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Low Temperature Calorimetry and Alkali-Activated Slags Public

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The American Society of Civil Engineers’ (ASCE’s) “2013 Report Card for America’s Infrastructure” estimated that “32% of America’s major roads are in poor or mediocre condition.” An estimated $100 billion dollars are needed to maintain that condition, and an additional $79 billion is needed to improve the quality of American roadways to an acceptable level. In many regions around the US, the service lives of concrete pavements are limited by the damage caused by freezing and thawing of pore solution inside the pavements. Alkali-activated slags (AAS) are produced from ground granulated blast furnace slag (GGBFS), a byproduct of iron production, and exhibit cementitious properties. AAS concretes have been shown to have improved corrosion and freeze/thaw resistance compared to traditional cement-based concretes. A Guarded Longitudinal Comparative Calorimeter (GLCC) was used to determine when the freezing and thawing of internal water occurs in three AAS mortars using solutions of NaOH, Na2CO3, or waterglass compared to a control Ordinary Portland Cement (OPC) mortar. AAS mortars using NaOH and Na2CO3 showed comparable thermal properties to the OPC mortar using the GLCC, and the AAS mortar using waterglass was shown to have higher heat capacity compared to the other AAS mixes. The compressive strengths varied by the alkaline solution used, with AAS with Na2CO3 showing inferior compressive strength to OPC, AAS with NaOH showing similar compressive strength to OPC, and AAS with waterglass showing superior compressive strength to OPC, but poor workability. A computer model of the GLCC testing procedure was created and showed good agreement with the experimental data. The GLCC model can be modified to approximate the results of the GLCC using a wider range of materials and internal solutions, like PCMs.

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  • English
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  • etd-042914-201141
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  • 2014
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  • 2014-04-29
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