NSF Award
2301588
This Engineering Research Initiation (ERI) award supports research that will focus on improving dielectric mixing models used to estimate the relative permittivity of coarse aggregate mixes. Dielectric mixing models relate the physical characteristics of soil or aggregate (the water, air, and solid particles) to the bulk relative permittivity (bulk electrical material property) captured by ground penetrating radar (GPR). These dielectric mixing models in turn are what allow engineers to estimate properties such as water content, saturation, density, or object depth from GPR data. The research will investigate the effect of particle gradation on relative permittivity measurements by creating a high-quality open data set of relative permittivity measurements on gradations ranging from smaller particles to larger particles which will close an existing gap in the literature. From these data a new dielectric mixing model suitable for coarse aggregate will be created. In addition, the funding will allow for Smith College students to work with the Girls Inc Eureka! program which will have the synergistic benefit of putting Smith College students in a mentoring role to middle school and high school girls in engineering and STEM. Simultaneously, it is anticipated that the Eureka! program students will be inspired by the college-aged women in engineering. <br/><br/>In order to achieve the goal of producing an improved dielectric mixing model for coarse aggregates, large box tests (approximately 1 cubic meter in scale) will be conducted to produce a data set to develop a new dielectric mixing model. These box tests will consider a variety of materials with particle sizes ranging from sand-silt mixtures (which existing models should model well) up to cobble-gravel mixtures (which existing models are anticipated to model poorly). Specimens will be tested under dry, saturated, and partially saturated conditions. The work has three main objectives. The first objective is to establish the repeatability of common practices for specimen preparation and methods that produce the highest quality specimens. The second objective will be to create the data set of relative permittivity values covering a wide range of aggregate gradations, density, and water content. The third objective is to create and verify the dielectric mixing model suitable for coarse aggregates.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
