Cryogenic cooling using liquid nitrogen to produce massive concrete: temperature, setting time and compressive strength

Mixing cement with water in mass concrete production is associated with hydration heat generation, which may cause concrete mixes to dry out and crack. The experimental work aims to evaluate the effects of using liquid nitrogen (LN) in cooling mortar mixes and concrete. LN was used in doses of 0, 25, 50, 75 and 100% by water volume to either cool the mixing water at T = 4°C or to inject it into concrete mixtures directly. The concrete mix proportions were based on ACI PRC-207.1-21 for mass concrete. The mortars' initial and final setting times and temperatures indicated that a greater percentage of LN delayed the hardening process and the peak hardening rates, exhibiting slower cement hydration. LN cooling enhances the compressive strength of mortar and concrete cubes when V_LN/V_water≤1. However, concrete compressive strength decreased due to ice formation that turned into voids when V_LN/V_water>1. Cooling concrete with chilled water (T = 4°C) showed a 30% and 34.51% increase in mortar and concrete cubes' compressive strength, respectively, and a maximum of 16.45% and 12.97% when LN was injected into mortars and concrete mixes. Cooling the concrete with chilled water (T = 4°C) showed a slower cooling process, which improved cement hydration results.