Award Date

1-1-2008

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Committee Member

Nader Ghafoori

Number of Pages

370

Abstract

The research investigation presented herein was intended to study the influence of parameters, such as aggregate size, admixture source, hauling time, and temperature on the fresh and hardened properties of three distinct groups of self-consolidating concretes (SCC). Within each group, the selected SCCs were made with a constant water-to-cementitious materials ratio, a uniform cementitious materials (cement and fly ash) content, and a constant coarse-to-fine aggregate ratio that provided the optimum aggregate gradation. Three coarse aggregate sizes (ASTM C 33 #8, #7, and #67) obtained from two different quarries were investigated. Four sources of polycarboxylate-based high range water-reducing admixtures (HRWRA) and viscosity modifying admixtures (VMA) were used. All raw materials were evaluated for their physicochemical characteristics; The investigation presented herein was divided into two major phases. The first phase aimed at: (1) comparing the optimum dosage requirements of four different sources of polycarboxylate-based HRWRA and VMA in attaining the target slump flow of 508 mm (20 inches), 635 mm (25 inches), and 711 mm (28 inches), T50 of 2 seconds or more, and a visual stability index (VSI) of 0 (Highly stable concrete) or 1 (Stable concrete), (2) evaluating the flow rate/plastic viscosity, static and dynamic stabilities, passing ability, and filling ability of the selected self-consolidating concretes, and (3) examining the properties of the trial self-consolidating concretes as related to air content, bleeding, time of setting, adiabatic temperature, demolded unit weight, compressive strength and modulus of elasticity; In the second phase, the influence of hauling time, temperature, and combined hauling time and temperature on the fresh properties of the selected self-consolidating concretes was evaluated. Seven different temperatures (43, 36, 28, 21, 14, 7, and -0.5°C (109, 96, 83, 70, 57, 44, and 31°F)) and nine different hauling times (10, 20, 30, 40, 50, 60, 70, 80, and 90 minutes) were used to determine the loss in unconfined workability, dynamic stability, and flow ability rate of the designed matrices. The adverse effect of the above-mentioned variables was remediated by way of overdosing and retempering techniques which resulted in achieving the desired fresh characteristics of the designed self-consolidating concretes for different hauling times and temperatures.

Keywords

Admixture; Admixtures; Concrete; Consolidating; Parametric; Polycarboxylate; Remediation; Self; Self-consolidating Concrete

Controlled Subject

Civil engineering

File Format

pdf

File Size

6.67 MB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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