Date of Award

12-2001

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Civil Engineering

Advisor

Eric Landis

Second Committee Member

William Davids

Third Committee Member

Roberto Lopez-Anido

Abstract

Portland cement concrete is the most widely used construction material in the world. Its durability determines its service life and is a serious concern that has been studied by material scientists for almost two hundred years. It is well known that the pore structure in concrete, which includes porosity and the way in which pores are connected and distributed, strongly influences the transport of fluids, and therefore durability. Current techniques all have some limitations on interpreting pore structure and its relationship to transport properties of concrete. The goal of our work is to examine the pore system and the relationship between porosity, pore size distribution and chloride permeability. Specifically, we measure pore structure using a new experimental technique - x-ray microtomography - which allows us to make internal measurements at micron resolution.

X-ray microtomography is a nondestructive imaging technique that produces three-dimensional images of a specimen's x-ray attenuation. By using synchrotron x-ray and charge-coupled detector (CCD), the resolution of the image is very high, up to lpm, therefore pores as small as lPm3 can be observed. The advantage of this technique is that it provides not only images that can indicate how pores are distributed in the microstructure but also information in quantitative form so that different samples can be compared objectively.

In our research, 3D x-ray microtomography experiments and concrete chloride permeability tests were conducted. The pore structure results appeared to have a very good correlation to the permeability data. Concrete having lower porosity, few big pores and longer unconnected flow length generally has lower permeability.

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