Achieving environmental sustainability of the US transportation infrastructure via more environmentally sound construction is not a trivial task. Our proposal, which addresses this critical area (Focus Area 3), is aiming at transforming concrete, the material of choice for many transportation projects, into less environmentally harmful and better performing component of the US infrastructure. This will be extremely relevant to construction of pavements, bridges, tunnels, airports, marine installations and other transportation projects. Simultaneously, our project will address one of the most pressing public health issues, such as NO2 emissions from cement kilns, by developing new applications of crushed concrete aggregates (CCA), which are already contributing to resource conservation and elimination of solid waste disposal issues. NO2 emissions can cause various environmental and health problems. They contribute to the formation of acid rain, atmospheric particles, and various other toxic substances resulting in health problems, visibility reduction, eutrification and global warming [2]. One of the most prevalent problems with NO2 emissions is the formation of ground level ozone, which is produced by NOx (NO+NO2) reacting with volatile organic compounds (VOCs) and CO in the presences of sunlight [3, 4]. Ground level ozone can damage lung tissue and reduce lung function [5-9]. It is a significant problem nationwide as millions of Americans live in areas that do not meet the health standards for ozone [2]. Among many sources of NOx emissions cement kilns are very significant contributors. They emit over 219,000 tons/year of NOx, which amounts to approximately 20% of all industrial emissions [10, 11]. High temperatures reached in cement kilns are favorable for NOx emissions and cannot be avoided.

We propose an innovative approach of utilizing a waste concrete material which, based on our preliminary studies, can offer a new way of removing NO2 from flue-gas in a cheap and sustainable way. Afterall, more than 140 million tons of crushed concrete aggregate are produced in the US with 41 states utilizing it for transportation infrastructure applications [12]. This can be potentially a viable way to offset emissions from cement manufacturing factories (as well as other industrial installations) thereby minimizing their environmental impacts. Moreover, this project will explore the new paradigm of employing waste material and turning it into a useful product. The NO2 sequestered demolished concrete (NSDC) can be potentially recycled in new concrete either as a set accelerating admixture or as a corrosion inhibitor. The use of recycled concrete as aggregates for new concrete by itself is a big leap towards better sustainability, given that it conserves valuable natural resources and reduces landfill waste. The synergic effect of capturing NOx and using the NSDC as a corrosion inhibitor will further increase the positive impact on the environment and the longevity of the new reinforced concrete structures.