To its perceived low strength properties, the use of expanded polystyrene beads in concrete applications has been limited. The most of the conclusions in this regard comes from research that used the trial mix method. Given the significant number of trial mixes required to produce a valid result, obtaining a reliable mix ratio using this method is relatively more expensive, difficult, and time consuming. Most studies, on the other hand, have found that demonstrated that utilizing mathematical models to optimize concrete strength qualities to meet various purposes is more dependable and cost-effective. While certain optimization models have successfully predicted various polystyrene concrete strength qualities, only a few research, if any, have used this technique to forecast polystyrene concrete tensile strength. The flexural test is a crucial test that determines whether or not unreinforced concrete beams or slabs can withstand bending failure. The structural rigidity test, on the other hand, is a crucial test that determines if concrete is prone to tensile cracking as a result of the structural load. Both strength tests are crucial in structural design since they establish the tensile strength of the final concrete. The ability of concrete to resist cracking or breaking when under tension is known as tensile strength. Water, sand, coarse aggregates, inflated polystyrene beads, and standard limestone cement were used in this experiment. Except for polystyrene and coarse aggregates, which were stirred together and batched in volume, most materials were batched by weight. The partial replacement level considered was 12% replacement (88% coarse aggregate + 12% polystyrene) using an initial mix ratio of 1:3:6 (cement, sand and coarse aggregate) in accordance to BS EN 1992 for Structural Concrete of 20 N/mm2. The constituents were manually mixed in the laboratory to prepare 20 different mixes. The results obtained were used for developing the predictor and optimization models respectively. All specimens were cured in accordance with NIS 87 (2004). The laboratory flexural and split tensile strength test results for the 28th day were obtained. Most of the model results agreed with their respective laboratory experiments for both flexural and split tensile strength, particularly for mix1, mix4, mix5, mix6, mix8, mix9 and mix10. The optimized results yielded a flexural and split tensile strength results of 2.00 N/mm2 and 4.9 N/mm2 from a water, cement, sand and coarse aggregate mix ratio of 0.449, 1, 2.77 and 5.52 respectively at a 71% water absorption rate. The optimized result exceeds the minimum flexural and split tensile test results as specified by BS EN 12390 – 6 (2009). This has shown that polystyrene lightweight concrete can attain a concrete strength that is suitable for residential purposes and can also be used as partitions in high rising buildings due to their light weight property. If adopted, this model can help in achieving the UN SDG 11, which advocates for sustainable cities and communities, by providing affordable housing.
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