Mechanical performance of red mud polymer concrete composites fabricated using recycled pet resin

Introduction: Red mud (RM) is a hazardous waste and insoluble residue generated in Bayer’s process during the production of alumina (1). The large production and consecutive dumping activities of RM are causing serious threats to the environment and human health by polluting the water, land and air due to its high alkalinity value (2). With the addition of the RM in the polyester composite the compressive strength, hardness and density of the prepared composites have been improved (3). A significant improvement in the flexural behaviour of specimens has been observed when the RM has been admixed to the epoxy resin (4). In the present work, the amount of RM content has been varied to determine the effect on mechanical strength, and water absorption. The mechanical strength has been observed for the specimens cured for 7 days, 28 days and 56 days.

Methods: The recycled PET resin has been utilized as the binding agent for the fabrication of polymer concrete composites and aggregates are RM, fly ash, silica fume and foundry sand. The experiment has been conducted according to our previous research (5). In mixed proportions, the RM content has been varied from 0% to 25% by weight. The Compressive strength has been found using the cylindrical specimens having a diameter of 70 mm and length of 70 mm as per the procedure of ASTMC39. Flexural strength has been observed for the specimens having a cross-section of 40×45 mm and a length of 300 mm as per ASTM C293-02. Here, the water absorption has been tested according to the procedure of BS 1881-122, 2011 for the specimens cured for 28 days and having a cross-section of 40×40 mm and length of 120 mm.

Results & Discussions:  The compressive strength values have been observed in the range of 61.42-74.43 MPa, 72.89-88.75 MPa and 81.54-98.02 MPa for the specimens cured for 7 days, 28 days and 56 days, respectively. For the specimens cured for 56 days, with the increment of RM content from R5 to R35, the compressive strength has been increased by 1.12%, 9.02%, 14.16%, 20.26%, 13.08%, 10.6% and 2.24%. R20 has provided the maximum value of compressive strength i.e. 98.02 MPa. For the specimens cured for 28 days, the loss in the water absorption has been increased from R0 to R25 by 2.7%, 13.8%, 20.8%, 23.01% and 23.5% respectively. Thereafter, it decreased from R30 to R35, by 22.03% and 20.33%.

Conclusions:   The composites having 20% of RM content have shown maximum mechanical strength and with further increment, the binding forces have been reduced and that has further reduced the mechanical strength of the PC. The low values of water absorption indicate very low open porosity and obstruct the flow of water. Low water content in the mixture has increased the concrete strength and no imperfection has been seen in the present study.

Keywords: Red mud, PET, polymer concrete, mechanical strength.

References

1. Y. Liu, R. Naidu, Hidden values in bauxite residue (red mud): Recovery of metals, 2014. https://doi.org/10.1016/j.wasman.2014.09.003.

2. Zhang, T., Wang, Y., Lu, G., Liu, Y., Zhang, W., Zhao, Q., 2018. Comprehensive Utilization of Red Mud: Current Research Status and a Possible Way Forward for Non-hazardous Treatment 135–141.

3. Rachchh, N. V., Misra, R.K., Roychowdhary, D.G., 2015. Effect of red mud filler on mechanical and buckling characteristics of coir fibre-reinforced polymer composite. Iran. Polym. J.  24, 253–265. https://doi.org/10.1007/s13726-015-0317-4

4. Bharatkumar, B.H., Raghuprasad, B.K., Ramachandramurthy, D.S., Narayanan, R., Gopalakrishnan, S., 2005. Effect of fly ash and slag on the fracture characteristics of high performance concrete. Mater. Struct. 38, 63–72. https://doi.org/10.1617/14107.

5. Singh, G., Kumar, H, Singh, S., Performance evaluation-PET resin composite composed of red mud, fly ash and silica fume. Const. Build Mater. 214, 2019, 527-538 https://doi.org/10.1016/j.conbuildmat.2019.04.127.