Alkali activated concretes (AACs) are promising green alternatives to conventional portland cement concrete, as they offer significant energy and CO2 savings that results from full (100%) replacement of portland cement with industrial waste products. However, these materials have not yet received broad industry acceptance, primarily due to their uncertain long-term durability performance against shrinkage/cracking, carbonation/corrosion, and alkali-aggregate reaction. The objectives of this work are to (1) advance the knowledge on the causes and mechanisms of shrinkage and carbonation of AACs at multiple length-scales, and (2) utilize this new knowledge to propose and evaluate effective mitigation strategies to promote production of high performance AAC materials. Three main alkali activated binders with vastly different compositions will be studied; a Ca-rich slag-based AAC, an Al-rich class F fly ash-based AAC, and a composite slag-fly ash binder, containing moderate levels of both Ca and Al. A novel research approach is proposed where the macro-scale shrinkage and carbonation performance is quantitatively linked to the material?s microstructure and phase-specific compositions and properties. This approach is based on integrating advanced characterization techniques (e.g., FIB, nano-indentation, NMR, SEM/EDS/ QXRD) with object oriented FEM simulations; and allows identifying the optimum material proportioning and processing practices that result in stable phase formation, and low risk of shrinkage and carbonation, without compromising strength and other performance requirements. In addition, chemical speciation modeling is used to design novel admixtures to reduce carbonation and to induce expansive reactions.
The research outcomes can be extremely beneficial towards improving the performance of alkali activated concretes, as well as portland cement and other alternative concrete materials. The research is well integrated with educational plans, including (a) outreach, recruitment, and retention of female and minority students in civil engineering education, research, and careers, and (b) providing a world-class research and teaching experience for graduate and undergraduate students. In addition, this work will contribute to engineering education literature by developing active learning and innovative student-centered instructional methods, and assessing the effectiveness of such methods in improving learning, engagement, and retention of students.
