Blistering of a terrazzo floor in a university campus building

Abstract

This paper concerns the blistering of a terrazzo flooring system in a university campus building. The terrazzo began to blister only ten months after installation and became increasingly worse with time. A typical failure analysis sequence was applied to this nonmetallurgical problem in order to determine the cause of the blisters. It was determined that a vapor pressure differential caused moisture to travel up through the concrete slab subfloor and become trapped beneath the terrazzo, creating blisters. This differential in above-slab and below-slab vapor pressure was attributed to a lack of circulating conditioned air in the building at the time of terrazzo installation. Although acceptable moisture measurements of the concrete slab were taken prior to terrazzo installation, they were invalid due to this lack of circulating conditioned air. It was recommended that the entire terrazzo flooring system be removed and an additional curing time be employed to ensure the concrete slab is acceptable to receive a new terrazzo flooring system. It was emphasized that the above-slab air conditions must closely match in-service operating conditions in order to eliminate the vapor pressure differential.