Abstract
The fabrication of cement clinker releases CO2 due to the calcination of the limestone used as raw material, which contributes to the greenhouse effect. The industry is involved in a process of reducing this amount liberated to the atmosphere by mainly lowering the amount of clinker in the cements. The cement-based materials, such as concrete and mortars, combine part of this CO2 by a process called “carbonation”. Carbonation has been studied lately mainly due to the fact that it induces the corrosion of steel reinforcement when bringing the CO2 front to the surface of the reinforcing bars. Thus, the “rate of carbonation” of the concrete cover is characterized by and linked to the length of service life of concrete structures. The studies on how much CO2 is fixed by the hydrated phases are scarce and even less has been studied the influence of the type of cement. In present work, 15 cements were used to fabricate paste and concrete specimens withwater/cement (w/c) ratios of 0.6 and 0.45 which reproduce typical concretes for buildings and infrastructures. The amount of carbon dioxide uptake was measured through thermal gravimetry. The degree of carbonation, (DoC) is defined as the CO2 fixed with respect to the total theoretical maximum and the carbon storage capacity (CSC) as the carbonation uptake by a concrete element, a family or the whole inventory of a region or country. The results in the pastes where analyzed with respect to the uptake by concretes and indicated that: (a) the humidity of the pores is a critical parameter that favours the carbonation reaction as higher is the humidity (within the normal atmospheric values), (b) all types of cement uptake CO2 in function of the CaO of the clinker except the binders having slags, which can uptake additional CO2 giving aDoC near or above 100%. The CSC of Spain has been updated with respect to a previous publication resulting in proportions of 10.8–11.2% of the calcination emissions, through considering a ratio of “surface exposed/volume of the element” of 3 as an average of the whole Spanish asset of building and infrastructures.
Highlights
Climatic change is a threat for the wellbeing of humanity
The degree of carbonation, (DoC) is defined as the CO2 fixed with respect to the total theoretical maximum and the carbon storage capacity (CSC) as the carbonation uptake by a concrete element, a family or the whole inventory of a region or country
300 kg of CO2 per ton of clinker is produced from the combustion of fuel. These concerns helped to promote the formation of the Intergovernmental Panel for Climatic Change (IPCC) [1], created in 1988 by the World Meteorological Organization (WMO) and the United Nations Environment Program (UNEP), to produce reports by experts and scientists on the of climate change, as well as its impacts and future risks
Summary
Greenhouse effects seem to be increasing the average atmospheric temperature with all the undesirable side consequences of extreme climatic events. One of the pollutants that produces the increase in temperature is known to be carbon dioxide evolved from combustion engines and industrial activity. Cement manufacture is one of the contributors to the increase of carbon dioxide in the atmosphere due to in its fabrication releases around 825 kg of CO2 by ton of clinker produced of which only around 525 kg of CO2 per ton of clinker is due to the calcination of limestone and clays. 300 kg of CO2 per ton of clinker is produced from the combustion of fuel. These concerns helped to promote the formation of the Intergovernmental Panel for Climatic Change (IPCC) [1], created in 1988 by the World Meteorological Organization (WMO) and the United Nations Environment Program (UNEP), to produce reports by experts and scientists on the of climate change, as well as its impacts and future risks
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