Effect of calcination on the physical, chemical, morphological, and cementitious properties of red mud

Abstract

Red mud (RM) is a by-product of the Bayer process in aluminum industries, and its disposal leads to environmental imbalance. This study aimed to utilize RM as a cementing material in concrete to mitigate the negative environmental impact associated with its disposal. Initially, red mud was subjected to calcination at 600ºC for 0-6 hours with increments of 1 hour. Various characterization studies, including particle size analysis, BET analysis, XRF, XRD, TG-DTA, and SEM, were conducted to investigate the physical, chemical, and morphological changes in the RM resulting from calcination. Regarding the physical properties, specific gravity, and particle size values significantly decreased, while specific surface area and mass losses increased up to 2 hours of calcination due to moisture loss. Subsequently, contrasting results were observed. XRF analysis revealed abundant presence of iron oxide (Fe2O3), alumina (Al2O3), and silica (SiO2) in all the calcined red muds. Mineralogical phase changes, such as the transformation of goethite to hematite and gibbsite to alumina, were observed through XRD analysis. Morphological changes were observed using SEM analysis, showing a loose structure up to 2 hours of calcination, followed by a denser structure. Furthermore, all the calcined RMs were incorporated into cement at a 10% weight ratio, and their pozzolanic properties were investigated. Based on the results, the 2-hour calcined RM exhibited superior cementitious properties, including high compressive strength and strength activity index (46.27 MPa and 117.24%, respectively). Similarly, scanning electron microscope analysis was conducted to understand the behavior of the 2-hour calcined red mud in cement mortar, demonstrating better C-S-H gel formation in the corresponding mix. The present study concludes that 2-hour calcined red mud can be effectively used as a cementing material in concrete.

Synergistic effects of GGBFS addition and oven drying on the physical and mechanical properties of fly ash-based geopolymer aggregates

“…Compressive strength testing was conducted according to the specifications outlined in IS 516-1959 [50][51][52], utilizing a compression testing machine with a capacity of 2000 kN. The cubes underwent a cleaning process to remove any loose sand or particles, ensuring accuracy in the test results.…”

“…For testing flexural strength, five beam specimens of 500 mm x 100 mm x 100 mm dimensions were prepared and moist cured for 28 days as per IS 516 [50][51][52][53][54]. The test procedure followed IS 516 specifications using a 200 kN capacity flexural testing machine.…”

Flexural and cracking behavior of reinforced lightweight self-compacting concrete beams made with LECA aggregate

“…The developed cellular struc-ture is held in place as the product cools and is employed as a lightweight aggregate. Lightweight Expanded Clay Aggregate (LECA) uses alternate sources of aggregates, such as LECA in Concrete, which is beneficial in achieving sustainable construction practices [6][7][8].…”

Corrosion characteristics of rebar in Fly Ash-GGBFS synthesised alkali activated concrete

“…One promising approach is the utilization of supplementary cementitious materials (SCMs), which not only reduce the consumption of Portland cement (PC) but also offer a means to manage waste materials generated across various industries [23,24,25]. Given the continual increase in the generation of FA and GGBFS, these materials can serve as valuable mineral admixtures to enhance the durability and strength of concrete, leveraging their inherent pozzolanic properties [26][27][28][29][30][31][32][33][34][35][36][37][38][39]. Incorporating Fly ash and Ground granulated blast furnace slag in concrete not only reduces cement usage but also has a significantly lower impact on the environment and energy consumption, resulting in reduced CO2 emissions.…”