Abstract

Concrete compaction is one of the indispensable fundamentals of concrete manufacturing. However, thorough compaction cannot always be insured. This can be wholly or partially encountered in congested sections, out-of reach deep foundations and narrow or irregular precast components. On the other hand, typical vibrators were considered as contributor to health hazards to workers. Self-compacting concrete (SCC) is an emerging concrete where the cohesive yet flowable consistency of the concrete itself secures adequate placement with high level of homogeneity and little or no segregation. Such concrete is primarily achieved by incorporating admixtures that is referred to as viscosity modifying (VM) admixtures with no vibration. Yet, the impact of mix proportions and the role played by the VM admixtures as opposed to superplasticizers (SP) or other admixtures is not clearly understood. In addition, there seems to be no unique means for assessment of such concrete and the correlation between various test methods is not well established. This study aims at achieving better understanding of the influence of mix parameters including the dosage of VM and SP on the properties of SCC. A review of literature was conducted with an emphasis on literature pertinent to the scope of this study. Twenty-six mixtures were prepared with various water-to-cement ratio (w/c), fine-to coarse aggregate ratio and VM and SP dosages. An experimental program involving new test techniques was designed to assess the performance of SCC in the fresh and hardened state. This includes the slump flow, L-box, U-box, hardened density, compressive and flexural strength as well as Schmidt Rebound Hammer. Means to assess hardened density and segregation were implemented through sectioning of column specimens. The results of this work reveal that thorough and homogenous compaction can be realized by employing self-compacting concrete without neither external nor internal compaction. A good performance is witnessed when incorporating VM admixtures that can not be matched by the conventional superplasticizer admixtures. Evidence is shown that the dosage impact of VM is more significant on mixtures made with w/c = 0.3 mixtures than mixtures of w/c = 0.4. Incorporating higher fine-to-coarse aggregates ratio seem to decrease flow capacity and velocity yet it yields higher resistance to segregation. The superior performance of VM mixtures is supported by less segregation and more consistent mechanical properties and less variation in its density within the sections of SCC components. Tests methods such as the Schmidt hammer should not be applied to SCC unless re-calibration and interpretation of its readings is adopted. Further research work is needed particularly in the domain of SCC durability and long-term performance. Recommendation is provided to include SCC in future Egyptian Code of Practice

School

School of Sciences and Engineering

Department

Interdisciplinary Engineering Program

Date of Award

6-1-2004

Online Submission Date

1-1-2004

First Advisor

Mohamed Nagib Abou-Zeid

Committee Member 1

Farouk El Hakim

Committee Member 2

Safwan Khedr

Committee Member 3

Ezzat Fahmy

Document Type

Thesis

Extent

142 leaves

Library of Congress Subject Heading 1

Concrete construction

Rights

The American University in Cairo grants authors of theses and dissertations a maximum embargo period of two years from the date of submission, upon request. After the embargo elapses, these documents are made available publicly. If you are the author of this thesis or dissertation, and would like to request an exceptional extension of the embargo period, please write to thesisadmin@aucegypt.edu

Call Number

Thesis 2004/40

Location

mgfth

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