Scientific Reports recently published a research paper explaining that Bayer red mud (BRM) from the Shandong Xinfa Group can be used as a partial replacement for cement in concrete. The market performance and environmental implications are positive, but the results of long-term implementations are yet to be ascertained.
Image generated with AI tool (for referential purpose only)
Explore- Most accurate data to drive business decisions with 50+ reports across the value chain
The primary solid waste generated from alumina production is red mud. Out of this, Bayer red mud constitutes approximately 70 per cent of it. It can be challenging for reuse purposes, with its strong alkalinity, richness in carbon and low calcium deposit. Safe application is limited due to the high alkaline nature, rendering responsible disposal and potential resource recovery alarming concerns.
China, the country to produce 55 per cent of global alumina, generates a huge amount of red mud. Yet, only 9.8 per cent of the by-products are currently recycled. Consequently, the rest poses a threat to the environment. Thus, finding viable and effective uses of BRM is a necessity, both on environmental and industrial levels.
It has been observed in previous studies that BRM can be integrated into cement. However, there are several drawbacks to increasing BRM content. These include lower mechanical strength, higher water absorption as well and reduced reaction temperatures, especially when the BRM content exceeds 20 per cent.
Information gleaned from further studies reveals that up to 15 per cent of dry or calcined red mud can be used in microstructures and providing strength for civil engineering. However, many factors depend on the specific red mud’s chemical and mineral makeup, which varies from one source of the bauxite to another, accompanied by techniques used in the processing.
In this particular research, the team investigated the use of Xinfa BRM as a partial cement replacement or cement supplement by partially replacing cement at small percentages, with 100 per cent pure cement used as the control. The effects were examined on 3- and 28-day compressive strength, setting time, and microstructural characteristics.
In the experiment, a high-speed FII-1000C mill was used for drying and milling the BRM. The BRM particles produced were fine and spherical, serving as micro-fillers. Specific surface area of BRM - 0.6897 m2 per tonne - was also remarkably more than that of cement, which was 0.39 m2 per tonne, leading to an increased water demand for hydration purposes.
At 3 and 28 days the compressive strength was to the control group for BRM contents that were below 5 per cent, and the highest 28-day strength was achieved by 1 per cent BRM. Regardless of the dosage differences, XRD confirmed that at the end of 28 days hydration products were largely consistent in all the mixes.
Significantly, it was observed from the TLP results that heavy was considerably below stipulated thresholds (TCLP and GB 5085.3-2007). This confirmed the safety in the application of Xinfa BRM.
The study concluded that BRM, if used in a regulated amount, can safely and effectively be added in concrete mixtures as a substitute portion of cement. The 1 per cent BRM produced optimal outcomes with maximum mechanical strength as well as guaranteed environmental safety. Nonetheless, it still remains a question as to whether or not BRM can be implemented in larger amounts. Further research and study are required to ascertain its long-term performance and durability as well as environmental implications.
Must read: Key industry individuals share their thoughts on the trending topics
Responses
