Bricks, Masonry, Asphalt and Concrete - Patio concreate sank

There is an area in my back yard patio concreate cracked and sank for about 1/4 inch. The size of the area that sank is about 2 feet by 3 feet. Is there any material that I can pour and level it up to its neighboring area?

I asked a general contractor. He said the best way is to sledge hammer the area into small pieces; remove; and put in new concreate.

I am just wandering if there is a leveler material that I can pour on and bring it back up to the same level, but I am afraid that it may not bind well.

Can you give me some advice?
Thanks
fh

There is a product made for the purpose of leveling out a low spot in concrete, Concrete Resurfacer. Check the building supply houses in your area. Generally, a thorough cleaning of the surface with a pressure washer is all the preparation that is needed.

Hi,

With your suggestion, I went to HomeDepot and bought a 40 pound box Concrete Resurfacer from Quikrete yesterday.

http://www.quikrete.com/diy/ResurfacingConcrete.html

I used up the first box/bag but did not finish all the area. So, I went and bought a second box/bag. After I poured and fixed a new areas that I think I did not do a smooth job, I let the whole area dry.

Today, when I check on the job, I found out that these 2 boxes/bags created quite different color. The first box was smooth and lighter in color, and the second box is more rough and much darker in color.

I look the box cover and instructions, they are identical to me. So, is this because of the amount of water and time to mix that is creating the difference?

I still have half a bag left from the 2nd purchase, so I could mix it again and thinly pour on the area that is much ligher to make them look the same, but I just want to make sure if I need to improve my method.

thanks