Question: We have been engaged to replace a floor in a brass foundry which has disintegrated from spillage of hot molten brass from ladles that move across the floor between the melting furnaces and the casting area. What is the best way to install a floor that will provide maximum resistance to continuing spillage of this kind?
Answer: A refractory concrete might be able to survive such high-temperature abuse. We suggest investigating the use of a calcium aluminate cement such as produced by Universal Atlas Cement Division, United States Steel Corporation, 600-T Grant Street, Pittsburgh, Pennsylvania 15230 or Lone Star LaFarge Inc., 18 Koger Executive Center, Suite 220, Norfolk, Virginia 23502. The old floor should be taken out completely and a full-depth floor built with concrete made of the special cement and a refractory aggregate. The two producers mentioned can undoubtedly provide technical guidance.
Guy H. Wilson, Special Products, Tews Lime and Cement Company, Milwaukee, has sent the following procedure for applying a heat-resistant heavy-duty topping for concrete floors.Start with a clean subbase from which all laitance has been removed. Prepare a bonding grout composed of one part aluminous cement, one part fine emery and enough water to produce the consistency of heavy cream. Predampen the base and apply the bonding grout.The topping should be placed immediately, before the bonding grout has had a chance to dry. This topping should be proportioned 94 pounds of aluminous cement to 300 pounds of emery graded from 3/8 inch to fines. Potable water should be used up to a maximum of 3 1/2 gallons per 94-pound bag of aluminous cement (w/c = 0.31).This should produce an extremely dry topping that will require placement with a tamper or roller followed by screeding to final level. Float with a compactor-type power float and trowel to the desired finish. If there are joints in the subbase, joints should be installed in the topping directly above those in the subbase. Curing is extremely important. Use only water, either by spraying at frequent intervals or ponding for a minimum of 24 hours. Do not cure with membrane curing compounds.A rule of thumb is to provide 1 1/2 inch of thickness per 1000 degrees F plus 1/2 inch for each additional 500 degrees F. As the melting point of aluminum is 1220 degrees F, a 2-inch-thick topping would be adequate for the floor described in the previous Problem Clinic item.