This research project aims at understanding the nature of calcium-silicate-hydrate (C-S-H) as the main cement hydration product and its responsibility in the strength and fracture of cement based composites. The recent fracture of oil well in the Gulf of Mexico and its associated environmental impact necessitate a thorough understanding of the significance of cement curing regimes, including high pressure and temperature on the microstructure of cement hydration products and the influence of that microstructure on the mechanical, impact and fracture resistance of cement. The goal of the research is to investigate the fundamental process for synthesis of C-S-H, to correlate its nano and microstructure features, and to further understand its mechanical characteristics including creep, impact strength and fracture toughness. The scope focuses on how the nano and microstructural features of C-S-H are altered when the calcium-silicate (C/S) ratio is changed (ratios ranging from 0.6 to 1.5) and when the hydration process occurs under different combinations of temperatures and pressures. By testing C-S-H synthesized under varying curing conditions, we will understand the significance of hydration conditions on silicate polymerization and water structure of C-S-H and how C-S-H nanostructure affects its creep, fracture and impact strength.
Funds will be used to support graduate and undergraduate students in University of New Mexico (UNM): a minority serving institution. This work will fill a major knowledge gap as most researchers working in the field have focused on the chemical and microstructural nature of C-S-H and very limited research has provided information on the mechanical characteristics of C-S-H. If successful, we will reveal some major mechanical characteristics of C-S-H including creep, fracture and impact strength. Successful research investigation shall lead to necessary changes in cement manufacturing to produce impact-tolerant cement-based composites.
This research aimed at understanding the nature of calcium-silicate-hydrate (C-S-H) as a main material in hydrated cement that is responsible for the strength and durability of concrete. We successfully synthesized and characterized this product at varying CaO/SiO2 ratios ranging from 0.6 to 2.0. This process helped us understanding the role of silicate on strength and long-term behavior of cement. One major outcome is we developed an understanding the significance of silica content on the mechanical and durability of cementing material. This finding helps us selecting appropriate alternative cementing materials by choosing their silica content. By identifying alternative cementing materials from sustainable sources, we will help reducing the daily use and production of Portland cement which will have an immense impact on CO2 emission for global warming concerns. Research findings were published by the principal investigator (PI) and his research team in top journals and presented in international meetings. Moreover, this study was conducted at University of New Mexico (UNM). UNM is the only Carnegie, Very High Research University in the country designated as a Minority and Hispanic-Serving Institution (MHSI). UNM School of Engineering (SOE) graduation rates for Hispanic and Native American students are among the highest in the U.S. Currently, 40% of UNMâ€™s Engineering undergraduates come from underrepresented groups (Hispanic and Native American ) and 20% of SOEs students are female, on par with the national average. With the above student environment at UNM, the PI was able to use the above grant to hire and train four graduate students towards their Masters and PhD degrees. Successful outcome of this project is graduation of three Master of Science students with state of the art training on nanomaterials technology. These three students include two women students. Furthermore, one of the female students was Native American. Both female students were hired by Government agencies to continue their work in the field of science and engineering. The third student to graduate with Masters of Science degree was hired by an engineering consulting firm. Finally, the PI and his research team used this funding to attract students from visible minorities to science and engineering. The PI extended collaboration with UNM Valencia campus where more than 50% of their students are minority students. The PI visited UNM Valencia campus and presented interesting science and engineering activities. The PI also visited elementary and junior high schools in New Mexico. A major outcome of this grant is attracting young students to science and engineering some of them joined the PIâ€™s lab as summer junior interns.