Geological Alterations and Chemical Treatment of a Polluted Limestone Foundation

A large factory for the production of concentrated sulphuric acid is constructed in 1977 and located in the west of Iraq near Al-Kaim city. The footings carrying the installations rest on calcareous rocks which extend deep into the ground. For many years, about 1.5 tons per day of acid seeped and percolated into the ground apart from frequent accidents when larger amounts took their path down into the ground. A record of the footings movement revealed that the footings experienced significant heave and settlement indicating a cyclic movement which depends on the frequency of seepage. The results of the past geotechnical and geochemical investigations have been carefully studied in order to trace the geological alterations occurring in the ground due to the percolation of sulphuric acid over years. It appeared that at certain depths the limestone rock has been almost converted to dough and that a significant amount of dolomitization has taken place in the factory ground. Contaminated samples have been obtained from boreholes executed in the factory site. Many chemical materials have been chosen to treat the contaminated samples. Among these materials are sodium silicate, sodium carbonate, sodium silicate plus calcium chloride, barium sulfate, aluminum oxide, ferric oxide and bentonite. Unconfined compression, ultrasonic wave, physical, wet chemical and XRD tests were performed on intact, contaminated and treated specimens. The results proved that sodium silicate is the best alternative to be used for chemical grouting of the ground. The use of calcium chloride with sodium silicate did not show an additional advantage. Samples contaminated to the degree of having the form of dough have almost regained their original solid state strength when treated with sodium silicate