EARLY STRENGTH GAIN OF RAPID HIGHWAY REPAIR CONCRETE

Concrete used for rapid repair of pavements must meet minimum strength levels before the pavement can be opened to traffic. These strength levels are usually accomplished by using a concrete with a high cement content, low water-cement ratio (w/c), and accelerating admixtures. After a Federal Highway Administration (FHWA) survey confirmed the long-term performance of Fast Track techniques, FHWA initiated a demonstration project to promote the development of such products. This article reports on the scope of the investigation, field test techniques, and the findings at field sites. Based on the results of the study, the authors draw five conclusions: 1) microwave oven drying is a rapid means to determine water content of fresh concrete, 2) early strength gain can be monitored via maturity and pulse velocity during the curing period in pavement repair slabs, 3) the maturity approach offers a more exact prediction of strengths close to time opening, 4) nondestructive test readings must be calibrated to strength prior to construction, and 5) curing test cylinders in a well-insulated curing box may offer a simple means of predicting in-place strength of rapid repair mixes.