I have recently laid a cement patio using a brick form that you pour cement into, thereby making your own bricks. I have used play sand to fill inbetween the bricks. It seems that this sand dries out and the dogs track it into the house. Did I use the wrong type of sand? Shoudl the bricks be sealed with some product to protect then from the weather. I live next Chicago and winters can be bad. If anybody has any experince using these new form I would appreciate any advise.