The use of ice has long been thought to be the most practical way of cooling concrete. In recent years, use of liquid nitrogen has been shown to be economical and practical, especially where ice and handling costs are high or where concrete temperature specifications are very low. Another major consideration is quality. Cooling with ice may produce uncertain results from one batch to another. Liquid nitrogen (LIN) cooling can be controlled more closely and does not add unnecessary water. It is well to remember, however, that liquid nitrogen is easily available only in industrial areas having the manufacturing facilities to produce it.
Liquid nitrogen can be used to cool the aggregate, the mix water, or the concrete. Attempts to cool the aggregate directly with LIN, however, have not been very successful for several reasons. Directed onto the aggregate through injection lances, LIN causes localized freezing and creates agglomerations of material that clog discharge gates. If applied as a spray, LIN does not cool the aggregate sufficiently to reduce concrete temperatures by more than 5 degrees F.
A typical LIN water cooling system consists of: a cryogenic storage tank that can be refilled from the LIN supplier's tank truck; a flow control system operated from a panel that includes an automatic temperature controller; a temperature indicator and switches for the lance heaters; injection lances which extend into the water. For high production rates, two bins would probably be needed. With a few modifications the control panel could be used to operate both systems and both could draw from the same tank. For maximum effectiveness in very hot weather the mix water and the aggregate should be cooled to a temperature as close to freezing as possible.