The binder and the aggregates are matched so as to wear at substantially identical rates.doi:US5908350 ARoy J. WaltersUSUS5908350 1997年5月21日 1999年6月1日 Ralph Dalton Device for removing stains from swimming pool walls and concrete...
You can also try lemon juice which is citric acid. For stains at the bottom of the bowl, empty all the water out of the toilet and pour in straight vinegar high enough to cover the stain. Then just let it sit until gone. Use a stronger acid as above if needed. ...
US6180588 Jan 13, 1999 Jan 30, 2001 Tracey Dalton Device for removing stains from swimming pool walls and concrete and the method of making the sameUS6180588 * Jan 13, 1999 Jan 30, 2001 Tracey Dalton Device for removing stains from swimming pool walls and concrete and the method of making...