Q.: When sulfate concentration is given in percent of soil or parts per million of water, is there a way of converting this value to pH so that the value could be used to predict potential sulfate attack on concrete?
A.: No. The pH of a solution (in this case sulfate in water) is a measure of its acid concentration; but it is really the concentration of sulfate ion which directly determines the rate of sulfate attack. For any particular sulfate salt the rate might be influenced by pH but not primarily determined by it.
As a matter of information it would be possible to convert the concentration of sulfate salt in water into pH, but only if one had a separate table for each sulfate salt. Furthermore, any pH value picked from such a table would be inaccurate if any other salts, alkalies or acids were present in the water. To convert percent sulfate in soils to pH would be even more complicated and impractical as a means of predicting sulfate attack.