ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
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- Creators: Mobasher, Barzin
Description
Concrete develops strength rapidly after mixing and is highly influenced by temperature and curing process. The material characteristics and the rate of property development, along with the exposure conditions influences volume change mechanisms in concrete, and the cracking propensity of the mixtures. Furthermore, the structure geometry (due to restraint as well as the surface area-to-volume ratio) also influences shrinkage and cracking. Thus, goal of this research is to better understand and predict shrinkage cracking in concrete slab systems under different curing conditions. In this research, different concrete mixtures are evaluated on their propensity to shrink based on free shrinkage and restrained shrinkage tests.Furthermore, from the data obtained from restrained ring test, a casted slab is measured for shrinkage. Effects of different orientation of restraints are studied and compared to better understand the shrinking behavior of the concrete mixtures. The results show that the maximum shrinkage is near the edges of the slab and decreases towards the center. Shrinkage near the edges with no restraint is found out to be more than the shrinkage towards the edges with restraining effects.
ContributorsNimbalkar, Atharwa Samir (Author) / Neithalath, Narayanan (Thesis advisor) / Mobasher, Barzin (Thesis advisor) / Rajan, Subramaniam (Committee member) / Arizona State University (Publisher)
Created2023
Description
Alkali activated mine tailing-slag blends and mine tailing-cement blends containing mine tailings as the major binder constituent are evaluated for their setting time behavior,
reactivity properties, flow characteristics, and compressive strengths. Liquid sodium
silicate and sodium hydroxide are used as the activator solution. The effects of varying
alkali oxide-to-powder ratio (n value) and silicon oxide-to-alkali oxide ratio (Ms value) is
explored. The reactivity of all blends prepared in this study is studied using an isothermal
calorimeter. Mine tailing-cement blends show a higher initial heat release peak than mine
tailing-slag blends, whereas their cumulative heat release is comparable for higher n values
of 0.050 to 0.100. Compressive strength tests and rheological studies were done for the
refined blends selected based on setting time criterion. Setting times and compressive
strengths are found to depend significantly on the activator parameters and binder
compositions, allowing fine-tuning of the mix proportion parameters based on the intended
end applications. The compressive strength of the selected mine tailing-slag blends and
mine tailing-cement blends are in the range of 7-40 MPa and 4-11 MPa, respectively.
Higher compressive strength is generally achieved at lower Ms and higher n values for mine
tailing-slag blends, while a higher Ms yields better compressive strength in the case of mine
tailing-cement blends. Rheological studies indicate a decrease in yield stress and viscosity
with increase in the replacement ratio, while a higher activator concentration increase both.
Oscillatory shear studies were used to evaluate the storage modulus and loss modulus of
the mine tailing binders. The paste is seen to exhibit a more elastic behavior at n values of
0.05 and 0.075, however the viscous behavior is seen to dominate at higher n value of 0.1
at similar replacement ratios and Ms value. A higher Ms value is also seen to increase the
onset point of the drop in both the storage and loss modulus of the pastes. The studied also
investigated the potential use of mine tailing blends for coating applications. The pastes
with higher alkalinity showed a lesser crack percentage, with a 10% slag replacement ratio
having a better performance compared to 20% and 30% slag replacement ratios. Overall,
the study showed that the activation parameters and mine tailings replacement level have
a significant influence on the properties of both mine tailing-slag binders and mine tailing-cement binders, thereby allowing selection of suitable mix design for the desired end
application, allowing a sustainable approach to dispose the mine tailings waste
ContributorsRamasamy Jeyaprakash, Rijul Kanth (Author) / Neithalath, Narayanan (Thesis advisor) / Rajan, Subramaniam (Committee member) / Mobasher, Barzin (Committee member) / Arizona State University (Publisher)
Created2023
Description
