Rapid assessment of life cycle CO2 absorption in conventional and carbonation-injected construction blocks, and microstructural characterization of carbonation-injected pavers

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Over time, cement based products such as concrete absorb atmospheric CO2 in a process called carbonation. Carbonation helps to offset some of the CO2 emissions associated with portland cement production. Approximately half of the CO2 emitted during cement production originates from the calcination of limestone. Ideally, all of the CO2 attributed to calcination is eventually re-absorbed by concrete through the carbonation process. In most cases carbonation slowly progresses from the exposed surface of the concrete inward over a period of years, decades, and in the case of Roman concrete, millennia. The rate of carbonation in concrete is a well-studied parameter, both from the standpoint of quantifying the life cycle absorption of CO2, and from the standpoint of quantifying the service life of the concrete itself, as carbonation can be a contributing factor in the corrosion of embedded steel reinforcement. Although potentially detrimental in terms of corrosion, carbonation can also be beneficial, especially when the process is incorporated into the early-age curing of fresh concrete. Accelerated carbonation has been shown to improve compressive strength, and reduce permeability. Carbonation-injection technology is relatively new, but has been adopted commercially for concrete construction block production, and is looking to expand into the concrete paver industry. However, pavers are exposed to harsher service environments than construction blocks, and require enhanced durability. This research program aims to better understand how carbonation-injection influences the microstructure, and hence the performance, of concrete pavers. In addition to the paver issue, the research program also tackles the issue of whether carbonation-injected blocks absorb more or less CO2 than traditionally-manufactured blocks over their service life. For carbonation-injected blocks, much of the carbonation occurs up front, but carbonation reactions continue to occur over time. Specifically, the research program will determine the carbonation rate for traditional and carbonation-injected blocks in a chamber that simulates the natural long-term carbonation that would occur over a period of decades.