Human disturbance of North American forests and grasslands: The fossil pollen record

Abstract

Severe blistering of a concrete floor slab has occured over an extensive area in a 10 year old building, resulting in unevenness of the surface and rupturing of vinyl tiles covering the floor. The blistering was found to be caused by the oxidation of pyrite in pyritic aggregates located at the surface of the slab. Oxidation of pyrite resulted in the formation of sulfuric acid and ferrous sulfate which reacted with other mineral components of the aggcgate to form complex sulfates such as jarosite, halotrichite and small amounts of other sulfates, and reacted with the mortar surrounding the aggregate to form gypsum. The portion of the vinyl tiles in contact with the highly acidic envirenment near the degrading aggregate became very brittle and upward movement of the soluble salts and their accumulation beneath the brittle portions caused blistering which grew end finally ruptured the tiles. Pyritic aggregates within the co.fete were not affected due to complete protection by the mortar and a general sulfate att~-k was not observed. Introduction