We had a patio poured on Friday when the weather was rainy in the AM and humid the rest of the day. The contractor put sealer on it when they were finished and now the patio looks spotted and some of the edges look dirty. Anyone know why? It looks horrible. We were gone all weekend and came back pretty unhappy.

It's not uncommon for new concrete to have uneven color or appear to have stained areas. In most cases, the cause is due to the lime (part of the concrete mix) leaching out of the slab as it dries or areas of the concrete that are curing/drying at different rates. If you wash the new slab off with a hose for a few days... you'll probably notice a significant improvement in the way it looks. After a month or two... your concern will just be a "fond" memory.

Good luck.

The sealer put on the concrete may have created areas where as Kstar mentioned the lime leaching out. Concrete sealer, seals the concrete from Hydration if put on to early. Hydration is the process in which concrete dries. Concrete with out sealer can stain or discolor. After the hydration process has had ample time usually 4-7 days depending on the weather then the sealer can be applied. The best method for curing concrete is to allow the hydration to take place using no sealer and keeping the surface of the concrete moist, usually by placing water on the surface over a period of 7 days. It is not the surface of the concrete that needs to hydrate it is the very most middle part of the slab that needs to hydrate. If this hydration is limited in anyway you will have concentrated areas where the path of least resistance is utilized thus spotted and dirty.

I had a patio put in last summer and it became darkened and spotted. As time went on it got worse. The company claimed it was a reaction with the sealer. They removed the sealer, cement became clean and we waited all winter. This spring they put a different kind of sealer on and we now the darkened spots are back. Is it possible that it is coming from the cement and the contractor needs to rip it up and start over?