Discipline: Biological Sciences
Room: Exhibit Hall A
Lillian Richardson - Norfolk State University
Co-Author(s): Dr. Nazir Barekzi, Norfolk State University, Norfolk, Va
A major issue that impacts the Hampton Roads region is the deterioration of bridge pilings. The roads and highways crossing the rivers and tributaries of the Chesapeake Bay are battered by many forces. As a result of natural forces, the bridge pilings erode and corrode on a regular basis. In this project, the forces exerted on composite materials that make up bridge pilings are investigated with an emphasis on the physical, chemical, and biological properties that are altered due to water erosion, salt corrosion, and bacterial biofilm. Our working hypothesis is that biological factors such as bacterial presence result in the deterioration of structural materials composed of concrete. To test the durability of concrete pilings, small concrete cylinders (1 cm x 10 cm) were produced using Quickcrete ? and placed in 50 ml conical tubes with different media with and without Escherichia coli. To evaluate water erosion, one set of samples were placed on a rotating shaker to simulate waves (dynamic samples). The second sample was placed on the bench (static samples). In order to test the effect of salt, a solution of Enriched Seawater was made of nutrient broth supplemented with 3.5% NaCl was used. The enriched seawater media was added to the conical tubes to cover approximately three-fourths of the concrete sample. The presence of the bacteria and movement was used to model the environment that normal bridge pilings are commonly exposed to. Optical density, the pH of the media, weight change of the concrete sample and concentration of bacteria were all measured in time intervals up to 9 days. Surprisingly, the weight of the concrete pieces increased by ~22%, which was unexpected. This was most likely due to the porous nature of the concrete allowing it to absorb some liquid. A second unexpected result was that the pH increased to ~12 producing a very basic environment in all samples with concrete. Furthermore, all samples with concrete resulted in zero bacterial counts. These two findings suggest that the concrete may have released chemicals that decreased the pH of the media and this change in pH was enough to kill the E. coli added to the sample solution. Since the bacterial counts were zero, the bacterial effect or biofilm on the deterioration could not be measured. However, the results indicate that the concrete increases the pH and killed all the bacteria that was seeded. Therefore, we can conclude that concrete may be an ideal substance to inhibit bacterial deterioration. However, we cannot be sure what other negative effects may occur with the use of this concrete material. Future work will focus on why the concrete sample is changing the pH of the media and alternative piling material will be investigated. References: Department of Defense. (2018). Waterfront And Coastal Structures Knowledge Area. Corrosion Prevention & Control Source, Volume 7(Issue 2).
Funder Acknowledgement(s): This study was supported, in part, by a grant from NSF (HBCU-UP-RIA Grant 1900164) awarded to Dr. Nazir Barekzi, Assistant Professor, Norfolk State University, Norfolk, Virginia.
Faculty Advisor: Dr. Nazir Barekzi, email@example.com
Role: I participated in the whole project from start to finish. This project was part of a summer research program that I was selected for. I helped my advisor figure out experiments and performed them with his supervision. I collected all the data and the necessary measurements. Then utilizing the data I was able to write a final report, prepare a poster, and present my data.