New Heatec hot oil heater at United.

Hot oil flows through copper pipes embedded in the concrete pad under this stockpile of sand. However, there is no piping under the front third of the pad. A thermal image of this same stockpile is shown below.

This thermal image of the stockpile was made with an infrared camera. It reveals how the heat from the coils is distributed in the sand. The temperature of the ground in front of the stockpile was freezing, ranging from 23 to 29 degrees F. Surface temperatures of the stockpile ranged from 74 to 123 degrees F. Internal temperatures were even higher.

One hot oil heater can provide all the heat needed for making concrete in cold weather.

United Ready Mix is the second largest concrete producer in Peoria and has been in business for 38 years. They heat sand and water ingredients for their concrete from November 1 to April 1, enabling them to make concrete year around.

Because of the extra costs related to heating, United adds a surcharge ranging from $3.00 to $3.50 per yard to the price of their mix during those months. This allows them to recoup the expense of fuel for heating as well as capital costs for heating equipment.

Jon Vrabel, General Manager of United's plants in Peoria and Pekin, IL says the mixes they produce must meet demanding requirements. That's because most of their customers are contractors doing commercial, industrial, or state projects. These projects include building roads and bridges.

Jon believes their concrete consistently meets strict specs because they use a central mix batch plant instead of mixing in the truck. He insists that a central mixer allows closer control, which gives better uniformity and higher strength. Moreover, Jon prefers to heat both the sand and the water used in the mix. This, he says, gives a more uniform distribution of heat in the mix, an important factor that improves strength.

Jon describes some of the things they have learned about heating materials over the years. They use a hot oil (thermal fluid) heater for heating materials. A new heater from Heatec replaces the one they used for the past 18 years. It heats oil that circulates through a serpentine coil imbedded in the concrete pad under the sand stock pile.

The coil is made from 2-inch copper pipe joined with high-temperature solder. Loops of the coil are spaced on 24-inch centers and cover the back two-thirds of the pad area. The operating temperature of the oil is 300 to 325 degrees F.

As a result of heating the materials, the temperature of the final mix ranges from 65 to 70 degrees F, well above the 40 degree minimum temperature needed for hydration.

Jon's new heater from Heatec has an output of one-million Btu/ hour and is highly efficient. His total heating cost for the month of December was $2172. That includes the cost of fuel for other heating equipment, not just fuel for the heater. Even so, that works out to a very low cost per cubic yard. Jon plans to connect additional piping circuits to the heater for heating mix water and plant offices.

Heatec is interested in working with other ready-mix producers to provide heating equipment and services for their specific needs. Heatec offers a wide range of thermal fluid heaters and storage tanks that are extremely well-suited for the concrete industry.

Our ongoing communications with major producers such as United Ready-Mix helps us to better serve anyone interested in this technology. Feedback of actual field experiences from producers greatly enhances the capabilities of our engineers. For example, we made thermal images of the heated sand at United to learn more about the distribution of heat in stockpiles. And Jon also expressed his willingness to offer suggestions to anyone who wishes to contact him directly.

Jon's choice of heating with hot oil appears to be the ideal solution for heating concrete materials. Using a hot oil heater as a single source of heat provides high efficiency and simplifies maintenance.

It's a better way to heat sand than using steam. Steam has numerous drawbacks, some serious. It's a better way to heat water than a direct-fired tank. And the same hot oil can be used to heat other equipment, including offices.

Heatec can provide a complete system, including the hot oil heater. We also offer water tanks equipped with a burner and fire-tube. These work well if you do not intend to heat stockpiles— or other things.

If you are a concrete producer and would like to discuss various heating options, please contact us for further information.

Article courtesy of Heatec, Inc., a division of Astec Industries, Inc.