate-like structure;however,its distribution was more uniform in the NSF-containing samples.When the red mud content reached 50％,the mechanical properties were ad-versely affected,which may be attributed to the increased alkalinity of the system and the instability of NSF in highly alkaline environments.Conclusions These results provide theoretical guidance for improving the performance of red mud-based cementitious materials.