Non-air-entrained concrete with a moisture content near saturation is susceptible to surface scaling caused by freeze-thaw cycles.
"To stay on schedule, especially for fast-track projects, general contractors may be tempted to have floor coverings installed on concrete slabs regardless of the water-vapor emission rate of the slab. But before assuming responsibility for floor-covering performance, they should assess the probability of distress, which may include loss of adhesion between the covering and the concrete."
In March of 1998, the Federal Aviation Administration issued revisions to P-501 "Portland Cement Concrete Pavement" and P-110 "Methods of Estimating Percentage of Material Within Specification Limits." The specification revisions affect the statistical acceptance criteria for strength and thickness. Paving contractors should take particular note of the payment section of the new P-501 specification, which has been substantially revised. This article details the principal changes and how they differ from the previous requirements. Also included is a reprint of the payment section, along with a table showing the new price adjustment schedule.
Petrographers' reports often cite premature finishing as a major cause for blistering and delamination. And numerous publications tell finishers to avoid floating slabs too soon. But what is premature finishing, and how precise are the methods finishers use to judge the proper time for finishing operations to begin?
