Application of Industrial Waste in Manufacturing of Self Compacting Concrete

Abstract

Red mud derived from alumina refineries through the Bayer process is a waste material with a density of 2187 kg/m3. The particle size distribution of the red mud is similar to fly ash. In this paper, the physical and chemical properties of the red mud including oxide and mineral contents are studied. The potential use of the red mud as a pozzolanic material to replace fly ash in self-compacting concrete (SCC) is assessed by conducting a range of fresh and hardened properties test (such as slump flow, density, porosity, compressive strength, splitting tensile strength, elasticity modulus and drying shrinkage). The XRF and XRD results show that the oxide forms in the red mud are mainly SiO2, Al2O3 and CaO at 45.76%, 40.69% and 4.98% respectively, and the crystalline phases are mainly gismondine, goosecrekite and epistilbite which belong to the zeolite family. The results show that the strength activity indeces (SAI) of the red mud are 79.60 and 88.46 at 7 days and 28 days respectively, which are approximately equal to that of a common Class F fly ash. Meanwhile, with the use of the red mud to replace fly ash in SCC, the compressive strength, splitting tensile strength and elasticity modulus are enhanced. Moreover, with the addition of the red mud, the drying shrinkage decrement is observed in SCC, which might be due to the red mud\\\'s internal curing. Therefore, the feasibility of utilizing the Bayer red mud in SCC is demonstrated.

Introduction

Recent research has explored the reuse of industrial waste materials like waste glass and concrete waste in concrete to improve properties. Bauxite processing produces a highly alkaline solid waste called red mud, which poses environmental challenges due to its disposal. To address this, studies have investigated reusing red mud in various applications, including ceramics, bricks, and polymer composites. However, its effects on concrete’s mechanical properties remain less studied.

This paper investigates incorporating red mud as a partial replacement for fly ash in self-compacting concrete (SCC). The red mud used contains zeolite-type minerals, known for their pozzolanic activity and internal curing potential, which could enhance concrete properties.

Experimental Work:

• Red mud from an alumina plant in China was characterized chemically and mineralogically.

• SCC mixtures were prepared with varying red mud replacement levels (10%-40%) replacing fly ash.

• Tests included workability (slump flow, J-ring), compressive strength, tensile splitting strength, elastic modulus, drying shrinkage, density, and porosity.

Key Findings:

• Red mud exhibited pozzolanic activity comparable to fly ash.

• Increased red mud content required more superplasticizer due to its higher water absorption.

• Workability decreased slightly with higher red mud but segregation was reduced.

• Hardened density slightly decreased with red mud replacement; porosity increased significantly only at 40% replacement.

• Compressive strength at 7 and 28 days was similar to control; at 56 and 90 days, higher red mud content (30-40%) improved strength by ~8-9%, likely due to internal curing.

• Tensile strength was slightly lower at early ages but improved by 90 days with red mud.

• Elastic modulus increased with up to 30% red mud replacement, showing no negative impact.

Conclusion

The pozzolanic activity and the effects of the red mud on properties of SCC have been assessed in the present study. The results show that the red mud has good pozzolanic activity roughly equivalent to that of FA. Also, the red mud slightly reduces the flowability and passing ability of SCC; however, the added red mud enhances the viscosity of SCC and significantly prevents segregation and bleeding. The results from the effects of the red mud on the hardened properties of SCC show that the hardened density slightly decreases with increasing red mud content; meanwhile, as the red mud content is 30%–40% of that of FA, enhanced compressive strength and splitting tensile strength of SCC are observed after 90 curing days. In addition, with the addition of the red mud in SCC, the drying shrinkage is reduced, which might be due to the internal curing effect. Overall, the results of this study have demonstrated that it is feasible to utilize 10%–40% of the red mud to replace FA in the production of SCC.

References

[1] Use of natural zeolite as a supplementary cementitious material Cem. Concr. Compos, 32 (2) (2010), pp. 134-141 [2] ASTM,2008: C109/C109M Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2-in. Or [50-mm] Cube Specimens) [3] Use of natural zeolite to produce self-consolidating concrete with low portland cement content and high durability J. Mater. Civ. Eng., 25 (2013), pp. 589-596 [4] Thermal behavior of clay mixtures with bauxite residue for the production of heavy-clay ceramics J. Eur. Ceram. Soc., 27 (2007), pp. 1645-1649 [5] Effect of the addition of red mud on the corrosion parameters of reinforced concrete Cem. Concr. Res., 42 (2012), pp. 124-133 [6] The investigation of sulfuric acid sorption recovery of scandium and uranium from the red mud of alumina production Hydrometallurgy, 45 (1997), pp. 249-259 [7] High-volume natural pozzolan concrete for structural applications ACI Mater J., 104 (5) (2007), pp. 535-538 [8] Experimental study on acid leach of red mud Light Met., 2 (2005), pp. 13-15

Copyright

Copyright © 2025 P Balaji. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.