Flexural Strength and Compressive Strength Relations of Spent Foundry Sand Concrete

This research work was on the evaluation of the flexural strength and compressive strength relationship of spent foundry sand (SFS) concrete. The relationship was established using a concrete mixture of 1:1.71:2.56, a cement content of 404 kg/m(2), and a water-cement ratio (w/c) of 0.52. This was used to cast beams of dimensions 150 x 150 x 500 mm (6 x 6 x 20 in.) cured for 90 days in a water curing tank under laboratory conditions. The SFS was used to replace fine aggregate (FA) 0 to 40% by wt. The evaluations on the statistical characteristics of the flexural strength data results showed that the addition of SFS to concrete improved the hydration process. This was reflected in the strength development of the concrete and the strong correlation and level of significance observed with the variables (mixture and age). The values of the modulus of rupture (MOR) obtained are in the range of 4.6 to 6.6 MPa; this was at the optimum replacement of 10%. At this level, the value of the flexural strength was approximately 29% of the compressive strength. The two models chosen that represented the flexural strength and compressive strength relations are the square root and 2/3 models. The relative predictive error (RPE) for each is 0.1 and 0.2, respectively.