NIU H C, HUANG M H, WANG X G,et al.Preparation and mechanical properties of red mud-based geopolymer mortar[J].Journal of Henan Polytechnic University(Natural Science) ,2025,44(5):180-186.

DOI:10.16186/j.cnki.1673-9787.2023120013

Received:2023/12/07

Revised:2024/02/18

Published:2025/07/23

Preparation and mechanical properties of red mud-based geopolymer mortar

Niu Haicheng, Huang Minghui, Wang Xingguo, Li Yuxuan, Qin Ziheng

School of Civil Engineering， Henan Polytechnic University， Jiaozuo 454000， Henan， China

Abstract: Objectives To explore the potential of utilizing red mud， a solid industrial waste， in construction materials by investigating the preparation and mechanical properties of red mud-based geopolymer mortar. Methods Red mud was used as the primary raw material for the preparation of geopolymer mortar. An orthogonal experimental design was adopted to examine the effects of slag content （20%， 30%，  40%， 50%）， sodium silicate solution mass concentration （60%， 50%， 40%， 30%）， lime content （0%， 5%， 10%， 15%）， and gypsum content （0%， 5%， 10%， 15%） on the mechanical properties of the mortar. The polymerization process and synthesis mechanism were analyzed using scanning electron microscopy （SEM） and X-ray diffraction （XRD）.  Results The sodium silicate solution mass concentration was identified as the most critical factor influencing the mechanical properties of the mortar， followed by slag content. Lime and gypsum had relatively minor effects. The optimal mix design was identified as containing 30% sodium silicate solution mass concentration， 40% slag， 5% lime， and 0% gypsum. As the sodium silicate solution mass concentration decreased， the 3-day and 28-day compressive and flexural strengths increased， but decreased when the concentration dropped below 30%. Increasing slag content improved the 3-day and 28-day strengths， but when the content exceeded 50%， the 3-day compressive strength continued to increase， while the 3-day flexural strength and 28-day compressive strength decreased. Conclusions Under the activation of sodium silicate solution and lime， minerals in red mud and slag undergo depolymerization， releasing active components such as calcium， silicon， and aluminum. During the geopolymerization and hydration processes， a hybrid structure composed of a zeolite-like geopolymer framework and calcium-aluminosilicate hydrate （C—A—S—H） gel is formed， which contributes to the excellent mechanical properties of the red mud-based geopolymer mortar.

Key words:red mud-based geopolymer mortar;slag content;sodium silicate solution mass concentration;polymerization reaction