Date of Award

Spring 1-1-2016

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Mija H. Hubler

Second Advisor

Yunping Xi

Third Advisor

Jeong-Hoon Song

Abstract

This work addresses the hypothesis that modern concrete admixtures and inclusions have changed the microstructure mechanical properties sufficiently to result in undocumented concrete response to dynamic loading. The macro-, micro-, and nano- scale fragmentation of concrete as a function of different admixtures and inclusions is studied. This was done by loading them rapidly in a materials testing machine, with air sampling equipment standing by to sample the air, and collect the dust that resulted from the impact event. Four mixes were studied: regular Portland cement concrete for comparison, fly ash and slag admixtures to study effects of micro-scale inclusions, and steel-fiber reinforced concrete to study effects of macro-scale inclusions. Previous studies have shown that concrete fragments follow the Rosin-Rammler distribution as predicted by brittle fracture probabilities. This work concludes that such information is not representative of the aerosol particles that are generated, which are of primary importance for health. It is found that in particular the inclusion of large fibers generates a higher concentration of nanoscale fragments than the other admixtures. An improved analytical formulation for the probability of formulation of small fragments is developed.

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