This Broadening Participation Research Initiation Grants in Engineering (BRIGE) grant provides support to combine physical and chemical numerical tools to predict the performance of concrete made with glass filler. Waste glass that cannot easily be recycled into new glass has the potential to be used in concrete in place of part of the Portland cement, if the glass is finely ground. Both experimental and modeling approaches will be used to (1) measure the chemical reaction properties and rates for individual glass types of different fineness in concrete, (2) measure the water absorption and strength development of mortar containing ground glass, and (3) integrate the thermodynamics into an existing numerical tool that simulates the structural arrangement of the cement chemical reaction products. The model will then be used to simulate the mortar strength and water absorption when glasses of different type and fineness are used. Finally, a sensitivity analysis will be performed to determine the optimum grinding needed for mixtures of different glass types and fineness.
The results of this research will potentially allow for increased commercial use of waste glass in concrete, benefiting both the environment and infrastructure. This project will reveal fundamental information about glass reaction in concrete that is currently lacking, but vital for modeling performance. The results of this study will provide insight into the mechanisms of other materials used to replace portions of the Portland cement in concrete, such as volcanic ash, ground granulated blast furnace slag, and coal combustion fly ash. The modeling component developed will also be applicable to the reaction of any particle system at variable temperature. The education plan, to be integrated with the research program, will result in a day-long program on recycling engineering for middle school-age girls and boys with representation from underrepresented groups. Evaluations from the participants will provide valuable insights into the role of gender in designing outreach programs.
In portland cement concrete, portland cement is the most expensive ingredient with the highest carbon footprint. Replacement of a portion of the portland cement in concrete with lower cost, lower carbon footprint materials would benefit both consumers and the environment. Materials that can replace a portion of portland cement in concrete and still contribute to strength gain are referred to as supplementary cementitious materials (SCMs). Finely ground glass is one such potential SCM that could provide a valuable use of material that would otherwise be landfilled. Finely ground glass SCM particles also serve as ideal model particles for examining how glassy SCM particles react in cementitious systems because they have a uniform composition, amorphous nature, high silica content, and can be classified into different size fractions. As part of this study, experimental and modeling activities were conducted to (1) measure glass reaction rates and reaction properties for individual glass types of different narrow particle sizes, (2) measure the fluid transport and mechanical property performance of mortar containing ground glass as an SCM, and (3) develop a thermodynamic module to integrate with a microstructural model for cementitious systems. Results showed that ground glass reaction rates are proportional to the particle surface area. The particle reaction rates for combined particle sizes and types could be accounted for by the principle of superposition of their individual reaction rates, or an average. The mechanical properties however behaved differently as they were below the average of the particles and more towards the mechanical properties developed by the weaker material because the mechanical properties are dependent not just on how much solid binder material was formed, but its spatial arrangement as well. Simulations showed that thermodynamic models were not able to properly account for the reactivity of the mixed glass particle system. The outreach portion of this project focused on developing an outreach program that would include boys from underrepresented groups, a previously untargeted group for outreach in Kansas. An outreach program called Planet Keepers was developed and delivered to both boys and girls from underrepresented groups. Participant surveys showed that students felt connected and benefited more from activities that required participants to actively participate, rather than passively listen or observe. The project successfully trained a graduate student in research in civil engineering materials and helped prepare the student for his current career in engineering consulting. Project findings have been presented at international conferences and have been published in well-respected peer reviewed journals.
