Browsing by Subject "Cement"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Carbon Nanotube Addition to Cement-Sand Based Piezoelectric Composites
    (2016) Kadlec, Alec; Wang, Shifa; Zhao, Ping
    Carbon Nanotubes (CNTs) were added to a cement-sand based piezoelectric composite with consideration of Structural Health Monitoring (SHM) to improve conductivity and poling efficiency, increasing piezoelectric effects. The addition of CNTs to the composite structure formed continuous electric networks between the Lead Zirconate Titanate (PZT) particles, allowing more effective poling. Samples of 50 volume percent PZT were fabricated with a mixture of PZT powder, white Portland cement, graded silica sand, CNTs and a superplasticizer, and cured at room temperature. The properties of the composite, including piezoelectric coefficient and sensing effects were characterized for a range of CNT inclusion from 0 to 0.9 vol %. Results showed that CNT inclusion allowed for effective room temperature poling, improving piezoelectric properties of the composite. The modified composite was optimal at 0.6 vol % CNTs.
  • Thumbnail Image
    Item
    Developing and Verifying a Bottom-up Methodology for Bulk Material Flow Analysis in China’s Urban Infrastructure Sectors
    (2015-12) Yang, Ziyi
    With rapid urbanization rate in China, cities will use more cement, one of the most important construction materials, to build new infrastructure to satisfy the dramatically increasing urban population in the next few decades. In 2010, China’s cement industry contributed 11% of nation’s total fossil-fuel carbon dioxide emissions. However, little research has been done on studying cement use in cities, which is an essential part in order to learn the details of cities’ current cement use and to provide policy makers as well as governors with a powerful tool to organize a city’s future cement use. This thesis achieves two goals. The first one is to develop construction cement intensities for China’s cities’ infrastructure, which are classified into 9 sectors: road, public transit, building, gas supply, heat supply, solid waste disposal, wastewater treatment, storm water control, and water supply. The second goal is utilizing a bottom-up method to estimate annual cement use in three of China’s cities: Beijing, Tianjin and Shanghai, then compare the estimation result with at-scale apparent cement use data to verify the method. Our results find cement intensities in the various sectors, i.e., the cement intensity for highway, urban road, and residential building is 0.71 tons/m, 0.034 tons/m2, and 0.19 tons/m2 respectively. Our bottom-up citywide method estimates cement use in new construction to be around half (50%) of each city’s yearly total cement use (from 2004 to 2012), which is useful for evaluating the cement distribution and relevant environmental problems. The three main cement use sectors for new construction are residential building, other building, and road system (urban road, highway, subway & light rail, railway, and bridge) in these three cities. We believe that the unaccounted cement may be for maintenance of old stock, which was confirmed by conducting a first-order estimation that yield overall difference between bottom-up method of this paper and at-scale numbers from the city to be less than 15%. While cement use of residential buildings is decreasing during the past years in Beijing and Shanghai, Tianjin keeps a very stable status on cement use in this sector. Prior to this research, there is no study that shows cement use by infrastructure sectors, indicating the value of conducting bottom-up estimates.
  • Thumbnail Image
    Item
    The Effect of Composition on the Alkali-Silica Mitigation Potential of Fly Ash-Ground Glass Blends in Concrete
    (2019-08) Doolittle, Nathan
    This research investigates the use of ternary blends of Portland cement, ground glass and four different fly ashes as a mitigation method for alkali-silica reaction (ASR) in concrete. ASR is the reaction between select reactive aggregates and alkalis in the pore solution of concrete added by the hydration of portland cement. The inclusion of fly ash and waste glass has potential to reduce the deleterious expansive effect of ASR. Testing conducted involves measurement of length change, compressive strength and the fresh mix properties.
  • Thumbnail Image
    Item
    Evaluation of implant restoration retention on various custom abutment materials and surfaces
    (2018-05) McMillan, Kale
    Purpose: Clinical use of cement-retained implant crowns requires selecting the appropriate abutment materials, surface characteristics, and cement type, based on finding the right balance between the desired level of retention form and the potential need for retrievability for each patient case. The purpose of this study was to evaluate the forces needed to vertically displace a cement-retained implant crown, using a provisional cement and five different combinations of abutment materials and surface characteristics. Material & Methods: A clinical master cast with an implant analog in the maxillary right central incisor site was fabricated and facilitated the design and manufacturing of 25 implant custom abutments planned for cement-retained restorations. Although all 25 implant custom abutments were designed to be identical in contour, each group of five abutments was fabricated from different materials or had different surface characteristics. The five different implant abutment groups were titanium smooth surface (Ts), titanium with retentive grooves (Tr), titanium with a nitride coating and smooth surface (Gs), titanium with a nitride coating and retentive grooves (Gr), and zirconia (Z). A total of 25 lithium disilicate crowns were fabricated and each crown was cemented to its corresponding abutment with non-eugenol temporary resin cement. With the use of a universal testing machine, the maximum tensile strength needed to dislodge the crown from the abutment was recorded and evaluated. Results: The mean tensile force needed to decement the lithium disilicate crowns within each implant abutment group was 31.58 N for titanium smooth surface (Ts), 29.29 N for titanium with retentive grooves (Tr), 32.90 N for titanium with nitride coating with smooth surface (Gs), 28.75 N for the titanium with nitride coating with retentive grooves (Gr), and 139.49 N for zirconia (Z). The titanium abutment groups did not differ significantly (P=.92); however, the zirconia abutment group required a statistically significant higher tensile force to decement the lithium disilicate crowns cemented with non-eugenol temporary resin cement compared to the titanium abutment groups (P<.05) Conclusion: Surface characteristics of the titanium implant abutments, including retentive grooves and nitride coating, did not increase the tensile force required to decement the crowns compared to a smooth titanium surface. The fabrication of zirconia abutments has the potential to generate discrepancies in the size and shape of the zirconia abutments, especially compared to the milled titanium abutments. The possible discrepencies in the zirconia abutments, including larger surface areas and need for nonstandardized crowns to fit the zirconia abutments may contribute more significantly to the increased retention compared to the interaction of the abutment material and provisional cement.