Rheology limits for grout materials used for precast bent cap pile pockets in hot weather.
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2017-02-28
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Abstract:While prefabricated bridge elements and systems (PBES) have been used for many years in Florida, The Florida Department
of Transportation (FDOT) is currently developing local specifications for PBES to ad- dress the Federal Highway
Administration (FHWA) Every Day Count (EDC) initiative. The construction on the first designated PBES project in Florida
started in 2013 on the US90 between Tallahassee and Quincy. Individual pre-fabricated elements were pieced together and –
if needed – grouted to complete the connection details. During the pilot project, grout material was wasted due to the
restrictive temperature range and flow rate limitations, specified by the grout manufacturer, or due to inadequate sealing of
the connection point. This research aimed to evaluate grouted pile pocket connections to assist the standardization pro- cess.
Information was gathered through simulating different flow spaces (grout gaps) as well as varying grout consistencies and
temperatures, while documenting the flow, final air voids, the temperature development during the hardening process, and
final grout strength. For acceptance testing, contractors generally model the structural elements from plywood. Therefore,
the pile head for the mockup specimens was made from plywood as well. However, to allow for grout flow observations, the
pile pocket was constructed from acrylic glass. PVC pipes were installed on top of the pile-pocket model to aid the filling
and ventilation process, simulating ducts used in field construction. Throughout the research, it was determined that the fresh
grout temperature, the viscosity of the material and the thickness of the gap between the pile head and the bent cap does not
significantly affect the quality of the grout flow and fillability. However, it was found that a tapered roof (7%) inside the pile
pocket promotes proper ventilation for the displaced air and helps to avoid air entrapment above the pile head corners.
Additionally, it was noted that the current construction tolerances may lead to critical hydration temperatures for massive
(high volume-to-surface ratio) grout volumes under hot weather conditions. The research suggests more rigorous
construction tolerances to achieve a desired maximum gap size opening of less than 4 in. (100 mm).
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