The Development of Ultra High Strength Concrete Mixtures using Waste Foundry Sand
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This study presents the development of Ultra High Strength Concrete (UHSC) mixtures using waste foundry sand (WFS). This was done through an iterative laboratory trial batching process and experimental evaluation of the compressive strength and splitting tensile of UHSC, produced at different replacement levels of WFS. Multiple concrete specimens were produced which included, control specimens and specimens with WFS replacement percentages of 10%, 20%, and 30%. Initial trial batching consisted of manufactured sand that passes through #30 sieve, silica fume, Type I Ordibary Portland Cement, high range water reducing admixture (HRWRA), water, and steel fibers. After initial testing, the manufactured sand was replaced with river sand, and batch proportioning was adjusted until a suitable UHSC control was developed. Once the control mixture was developed, the river sand was replaced with WFS by volume in 10%, 20%, and 30% increments, and the impact of WFS on two very important mechanical properties was investigated. Compressive strength and splitting tensile strength are the mechanical properties investigated in this research. All concrete mixtures surpassed 18000 psi; which was the compressive strength benchmark used in this study. The final compression strength ranged from 17,471psi - 19614 psi. The splitting tensile strength results ranged from 2124 psi - 2355 psi. A statistical analysis of the 10% WFS mixtures showed a 10% drop in compressive strength (7days) and 5% drop in compressive strength (28 days), compared to the 7 and 28 days strength of the control mixtures. There was no significant change in compressive strength from the control at 20% and 30% WFS replacement. A statistical analysis shows a 16% drop in splitting tensile (28 days) at 10% WFS replacement level, compared to the control mixture at equivalent age. There was no significant change in splitting tensile strength from the control at 20% and 30% WFS replacement.