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The critical element for sustainable growth in the construction industry is the development of alternative cements. A new technological process called geopolymerization provides an innovative solution, and the presence of aluminum and silicon oxides in fly ash has encouraged its use as a source material. Many previous investigations have involved curing the binder in a heated environment. To reduce energy consumption during the synthesis of geopolymers, the present study investigated the properties of ambient cured geopolymer mortar at early ages. An experimental program was executed to establish a relationship between the activator composition and the properties of geopolymer mortar in fresh and hardened states. Concentrations of sodium hydroxide and sodium silicate were ascertained that are advantageous for constructability and mechanical behavior. Scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction techniques were also used to characterize the material. Test results indicate that there is potential for the concrete industry to use fly ash based geopolymer as an alternative to portland cement.

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Dr. Torres, a native of New Mexico, joined the Department of Engineering Technology (Concrete Industry Management program) in August 2013 where he teaches Concrete Construction Methods and a variety of project management courses. He received both of his graduate degrees, Ph.D. and M.S., in Civil Engineering (Structural), from the University of New Mexico. He obtained his B.S. degree, also in Civil Engineering, from New Mexico State University. Dr. Torres' research areas include the science and advancement of materials, such as concrete and cementitious materials, glass fibers, and composite materials. Dr. Torres' research interest also extends to the classroom, where he is constantly evolving his courses to provide the best education to his students.

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Abstract:The major environmental impact of concrete comes from the CO 2 emissions, produced during the cement manufacturing process. The main goal of this research project is to evaluate the efficiency of limestone powder as a partial cement replacement, in order to reduce energy consumption and CO 2 emissions. This study utilizes limestone powders, with different particle sizes, to replace a portion of Portland cement using various ratios. Due to the dilution effect when partially replacing cement, there is a reduction in the concrete's physical properties. To assess the dilution effect, a modification to Féret's equation is used to calculate an efficiency factor for the limestone powder when compared to cement. To measure the environmental impact, a life cycle assessment is conducted on concrete made with limestone powder combined with cement. This allows for an evaluation of the various cement/limestone powder ratios that will maximize the environmental benefit, with minimal reduction in concrete strength. Additional microstructural analysis using petrographic examination was completed to provide a visual understanding of the distribution of the limestone particles within the cement paste. The results indicate that the efficiency of limestone powder in partially replacing cement can be achieved by particle packing and particle distribution in the concrete and the benefits of emission reductions exceed the loss in compressive strength when higher levels of limestone powder is used to replace cement.

Her research interests include studying the role of engineering as a curricular context and problembased learning as an instructional strategy to facilitate students' mathematics and science learning. She works with teachers and students from traditionally under-served populations and seeks to understand challenges and solutions to support student academic readiness for college and career success.

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