The freeze-thaw effect describes the cycle water goes through as it turns into ice and then melts back into its liquid form. The freeze-thaw effect is part of the reason why it’s so important to protect your concrete from moisture exposure if you want to prevent structural damage. When water turns into ice, it expands by about 9%. It may not seem like it, but expanding ice is fully capable of displacing concrete particles. Every time there’s some sort of displacement, the concrete becomes structurally weaker with time. The freeze-thaw cycle is capable of creating small craters both inside and along the surface of the concrete. Concrete is already impermeable, but with each new micro-tear, it allows moisture to seep through even more. As more and more water gets past the structure, the freeze-thaw cycle also displaces the soil underneath. Concrete settling advances, and then you have an uneven, structurally weak slab. The more porous concrete is, the worse its tensile strength is, so cracking is inevitable on a slab that has been exposed to moisture during the winter. How dangerous exposure to the freeze-thaw cycle is depends on the severity of the winter climate. Although Greenville, SC, isn’t exactly a winter wonderland, there are enough nights out of the year where the temperature reaches at or below freezing for it to have an effect. Freeze-thaw is a lot more impactful on concrete with low psi, which is typically the case for slabs made for walkways, since they aren’t considered to be “heavy duty” slabs. Keeping the snow off of your concrete is an integral part of slab protection, so consider covering your concrete during the winter. This way, if your slab does settle, you can avoid having to replace it due to breakage that prevents repairs.