The concrete impact on the environment is mainly on cement production, which accounts for 7 percent of total global carbon dioxide emissions. The amount of Carbon dioxide emissions is estimated to 700-800 kilo of carbon dioxide per 1000 kilo of cement produced. About 60 percent of emissions comes from the calcination of limestone, and the remaining 40 percent comes from the burning of fossil fuels due to the heat that must be added during the calcination [2]. Every year it produced around 2 million tonnes of cement in Sweden, which in turn results in the emission of approximately 1.5 million tonnes of carbon dioxide [5]. A suitable solution has been found in the use of supplementary cementitious materials, also known as mineral admixtures[3]. These materials can be used to replace cement in concrete as they possess pozzolanic and cementitious properties. The most common industrial by-products used in Sweden at the moment are fly ash and granulated blast furnace slag. To find out how big of an amounts of carbon dioxide emission can be reduced by replacing the parts of the cement with by-products, you have to conciderate the whole concrete life cycle beacuse concrete also ties up carbon dioxide. When carbon dioxide comes in contact with water in the pore solution of the concrete bicarbonate plus a hydrogen ion is formed. Bicarbonate is then dissolved to form carbonate plus a hydrogen ion. When carbonate comes in contact with calcium, calcium carbonate is formed. This process is called carbonation and continues throughout the life of the concrete. Calcium hydroxide has a very low solubility compared to other hydroxides and will be the first to dissolve and release calcium ions in the pore solution. Calcium silicate stabilized by high pH - value and Ca ions in the pore solution. Calcium Hydroxides releaseing of lowers the pH content in the pore solution which results in calcium silicate hydrate also begins to dissolve and release ions. However, changing the release of structural reconstruction of Calcium Silicate Hydrate results in a lower Ca / Si - ratio. When this ratio falls to less than 1 and the pH of the pore solution is around 10, silica gel is formed. Mineral admixtures in form of bee products such as fly ash and granulated blast furnace slag will reduce the amount of calcium hydrate in the cement paste and increase the amount of calcium silicate hydrate. Simplification of Fick's second law developed by the CBI has been used in numerical calculations for the concrete's carbon uptake over time. 3 different types of cement, Portland cement, fly ash cement and slag cement has been set against each other from a carbon dioxide perspective.Portland cement: 1 m^3 concrete of type CEM I with strength C30/37 contribute with 263 kg of carbon emissions during production. Over time, this 1 m^3 of concrete have tied up a total of 134 kg of carbon dioxide through carbonation. The total carbon emissions for 1 m^3 concrete of type CEM I with strength C30/37 remains 129 kg. Flygaskecement: 1 m^3 concrete of type CEM II / B-V (35% F) with strength C30/37 is contributing with a total of 75 kg of carbon dioxide emissions. Slag Cement: 1 m^3 concrete of type CEM II / B-S (35% F) with strength C30/37 is contributing with a total of 41 kg of carbon dioxide emissions.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:kau-46892 |
| Date | January 2016 |
| Creators | Zakhoy, Avan |
| Publisher | Karlstads universitet |
| Source Sets | DiVA Archive at Upsalla University |
| Language | Swedish |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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