We do not have anything in writing saying that the cables will not have a detrimental effect on concrete, however, Pyrotenax MI heating cables have been installed many thousands of snow melting jobs over the past, probably, close to 50 years or longer. I personally have designed about 650 to 700 snow melting jobs per year for the past nine years, most of them for installation in concrete. I know of one contractor alone who has installed over 2000 snow melting jobs in the Toronto area over the past 15 years. One of our wiring sales persons, who formerly worked for a competitor said that they had tested their MI cable up to 45 watts/foot in concrete with no effect on the concrete. We run ours up to 30 watts/foot maximum in concrete, so I would have to assume that this lower wattage would have less of an impact on the concrete. Because of heat conduction into the surrounding slab, the sheath temperatures of heating cables embedded in concrete do not run much higher that the temperature of the slab itself, so the slab surrounding the heating cable should run cooler than the concrete during a hot summer day. If the slab is structurally sound to begin with, and the heating cables are installed as shown in Enginering Information Sheet H1, the cables and the slab should last a long time. This does not mean that concrete will not crack. Concrete cracks, period, due to stresses placed on the slab. Our 50 foot long snow melted front entrance has a crack about every four feet and the cables are still working fine, but this 50 foot long slab does not have any control or expansion joints. Expansion joints should be installed at least every 20 feet in any one direction to relieve these stresses. If this is not possible, then control joints (saw cuts) should be installed every 20 feet and crossed as shown in engineering sheet # H1 if using MI cable. Contact Technical Support at 650-474-7709 or emailto: email@example.com"> for a copy of engineering sheet # H1.