Concrete is used heavily in shielding of nuclear power plants, and storage of nuclear waste. In such environments, exposure to radiation is inevitable. While concrete is optimal for shielding such radiation from the outside (due to its water content), collision of high energy radiation with the aggregates (i.e. rocks and gravel bound together by cement) can lead to amorphization and increases in reactivity. When this radiation damage occurs for aggregates containing silica, the result is alkali-silica reaction (ASR). ASR is commonly known to result in expansion, cracking, and ultimate failure of the concrete. This research uses molecular dynamics simluations, which model physical movement of atoms and molecules, to assess the extent and nature of this radiation damage. Results provide a basis for developing mitigation strategies to prevent ASR from occurring in concrete exposed to radiation.
Global carbon dioxide emissions, 8-10% of which originate from the cement industry, are a growing problem. Ordinary portland cement and calcium hydroxide both have the potential to carbonate, thus consuming some of this carbon dioxide. This research investigates the carbonation of both of these materials in liquid and supercritical carbon dioxide. High levels of carbonation (>80%) are achieved within two hours in both forms of carbon dioxide, and carbonation in the presence of silica sand results in the formation of stable pellets. Though cementation quality remains to be tested, carbon neutral cementation by such a means would not only mitigate emissions from the construction industry, but could be used to consume flue gas from coal fired power plants or other major emissions sources. Results provide a basis for further investigation into the production of carbon neutral building elements, and hold the potential to revolutionize the green construction industry.