Brenden is making cylinders of concrete after mixing it in the Grady E. Harvell Civil Engineering Research and Education Center.
Author: Brenden Simmons | Major: Civil Engineering | Semester: Summer 2022
When I started to take civil engineering classes at the University of Arkansas, I quickly developed an interest in concrete. One of the best qualities of the professors in the Department of Civil Engineering is their ability to create hands-on learning experiences for their students. As I started to think about research topics for my honors thesis, I knew I wanted to do something with concrete. I had heard about some of the research that Dr. Murray was doing, and it sounded like something I would be interested in. He was doing a lot of work with belitic calcium sulfoaluminate cement (BCSA) concrete, which is a type of rapid-set concrete that reaches its working strength quicker than traditional portland cement concrete. After looking into some of Dr. Murray’s research, I met with him and asked if I could help him with some of his research and develop an honors thesis based on the results. Dr. Murray loved the idea, and we talked about how there was a need for us to understand the bond strength of BCSA concrete in repairing applications.
When a concrete structure needs to be repaired, it is essential to perform the repair as quickly as possible. Many broken structures can be a safety hazard, especially if they are above level ground. Bridges are a good example of this. In addition, the operation of these structures must be suspended until the repair is complete. If a bridge is shut down for an extended period of time, this slows down traffic. If the time it takes to repair the bridge can be decreased, then the total economic cost of the repair also decreases. Therefore, it is advantageous to use a type of cement that will allow the concrete to set as quickly as possible. BCSA concrete may be the ideal candidate. However, the setting time will not matter if the BCSA concrete is unable to effectively bond with the original material. At the end of the day, the composite material must be able to hold the loads that the bridge was designed to hold.
To test the bond strength of the BCSA Concrete with the traditional portland cement (PC) concrete, I decided to perform slant shear tests this summer. I worked closely with Elizabeth Poblete, a graduate research assistant for the Department of Civil Engineering, who is also conducting research on BCSA concrete. We created a mix design for both BCSA concrete and self-consolidating (SC) concrete. Self-consolidating concrete is highly flowable, making it ideal for conformity to uneven break surfaces. SC concrete is what would traditionally be used for repair applications. We made 24 composite cylinders in total, with 24 companion samples to test the strength of the materials themselves. Twelve of the 24 composite cylinders are made up of normal PC concrete bonded with BCSA concrete. The other 12 composite cylinders are made up of normal PC concrete bonded with SC Concrete. Once the strength testing is finished, we will know the relative bond strengths of both materials.
After this testing is complete in the Fall, we will create our own test to better isolate the bond strength from the compressive strength of the materials when compared to the slant shear test. Once I have the results from both the standardized test and our own custom test, I will be able to develop a thesis that summarizes the conclusions of this study. I am extremely thankful for the work I have been able to do this far, and I am excited to see what further research may bring in the future!