There is a high demand for customized designs of various types of cement-based materials in order to address specific purposes in the construction field. These demands stem from the need to optimize the cementitious matrix properties and reinforcement choices, especially in high reliability, durability, and performance applications that include infrastructure, energy production, commercial buildings, and may ultimately be extended to low risk/high volume applications such as residential applications. The typical tools required to guide practicing engineers should be based on optimization algorithms that require highly efficient capacity and design alternatives and optimal computational tools. The general case of flexural design of members is an important aspect of design of structural members which can be extended to a variety of applications that include various cross-sections such as rectangular, W-sections, channels, angles, and T sections. The model utilized the simplified linear constitutive response of cement-based composite in compression and tension and extends into a two-segment elastic-plastic, strain softening, hardening, tension-stiffening, and a multi-segment system. The generalized parametric model proposed uses a dimensionless system in the stress-strain materials diagram to formulate piecewise equations for an equilibrium of internal stresses and obtains strain distributions for the closed-form solution of neutral axis location. This would allow for the computation of piecewise moment-curvature response. The number of linear residual stress implemented is flexible to a user to maintain a robust response. In the present approach bilinear, trilinear, and quad-linear models are addressed and a procedure for incorporating additional segments is presented. Moreover, a closed-form solution of moment-curvature can be solved and employed in calculating load-deflection response. The model is adaptable for various types of fiber-reinforced and textile reinforced concrete (FRC, TRC, UHPC, AAC, and Reinforced Concrete). The extensions to cover continuous fiber reinforcement such as textile reinforced concrete (TRC, FRCM) strengthening and repair are addressed. The theoretical model is extended to incorporate the hybrid design (HRC) with continuous rebar with FRC to increase the ductility and ultimate moment capacity. HRC extends the performance of the fiber system to incorporate residual capacity into a serviceability-based design that reduced the reliance on the design based on the limit state. The design chart for HRC and as well as conventional RC has been generated for practicing engineering applications. Results are compared to a large array of data from experimental results conducted at the ASU structural lab facilities and other published literature.
Contributorspleesudjai, chidchanok (Author) / Mobasher, Barzin (Thesis advisor) / Neithalath, Narayanan (Committee member) / Rajan, Subramaniam (Committee member) / Arizona State University (Publisher)
Created2021
Description
Layer-wise extrusion of soft-solid like cement pastes and mortars is commonly used in 3D printing of concrete. Rheological and mechanical characterization of the printable binder for on-demand flow and subsequent structuration is a critical challenge. This research is an effort to understand the mechanics of cementitious binders as soft solids in the fresh state, towards establishing material-process relationships to enhance print quality. This study introduces 3D printable binders developed based on rotational and capillary rheology test parameters, and establish the direct influence of packing coefficients, geometric ratio, slip velocities, and critical print velocities on the extrudate quality. The ratio of packing fraction to the square of average particle diameter (0.01-0.02), and equivalent microstructural index (5-20) were suitable for printing, and were directly related to the cohesion and extrusional yield stress of the material. In fact, steady state pressure for printing (30-40 kPa) is proportional to the extrusional yield stress, and increases with the geometric ratio (0-60) and print velocity (5-50 mm/s). Higher print velocities results in higher wall shear stresses and was exponentially related to the slip layer thickness (estimated between 1-5μ), while the addition of superplasticizers improve the slip layer thickness and the extrudate flow. However, the steady state pressure and printer capacity limits the maximum print velocity while the deadzone length limits the minimum velocity allowable (critical velocity regime) for printing. The evolution of buildability with time for the fresh state mortars was characterized with digital image correlation using compressive strain and strain rate in printed layers. The fresh state characteristics (interlayer and interfilamentous) and process parameters (layer height and fiber dimensions) influence the hardened mechanical properties. A lower layer height generally improves the mechanical properties and slight addition of fiber (up to 0.3% by volume) results in a 15-30% increase in the mechanical properties. 3D scanning and point-cloud analysis was also used to assess the geometric tolerance of a print based on mean error distances, print accuracy index, and layer-wise percent overlap. The research output will contribute to a synergistic material-process design and development of test methods for printability in the context of 3D printing of concrete.
ContributorsAmbadi Omanakuttan Nair, Sooraj Kumar (Author) / Neithalath, Narayanan (Thesis advisor) / Rajan, Subramaniam (Committee member) / Mobasher, Barzin (Committee member) / Hoover, Christian (Committee member) / Chawla, Nikhilesh (Committee member) / Arizona State University (Publisher)
Created2021