Liquid nitrogen for cooling concrete : safety precautions, methods of injection, and effects on setting time and drying shrinkage
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This study investigated the effects and use of liquid nitrogen for cooling concrete. In the past, ice and chilled water have been the mainstays to cool concrete for mass pours in which the concrete must be a specified temperature as required by the Texas Department of Transportation (TxDOT). Cooling the concrete prevents large thermal gradients from developing between the core of the concrete and the outer layer of the concrete caused by the cement hydration reaction. Preventing these large thermal differences directly affects thermal cracking and thus concrete durability. Liquid nitrogen has been actively used to cool concrete in projects all over the world, and is becoming increasingly popular. However, the various effects of LN on concrete have not been studied in depth and assembled into a published document. This thesis covers basic safety precautions and methods of injecting liquid nitrogen which were documented and recorded by conducting surveys and visiting sites in Austin, Texas where LN was in use. In addition, lab experiments were conducted to study the effects of LN on setting time, admixtures, and drying shrinkage. The results of these tests are reported in this thesis.