Date of Graduation
Honors Research Project
Bachelor of Science
Dr. David Roke
Dr. Teresa Cutright
Dr. Stephen Duirk
The objective of this study is to determine how integrating abundant waste materials into concrete affects its compressive strength. This research will be used to benefit the construction industry by replacing a portion of a conventional concrete mix (cement, stone, sand, and water) with more sustainable materials. In order to create a more sustainable concrete mixture, the following mix design and methodology was followed.
The initial step was to create an updatable MS Excel spreadsheet to aid in the mix development (the spreadsheet is shown in Appendix A). These sheets allowed for easy transitions from one mix to another by controlling variables such as mass and water-to-cement ratio to determine the total volume of the small-scale mixes. After the spreadsheet was created, the materials were selected for mix design and their proportions were determined.
Nine total mix designs were developed during experimentation. The mixes contained a percentage replacement of the abundant waste materials. The replacement percentages were chosen at the discretion of the mix developer, considering most materials would result in a decrease in compressive strength. The waste material included slag cement, silica fume, plastic, alum residual (alum), and granular/powder active carbon (GAC/PAC).
The sustainable waste aggregates and cements yielded different compressive results based on their replacement percentages. Plastic mixes resulted in a -17.5% and -30.9% change in the compressive strength for 2.5% replacement and 5.0% replacement respectively, when compared to the Control mix. Plastic mix strengths decreased with the addition of more plastics, where 5.0% replacement had lower strengths than 2.5% replacement. The Cements Mix resulted in a +20.6% change in compressive strength compared to the Control mix at 28-day strength. The Alum mixes followed the same trend as the plastics, a percent decrease, but had slightly higher compressive strengths than the Plastics mix (6595 psi vs. 5930 psi). The GAC/PAC yielded no results because the concrete did not set. The Composite mix containing plastics, slag, and silica fume, contained the most waste material and had the most comparable compressive strengths to the Control mix, with only a -7.3% difference at 28 days.
The overall results showed that the abundant waste material is a viable alternative to conventional concrete and could help remove a portion of these waste materials from landfills. The research can continue to be expanded upon by controlling the water-to-cement ratio, adding admixtures, and continuing percent replacements of sustainable waste materials.
Harvey, Brad, "Compressive Strength Relative to Sustainable Materials in Concrete" (2017). Honors Research Projects. 538.