FHWA Pooled Fund Study TPF-5(205)
Peter Taylorptaylor@iastate.edu email >
Director, CP Tech Center
About the research
Concrete setting behavior strongly influences scheduling of construction operations, such as surfacing, trowelling, jointing, and saw-cutting. To conduct pavement sawing activities effectively, it is useful for contractors to know when a concrete mixture is going to reach initial set, or when the sawing window will open. Monitoring the set time of a fresh mixture also provides a tool to assess the uniformity between material and concrete batches.
The aim of this project was to confirm that initial set could be measured using an ultrasonic pulse velocity (UPV) approach, and to assess whether there was a relationship between initial set and sawing time for pavement concrete in the field.
Eight construction sites were visited in Iowa over a single summer/fall period. At each site, initial set was determined using a p-wave propagation technique with a commercial device. It was also determined on mortar samples in accordance with ASTM C 403. Calorimetric data were collected using a commercial semi-adiabatic device on some of the sites.
The data collected to date revealed the following:
- UPV approaches appear to be able to report initial set times
- Early entry sawing time can be predicted for the range of mixtures tested here