Heating Aggregates

Heating Aggregates

Postby LeeMR on Sat Nov 28, 2009 11:43 pm

Does anyone know if heating your aggregates with a #2 fuel powered salamander heater would have any non-desirable affect on the aggregates? I don't know if the exhaust from the heater would create any deposits on the aggregates that might have an affect on the finished concrete product.
Lee Gentile

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Re: Heating Aggregates

Postby smnstn on Sun Nov 29, 2009 10:19 am

That sounds like a question for the Freshman Class at MIT. I doubt that the aggregates themselves would become saturated with residual and unstable CO. Any "pockets" residing between aggregate particles would likely stabilize with atmospheric oxygen and interaction with mix water. However, I'd be more concerned with the question, WHY? This would heat only the top few inches of aggregate unless the pile were constantly turned, or perhaps if the Salamander fed a plenum that in turn distributed hot air through ventilating tubes permeating the lower 1/3 of the aggregate piles. But sand packs densely in place, and would be better served through conductive or radiant heating, not convection, as there would be little air circulation throughout the matrix of the pile. I think this could be a costly way of attempting to warm aggregate. As far as stone is concerned, I think it's also a pretty good insulator and resists natural air circulation. I remember when I was hauling crushed limestone for county highways, we had gotten to the center of the huge stockpile of roadstone at the quarry, and the big loader chopped into a layer of snow and ice from the previous winter. It was near the end of July at the time.

Sioux brand water heaters, as well as some others, market steam generators that can be fitted with probes to shoot streams of steam into aggregate piles. But those units, which can also provide hot water and steam clean equipment, are very pricey. They can be checked out at the World of Concrete in Las Vegas, Feb 1-5.

A customer of mine in Chicago set up a continuous, recirculating hot water heater with a thermostatically controlled reservoir, and diverted his heated water into radiant heating tubes embedded in the floor of his aggregate bins. When he fired the system up, water would recirculate until the thermostat sensed the entire hot water supply had been heated to target temperature. This included the network of sub-grade slab tubes and a 500 gallon reservoir. Usually recovery could be achieved in the time it took to deliver one load of materials. He also inserted a livestock water trough heater in his truck water tank, heating that overnight. He also employed standard hardware store heat tape for wrapping home water pipes against freezing, and encompassed critical valves and tubes with it to remain in place overnight plugged into the shop wall outlets. In the morning they'd get unplugged as part of the readiness routine. Finally, he constructed his shop out of a "hoop"-style temporary structure that used double-thick solar/thermal greenhouse plastic for the skin. This captured solar energy for heat and light even when cloudy, and helped heat the aggregate piles from the top.

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