UNITED STATES ATOMIC ENERGY COMMISSION UCRL-2988 TREATING CONCRETE SURFACES WITH PARAFFIN By Albert E. Salo May 18, 1955 Radiation Laboratory University of California Berkeley, California Technical Information Service, Oak Ridge, Tennessei Subject Category, CHEMISTKT. Work performed under Contract No. \f- r jk0^i-&cig-kS. The Atomic Energy Commission makes no representation or warranty as to the accuracy or usefulness of the Information or statements contained in this report, or that the use of any information, apparatus, method or process disclosed In this report may not infringe privately-owned rights. The Commission assumes no liability with respect to the use of, or for damages resulting from the use of, any information, apparatus, method or process disclosed In this report. This report has available copy. been reproduced directly from the beet Reproduction of this information is encouraged by the United States Atomic Energy Commission. Arrangements for your republication of this document in whole or in part should be made with the author and the organization he represents . AEC, Oak Ridge, Tenn. TREATING CONCRETE SURFACES WITH PARAFFIN' By Albert E. Salo It is difficult or impossible to remove radioactive contamination from ordinary concrete surfaces. A penetrating application of paraffin, however, seals the pores of the surface and makes decontamination relatively easy because it reduces absorption of liquids that might carry radioactivity. Molten paraffin (mp 125°F) is applied to a clean concrete surface that has been heated to about 500°F. Penetration depths of Vi inch are usual, but penetration may range up to \ inch. Pore spaces in the concrete are sealed when the paraffin cools. The concrete surface is prepared by acid etching and wire brushing. A thorough rinse with running water is followed by a drying period of at least four days. Batteries of infrared lamps may be used to help the drying process. In melting the paraffin, provisions should be made to conduct fumes away and to extinguish any flash flames. Probability of flashing can be reduced if an electric hotplate is used in pref- erence to an open flame, and if the liquid temperature is kept below 200°F. A wide-tip oxyacetylene torch is used to heat the concrete. Great care must be taken in applying the flame slowly and evenly. Areas of 5 to 10 square feet are heated at one time. The torch operator should be protected against the possibility of spalling particles by wearing a face shield and heavy clothing. Molten paraffin is brushed on the heated section until no more absorption takes place. Paraffin requirement is approximately 0.1 pound per square foot. A layer of paraffin more than a few mils thick on the surface is both unnecessary and un- desirable. Protection against possible radioactive contamination is provided by the paraffin that is absorbed into the concrete, not that which remains on the surface. An excess on the surface makes floors slippery and dangerous. Depth of penetration can be checked by the use of concrete test blocks, similar in texture and mix to the surface to be treated. After treatment the test block may be fractured with a hammer and chisel. The penetration line will usually be clearly discernible. Fig. 1 shows a typical cross section of a treated and fractured test block. The dark band at the top of the piece indicates how far the paraffin has penetrated into the block from application at the top. The band is wider at the left because in this area penetration also took place through the side surface. The dark spot on the right of the face and slightly below the surface penetration line indicates where a small amount of paraffin penetrated through a fissure into the underlying body of concrete. Fig. 2 shows a stairway that has been treated with paraffin in the manner described. This work was done under the auspices of the U. S. Atomic Energy Commission. *Permission for publication of this information in whole or in part is granted by the author and the University of California Radiation Laboratory operated for the United States Atomic Energy Commission. UCRL-2988 3 UCRL-2988 Fig. 1 — Treating concrete with paraffin. Fig. 2 — Treating concrete with paraffin. Digitized by the Internet Archive in 2012 with funding from University of Florida, George A. Smathers Libraries with support from LYRASIS and the Sloan Foundation http://www.archive.org/details/treatingconcrete0988lawr UNIVERSITY OF FLORIDA 3 1262 08917 0988 J