Early Life Flexural Performance and Behavior of Reinforced BCSA Concrete Beams
Project completed: December 2018
Funded by: Material donated by CTS Cement
Belitic calcium sulfoaluminate cement (BCSA) is a hydraulic, rapid setting alternative to ordinary portland cement (OPC) with reduced energy demands and CO2 emissions. BCSA cement has numerous current and potential applications including transportation repair and precast manufacturing. Currently, limited research exists regarding the structural performance of CSA cements, restricting its potential implementation. Thus, the purpose of this research is to provide insight into the flexural performance and behavior of reinforced BCSA concrete beams. Overall, BCSA concrete had similar cracking and loading behavior to the OPC beams, with increased moment capacity for compression controlled specimens. Furthermore, BCSA concrete showed increased tensile strength and ductility when compared to OPC. Overall, the flexural strength of the BCSA concrete exceeded the predicted flexural strengths, indicating the current flexural strength equations are applicable for BCSA reinforced concrete design
Understanding ultimate shear behavior of prestressed concrete girder bridges as a system through experimental testing and analytical methods
Project completed: Summer 2017
Funded by: Oklahoma Department of Transportation
A prestressed concrete bridge is a complex system. The interconnectivity of several girders, a deck, and secondary elements such as diaphragms makes their behavior difficult to represent. Additionally, the shear behavior of in service prestressed concrete girders can be difficult to predict, particularly when older codes were used in design and where damage is present in the girders. This work contains laboratory testing to investigate the residual shear performance of two older American Association of State Highway and Transportation Officials (AASHTO) Type-II prestressed concrete girders, as well as the behavior of a scale prestressed concrete bridge loaded in shear to failure. The full-scale girders were found to be capable of carrying their full capacity even when corrosion affected the failure mechanism. Based on these tests, the modified compression field theory (MCFT) methods were recommended for estimating the capacities of older girders. The scale bridge provided information about load distribution at ultimate capacity, and the influence of secondary elements (diaphragms) on load transfer after girder failures. The bridge test also documented the ultimate behavior of a prestressed concrete bridge, findings that are not common in the literature. The bridge failure was controlled by punching shear, and the diaphragms were seen to provide a significant means of load transfer after a girder failed. Finally, simple computer models were built that are capable of reducing the conservativism of the codified distribution factor (DF) methodology, increasing the usable capacity of bridges. These models simplify the girders and slab into a “grillage” of beam elements with appropriate stiffnesses. A parametric study suggests that for AASHTO Type-II girder bridges, load ratings tend to be conservative for smaller girder spacing and shorter span lengths. Code DFs were generally found to be conservative for all configurations of typical Type-II girder bridges.
This was the topic of my Ph.D. dissertation, I was advised by Dr. Royce Floyd.
Click here for the dissertation
Papers resulting from this project (click for access):
Durability of Silane Sealer in a Highly Alkaline Environment
Project Completed: Summer 2014
Funded by: Simmons Foods
Alkali-silica reaction (ASR) is a chemical reaction between siliceous minerals present in certain aggregates and alkalis in the concrete pore solution. The reaction can lead to expansion and severe damage in concrete members. One method to mitigate ASR expansion is to use a penetrating sealer such as silane. A set of columns located in a food preparation facility was treated with silane and a complimentary laboratory study was performed. A cleaning regimen involving application of an alkaline cleaner is employed at the facility, followed by rinsing with hot, pressurized water. The purpose of this research is to evaluate the effectiveness of silane when used in this alkaline environment. The research shows that silane was effective at reducing expansion in new concrete, less so when the pH of the environment is high; other measures were recommended for previously cracked concrete.
This was the topic of my M.S. thesis, advised by Dr. Micah Hale