Concrete is second only to water as the most used material by humans. Its use continues to grow to build new structures as well as to meet an increasing need for repair of existing structures. The projected use of ordinary Portland cement, the main component responsible for binding capacity of concrete, in 2020 is to be three times the level of 1990. As every ton of ordinary Portland cement is known to produce 0.8 tons of carbon dioxide, reduction of cement consumption by use of supplementary cementitious materials is extremely important to reduce greenhouse gas emission associated with construction industry. However, supplementary cementitious materials can be slow to react and greater use of such materials in concrete requires external activation. External activation of supplementary cementitious materials can produce binders with similar to superior mechanical properties and have been used in actual construction. However, there are still many factors, including their high early age deformation due to moisture loss and limited understanding of long-term time dependent deformation, that affect their wider use. This proposal, for the first time, will study processing of such sustainable alternative binders and its relationship with time-dependent deformation to ultimately control it. The proposed work plan also aims to a) advance the integration of research and education through training civil engineering graduate students in materials science, b) encourage study of sustainable infrastructure materials among undergraduates through middle school students and c) increase participation of women and underrepresented students in research.
The research objective of this proposal is to provide fundamental understanding of how the reaction mechanisms, and the molecular and nano structural arrangements of the reaction products in alkali activated sustainable alternative binders made from supplementary cementitious materials, are related to the time dependent deformation of the binder. This proposal hypothesizes that the abovementioned factors can be controlled through the addition of nanocrystalline seeding agents. In this project, the effects of the addition of nanocrystalline seeding agents on the reaction mechanism of alkali activated binders will be studied through the use of high resolution electron microscopy and X-ray scattering. Precise information on the growth mechanism will be transformative as it will permit modification and possibly improvement of predicting capability of existing models for reaction kinetics of such binders. Fundamental understanding achieved through this proposal will be equally important for improving resistance of alkali activated binders against leaching, efflorescence and other chemical degradations as they also depend on the molecular and nanostructure of the binder.
