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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- All Subjects: Building materials
- Creators: Mobasher, Barzin
- Creators: Kavazanjian, Edward
Description
Manufacture of building materials requires significant energy, and as demand for these materials continues to increase, the energy requirement will as well. Offsetting this energy use will require increased focus on sustainable building materials. Further, the energy used in building, particularly in heating and air conditioning, accounts for 40 percent of a buildings energy use. Increasing the efficiency of building materials will reduce energy usage over the life time of the building. Current methods for maintaining the interior environment can be highly inefficient depending on the building materials selected. Materials such as concrete have low thermal efficiency and have a low heat capacity meaning it provides little insulation. Use of phase change materials (PCM) provides the opportunity to increase environmental efficiency of buildings by using the inherent latent heat storage as well as the increased heat capacity. Incorporating PCM into concrete via lightweight aggregates (LWA) by direct addition is seen as a viable option for increasing the thermal storage capabilities of concrete, thereby increasing building energy efficiency. As PCM change phase from solid to liquid, heat is absorbed from the surroundings, decreasing the demand on the air conditioning systems on a hot day or vice versa on a cold day. Further these materials provide an additional insulating capacity above the value of plain concrete. When the temperature drops outside the PCM turns back into a solid and releases the energy stored from the day. PCM is a hydrophobic material and causes reductions in compressive strength when incorporated directly into concrete, as shown in previous studies. A proposed method for mitigating this detrimental effect, while still incorporating PCM into concrete is to encapsulate the PCM in aggregate. This technique would, in theory, allow for the use of phase change materials directly in concrete, increasing the thermal efficiency of buildings, while negating the negative effect on compressive strength of the material.
ContributorsSharma, Breeann (Author) / Neithalath, Narayanan (Thesis advisor) / Mobasher, Barzin (Committee member) / Rajan, Subramaniam D. (Committee member) / Arizona State University (Publisher)
Created2013
Description
Buildings consume a large portion of the world's energy, but with the integration of phase change materials (PCMs) in building elements this energy cost can be greatly reduced. The addition of PCMs into building elements, however, becomes a challenge to model and analyze how the material actually affects the energy flow and temperatures in the system. This research work presents a comprehensive computer program used to model and analyze PCM embedded wall systems. The use of the finite element method (FEM) provides the tool to analyze the energy flow of these systems. Finite element analysis (FEA) can model the transient analysis of a typical climate cycle along with nonlinear problems, which the addition of PCM causes. The use of phase change materials is also a costly material expense. The initial expense of using PCMs can be compensated by the reduction in energy costs it can provide. Optimization is the tool used to determine the optimal point between adding PCM into a wall and the amount of energy savings that layer will provide. The integration of these two tools into a computer program allows for models to be efficiently created, analyzed and optimized. The program was then used to understand the benefits between two different wall models, a wall with a single layer of PCM or a wall with two different PCM layers. The effect of the PCMs on the inside wall temperature along with the energy flow across the wall are computed. The numerical results show that a multi-layer PCM wall was more energy efficient and cost effective than the single PCM layer wall. A structural analysis was then performed on the optimized designs using ABAQUS v. 6.10 to ensure the structural integrity of the wall was not affected by adding PCM layer(s).
ContributorsStockwell, Amie (Author) / Rajan, Subramaniam D. (Thesis advisor) / Neithalath, Narayanan (Thesis advisor) / Mobasher, Barzin (Committee member) / Arizona State University (Publisher)
Created2013
Description
Concern and interest about the environment and ecologic systems have promoted the usage of earth as a construction material. Technology advancement has resulted in the evolution of adobe into compressed stabilized earth blocks (CSEB). CSEB’s are prepared by compressing the soil-stabilizer mixture at a particular stress. In order to accomplish the required strength, cement has been used in a regular basis as stabilizing agent. It is of interest to find means to reduce the cement used in their construction without affecting its dry strength and durability. In this study, natural fibers were used along with lower proportions of cement to stabilize soil with varying fine content. Blocks were compacted at 10MPa stress and prepared by using 7%, 5% and 3% cement along with fiber content ranging from 0.25% to 2%. The effect of fine content, cement and fibers on strength and durability of the CSEB blocks were studied. Different sand/fine fractions of a native Arizona soil were used to fabricate the blocks. Results indicate that the compressive strength reaches a maximum value for blocks with 30% fine content and inclusion of fibers up to 0.5% increased the dry compressive strength. The use of 0.25% fiber by weight and 5% cement content showed comparable dry compressive strength to that of the 7% cement blocks with no fibers. The dry strength of the blocks reached an optimal condition when the combination of materials was 30% fines, 5% cement and 0.5% fibers, which satisfied the strength requirement given by the ASTM C62 and ASTM C216 standards for construction material. The CSEB’s with 0.5% fiber had higher toughness. The durability was determined by subjecting the CSEBs to wetting and drying cycles. The blocks with 5% cement withstand the durability test as the dry strength was higher than that required for construction use.
The blocks were also submitted to heating and cooling cycles. After 12 cycles, the specimens showed a reduction in strength, which further increased as the number of cycles increased. Finally, the thermal resistivity of fiber reinforced CSEB was found to be higher than that for clay bricks.
The blocks were also submitted to heating and cooling cycles. After 12 cycles, the specimens showed a reduction in strength, which further increased as the number of cycles increased. Finally, the thermal resistivity of fiber reinforced CSEB was found to be higher than that for clay bricks.
ContributorsPadmini Chikke Gowda, Rakshith (Author) / Zapata, Claudia (Thesis advisor) / Kavazanjian, Edward (Committee member) / Jang, Jaewon (Committee member) / Arizona State University (Publisher)
Created2016