Date of Award

Spring 2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Materials and Infrastructure Systems

First Advisor

Sven Eklund

Abstract

The manuscript presented herein is based on the investigation of the mechanical properties of fly ash-based geopolymer concrete and their link to fly ash (FA) characteristics. A database of 32 FA samples was created. Each FA sample was analyzed in terms of chemical composition, crystallographic properties and particle size distribution. The mechanical performance of geopolymer concrete (GPC) made from each FA sample was evaluated in terms of density, setting time, compressive and flexural strength, static elastic modulus and Poisson's ratio. It is worth mentioning that the author has already published preliminary results of this study (Diaz and Allouche, 2010; Diaz et al. 2010) in peer-reviewed journals. The database was randomly divided into two sets; one consisting of 24 FA samples for model building using linear regression and another consisting of eight FA samples for validation. The first set was analyzed to detect correlations between fly ash characteristics and mechanical properties of GPC. Correlations within the elastic modulus, the compressive and flexural strengths of GPC were also sought and correlations were developed. These equations were tested on the second set of eight FA samples that were not included during the model building process. The results show that the elastic modulus, as well as the compressive and flexural strengths of GPC can be predicted with reasonable accuracy by analyzing the chemical, physical and crystallographic properties of a given FA and following the steps presented in this study.

Additionally, it was also found that the mechanical behavior of CPC is similar to that of ordinary Portland cement (OPC) concrete, suggesting that equations, akin to those given by the American Concrete Institute's Building Code (ACI 318, 2008), could be applied for CPC to determine its flexural strength and static elastic modulus.

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